The Hong Kong Polytechnic University

Industrial Centre

IC349 – Manufacturing Project for BENG (Hons)

Final Report

 

Project No: ME07

Project Title:

Quick Shell Drying System (QSDS)

 

 

Overall Project Supervisor

Ir Dr Martin CM WONG

 

Project Supervisor

Ir Sidney WF WONG

 

 

Group member list

LI Xuesen (Tony)

LIU Chang (Will)

LIU Chang (Steve)

IP Kai Cheung (Morris)

NG Lun Hoi

SUN Xiaoxuan (Jenny)

TAM Kam Piu (Bill)

YE Han (John)

 

 

Index

Introduction………………………………………………………………………..…3

Design…………………………………………………………………………………5

Control System……………………………………………………………………...22

Manufacturing………………………………………………………………………31

Conclusion…………………………………………………………………………...53

Reflection…………………………………………………………………………….56

References………………………………………………………………………...…71

Appendix…………………………………………………………………………….72

 

 

 

 

Introduction

______By LIU Chang (Steve) ______

Investment casting is one of the most traditional and also extensively used methods for metal production. This method is also called lost wax casting, basically consists of 8 steps: wax injection, pattern assembly, shell building, de-wax operation, pre-heat, casting, knockout and cutoff, as illustrated by Fig. 1 below:

investment-casting-process-diagram

Figure 1: Investment casting process (picture from [1] Palmer Associates)

The technology of RP (rapid prototyping has been widely incorporated with investment casting, including in the Industrial Centre of Polytechnic University. However, the conventional relatively long shell building time (one of the above-mentioned steps), usually 3-5 days, largely limited the advantage of RP technology [2].

A number of studies were conducted to accelerate the process of shell building [3] [4], including one proven method (an US patent) [4] which was developed to remarkably shorten the shell drying time, down to as short as half hour for each ceramic layer. Fig. 2 shows the general configuration of the patent design.

Figure 2: Side view of the system described in the patent

(Picture from [4] Kungelgen et al)

Based on above-mentioned studies and existing patent, this project aims to design and manufacture a small scale Quick Shell Drying System. With a shorter shell building time, the product should be able to incorporate with the RP technologies of the Industrial Centre for investment casting.

As per the requirement of the customer (The Hong Kong Polytechnic University Industrial Centre), the basic configuration of the product should include ventilation system, infrared light, rotational device, sensing devices and control system. Feedback systems in both temperature and humidity are required to maintain an environment as listed in the specifications below [2] (Table 1). Rotation speed, air flow rate and the dimension of shell inside are also requested. However the design of the capacity of final product should be based on the actual was tree produced by our customer.

Max size of shell

300 mm x 500 mm (H)

Max weight of shell

5 kg

Rotation speed of shell

1.5-4 rpm

Moisture content

10-20 %

Drying Temperature

30-36 oC

Flow rate

1-5 m/s

Control

PLC control and signal feedback

Indicator

Temp./Humidity/Time/Flow rate

Electrical supply

Single phase 220 V 13 A

Table 1: Product Specifications from customer

 

Design

______By SUN Xiaoxuan (Jenny) ______

Concept design

According to the objectives of our project, to fasten the procedure to dry an investment casting shell, fans and lights are needed. With the ability to take the wet air, which is full of vapor, away from the surface of the shell, fans can accelerate the drying process. Similarly, infrared lights can bring more energy to the water molecules to make it easier for them to evaporate.

And after certain discussion process, such as mind storm and concept selection, concept of the quick drying system comes out. Fans and lights need work straightly to the surface of the shell. Therefore, it is better to arrange them in a circle pattern. So a structure needs to be designed to hold these facilities. Outside the inner part, a frame should be constructed to support the hold body, which is designed as in a cubic shape.

There are three parts of the machine body that is the inner part, which is hexagon shape and with fans and lights fixed on, the frame to support the whole body of the machine, and the iron plate to cover over the frame with a door in front. The sketch is showing as follows (Fig. 3).

    

Figure 3: Sketch of concept design

Configuration

To fix the dimension of the machine body, several factors should be taken into consideration. First of all, for the inner part, to determine the length of the side of the hexagon, we need to confirm the position of the fans and lights. As we hope to dry the shell as soon as possible, we need to try to make the wind flow from the fans pass through the surface of the shell as long as possible. It is especially optimized, if a vortex could be form in the middle. Therefore, we make the wind blowing path tangent to the circle which indicates the shell , and the position of the fans could be fixed. The size of the hexagon is determined by the size of the shell, the size of the fans and the distance between the shell and the fans.

Figure 4: Design of inner structure

It can be seen from the Fig. 4, that certain changes are made to the hexagon in the middle, and it is to hold the lights. As we hope to make the lights work at the highest efficiency, infrared ray from the lights should shine directly to the surface of the shell. Therefore, the infrared ray is perpendicular to the circle in the middle and the plate to hold to lights has an angle of 15 degree with horizontal.

Secondly, come to determine the dimension of the frame. Consider assembling requirements, at the back of the box, certain space should be kept, and the distance is equal to the length of the light. And at both right and left side of the box, certain space should be spared to make sure that the fans will not collide with the edge, as the fans have their thickness.

Thirdly, it comes to the height of the frame. The length of the hook, which can be measured from the motor and of which the value is about 115mm, the height of the shell, which is defined based on the condition during actual manufacturing, and the spare space from the bottom that is about 200mm, should be added up, as showing in the following Fig. 5.

Figure 5: Design of dimensions

At last, the fans and the lights should be fixed at appropriate height to ensure the wind and the infrared ray can work on the shell directly. 

Design for manufacturing

Material

The inner part should be thick and strong enough to hold the fans and the lights. In addition, the material of the inner part must be easy to manufacture, as several holes, which are the positions of the fans and lights, need to be punched on it and the material must be able to be bend to certain angles. Therefore, aluminum plate with thickness of 3mm is selected as the material.

The frame must have enough strength and stiffness. We choose angle iron as the material. And it has the advantage of low cost. Welding should be processed to join the angle irons together, as welding could ensure the strength of the frame.

For the cover, to reduce the cost of the project, iron plate is selected as the material. But there is a problem that the iron plate is not strong enough and easy to deform. Therefore, we decide to do some bending at the edges of the plate to increase the strength. As a result the related manufacturing processes are cutting, and bending.

Parts

Material

Manufacturing Process

Inner part (hexagon)    

Aluminum

bending & punch

Frame

Angel Iron

welding

Cover

Iron plate

Cutting & bending

Table 2: List of DFM of our product

Tolerance

The thickness of the materials should be taken into consideration, because there may be some overlaps of the material in the product, for example, at the joint of the angel iron and the connection of the cover and the frame. Without the consideration of overlap, the assembly of the inner part with the bottom will meet problems and it may affect the whole machine.

And certain inaccuracy during manufacturing cannot be omitted. Inaccuracy becomes the most important problem during the progress of our project, and it brings great difficult to assembly. It should be more careful when the cutting and bending are being done. However, sometimes such inaccuracy cannot be avoided, and tolerance design will become extremely important. If the project can be done a second time, more effort should be put in this part!

Shape

Materials should be cut to certain shapes to avoid overlap and collide after bending. It is most significant for the bending of the cover board and the inner part. Meanwhile, the angle iron should be manufactured to certain shape for welding. There is an example showing in the following Fig. 6.

 

Figure 6: Design for the bending of sheet metals

 

 

 

______By YE Han (John) ______

After we define the design configuration, we start to design our Quick Shell Drying System. There are totally three versions through our design process; each version is established by modifying the previous version.

Design Version 1

Version one only specifies the box without details of the inner plate that is for supporting the fans and the inferred lamps. The frame of box is made by bent metal (shown in the Fig. 7), but the thickness of the metal is too small, which might result in the deformation of the box when there is heavy load on this frame.

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Figure 7: Frame of the box

The connection between each metal part is by imbedding and few screws would be needed to fix the frame. Although the method of connection is simple, the complicated shape of the metal parts would be difficult to manufacture and the destruction of the frame would be result from the unstable connection.

The cover of the Version 1 is easy to be installed in the frame (shown in the Fig. 8); this kind of installation is practical. But the cover would be too weak because the only one bend on the boundary of the cover could not avoid the twist of the metal, which might cause the big problem of deformation of the cover. And this kind of installation requires accuracy of the manufacturing for the metal, which might not be easy for student.

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Figure 8: Cover design in version 1

Another feature that might be considered in the latter design is the ventilation hole at the rear cover (shown in the Fig. 9). These holes are for dismissing the heat generated by the inferred lamps. But due to the manufacturing process for these holes would be too complicated and the air leakage might occur by these ventilation hole, actually this ventilation hole design is not adopted by the latter design.

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Figure 9: Rear cover design in version 1

The Version 1 of the design roughly sketch the outline of our QSDS, but still there are lots of modification that we need to consider in the following version of design.

Version 2

In Version 2 of our design, many correction and modification have been conducted, and changing the idea of solution has solved many problems. The overview of the Version 2 is quite similar to the final version (Fig. 10).

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Figure 10: Overview of Version 2

Some specifications have been finalize, like the shape and connection of the inner plate (Fig. 11). The inner plate is inconsist of four parts, left plate and right plate are for installation of the fans and the middle plate and the back plate is for installation of the infrerred lamps. The dimension and the position of the installation is base on the design configuration which should be mentioned before. The connection of each plate is by wielding and also the fixxing of the plate is by wielding with the bottom cover.

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Figure 11: Inner plate design in Version 2

The bent part at the bottom boundary of the plate is to increase the area for wielding, and stabilize the plate in order to hold the position of devise such as fans and inferred lamps. And the slot in the bent part is for avoiding the interference with the angle iron that is the part of frame.

To support the whole system, the frame made by the angle iron comes out after our consideration (shown in the Figure 6). Three different sizes of the angle irons are chosen to build the frame. A right angle isosceles triangle should be cut off on both side of the angle iron for the upper square frame and the bottom square frame, because both 45 degrees on the side could form the two angle irons in right angle (shown in Fig. 12). The connected angle iron between upper frame and the lower frame would insert in the inner side of frame (shown in Fig. 12). There are each two angle irons across the upper frame and the bottom frame (shown in Fig. 13). Two on the upper side is for supporting the motor, while the other two on the bottom side is for fixing the inner plate. Several holes would be drilled on the angle iron for installing the cover, four holes on the horizontal angle iron and three holes on the vertical angle iron.

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              Figure 12: Angle steel design             Figure 13: Upper and bottom design

As mentioned in the Version 1 of design, the cover needed to bend twice on the boundary for preventing twist of the cover. Since the upper cover and the bottom cover would not occur twist easily, so only the two doors, left and right cover with the back cover designed to bend on the side. Also several holes should be drilled on the side for driving the screw. Besides that a hole on the left cover for injecting compression air also should be punched out. Two hinges would be connected between frame and the doors. The Version 2 is almost the final version until we found out that the reference shell is too big which result in our design is oversized.

Version 3

Version 3 is quite similar to the version 2, beside the big difference in dimension. All dimensions have been reduced due to the shrinkage of reference shell. The shape of the inner plate is like the hexagon whose length is reduced to 370mm. Following is the description of the detailed dimension for inner plate.

Right plate (Fig. 14):

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Figure 14: Right inner plate in Version 3

Total horizontal length: 740mm             Side length: 370 mm

Total height: 470 (unbent) & 440 (bent)

Slot depth: 56mm      Slot width: 60mm

Diameter of Fan hole: 146mm        Distance from fan hole to left side: 85mm

Distance from upper fan hole to upper side: 110mm        

Distance between fan holes: 200mm

Diameter of screw hole: 4.5mm

Left plate (Fig. 15):

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Figure 15: Left inner plate in Version 3

Left plate is the axial mirror with the left plate.

 

Middle plate (Fig. 16):

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Figure 16: Middle inner plate in Version 3

Total length: 384mm         Side length: 191mm  

Diameter of the inferred lamp: 119mm         Distance between lamps: 200mm

Distance between upper lamps with upper side: 110mm

Distance between lamp and the left side: 96mm

 

Back plate (Fig. 17):

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Figure 17: Back inner plate in Version 3

Total length: 383mm                Slot depth: 32mm            

Upper slot width: 22mm                Lowe slot width: 36mm

Bending angles of inner plates (Fig. 18):

4

 

3

 
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1

 

2

 

Figure 18: Bending angles of inner plates


 

Bending angle 1: 120 degrees        

Bending angle 2: 135 degrees

Bending angle 3: 150 degrees        

Bending angle 4: 150 degrees

The connection method of upper frame and lower frame has been changed (shown in Fig. 19). One angle iron would be cut off a square piece on the side to match the other angle iron with a right angle.

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Figure 19: Connection method of upper and lower frame

The three difference dimensions are 900mm, 848mm, and 535mm respectively.

900mm comes from one hexagon length of 370mm plus two-hexagon length time sin30 as 370mm plus two buffer space of 80mm. 535 comes from the hook length of 185mm plus the shell length of 200 plus the buffer space of 150mm. 848mm comes from two hexagon length time cos30 plus half hexagon length time tan15 plus the lamp’s length of 158.

The covers do not change a lot, but the new version only has one door due to the size reduction. All the bending width of the left cover, right cover, door, and the back cover is 17mm. The detail dimension of cover would be shown below.

 

Door (same dimension as cover back; shown in Fig. 20):

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Figure 20: Door in version 3

Length: 900mm                        Height: 535mm

Cover left (same dimension as cover right, shown in Fig. 21)

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Figure 21: Cover left in Version 3

Length: 858mm                        Height: 535mm

Cover Top (same dimension as Cover bottom, shown in Fig. 22)

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Figure 22: Top cover in Version 3

Length: 934mm                        Width: 892mm

Detail dimension of top cover (shown in Fig. 23):

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Figure 23: Top view of top cover

Diameter of ventilation hole: 60mm            

Distance between ventilation hole and left side: 400mm

Distance between ventilation hole and front side: 480mm

Diameter of motor hole: 40mm

Distance between motor hole and the left side: 465mm

Distance between motor hole and the front side: 333mm

Diameter of screw hole: 8mm

Finally it is the whole QSDS (shown in Fig. 24)

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Figure 24: Whole QSDS design in Version 3

 

Control System

______By LI Xuesen (Tony) ______

Overview

Control system is built to control the temperature and humidity. 8 venting fans are implemented to control the humidity and 4 infra-red light are used to control the temperature. The control box is built by sheet iron, which contains the micro circuit brake to ensure the safety. Emergency switch is implemented for emergency stop. 4 individual switches are used to fans infra-red light and main motor separately. The overview of the control box is shown in the following Fig. 25:

Figure 25: Overview of control box

Technical Specification

The technical specification is listed as follow:

Hardware Used:

      Arduino UNO

      HD44780 LCD

      SHT10 Temperature and Humidity Sensor

      8 Channel Relay 250VAC/10A OR 30VDC/10A

      Motor Driver 55V110ANMOS Max:40V/170W

      Switch

Input Voltage

      220V AC

Functions

      Driving DC motor

      Driving 4 venting fan

      Keeping Temperature and Humidity inside a proper range based on FeedBack

      Controlling 4 infra-red heater

Operating Range

      Temperature:-40 - 120 C

      Humidity: 0 - 100%RH

Circuit connection

Figure 26: Circuit connection

Working Flow

Infra-red light is used to control the temperature automatically. The threshold is 30 to 36 Deg. When the temperature is less than 30, the control box will turn on the light to increase the temperature; when the temperature is greater than 36, the control box will turn off the light to let the control box cool down.

The humidity is control by the compressed air and the venting fans. Because the humidity should be kept as low as possible, the compressed air is consistently blown into the container and the venting fans are kept on. However, if the user wants to control the air flow, he/she can control it manually through is switch although doing this is not necessary during the process.

Figure 27: Working flow

 

Programming

Arduino Uno is used as the micro controller. Most of the programming is based on the built in library of Arduino.


 

Arduino Uno

http://arduino.cc/en/uploads/Main/ArduinoUno_R3_Front_450px.jpghttp://arduino.cc/en/uploads/Main/ArduinoUno_R3_Back_450px.jpg

Figure 28: Pictures of Arduino Uno

The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.

Microcontroller   ATmega328

Operating Voltage      5V

Input Voltage (recommended) 7-12V

Input Voltage (limits) 6-20V

Digital I/O Pins   14 (of which 6 provide PWM output)

Analog Input Pins      6

DC Current per I/O Pin    40 mA

DC Current for 3.3V Pin  50 mA

Flash Memory     32 KB (ATmega328) of which 0.5 KB used by bootloader

SRAM   2 KB (ATmega328)

EEPROM     1 KB (ATmega328)

Clock Speed 16 MHz


 

USB Overcurrent Protection

The Arduino Uno has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port, the fuse will automatically break the connection until the short or overload is removed.

Code and explanation

Detailed code and explanation is listed in App. II.

Electronic Components

Micro Controller, Relay, Motor Driver and Temperature and Humidity Sensor are used to sensor the condition and control the temperature and humidity.

The characteristics of the components are listed in the following table:

Picture

Name

Characteristics

http://arduino.cc/en/uploads/Main/ArduinoUno_R3_Front_450px.jpg

Arduino Uno

l  Integrated micro-controller

l  Build-in libraries for LCD and PWM

l  Standard I/O

l  Stabilized Power Supply

http://img01.taobaocdn.com/bao/uploaded/i1/T1FqGWXdRrXXbfxkc9_104225.jpg_310x310.jpg

8 Channel Relay

l  250VAC/10A

l  Little driving current, only 5mA

l  Pull-down resistors to avoid malfunction

l  Extendable Channels

http://img02.taobaocdn.com/imgextra/i2/230039547/T2WNXPXc4cXXXXXXXX_!!230039547.jpg_620x10000.jpg

Motor Driver

l  40V/170W

l  PWM Duty ratio 0 – 100%

l  Immediate braking for safety

http://img03.taobaocdn.com/bao/uploaded/i3/T1FfOkXiReXXbycHE._111413.jpg_310x310.jpg

SHT10 Temperature and Humidity Sensor

l  Fully calibrated : individually calibrated in a precision humidity chamber

l  Low power consumption

l  Digital output: I2C protocol

Arduino Uno Pin Designation

LCD

11: Enable pin

12: RS Pin

2: four bits trans (D4)

3: four bits trans (D5)

4: four bits trans (D6)

5: four bits trans (D7)

Motor Driver

6: PWM Main Motor

Relay

9: PWM for fan

A0: Infar-red G1

A1: Infar-red G2

SHT10 (5V Mode)

7 DATA

8 SCK

Switch

0 Power

1 Fan On/Off

10 Main Motor

Electrical Component

Safety is first factor we considered in our design. Various components are used to ensure the safety

Electrical Component

Picture

Name

Characteristics

http://image.made-in-china.com/2f0j00dButgjnykroM/MCB-CYK13-.jpg

Micro Circuit Brake (MCB)

Max 6.0 A

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.

http://www.electric-china.net/images/electrical-terminal-block.jpg

Terminals

Terminal blocks provide a convenient means of connecting individual electrical wires without a splice or physically joining the ends. They are usually used to connect wiring among various items of equipment within an enclosure or to make connections among individually enclosed items.

http://www.kunshanprint.com/wp-content/uploads/2011/10/20090627051040286.jpg

Ground Wire

Equipment earthing conductors provide an electrical connection between non-current-carrying metallic parts of equipment and the earth. The reason for doing this according to the U.S. National Electrical Code (NEC), is to limit the voltage imposed by lightning, line surges, and contact with higher voltage lines. The equipment earthing conductor is usually also used as the equipment bonding conductor.

 

 

Manufacturing

Planning for Manufacturing

We have learnt that planning for manufacturing is procedural aspect of manufacturing systems. The manufacturing system plans and implements the productive activities to convert raw materials into products to meet production objectives, and controls this process according to the degree of deviation of actual performance from the plan. So, our group formulated a forehand planning for manufacturing. It consists of two parts, the workflow of manufacturing and distribution table. Detailed content will be demonstrated below.

Workflow

The workflow describes whole process of the manufacturing and their sequence which were estimated in planning stage. Actually, there are some differences in practical operation.

According to the final design, we selected the sheet iron with 0.7mm thickness for outer covering, the aluminum plate with 3mm thickness for inner hexagon structure and the angle-iron for main frame. We were divided into some small groups to process different materials. As shown in the workflow, Steve and Tony were responsible for the manufacturing of control box which included programming for control system. Jenny and Will mainly worked on welding and cutting the iron sheet base on design drawing. Bill and Hoi planned to process and install basement structure. Other teammates were responsible for the processing of the angle-iron. After that, some of us started to punch and bend. When the welding for frame and sheet metal for outer covering had been finished, we drilled both in angle-iron frame and outer covering. Quality control was also applied for the accuracy in assembly session. And then, main frame and outer covering should be painted for anticorrosive. The final stage for manufacturing is to assemble all components.

Figure 29: Manufacturing workflow

Distribution table

This is our work distribution (Table 3). It is only a general distribution. Actually, we would help other teammates when we finished the intraday task which illustrates the power of teamwork.

 

 

Name

Distribution

LIU Chang (Steve)

Control Box & Angle-iron Processing & Assembly

LI Xuesen

Control Box & Angle-iron Processing & Assembly

YE Han

Detailed Design & Sheet Metal & Assembly

SUN Xiaoxuan

Detailed Design &Drilling & Assembly

LIU Chang (Will)

Welding & Sheet Metal & Assembly

TAM Kam Piu

Angle-iron Processing & Sheet Metal & Assembly

NG Lun Hoi

Angle-iron Processing & Basement Installation & Assembly

IP Kai Cheung

Angle-iron Processing & Basement Installation & Assembly

Table 3: Work distribution

Welding

MIG Arc Welding

MIG welding is a welding process in which an electric arc will form between the welding electrode and the working piece, causing the metal melt and join. This is a process that was developed for welding aluminum and other non-ferrous metals. It is a semi-automatic process in which a wire connected to the direct current which joins two pieces of metal as it is continuously passed through a welding gun. The inert gas flow, originally argon, also passes through the welding gun at the same time as the wire electrode. This inert gas acts as a shield, keeping airborne contaminants away from the weld zone. One advantage of this welding process is that it allows the metal to be joined much more quickly compared with other processes

In our project, we used MIG welding to join the angle-iron for main body structure. In order to grasp the basic principles of MIG welding, Will and Jenny practiced welding for one half day under the guide of IC advisor. And we find that there are too many overlaps between the jointed angle-iron. So we need to process the angle-iron based on updated design.

We made trial frame welding for twice. The first step is preparing the welding materials. We used “L” shape angle-iron in our project with two sides. For the first trial, we processed the angle-iron by milling machine to achieve the specific length and remove a triangle with 45 degree on the one side of angle-iron. The angle-iron processed is shown in Fig. 30.

 

 

 

Figure 30: Pictures of processed angle steels

After that, we make up the angle-iron in this way (Fig. 31).

IC349

Figure 31: Angle steel welding

And then, fix them on the table for welding. However, some cracks between two angle-irons are not accurate enough, so we need operate the welding rod with “Z” route to joint cracks.

Due to the design change, we made second trial for frame welding. In this time, we processed the angle-iron in another way which is shown in the Fig. 32 below.

                                            

Figure 32: Amended angle steel welding joint

We remove a rectangle on one side of angle-iron for connection with the saw. After that, we arrange the angle-iron with specific structure and keep the alignment of the frame. And then, Will weld the junction by MIG welding. In order to keep the accuracy, we weld the junction with a welding spot for orientation. After the whole structure is welded with the welding spot and alignment, we weld the whole junction with “Z” welding route. The Fig. 33 shown below is our welding process.

 

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Figure 33: Welding process

Gas Welding

Gas welding, also called oxy-fuel welding, is welding process using oxygen and other gases to form a torch, heating the metal to cause them to melt and join the two ends of the metal together. Common gases used in gas welding include natural gas, propane, hydrogen, MAPP gas, liquefied petroleum, propylene, and acetylene, with acetylene being the most common.

The Fig. 34 shows the location for gas welding.

Rounded Rectangle: Gas welding is used to join the inner plate and the base plate.EB}V[1D))4NXQ1YXNRCF)5O

Figure 34: Location of gas welding

For our design, the material we used in this gas welding process is inner aluminum plate and base plate with the thickness of 3mm. So we need use gas welding to join them. After processing the aluminum plate in sheet metal workshop, we have got the bended aluminum plate for welding. We fasten the inner hexagon plate with the base plate by pliers and joint them with the means of gas welding. However, the concrete gas welding was operated by the IC advisor, because gas welding is too difficult and dangerous for us to handle.

There several problems we have met in the process of conducting the welding process, for example, we should weld the inner plate with the base after the frame welding according to the planning for manufacturing. So it increases the difficulty of the operation because of the block caused by welded frame.

What is more, high temperature generated during gas welding has made some deformation on the base plate which made difficulties in assembly session because the temperature of gas welding can reach 2925 when the melting temperature of aluminum is 660.

In order to solve this problem, we have come up with solution to fix the base plate to the iron structure to resist the force and prevent the base plate from changing shape. Actually it could also be improved by using the screws to fix the base plate instead of using the method of gas welding if we have more time. And we have obtained the experience in aluminum plate joint. We should choose the screws for connection based on the thickness of the aluminum plate.

Resistance Welding

Resistance welding is a kind of welding process using the heat generated by current passing through the resistance to melt and join the metal. It is a kind of welding process with the advantage that it could join the metals very fast comparing to other welding processes and the operation is quite simple and safe.

The material we have used in the resistance welding is sheet iron with the thickness of 0.7mm. We have carried out resistance welding in order to weld small iron plate onto gap of the outer covering to prevent the gap from leaping air. The Fig. 35 shows the process to make up for the crack on the outer covering.

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        Figure 35: Make up for crack     Figure 36: Resistance welding process

In addition, the iron plate is bent into a shape of “U” shape which is used to reinforce the door. So we also used resistance welding to join the “U” shape iron sheet with the door which can keep the smooth of the door surface comparing to other welding methods. The Fig. 36 shows the process when we used resistance welding to reinforce the door.

Sheet Metal

______By IP Kai Cheung (Morris) ______

In our project, we did lots of work in sheet metal workshop as many major parts of our quick shell drying machine, including the outer covers and inner hexagonal plates, need metal cutting, punching or bending. The following parts show the procedures and details in these three processes.

Metal Cutting

In the design process, we first calculate the total size of sheet metal we needed. Then, we ordered the sheet metals from IC work shop, including 0.7mm iron sheet and 3mm Aluminum sheet.  As the piece of sheet metal that we ordered is large, we needed to cut the metal sheet to a suitable size to punch or bend.

 

First, we used long ruler to measure and mark the dimension of the sheet metal we needed. Then, we used the shearing machine to cut the metal sheet at the marking point. At last, we double checked the dimension of the metal sheet to confirm it is correct.

Punching

The CNC punching machine called “Turret Press”. We used this machine to punch the sheet metal to the shape we want. The procedures of punching of sheet metal are shown below:

We transform the CAD drawings to DXF file.

We use the DXF file to draw the tool path by selecting different punching tools.

We input the tool path into the computer for punching.

We also change the punching tool for the punching of sheet metal in the Turret Press if necessary.

We hold the sheet metal in the corresponding place by the clamps.

We start the Turret Press; the punching machine follows the tool path to punch the sheet metal by different tools punching.

We file the edges after punching.

Bending

After the punching stage, some of the sheet metals needed the bending process. The CNC bending machine called “Press Brake”. We used this machine to bend the metal sheet to different shapes. The following steps are the procedures of bending:

Set all the parameters about the bending to sheet metal, including the thickness of the sheet metal, the bending angle, the bending length and etc, into the computer.

Set the program and add other remaining items including the offset distance and etc.

Place the sheet metal on the die block.

Push the sheet metal until it touch the back gauge. (Shown in the figure below)

Hold it steadily and step on the pedal to move the sheet metal upward to the offset point.

Step on the pedal again without releasing the pedal until the press brake punch bend the sheet metal.

Push the sheet metal upward manually while the press brake punch touch the metal sheet to allow more accurate bending angle.

Check the bending angle to make sure it is correct.

Figure 37: Working on the CNC bending machine

Problems encountered

During the manufacturing stage in sheet metal workshop, we faced some problems in punching and bending processes. We listed out the major problems that we faced and the solutions of the problems.

Problem 1

Punching tool accidentally hit the clamps which holding the metal sheet.

Solution

We found that the punching tool hit the clamp as there are many places of the metal sheet needed punching. To solve this problem, we divided the whole tool path into two parts. We first punched one side of the sheet metal and then we held the other side of the metal sheet by clamps. Finally, we punched the remaining side to finish the whole punching process.

Problem 2

During the bending process, some of the iron sheet needed to double-fold on four sides to strengthen the sheet metal. After bending two opposite sides of the metal sheet, we started bending the remaining two sides. However, while bending the remaining sides, the press brake punch hit the bended side. It leaded the bended side deform and out of shape at the corner (Shown in Fig. 38 below).

Figure 38: Problem during double bending

Solution

As the sheet metal for the panels are made of iron with thickness 0.7mm, the material is quite soft. We used plier to bend back the deformed sides and used a hammer to hit and flatten the sheet metal.

To avoid this problem occurs, we used plier to bend two near sides upward a little bit. Then after bending the corresponding side, we bent two near sides back to the original place and check the angle.

Problem 3

The bending angle is not exactly equal to the desire bending angle which we inputted. This problem usually occurs while bending 3mm Aluminum sheet instead of bending 0.7mm Iron sheet due to the higher spring-back effect of Aluminum.

Solution

The bending angle is adjusted slightly by the manual folding machine and check the bending angle by protractor.

To avoid this problem, over-bending the aluminum sheet can compensate the spring-back effect.

Problem 4

While holding the sheet metal on the die block, sometimes the sheet metal accidentally felt in the gap under the back gauge, which causes incorrect bending length of the work piece.

Solution

We used a hammer to flatten the sheet metal (Shown in the following figure) as the iron sheet with only 0.7mm is soft.

To avoid this human error happen again, we need to hold the sheet metal carefully and step on the pedal slowly.

 

 

 

 

 

Figure 39: Using hammer to flatten the cover

Locking System

______By NG Lun Hoi ______

Purpose

Door lock was designed to lock the door in order to prevent leakage of compressed air. It helped to maintain the stability of temperature and humidity inside the machine.

Requirement

-          Easy to open

-          Easy to lock

-          Operated by one person

-          Reliable

-          Sufficient pulling force

Initial Design

An impact type door lock was initially designed for the front door. The pins were installed on the door and the locks were installed on the main body. When the door was closed, the pin would be inserted into the gap between the two rollers of the lock. The pin would be clamped by the repulsive force generated by the spring system.

Drawback

n   Wrong alignment of pin and lock due to

u  Vibration of door

u  Deformation of door due to gravity

n   Insufficient pulling force to seal up door

n   Low reliability due to the impact between pin and lock that cause damage to the locking system

Solution

The impact type door lock was replaced by a buckle type lock. A hook was installed on the door and a buckle was installed on the main body. Two aluminum blocks were made to extend the door for installation of the new locking system.

 

 

Figure 40: Initial design for locking                  Figure 41: Final design for locking

Improvement

-          More tolerance in the buckle and the hook. As a result, more clearance in alignment and the door would be easy to lock.

-          The length of buckle arm was adjustable so that larger pulling force could be generated to seal up the door.

Painting

Purpose

Due to the limitation of budget, many parts of the machine, such as panels and top cover, were made by steel instead of aluminum. Corrosion of steel parts could not only affect the out-looking of the final product but also lower the strength and cause damage to the machine. As a result, painting was required to prevent corrosion of steel part.

Methodology

There were two ways to paint the steel parts: oil paint and spray paint. To shorten the time in painting, spray paint was chosen.

 

 

 

Figure 42: Oil paint and spray paint

Procedures

1.      Use sand paper to remove rust from the steel parts.

2.      Use alcohol or thinner to remove dust or grease from the surface of steel part.

3.      Paint in a room with poor ventilation of air.

 

Safety

1.      Wear mask when conducting spray paint in order to prevent inhaling organic gas.

2.      Keep away fire or sparks when painting because the spray gas was flammable.

3.      Turn on the ventilation system of the room when finished in order to prevent accumulation of harmful gas in the room.

Problem

It was found that the spray adhered on the steel surface poorly. After investigation, it was found that the adhesion between spray paint and steel was not strong enough. Intermediate layer should be added.

Solution

After consulting opinions from different ways, it was decided to paint a layer of red oxide primer on the steel surface first. Red oxide primer is a lead-free, oil-based, high-quality, rust-resistant primer ideal for use on metal surfaces such as aluminum, iron and steel. The corrosive resistant pigments of red oxide primer make it an ideal choice for use on farm equipment, railings, window frames, fences, structural steel, pipes, field machinery and storage tanks to act as protection from exposure to chemical fumes, excessive heat and humidity, rain and wind.


Figure 43: Anti-corrosive red oxide primer used

 

Figure 44: Picture of painting work

 

Assembly

______By TAM Kam Piu (Bill) ______

After all the units and parts were prepared and manufactured, the assembly process could be started.

Units to be installed:

Fans

Lights

Covers

Wires

Sensors

Control Box

Compress Air System

During the assembly process, some problems were found out. These had to be solved as to finish our project. It will be explained one by one in the following part.

Figure 45: Assembly process

Problem 1: Air leakage

As we install the cover onto the frame, we found out that there was air leakage. This would greatly lower the efficiency of our machine.

To solve this problem, rubber tape was used for sealing. As the rubber tape installed between the frame and the cover, because of its elastic nature, it ensured no air leakage. The rubber tape was also installed on the window.

Figure 46: Sealing added between the frame and covers

Problem 2

During the designing stage, we overlooked the dimension of the fans. This leaded to some overlap of the door and the installed fans and resulted the door was unable to be closed.

To solve this problem, the simplest way is to, by mechanical process, cut off the unwanted part. After the treatment, the door could be closed. The door was then undergone a re-painting process.

Figure 47: Dimension problem during assembly

 

Final Product

As the assembly process finished, the final product was done. In the picture below, you could see the pressure gauge, the control box and the main body of the machine.

The light system and the fan system could function properly. However, the efficiency of our machine still needed to be tested.

Figure 48: Our final product

 

 

Finance

______By LIU Chang (Steve) ______

As illustrated in the following Table 4, the total cost of our project is 3331.5 HKD, which was basically under control and accepted by our customer. Some expenses were unnecessary (as noted below). In this case, the actual development cost of our product is 3091 HKD.


 

 

Name

Unit Price

Qty

Cost

Control & Electricity

Arduino Uno

199.75

1

199.75

STH 21 Humidity and Temperature Sensor

133.45

1

133.45

*

STH 10 Humidity and Temperature Sensor

92

1

92

3.3V regulator

30.7

1

30.7

*

DC24V 6.5A Current Source

225

1

225

24VDC 10A Motor Driver

120.2

1

120.2

Relay 8 Channels 220V

107.9

1

107.9

Connection Terminal #12

14

2

28

Ceramic Terminal

11

1

11

2mm Shrinkable Tube

3.5

1

3.5

5mm Shrinkable Tube

5.5

2

11

Electricity Sign Pastor

5

1

5

Emergency Button

21

1

21

15A Switch

20

4

80

Electricity Connection

31

1

31

 

 

Sect. Total

1099.5

Ventilation

Fans

300

4

1200

#

Philip IR 100c Lamp

150

2

300

#

Manual control valve

38

1

38

Lamp holders 220V E27

7

2

14

Flow adapter

40

1

40

Tube adapter

35

4

140

 

 

Sect. Total

232

Frame & body

Aluminum Sheet 2mm x 4ft x 8 ft

540

1

540

Mild Steel Angle Bar

62

4

248

Base Shelf (with joints)

428

1

428

Steel Sheet 0.7mm x 4ft x 8 ft

100

3

300

Wood board 4ft x 4ft

98

1

98

Wheels for shelf

19

4

76

*

Rubber Sealing

80

1

80

 

 

Sect. Total

1770

Miscellaneous

Door hinge

7.5

2

15

Double-side tape

8

4

32

Spray paint

25

1

25

Small handles for cover

8

6

48

Clamps

4.5

3

13.5

Tape

3.5

1

3.5

Screws and nuts

93

 

 

Sect. Total

 

230

Overall Total Cost

3331.5

**

 

 

Notes:

# These strikethrough items were not counted into our cost as agreed by IC

* Purchased components not used in final design

** Total cost excluding above-mentioned fans and lamps

 

Table 4: Project financial statement

 

Safety

______By LIU Chang (Steve) ______

Safety is always the top priority in our project. It is not only the most important standard that should be implemented in each workshop and process, it is also the essential discipline in the industry. In our project, we treated every issue on safety seriously to ensure zero injury.

Work safe

At the beginning of our meetings, all group members agreed that completion of the product is only part of our objectives, we should also finish the work safe. The awareness of safety was stressed throughout our project.

To study and to think

Before each process or operation, all members learnt the safety regulations and areas to pay attention to, by either checking the information in Industrial Centre or consulting the instructors. And we also thought carefully before action.

 

 

Caring each other

We understood that our unsafe operation is extremely dangerous not only to ourselves but other teammates as well. Since they may not know the situation, it could be more dangerous for them. In our project, we all acted responsibly, considering others' position and the order of each work carefully. Also all the difficult work was completed by at least 2 persons so that emergent condition could be reported and dealt at once.

PPE and signs

PPE was always required in every workshop we worked in. Also we pasted safety signs of electricity to remind the operators.

 

Conclusion

______By LIU Chang (Steve) ______

Outcome of the project

After 7 design sessions and nearly 1 month of manufacturing, our product was finally completed. Our final product managed to deliver the general functions and features required by our customer, including infrared heating, ventilation by fans, feedback control system etc. The cost of our project was basically under control and generally satisfied the requirement of our customer with the total cost of 3331 HKD. The completion of our project was slightly beyond the schedule but still prior to the final presentation.

 

Our learning

Attitude of an engineer

Through this project, we obtained a better understanding of the attitude that a responsible engineer should have.

The outcome at the end of our design stage was not satisfactory, which to some extent made our manufacturing phase more difficult. One reason is that we often thought that we still had a plenty of time and the manufacturing phase was far ahead. We did not manage to figure out a detailed design, especially in terms of manufacturing processes, or DFM.

In this way, during manufacturing phase we found our schedule relatively harsh and we had to amend many designs because of lack of considerations for manufacturing in previous stage.

The attitude of an engineer is about effort from the very beginning of each project. The research and design work should be serious and detailed enough to ensure the success of the final product.

Our product is based on a patent. However, the purpose of a patent is to demonstrate and register the basic idea and concept of an invention, but not a detailed manufacturing handbook. As described in our 2nd design, we simply took the parameters in the paper as standards for our product, disregarding the actual requirement from our customer. This then led to over-sized design and we had to change our design during manufacturing.

As an engineer, we should always ask where the numbers come from, rather than directly take it from books and papers as a student. In each decision made the need of customers should always be considered seriously because that is the objectives of all products.

Communication and teamwork

Our communication between team members was extremely unsatisfactory during design stage, which was also one reason of the above-mentioned condition. We did not act proactively to share progress, experiences and ideas of our product. We merely focused on each person's own contribution and the completion of individual work. This method then proved to be inefficient.

It was fortunate for our group that we realized this problem shortly afterwards and after several discussions, we started to try our best to establish efficient and integrated connection between not only all team members but also our mentor and other instructors in Industry Centre, in Cantonese, Mandarin and English. Improved communication did help us to find out existing problems in our design and manufacturing and figure out practical solutions. The transformation from in-the-box work style into cross-the-wall was effective.

Through effective communication, we also learnt to work as a team. Each member should contribute in different areas. In our team, girls were often assigned to measure or to conduct precise welding while boys were responsible for material processing. During the application of various facilities, including electricity, we learnt to take care of each other especially in safety issues. Teamwork is also about to work safely as a team. We looked after those details, including warning others before conducting work, necessary isolation and metering, housekeeping etc to ensure every member in our team is safe.


 

Individual reflection

LIU Chang (Steve)

My contribution

In this project, I participated in a number of group-based activities, including discussion and decisions on design, material purchasing, processing of materials for welding and assembly, surface finishing and painting etc. I was also involved in several relatively separated sections, such as design and set up of the control system and electricity system, financial report, project log, communication etc.

In all group meetings I acted proactively as a responsible team member. I always tried my best to provide useful ideas or suggestions that could help my team. In all the discussion sessions and communication with our supervisor, I also contributed in some secretary work, including recording the log for our project, recording the outline of discussion and outstanding tasks and also contacting our supervisor.

In other stages mentioned above, such as design, purchasing and material processing, I also tried to make myself useful and always ready to give a hand. Basically I was in control and misc part so when I had some free time I often joined the team that needed the help most.

In the design part Tony and I worked on the layout and set-up of both the electronic and electrical systems which are based on the control program developed by Tony earlier. One important work is to consult the instructor on electrical checking after our connection to ensure the safety of the product as well as the manufacturing process.

My learning

In this project I learnt that there is no completely independent task in a project. At first we tried to develop the whole control system individually. However, without a clear understanding of demands from other sections and practical conditions of manufacturing, our plan on paper could hardly be feasible.

The communication with teammates on other tasks is vitally important. At the assembly stage, our control system failed in the first testing with electricity on. We then discovered that the reason is that we mistakenly moved the control box for upper box assembling. However such movement damaged the wires between control box and body. With better communication, such condition can be avoided. It really took plenty of time to re-connect all the damaged wires to test again.

 

SUN Xiaoxuan (Jenny)

During the project, I mainly worked in the process of detailed design, sheet metal, assembly, and worked as an alternative processer for welding process. A number of problems are met and solved during our process, and different from other projects we have ever done, the size of the project is much bigger and the process of planning and designing becomes extremely important. Many problems can be avoided if a perfect design is made.

During the detailed design process, I am mainly in charge of the determination of the dimension of the total product and detailed arrangement of necessary parts in the machine. The major problem comes to the part of design for manufacturing, which includes the design for material, shape and tolerance. The first problem comes to the selection of material. We choose to use iron plate for the manufacturing of the cover. But there is a problem that the iron plate is not strong enough and easy to deform. Therefore, we decide to do some bending at the edges of the plate to increase the strength. As a result the related manufacturing processes are cutting, and bending. And the most important problem is tolerance design. Certain inaccuracy during manufacturing cannot be omitted, and it brings great difficult to assembly. It should be more careful when the cutting and bending are being done. However, sometimes such inaccuracy cannot be avoided, and tolerance design will become extremely important.

The process of sheet metal includes the cutting of iron plate, punching of the pattern on the inner part, and the bending of both the inner part and the cover plates. The manual inaccuracy is the main problem for cutting. Being more careful is necessary; however, such kind of inaccuracy can hardly be avoided unless NCN machining is used instead of manual manufacturing. And the problem met during the punching is the unsuitability of the aluminum board with the CNC machine. The tutors in sheet metal workshop help us a lot! We found a way to solve the problem when we use to drawing files of the tool path to accomplish the punching of the pattern on one single plate. Inaccuracy occurs a second time when we are doing bending. According to the requirements of our design, an angle of 120 degree and 150 degree are needed, and such angles are difficult to control when bending is being done. Another problem is the thickness of the material. Different statistics should be put into the machine when a different kind of material is used.

Assembly is not a pleasant time for us as problems are made by tolerance design and sheet metal process. We tried to reprocess our material when it is not suitable for assembly. The inner part hits the angle iron when assembling to the bottom plate. At this time, we re-cut the opening on the inner part with saw. And to ensure the whole system is gastight, we use rubber to seal the connection of the cover plate and the frame.

During the whole project of construction of a quick drying system for investment casting, I found the importance of planning and designing. Without a good design or plan, more effort, more money and more time will be needed, because it is pretty likely need to be done for a second time. On the other hand, many problems can be avoided if designing is carefully made. Therefore, time spend during the design stage is quite necessary should be used efficiently.

Teamwork is another important factor to lead a successful project. Although we met many problems during our project and sometimes there are disagreements between our group mates, we optimistically discussed together and tried our best to solve the problem. It is teamwork makes the time of doing the project enjoyable.

Last but not the least, safety awareness is another achievement of the project. Safety is emphasized many times by the supervisors, and it becomes so clearly to my mind that I will always try to think about it before any action is taken during manufacturing. Safety is always the most important no matter in the campus and in the industry. And for an engineer, the safety of the users should also be taken into consideration.

 

YE Han (John)

During the past June, my teammate and I was working hard on our MU project, which is about the Quick Shell Drying System. In investment casting, this QSDS is aimed to reduce the shell building time from which conventionally take 3-5 days to 8 hours or less with no cracks occurring during the drying process. In this project, we are supposed to optimize the parameter of design by conducting the experiments and follow the patterns in the relevant paper to finalize our design. At the end of this project the QSDS should be manufactured out and run with no safety hazards.

The first step of our work is to find out the parameter used in design and optimize the efficiency of the QSDS. The team has been separated into four groups with responsibilities of control section, motor section, drying device section, and main body section. Actually during the end of our design process, we found out that this way of separation is not efficient. Some parts in the design process were ignored by us. When the deadline was approaching we start to find this problem, but the time left is not enough for us to make up and finalize the design, so we did spend some time in the manufacturing section to compensate for the miss of design part.

In the design process, we are supposed to conduct experiments to optimize the parameter of the design. But due to constrain of time, budget, and experimental devices, there is few test that can be carried out to find some data like the humility and temperature of the compression air used in QSDS. The rest of detail designs follow the pattern in the relevant paper and the previous QSDS which is made by IC staff.

We left the final design undone in the first section, but we need to start the manufacturing section as schedule. Morris and I was responsible for the detail design in the first week, Steve and Tony kept on working for the control part, Jenny and Will went to practicing wielding, Hoi and Bill went out for purchasing some device and material that we were going to use. Although our leader was absent for internship in the Australia, we worked together and devoted ourselves completely to our project. So the progress of our project was becoming better and it seemed that the schedule was catching up.

But thing would not always be so easy, in the beginning the second week we found that the size of the shell that we referred to was beyond the requirement of IC. So we need to redesign the size of our QSDS, but unfortunately we had already built up the frame, which means that we needed to destruct the frame. But the good news is we can control our budget since the material for the new version of design is less than the wrong one.

After the final modification of design had been done, we can apply ourselves to the manufacturing process. The frame was wielded up easily with small tolerance because we have done it once before, which was a good start. According to the actual size of the frame we decide the sizes of the cover for the box. But we encountered another problem when we bent the sheet metal. The cover had small gaps in each corner, which could lead to the air leakage. The cause of this problem is the dimensions of sheet metals were wrong when we did the shearing. Soon we found the solution, a bent rectangle iron piece was fit to the corner of the cover and wielded to the corner by spot wielding. But the air leakage is still a big problem, so we bought some plastic layer of 3mm and cut it into stripe of different size for sealing between the cover and the frame.

The inaccuracy of the dimension of the cover result in another problem, the door is inclined when we installed it to the frame. This problem also made us hard to install the locker on the door. After consulting from our supervisor we change the type of locker, actually this time the door not only can be closed but also the frame and the door is tight up together.

Before the final step of assembly, we still had encountered some problem, but we overcame it one by one and finally the result of QSDS came out with our satisfactions. There are lot of experiences that I would like to reflect, the previous that I mention are those impress me most. And I did learn a lot from this MU project about the teamwork, the preparation of design and how to conduct the manufacturing process. To sum up, it is a very valuable project and it will be my fond memory for these three years university life.

 

LI Xuesen (Tony)

In this MU project of designing a Quick Shell Drying System (QSDS), I was in charge of designing and implementing a controlling system. I was also engaged in the assembly process. I have trained myself on design and manufacturing skill and the same time gained the ability of find and solve problems. Additionally, my teamwork spirit and communication skills are enhanced.

Designing Stage

In the designing stage, I was in charge of designing the working flow of the machine and design the program. Since I am a student from department of Mechanical Engineering, I have to learn some basic programming and electronic skills first before I actually started.

After serious consideration I decided to use Arduino as the micro-controller due to its plenty of library for connection with other component. In addition, it have internal voltage stabilizer so that even the supply voltage fluctuated, it will keep working without problems. Then I design the flowing of the program. I used poking as the basic algorithm due to its simplicity than interrupt. Poking means the micro controller will check the condition of each component in the circuit, for example, the sensor, the switch, the timer, and take the correct action correspondingly. In my design, the micro-controller checks the temperature and humidity inside the chamber and turn on/off the light correspondingly and at the same time update the display of the LCD.

Manufacturing Stage

In manufacturing stage, the greatest problem I encounter is to choose the best matching components. There are thousands of sensor, lights, fans and switches in the market and I have to choose the most suitable ones. This was completed by reading the datasheet of these components.

For example, I choose SHT10 as the humidity and temperature sensor due to the following reason:

   Fully calibrated : individually calibrated in a precision humidity chamber

   Low power consumption

   Digital output: I2C protocol

This has greatly trained my skills in electronic area and provide me with rich knowledge in embedded systems.

Safety is first factor we considered in our control box, we specially added a Micro Circuit Brake(MCB) in our design to ensure the safety usage. Whenever a leakage occurs or the current is greater than 6Amp, the MCB will break the circuit. We have also implement ground wire in our systems. We have tested the resistant between any two point on the ground wire and the chamfer, from inside to outside, with the door open and closed. This can keep the safety for both the designer and the user.

Assembly Stage

In the last weeks, I was also engaged in the assembly stage. It is not simply put all things together, but we have to everything matching well. For some parts, we have to further machine them; for others, we may have to re-do them. For example, we assembly to door, to originally designed door cannot satisfy the requirements which is not tight enough; therefore we change the lock totally and added two metal to match the dimension and ensure the sealing.

Teamwork Skill and Time Management

Without the efforts from all group mates, we cannot complete the whole project. We have greatly enhanced our teamwork spirit during the process. When we met problems, we discussed actively to solve the problems. We also have clear work distribution, for sheet metal, welding, control system and assembly. These all contributed to our success.

In addition, time management is also very important in doing this project. We made schedule before we start working and try to follow it as tight as possible. We have also leave some time for emergency. We also have daily meeting to check the process and know each other’s condition.


 

LIU Chang (Will)

After three-week IC training and an additional week work for our group, I have attained a deep understanding about manufacturing processes, reviewed the basic operation and applied them for problem solving in our project.

We have gone through different manufacturing processes during this training and have practiced the whole process from designing and coming up concepts to realize the design. Various kinds of manufacturing processes and methods have been reviewed as what we have learnt in the course of IC348.

We have also met different kinds of problems and have included the characteristics of the various manufacturing processes into the designing stage of the product, in which way we have avoided and prevented many problems from occurring.

The main problem for our group is poor accuracy of the dimension which induces critical difficulties in assembly. In assemble section, several parts which have been manufactured previously were with wrong dimension, and terrible thing is that the variation of dimension was out of the tolerance range. So, we need to rework and modify several components casing the waste of the time. As a result, careful thinking and full understanding of the technical drawing in case of poor understanding of the shape and dimension are very necessary. And we should produce components based on the drawing and tolerance strictly. In addition, apply quality control for each step to ensure correct dimension.

Although we have tried to come up with different kinds of failure modes that could possibly occur in the manufacturing process or problems that we may met, problems and difficulties still occurred through the process which we are realizing the product we have designed. In order to overcome these problems and difficulties and successfully complete our product, we have also found out our solutions to the problems, for example, we have fixed the aluminum plate onto the iron structure in order to prevent it from being reshaped by the welding process. We have also analyzed the experience we have gained while manufacturing the product, such as welding two pieces of metal and paid attention to the operations which are conducted by the teacher. We have found out that by using the experience into the operation of manufacturing the product, much time and effort could be saved and thus the project could be completed earlier.

Other than reviewing the manufacturing knowledge and gaining experiences of realizing the concept generated, we have also used a systematic way to complete our product by dividing the whole project into small tasks and assigning them to different team members. Teamwork has performed a role which is of great importance in the process of completing our project.

There is another factor in the designing and manufacturing of the product which is the quality control and tolerance control. The quality control is very important since it will directly influence the assembly of the product. We have paid enough attention in making the machining of the product accurate to the designed dimension and thus we could make sure the parts will be perfectly ready for the assembly of the product. We have also made testing of our final product when we have finished assembling the parts in order to ensure that it could realize its functions which have been designed before. We have realized the importance of quality control and dimension control since we have paid so much effort to manufacture the product and any careless mistake could spoil the whole project.

In addition, I have grasped some conventional rules in manufacturing, especially in welding and assembly. Conventional rules is based on long-term practice which can help us to design the product avoiding manufacturing difficulties and enhance the accuracy in manufacturing.

During the project, we are working in a group. We got various solutions for problem and had a comprehensive understanding of the problem by discussion. And Innovation and creativities are more active. Teamwork made full use of the strength of each group member and everybody made great contribute to the group.

Actually, manufacturing experience requires long term practice again and again, and it is impossible for us to have gained all the essential knowledge in this short period of time. In addition, we obtain the instructions for further study from the training.

 

IP Kai Cheung (Morris)

Throughout the whole IC349 project, I think I learnt a lot. Participating in this project was a valuable experience that would help me to face future engineering work. Learning is not only about technical things, but also attitude towards our works. I would like to review and talk what I learnt from design stage and manufacturing stage.

First, planning plays an important role in this project. We leant that the better the planning, the more efficient the work. Unfortunately, we did not have a good planning as some of the parts we did not consider in the design stage. For example, we did not give much tolerance in our design. Therefore, after manufacturing the parts of the machine, they were difficult for us to assemble as some of the parts collide or cannot assemble in the worst case. We needed to file and cut some parts manually to allow the parts to assemble successfully. As a result, we used up and wasted a lot of time in reforming the manufactured parts. Thus, the assembly of parts was delayed and we did not have enough time for testing machine. Another example is that we did not have a good planning on manufacturing stage. We did not plan well which manufacturing part went first so that we needed to wait the CNC machine for bending and punching. Thus, we wasted some time and also human resources. We learnt a lesson from it and this reminded us planning is important. A good planning on design, on time and on human resources can facilitate the project significantly.

Secondly, I learnt troubleshooting in this project to find out the root of the problems and solve them. In this project, there were some problems existed such as incomplete enclosed of the machine due to the lock of the door. We first slightly adjusted the lock see whether it improved the situation or not. However, the action did not really improve the enclosure of machine. Then, we changed the location of lock completely. Finally, this was the best solution to the enclosure problem. This project provide us a good chance to practice our trouble-shooting and problem-solving techniques which equipped me to my future job.

Thirdly, I learnt never afraid to ask question. In this project, we do have a lot of things we do not familiar with no matter in design or manufacturing stage. However, if we asked IC mentors, they were able to answer our questions as they are well-equipped and helpful. Sometimes Hong Kong students are not eager to ask questions as they think asking question is a silly action or they are without curiosity. But what I learnt in this project is that the more you ask, the more you learn. I am not saying that asking silly questions, what I mean is to ask useful and meaningful question after our thinking. Through asking questions, mentors gave us useful information that help us to solve the problems. A counter experience in this project was we did not ask questions about the target user of our machine so we did not fully understand the need of designing our machine. Thus, we over-designed our machine and needed to redo it after 1 week in the manufacturing stage. This was an agonizing experience that reminded me ask questions to understand the needs.

Fourthly, I also learnt to be courage to try so as to maximize the learning process. I remembered that one day when I worked in the sheet metal workshop; I asked an IC mentor that if he knows whether the manual folding machine can bend all four sides of the sheet metal to double-fold. He answered me “You stand here and ask me about the folding machine so why don’t you try it yourself? If you go and try, you will know the answer.” His answer affected my mind profoundly. Trying is a self-learning process. The things you learn by trying can be remembered longer time as you are not just seeking for the answers. Trying by ourselves can learn and understand different things thoroughly.

Last but not least, I learnt to be humble. As I am a year three student, I learnt quite a lot about mechanics through different courses. However, this does not mean that I know more than a year two student. In some of the areas, other people may know more than you. Besides, when I did different manufacturing works in different workshops, I found that I know not much and many things I did not know. We did not have much practical experience so we needed to ask our experienced IC mentors to seek help in real manufacturing situation. Thus, after finishing this project inspired me that never thing you know a lot and be humble all the time.

To conclude, I learnt a lot of things in this project that I could not learn from books. Through the real experience and practice of manufacturing, I realized that planning is very important. I also gained some trouble-shooting experience to solve some engineering problems. Beside gaining some practical experience, I was reminded to be humble and eager to try and ask. This project provides us a good chance to consolidate my engineering knowledge and learn from my mistakes. This project equips me with the engineering knowledge and attitude towards working which I believe would help me in the future.

 

NG Lun Hoi

In this course, we were asked to finish a cell-drying machine for investment casting, including design, manufacturing and testing. To complete this mission, knowledge from different fields were required, for instant, project management, material, manufacturing, trouble shooting and problem solving. I will talk about what I have learnt from the IC349.

 

In the initial stage, we were told the basic requirements of this machine only. After lively discussion, almost design features, including dimension, material and operation, were confirmed. In this decision-making process, we had chances to apply the communication skills and project co-operation skills learnt in lectures into a real case. Everyone was encouraged to raise ideas and point out the potential problems and difficulties. It made our initial design as optimized as possible.

To speed up our progress, we divided into several teams to complete different tasks in parallel. For example, some of us drew the CAD drawings and some of us prepare and purchase materials for manufacturing. Moreover, some welded the frame, some bent the panel and some completed the PLC control system.

However, we quickly encountered problems in the manufacturing stage. There were big flaws in the initial design such that the size of the machine was too large. We had not only changed the design immediately, but also decomposed the semi-product into raw state. It wasted one week of time. This failure taught me that it was necessary to fully understand the requirements of a project. The mistakes in initial design based on wrong understanding of requirement could be un-repairable. As a result, put more time in the design stage could save more time in fixing problems in manufacturing stage.

Moreover, this course let me know that experiences and engineering knowledge are very important in making a project to be success. For example, we used to plan to paint the steel panel of the machine by spray painting in order to save the time. However, we found that the spray paint cannot adhere strongly on steel surface. After investigation, we had to paint a layer of red oxide primer by oil paint before spray painting. We could avoid this failure if we had experience in painting. Also, sufficient experience and engineering knowledge could shorten the decision making cycle as less consultation and investigation were required.

To conclude with, this course not only gave the chance to apply what I have learnt in my university study, but also let me know the world of engineering. The experience achieved in this course would surely benefit to my future study and career.

 

TAM Kam Piu (Bill)

During the IC 349 training, we had gone through design stage, manufacturing stage. Our project was about making a We have not only completed a product, along the way, I have also gained a valuable experience in terms of practical engineering project. We had an opportunity to apply what we have learnt from lectures, including some mechanical theories, manufacturing methods, some electrical theories and etc. We faced difficulties during the practical training. We worked together and tackled it one by one. We successfully finished our MU project finally. Other than this, we learnt about teamwork. Without the cooperation of each teammate, it is not possible to get the work done.

At the very beginning, we had meetings regularly. I involved in some design works including analyzing the model which was made by Mr. Lee, brainstorming the mechanism of our machine, and some CAD drawings. I also involved in some planning works.

On the manufacturing stage, we planned works and reported progress every day as to keep us on track. I worked with another teammate to build a base with angle bar to support the machine. I also was responsible to buy some parts and units from hardware stores, including screws, handles, paintings and etc. I also worked with teammates to do sheet metal. We also cut rubber tapes for sealing. At the last process, we did assembly and testing together.

To conclude, in this project, I have not only gain experience the practical engineering project, but also strengthen my soft skills, such as time management, work as a team player, and most importantly, communication. As the world is incessant changing, knowledge gained form lectures has to be updated. It provided us a chance to practice on how a real project developed from nothing with the aid of software and technologies. I will describe it as more effective learning than that in lectures or books. All in all, this was a good chance for students to experience a real engineering project before leaving school.

 

References

[1] “Investment Casting,” Palmer Associates, [Online]. Available: http://www.castingreps.com/casting/investment-castings.aspx. [Accessed: 13 July 2012].

[2] “Quick Shell Drying System,” The Hong Kong Polytechnic University Industrial Centre, 2011.

[3] M. Kugelgen, “From 7 days to 7 hours,” in 68th WFC – World Foundry Congress, 7th – 10th February, 2008, pp. 147-151

[4] Kugelgen et al, “Method and system for producting a shell mould in particular for investment casting.” U.S. Patent 2006/0086480 A1, issued Apr. 27, 2006.


 

Appendix

Appendix I: Our project log in manufacturing phase

IC349 Manufacturing Phase Logbook

Design note: in blue color, marking some key design stages and decisions

Preliminary design: Our preliminary design from design stage, as CAD in  "Previous Design" folder, depicts the general idea of the whole product with different functional components while containing some area difficult to manufacture, including:

a. Complicated and accurate shape using bending machine

b.Sliding motor and gear box for taking-out

11th June

8. Mild steel angle 2.5 x 30 x 30 and aluminum sheet 2mm confirmed as frame and body materials *

9. Rebuilding the whole CAD design accordingly

      New dimensions as required by paper **

      Steel Angle structure with welding consideration

      2 layers of lights for larger hight

* Instead of the difficult bending, we used steel angles which provide good structural strength and accurate angle without bending

** our new design dimension stick to the paper proved to be wrong later

12th June

       Materials received and checked

       Amending CAD design (John, Tony et al)

      2 layers of fans

       Welding study (Will, Jenny & Morris)

       Purchasing

      Electrical components (Tony & Steve)     

      Base shelf (Bill & Hoi)

13th June

       Steel angle cutting (3 length, completed)

       Steel angle milling (90 angle and 45 welding angle, completed)

14th June

       Establishing the base shelf (Bill & Hoi)

       Frame welding completed

       Materials re-calculated and added

       Extra parts for base shelf purchased

15th, 16th, 17th June Holiday

18th June

       CAD design on control box and inside layout finalized (Tony & Steve)

       Emergency meeting on design

      Decided to downsize the design

       Amended CAD completed (John, Will & Jenny)

19th June

       Additional Base shelf dimension amended (Bill & Hoi)

       Purchased sealing, screws, etc (Bill & Hoi)

       Angle steel frame disassembled and dimension amended (Morris, Steve & John)

       Sheet metal cutting completed (Will & Jenny)

       Control cover box completed (Tony)

20th June

       Control box layout set up (Tony)

       Angle steel processed (Morris, Steve et al)

       Base shelf and wood board processed (Bill & Hoi)

       Frame welding mainly completed (Will, Jenny & John)

21st June

       Control box connection & testing (Tony $ Steve)

       Frame welding completed (Will & Jenny)

       Sheet metal for cover processed (Bill, Hoi et al)

22nd June (Friday make-up session)

       Cover bending completed (Bill, Hoi, Will, Jenny & John)

       Pre-assembly

23rd, 24th June Holidays

25th June

       Cover processed and pre-assembly (Will, John, Bill & Hoi)

       Door processed, window added (Bill & Hoi)

       Electricity layout design and control re-assembly (Steve & Jenny)

26th June

       Inside holder punching (Will, John, Bill & Hoi)

       Control box EE set up (Steve & Jenny)

27th June

       Inside holder punching and processing for welding (Will, John, Bill & Hoi)

       Control box EE set up and testing (Steve & Jenny)

28th June

       Inside holder processing and welding (Will, John, Bill, Hoi)

       Pre-assembly processing and preparation (Bill & Hoi)

       Control parts purchasing (Steve)

29th June (Friday make-up session)

       Painting (Bill, Hoi et al)

       EE system finalizing (Tony & Steve)

30th June, 1st, 2nd July Holidays

3rd. 4th, 5th July (Final make-up session)

       Assembly (Bill, Hoi, John et al)

       Commissioning and testing

 

 

Appendix II: Code with explanations

(a) Define the constant

#define PWM_MainMotor 6

#define Infra_2       9

#define _DATA         7

#define _SCK          8

#define SwitchPower   0

#define SwitchFan     1 

#define SwitchMainMotor  10

#define SwitchInfra 13

 

//define constant

#define c1  -2.046

#define c2  0.0367

#define c3  -0.0000015955

#define d1  -40.1

#define d2  0.01

#define MainMotor 255

#define Fan 255

 

//define threshold

#define RH_HIGH 20

#define RH_LOW  10

#define T_HIGH 36

#define T_LOW  30

 

int error = 0;

 

(b) Initialization

void setup() {

  delay(30);

  lcd.begin(16, 2);

  lcd.setCursor(0, 0);

  lcd.print("Initializing...");

  delay(1000);

  pinMode(PWM_MainMotor, OUTPUT);

  pinMode(Infra_2, OUTPUT);

  pinMode(SwitchPower, INPUT);

  pinMode(SwitchFan, INPUT);

  pinMode(SwitchMainMotor, INPUT);

  pinMode(SwitchInfra, INPUT);

  lcd.setCursor(0, 0);

  lcd.print("Initialization");

  lcd.setCursor(0, 1);

  lcd.print("Completed!");

  delay(1000);

}

(c) Main Function

void loop() {

 

      //check main moter switch

      if(digitalRead(SwitchMainMotor))

        analogWrite(PWM_MainMotor, MainMotor);

      else

        analogWrite(PWM_MainMotor, 0);

        

    // read humidity and temperature and refresh LCD

    lcd.setCursor(0, 0);

    float RH = RHRead();   

    lcd.print("RH:   ");

    lcd.print(RH);

    lcd.print(" %   ");

   

    lcd.setCursor(0, 1);

    float T = TRead();   

    lcd.print("Temp: ");

    lcd.print(T);

    lcd.print(" C");

   

    //control infra-red light to maintain T and RH

    if(digitalRead(SwitchInfra) == 0)

    {

      analogWrite(Infra_2, 0);

    }

    else

    { 

       //change the condition of Group 2

       if(  T < T_LOW ) digitalWrite(Infra_2, HIGH);

       if( T > T_HIGH)  digitalWrite(Infra_2, LOW);     

    }

 

    delay(500);    // set update rate

 

}

 

(d) Temperature and Humidity Sensor SHT 10

// start up SHT10

void HTStart()

{

  pinMode(_DATA, OUTPUT);

  pinMode(_SCK, OUTPUT);

 

    digitalWrite(_SCK , 0);    digitalWrite(_DATA,  1);

    delay(1);

    digitalWrite(_SCK , 1);

    delay(1);

    digitalWrite(_DATA ,0);

    delay(1);

    digitalWrite(_SCK  ,0);

    delay(3);

    digitalWrite(_SCK , 1);

    delay(1);

    digitalWrite(_DATA ,1);

    delay(1);

    digitalWrite(_SCK , 0);

}

 

 

// write a command to SHT10

int HTwrite(unsigned char value)

{

  pinMode(_DATA, OUTPUT);

  pinMode(_SCK, OUTPUT);

  unsigned char i;

  int error = 0;

 

  for(i = 0x80; i> 0; i=i/2)

  {

    if(i & value )

      digitalWrite(_DATA , 1);

    else

      digitalWrite(_DATA , 0);

   

    digitalWrite(_SCK , 1);

    delay(3);

    digitalWrite(_SCK , 0);

  }

 

  digitalWrite(_DATA , 1);

  digitalWrite(_SCK , 1);

  delay(1);

  pinMode(_DATA, INPUT);

  error = digitalRead(_DATA);

  digitalWrite(_SCK , 0);

  return error;  // 0 for OK, 1 for with error

}

 

//read from SHT10

unsigned char HTRead(unsigned char ack)

{

  unsigned char i, val = 0;

  pinMode(_DATA ,OUTPUT);

  pinMode(_SCK, OUTPUT);

  for (i = 0x80; i>0; i = i/2)

  {

    digitalWrite(_SCK, 1);

    pinMode(_DATA, INPUT);

    if(digitalRead(_DATA) == 1) val = (val| i);

    digitalWrite(_SCK, 0);

  }

  pinMode(_DATA ,OUTPUT);

  digitalWrite(_DATA, !ack);

  digitalWrite(_SCK, 1);

  delay(3);

  digitalWrite(_SCK, 0);

  return val;

}

 

//read RH

float RHRead()

{

  float RH = -1;

  unsigned char val1,val2;

  float val=0;

  HTStart();

  error = HTwrite(0b00000101);

  delay(250);

  if(error == 0)

  {

 

    val1  = HTRead(1);

    val2  = HTRead(0);

    val = val1*256;

    val = val+val2;

    val  = float(val);

    RH = c1 + c2*val + c3*val*val;

  }

  else

    lcd.print("error");

  return RH;

}

 

 

//read temperature

float TRead()

{

  float T = -1;

  unsigned char val1,val2;

  float val=0;

  HTStart();

  error = HTwrite(0b00000011);

  delay(250);

  if(error == 0)

  {

 

    val1  = HTRead(1);

    val2  = HTRead(0);

    val = val1*256;

    val = val+val2;

    val  = float(val);

    T = d1+val*d2;

  }

  else

    lcd.print("error");

  return T;

}