THE HONG KONG POLYTECHNIC UNIVERSITY

INDUSTRIAL CENTRE

IC349 - Manufacturing Projects

 

 

 

Design and Fabrication of a Plastic Sheet Bender with Automatic Adjustable Bending Angle

 

 

 

 

 

 

 

 

 

 

 

 

 

Project Number      : ME02

Instructor                  : Pete Wong

Student                       : CHAN Man Chung         09625121D

LAU Kam Ming               09539187D

LO Kwun On                    09625133D

LUI Lok Shun                 09276585D

MOK Siu Wing                09595289D

SO Hin To                       09219597D

YIP Yan Wing               09525299D

YUEN Tsz Wai                09229142D

Submission Date    : 13th July, 2012


 

Contents

Abstract ………………………………………………………………………………………………….    P.3

Introduction …………………………………………………………………………………..………    P.4

Automation Process …………………………………………………………..………………...   P.5

Design

1.           Fixture …………………………………………………………………………...……..….  P.6

2.           Heating and Cooling …………………………………………………………………   P.7-8

3.           Folding Plate ………………………………………………………………………….…   P.9-10

4.           Platform ……………………………………………………………………...………..…   P.11

5.           Motor Selection …………………………………………………………………….…    P.12

Program Design

1.           Input Needed ……………………………………………………………….…...……..  P.13

2.           Checking of Standby Mode …………………………………………….…...……  P.13

3.           Folding Sequences ………………………………………………………........…….  P.14

4.           PLC Sequences ……………………………………….………………………......……  P.15-16

Electrical System

Circuit Design

1.           Specifications of Devices ……………………………………………………........ P.17

2.           Selection of Power Supply and Transformer ………………………........ P.18

3.           Safety Protection …………………………………………….……………….…......  P.19

Wire Connection………………………………………………………………………………    P.19

Problems and Solutions …………………………………………………………….…………    P.20-21

Recommendation …………………………………………………………………….……………   P.22-23

Conclusion …………………………………………………………….…………………….……......   P.24

Self-Refection …………………………………………………………………….…………………..   P.25-32

Appendix

User Manual …………………………………………………………….……………………..    P.33

PLC connection diagram ………………………………………………………………..…    P.34

Relay connection diagram ………………………………………………………..………    P.35

25P D-type connector – Control box ……………………………………….…………   P.36

9P D-type connector – Limit switches …………………………………….…………   P.37

9P D-type connector – Motors ……………………………………………….…………   P.37

Initial Design Data ……………………………………………………………………….……   P.38-54

Sketches ……………………………………………………………………………………….…..   P.55-73-

Financial Statement …………………………………………………………………….…...   P.74

Bill of Material ………………………………………………………………………………….   P.75-76

Gantt Chart ……………………………………………………………………………………...   P.77

Abstract

This paper presents an Integrated Manufacturing Project which aims to design and fabrication of a low cost Plastic Sheet Bender (PSB) with adjustable bending angle. The automatic system consists of a work platform and a control unit. The following parts will explain the design concept and functions of the system components with illustrations. Finally a recommendation and a conclusion of the project achievements will be drawn at the end.

Keywords: Plastic Sheet Bender, Automation, Adjustable bending angle


 

Introduction

Plastic bending is an important industrial process and is useful for manufacturers. In the plastic bending process, the plastics can be reshaped into different angles and be assembled with other parts. In the Polytechnic University Industrial Center, there is a Plastic Sheet Bender (PSB) at the Design Realization Studio (DRS) to facilitate the bending process of plastic sheet. It contributes in every student or staff project like FYP or industrial projects requiring plastic bending and the quality of the product is decent. However the machine is manually controlled which to certain extent is inefficient as users have to wait for the plastic to be heated and then bend the plastic by the application of hand tools. Also as it involves bending by human hands, sometimes human errors occur. It results in inaccuracy of angle and eventually lowers the quality of the final product.

Fig. 1 Final Design                                Fig. 2 Actual View

The purpose of this project is to increase the quality and efficiency of the plastic bending process. As the machine is fully automated, user just has to preset some parameters and then the machine will operate until the plastic is bent. In the meantime, users can deal with other works to save time. Apart from that, the accuracy of the bending angle is assured thanks to automation.

    Specification:

The following table shows the features of the bending machine:

Properties

Specifications

Bending Width

Max. 400mm

Thickness of Plastic Sheet

5mm

Bending Angle

0° – 150°

Electrical requirements

-          Voltage: 24V dc

-          Adjustable heat up time

-          Electrically insulated device

-          Buzzar showing heat up time’s up

Working environment

On wooden bench

Automation Process

The Four Steps Bending Process

There are total of four steps for an automated plastic sheet bending with adjustable angle. It consists of Clamping, Heating, Folding and Cooling. The existing PSB is preforming the heating process and bend the heated plastic sheet with the application of hand tools. The four main steps will be discussed as follow.

1.          Clamping

The clamping mechanism is to secure the plastic sheet together with the platform to prevent movement and separation through the application of inward pressure. Therefore, the clamp incorporating with the bending mechanism should be strong enough to provide sufficient mounting force for bending.

 

2.          Heating

The plastic sheet will heat until it reaches the glass transition temperature. It is the main duty for both the existing PSB and PSB with adjustable bending angle. Therefore, the heater is following the existing design and dimension that provide the similar data and performance.

 

3.          Folding

With the assistance of the automated system, the system provides a consistence performance that prevents unequal force applied to the plastic sheet by using hand tools. The quality can be improved by eliminate the human error.

 

4.          Cooling

The same as the normal practice, the plastic sheet can be cooled by nature when it left the heat source. The following parts will discuss the method to perform those requirements.


 

Design

1.         Fixture

Fixture is a holding device used in the PSB and is built to fit a plastic sheet with rectangular shape. The main purpose of fixture is to locate the work piece during the operation. It allows the system maintain a consistent quality and reduce operator errors. In order to enable the plastic sheet to be made to correct specifications, the following design were considered.

Fig.3 Different Holding Methods

The work piece can be fixed by clamp, vertical force or horizontal force. Since the specification provides a wide range of width of the work piece that is 50 mm to 400 mm, the flexibility is being considered. Among these three designs, the middle one can fix the plastic sheet with constant thickness while other designs depend on different variable such as width and size of the plastic sheet.

 

With the aim of holding the work piece by vertical force, the crank with offset centering is fabricated for controlling the holding gap that suit the thickness of plastic sheet form the range of 2 mm to 5 mm.

 

Fig.4 Design of Crank Handles                             Fig.5 Dimensions of Crank Handle


 

Design

2.         Heating and Cooling

The heat wire is supported by heat wire holder in which the design is similar to the existing PSB. Since the heat wire requires 3 minutes to preheat for each on and off, the heat source is suggested to be turn on even under cooling process. On the other hand, when the plastic sheet is heated until its glass transition temperature and then being folded, the plastic sheet will be deformed at the area of heating zone that shown in Fig.2. As the result, if the platform does not move forward to the folding position, undesired folding angle will occur.

Fig.6 Undesired Folding Angle due to Incorrect Position

In conclusion, the heater should be lower at least 6 cm under cooling process therefore the plastic sheet can be cooled by nature. At the same time, the platform should move forward with 2 cm that covers the heater and the middle of the heating zone will line on the folding axis.

 

These two motions can be performed by difference mechanisms such as rack and pinion, crank and shaft and Pneumatic system. The following table shows the advantages and disadvantages of those mechanisms.

Table 1 Properties of difference mechanisms

 

Rack and Pinion

Crank and Shaft

Pneumatic System

Response

Medium

Fast

Fast

Size

Medium

Medium

Large

Cost

High manufacturing cost

Comparative low manufacturing cost

High purchasing cost

Design

2.         Heating and Cooling

According to Table 1, Crank and shaft provides the most effective performance with respects to both response and cost. This mechanism is used to convert circular motion into reciprocating motion. Attached to the end of the crank by a pivot is a connecting rod. The end of the rod attached to the crank moves in a circular motion, while the other end is constrained to move in a linear sliding motion.

Fig.7 Dimensions of Crank and Shaft

The above figure shows the platform and heater are constrained to move along in a linear guide. When the crank rotates clockwise, the platform will move forward, hence the middle of heating zone can posit on the folding line. At the same time the heater will go down and allows plastic sheet cooled by nature.


 

Design

3.         Folding Plate

After heating, the platform will move 2cm forward to cover the heater and the heated part of plastic will be transferred onto the folding plate. To ensure the plastic sheet being bent accurately, there are two important points noted with regard to the folding plate.

1.         Heating Area Alignment

The middle of the heating area of the plastic sheet must be line on the folding line. Since two heat wires provided an effective area for plastic sheet reaching its glass transition temperature, the plastic sheet must be able to form an angle that provide enough soften material to being transform. If the folding line was misaligned with respect to the middle of the heating area, the radius of the forming angle will be narrowed down.

Fixture

The following figure will illustrate the exact alignment, misalignment of too close and too far from the folding line respectively.

Heating area

Folding Plate

Plastic sheet

Platform

Fig. 8 Different Alignment Performances

Design

3.         Folding Plate

2.         Folding Plate Turning Point

Turning center of the folding plate must be line on the surface of itself. Otherwise, the thickness of the folding plate will affect the bending area. The bending area will move forward as the folding angle increase.

The following figures represent the difference of turning center and its effect on the plastic sheet.

Fig. 9 Turning Pont on the Folding Plate Surface and the Center of its Thick

Fig. 10 Results of those Turning Points

As shown in the above figures, the middle of the heating area always lines on the folding line when the turning center lines on the folding plate surface. Therefore, the center of shaft should be coincident with the turning center. To facilitate this requirement, a clamp like component and a connector are produced. The clamp like component is installed to the folding plate so that the shaft from the component can be connected to the motor by the connector.

  

Fig.11 Clamp like Component                             Fig.12 Connector


Design

4.         Platform

For the platform, there are two main groups of material can be chosen for platform, wood and metal. The following table will show the different properties of those groups.

Table 2 Comparison of the Properties of Wood and Metal

 

Cost

Weight

Heat Resistance

Strength

Wood

Low

Low

High

Low

Metal

High

High

Low

High

 

Accounting to the requirements of the platform, it should be light that ease to move and gains certain strength to prevent defamation due to the loading. Although wood can fulfill the first requirement, it has lower strength compare with metal. Also, it will be charred when it is near the heat source. On the other hand, metal can fulfill the second requirement, but it may conduct heat from the heat source and release when cooling. It might affect the effectiveness of cooling process eventually.

 

Both materials gain its advantages and disadvantages, wood is a material suitable for the platform with respect to its cost. In order to minimize the effect of its weaknesses, sheet metal is installed near the heater to provide the reinforcement of the mechanical strength and prevent charring when the platform is near the heat source.

Fig. 13 Design of the Platform


 

Design

5.         Motor Selection

The motors are used to convert the power to the folding plate, heater and platform. For folding plate, it requires enough torque to fold the plastic sheet and support the folding plate during bending. On the other hand, the heater and platform require high torque to perform the movement through the application of crank. Both actions should perform within 2 seconds.

 

The following table will provide different types of motor properties that facilitate the selection.

Table 3 Difference Motors Properties

 

DC Motor

AC Motor

Stepping Motor

Servo Motor

Control

Simple

Difficult

Normal

Normal

Cost

Normal

Lowest

Normal

High

Speed

Accurate

Not Accurate

Limited

Normal

Torque

High Torque

Low Torque at Low Speed

High Holding Torque;

Low Running Torque

High Running Torque

Position

Normal

Normal

Excellent

Accurate

Response

Normal

Normal

Normal

Rapid

Maintenance

Needed

Less

Normal

Normal

 

With respect to torque and speed, DC motor and Servo Motor are the best choices to convert the power to the folding plate, heater and platform. However, with the aim of controlling the cost, the most cost effective actuator is DC motor.

 

 


 

Program Design

1.     Input needed

In this machine, programmable logic controller (PLC) is used to control the folding processes; the type of PLC is FX2-32MR. As the folding processes are step by step, Sequential programming is used. Five inputs, including start button, end button, timer, crank lock and angle plate are needed for PLC to control the folding processes. Timer is used to set heating time for different thickness of plastic plate. Crank lock is used to fix the plastic plate. Angle plate is used to set the target angle. Start button is pressed after setting the timer, crank lock and angle plate to start the folding processes. End button is pressed after the whole processes are completed.

 

The heating time can be changed by the user. According to several experiments, the heating time corresponding to different thickness of the Acrylic plastic sheet can be generated:

 

Table 4 Heating Time for Difference Thickness Acrylic Plastic Sheet

Thickness (mm)

Time needed (s)

2

120

3

180

4

240

5

300

 

2.     Checking of Standby Mode

After pressing the start button, PLC will check whether the machine is in the standby mode. If yes, the machine will start the folding processes. If no, the machine will move back to standby mode, user need to press the start button again to start the folding processes.


 

Program Design

3.     Folding Sequences

There are total of nine steps of folding sequences:

1.     After the start button is pressed, the heat wire will be moving up until the limit switch 1 is reached.

2.     Heating process: PLC cancels the reset signal of the timer, so the timer will start counting until the timer release an ending signal back to the PLC.

3.     Then, the heat wire will be moving down until the limit switch 2 is reached, and the Acrylic plastic sheet will be moved to the folding position.

4.     Folding process: The folding plate will rotate in the anti-clockwise direction until the limit switch 3 is reached.

5.     Cooling process: The mechanical system stops movement and wait for 35s in order to cool the acrylic plastic sheet.

6.     The folding plate will rotate in the clockwise direction until the limit switch 4 is reached.

7.     The buzzer will be switched on to let the user know that the folding processes are completed, when the limit switch 4 is reached.

8.     To turn off the buzzer, user needs to press the end button.

9.     After these eight steps, the machine is returned to the standby mode and ready for the next folding.

Limit switch 3

Motor 1

Limit switch 1

Limit switch 2

Motor 2

Limit switch 4

Fig.14 Positions of limit switch

Program Design

4.     PLC Sequences

 


Program Design

4.     PLC Sequences

Electrical Circuit

Circuit Design

There are three main issues needed to be concern:

1.          The applied current, voltage and power of all the main devices should be known

2.          The power supplies and transformers should be chosen properly

3.          The circuit should be able to fulfill the safety protection requirement

 

1.          Specifications of Devices

In our product, the main devices include PLC, two types of Motors, four Relays, one Timer and a Heat wire. Unless the heat wire, the applied current and voltage of other devices can be known from their specifications. The heat wire is given by our supervisor and it is the spared heat wire of the existing bender in the plastic workshop. Therefore, it is necessary to do a test for the heat wire.

 

In the heat wire testing, it is necessary to ensure the temperature of the heat wire is around 320oC. This value is recorded from the existing bender and it is the most suitable temperature for heating Acrylic plastic sheet. At the beginning of the test, when the temperature is increased to 200 oC, the applied current is also increased to the limit current of the power supply. Therefore, it is necessary to shorten the testing length of the heat wire in order to decrease the resistance. Since V=IR, if the applied voltage keeps constant and the resistance is decreased, the testing current can be increase.

After the testing, the list of results can be generated as the following:

Devices

Applied voltage

Applied current

Heat wire

15VAC

10A

Motor 1

12VDC

0.2A

Motor 2

12VDC

0.08A

Relay

12VDC

NA

PLC

220VAC

NA

Timer

220VAC

NA

Electrical Circuit

Circuit Design

2.          Selection of Power Supply and Transformer

With using the above list of results, there are three types of power supplies, including 220VAC, 15VAC and 12VDC. The 220VAC power supply can be directly used from the public socket. The 15VAC power supply can be used a transformer of 220V:15V to lower the applied voltage, but this transformer also needs to supply more than 10A. Therefore, the transformer should have a minimum power rating of 200VA. And, for the 12VDC power supply, since it needs to supply the power for four relays and two motors, it may make the distribution of power supply unstable. When the motors start rotating, it may draw most of the voltage, so the relays may not have enough power to work. Therefore, it is necessary to use two 12VDC power supplies separately for the four relays and the two motors.

 

The circuit diagram can be generated as following:

Electrical Circuit

Circuit Design

3.          Safety Protection

To protect the circuit and devices, it is necessary to add the multi-circuit breaker, fuse and emergency stop in the circuit. The single pole MCB is added in front of the live wire and it is regarded as the first defense. Also, the emergency stop and the on-off switch are used to protect the circuit in sudden case. And, since the heat wire require more than 12A current, it is necessary to add a double pole multi-circuit breaker.

 

After the wire connection, the circuit and the devices are placed inside a waterproof marble box. And, all the metallic parts of the product are earthed.

Fig.15 Electrical Circuit Wiring

Wire Connection

The wire connection of our product can be divided into two main parts, including the PLC connection and Relay connection. All the automatic processes are controlled by the PLC, so the PLC inputs and outputs should be connected with the input devices and output devices. From the Mitsubishi Electric, the PLC connection diagram can be found as shown in Appendix (a). Since the two motors need to rotate in both anticlockwise direction and clockwise direction, it needs to connect the motors with the relays. And, the relay connection diagram is shown in Appendix (b). Also, it is necessary to use some D-type connectors to separate the marble box and the outside devices. The 25P D-type connector is used to link with the control box, and it is shown in Appendix (c). One of the 9P D-type connector is used to connect with the four limit switches, and it is shown in Appendix (d). The other 9P D-type connector is used to link with the two motors, and it is shown in Appendix (e)

Problems and Solutions

There were three main problems found from this project which including both software and hardware. The following parts will discuss the problems and its solution respectively.

1.           Manufacture of Driving Plate

Crank and shaft are used to convert circular motion into reciprocating motion. Connecting rods are attached to the driving plate by a pivot. However, the driving plate diameter was relatively large compare with the shaft so that the difficulty of tapping for screw thread occurs.

Fig. 16 Driving Plate

With the aim of dealing with this manufacturing problem, a separation of plate and shaft were created. The manufacturing process will be required in the following sequence. The solid shaft was tapped for set screw and weld with the plate afterward. Then, the center of the shaft hole was drilled by lathe that ensures the center must be aligning with the plate.

            

Fig.17 Separation of driving plate

Problems and Solutions

2.         Heater Alignment

On the other hand, the heater was driven by the crank at middle of PSB. The unbalance weight and force were applied to the heater and cause the misalignment such that it rises at one side rather than both sides.

Although the mechanical design was uncompleted to perform the linear sliding motion with constrained movement, the parallel guides were installed in equal distance with the middle of PSB. The movement along the vertical axis had been improved.

Fig. 18 Heater with Parallel Guides

3.         Heat Generation

During the test, the temperature of the heat wire was discovered that can only increase to 200  which is less than the suitable temperature of 320 . To increase the temperature, it is necessary to replace the transformer. However, the purchased transformer was being used with only half of its power. Therefore, the power can be increased by correcting the wire connection in the secondary of the transformer. At the same time, the second problem was happened. The heat wire is overheated in this connection. The color of the heat wire was changed from brown to red that represents a fatigue signal.

 

In order to solve this problem, a dimmer was connected in the primary of the transformer to adjust the voltage as a result the temperature of the heat wire can be adjustable. Moreover, the PSB may be improved to suit for different type of plastic sheet with different glass transition temperature by adjusting the heating temperature.

Recommendation

Although the PSB can fulfill the project requirements, there are still several improvements for the further development.

1.         Heater’s Material Selection

For the heater, it is designed to be fabricated by the plywood, special carte and aluminum block holder currently. The plywood was act as the enclosure to fix the special carte and aluminum heat wire holder.

Although the cost of using plywood can control the budget rather than using aluminum block, plywood gains a disadvantage that it may be easily deform by external force or by the high temperature generated from the heat wire. Since aluminum has better resistance for both external force and heat, it is better to use aluminum to enclose the special carte and aluminum heat wire holder. As a result, the heater may have a longer life cycle.

2.         Detection System

With the aim of automating the PSB, the detection system was required for sensing the state of the PSB’s operation. Four limit switches were installed to sense the PSB’s operation and transmit the signal to PLC.

However, the limit switch has a relatively short life cycle compare with other sensor. The limit switch may finally be destroyed or lost functioning when it is frequently being used to directly contact with hard material. Therefore, it is unstable and dangerous in future even it was work in this moment.

 

In conclusion, the limit switch should be used in the limit position to act as a final protector of the machine. To improve the detection system, optical sensor should be used to cover the disadvantage of limit switch. It not only can effectively reduce the risks, but also increase the life cycle of the machine.

 

3.         Frame of the Main Body

Angle bars and flat bars were used to construct the main frame of PSB. Although the cost can be under control, the accuracy of the main frame dimension was difficult to maintain. If aluminum profile was replaced, the frame structure can easily to maintain and easily to perform the vertical or horizontal planes for constrained movement. Hence, the quality can be improved and the quantity of construction parts (angle bars and flat bars) can be largely reduced.

Recommendation

4.         Strengthening the Fixture

Although the fixture can secure the plastic sheet tightly together with the platform to prevent movement through the application of inward pressure in vertical direction, there is the possibility to slip during folding process when the plastic sheet is heated not long enough to reach its glass transition temperature. It may be caused by the faults in user input during the setting of heating time. In order to handle this manual mistake, a stopper in horizontal direction is suggested to be installed to encounter the reaction force created by folding process.

Stopper

Fixture

Plastic sheet

Fig. 19 Fixture with stopper

5.         Extension of the Adjustable Bending Angle

The bending angle is controlled by the pre-set angle plate that has the range from 15° to 150° with 15° each. With the aims of increasing the adjustable bending angle, various type of pre-set angle plate can be produced so that the bending angle for each segment can be narrowed down.

 
Conclusion

In conclusion, this project is to design and fabricate a Plastic Sheet Bender (PSB) with an automatic bending function for routine training, student project and industrial project. To achieve these purposes, lots of time was spent in research and design stages. There are lots of conceptual designs for the four main automation processes of PSB were generated such as the mechanism for performing different action, material selection and actuator selection. Compare the pros and cons with different mechanisms and material properties, the different designs were simulated by SolidWorks, and hence facilitated the selection among those concepts.

 

The PSB can be divided into two main parts, Mechanical System and Control System. In Mechanical System, conceptual designs were realized and the mechanical movement is performed smoothly. On the other hand, a PLC was selected to automatize the Plastic Sheet Bender in the Control System. User can follow simple instructions to setup the primary setting, the automation process including heating, folding and cooling will be worked automatically and sequentially.

 

After the combination of two systems and testing, the PSB is able to achieve the project requirement. It can bend the Acrylic plastic sheet of thickness from 2mm to 5mm. And, the user can adjust the bending angle in the range of 0° to 150° for 15° each segment. As the machine is fully automated after the user setup few parameters and it provides a consistence performance, user will not be idled during the machine operation. Time is saved and quality is increased.

 

All in all, the PSB still has some room for further development. Unless the above recommendations, the PSB can be improved to suit for more thicknesses and types of plastic sheet as well as the wider range of bending angle and width of plastic sheet.


 

Self-Refection

CHAN Man Chung   09625121D

Besides hardware, the software is also important to make the project run smoothly. Creating the program is not an easy task at all. People may think that our job is comfortable since we just sit here and think of the program. I can tell them that they are wrong! The program is difficult and it exhausted me every single day. The program is too complex and related too much knowledge that I have never learned before. I believe that I cannot finish it without the help from the IC instructor, so, thank you! Moreover, the choice of motor, wire, materials are more difficult than I think. There are so many different kinds of products for different kind of spec. It must be very careful and detailed in order to purchase the right materials. Otherwise, we would further out of budget. In my opinion, the IC project is a nice activity. It produces more chance for us to work together; therefore, we can maintain good relationship between each other. We will play together after the IC training and we have much fun at all!


 

Self-Refection

LAU Kam Ming                  09539187D

Design and fabrication is not only the task I had faced, but also the cooperation and management of a team I had learned. As a team leader, knowing the teammate abilities and talents can facilitate the project operation when their strengths are properly applied into the job division. Throughout this project, a clear continuous communication can clarify their understanding of their work and establish a common goal with a clear direction.

At the same time, good communication with the customer also provides useful information with the aim of designing the Plastic Sheet Bender. Design contributes the most affection of the whole project. Many factors were taken into consideration such as material mechanical properties, heat and electrical resistance, manufacturing cost and difficulties of manufacturing process. It means a high performance design but with a high level of manufacturing cost or difficult in manufacture processes still can generate a low level of product in such situation.

In preparation, the Bill of Material provided a full picture in purchasing raw material. Meanwhile, ordering a standard size of raw material in British standard and international standard should be clarified so that the manufacturing processes can operate smoothly.

Moreover, the use of machines and tools were strongly enforced during this project. I would like to express my heartfelt thanks to our supervisor Pete Wong and IC staff. They have given us a valuable chance to participate in the challenging project, together with unlimited support and professional advice.


 

Self-Refection

LO Kwun On              09625133D

Unlike lectures, we learn practical skills in industrial center. IC 349 project is a typical example. In our project, we are designing and also manufacturing an automatic plastic bending machine. There are many different kinds of works like designing and drawing, scheduling and planning, machining and milling. Within our groups, works are divided and different members are responsible to some of them.

 

For myself, I am responsible to design PLC program and also the electrical circuits of the machine. As mechanical engineering is my major, I only have very basic knowledge of programming and circuits. However, PLC and electrical circuits are essential for the machine. Without PLC and electrically, the machine can only run mechanically. In order to learn more about PLC and electric circuits, we try to research for different samples from books and internet. Although there are many samples in the books and internet, the process is not that smooth. The reason is there are too many sources that make it very difficult to figure out which is useful. Also we are not familiar with that information. As a result, we cannot understand thoroughly. We feel like we are going to give up.

 

Nevertheless, thanks to the help of the teachers and staff in industrial center, we finally are able to come up with a PLC program and electric circuits. Teachers and staff in industrial are so helpful that we don’t know what we should do to express our praise and thanks in our heart.

 

Maybe the best way to express our respect to the teachers and staff is to make best use of the knowledge learnt and become an engineer which contributes to the society.


 

Self-Refection

LUI Lok Shun            09276585D

From mid June to early July, I spent about a month time in the Industrial Center of the Hong Kong Polytechnic University. This one month experience is not long, but equips me with both hard and soft skills.

 

For hard skills, I learnt a lot about the manufacturing process. As a student, we learn from books. But sometimes our knowledge are too “theory” but not practical. In this project, there is a chance for us to do some “real” thing. From designing stage, scheduling and planning stage, manufacturing stage, assembly stage to presentation, I have lots like preparing BOM, using SolidWorks, making good use of the machine, practicing skills to calibrate parts etc. All these techniques and skills will be a great assess to my career.

 

Other than practical skills, we also learn some soft skills like interpersonal skills, team works, analyzing skills and time management. As there are eight people within a group, we must cooperate with each other. We need to discuss with others which enhance my interpersonal and communication skills. Meanwhile team work is a must in any groups and I think I learnt more from this project to be a team player. As to finish our work efficiently and make sure the machine is of good quality, we need to analysis every single steps of the project thoroughly and make a very good plan.

 

All in all, I learn a lot from this project. Also this is a very unforgettable memory working with schoolmates and teachers to construct a plastic bending machine.


 

Self-Refection

MOK Siu Wing                   09595289D

Throughout the whole training period, I have learnt and practiced a lot of technical skills such as milling, machining and PLC program writings. However the most valuable experience I gain is not only the hard skills but soft skills.

 

Human beings are of different personalities and abilities, it is impossible to find any others same as you. So it is always a big challenge to work in a group. In a group, there are different voices and ideas. For example, some may think that design stage is more important, some may think manufacturing stage is more important. Whenever different opinions appear, there is conflict. To be honest, there are conflicts between our group members especially when it comes to the final stage of the project. When deadline come closer and closer, members feel more and more stressful. The relationship between members turns worse. However as all of us know the importance of teamwork, we listen to others and work harmony with others. When we are working in a team, the efficiency is much higher. I really like the feeling working in a team.

 

Other soft skills I learnt are creativity. Creativity is required in many stages. Creativity is not only creating or designing something, but also solving problems creatively. For example, there is not enough space to add screws to fix the parts. We may try to remove something and make some spaces. But in fact we can create some spaces ourselves by acting an extra part.

 

In the future, I will try my best to become a very good team player and try to use my creativity to solve problems.


 

Self-Refection

SO Hin To                   09219597D

During this project, I am mainly responsible of the milling process. This work gives me chance to refresh my milling skill and enhance my knowledge about milling. There are many skills and tools about improving the accuracy of milling that I have never used before in the previous training. I have learned the automatic mode of the milling machine and the usage of different drill and also the edge finder. These are the invaluable experience that let improve my working efficiency and quality of the product. I have also done other important part of the product; say the wood platform of the machine. This is the first time for me to enter the wood workshop in the IC centre. It is really an interesting experience. If I am not doing this project, I think I will never go there and explore different machine there. The instructor and other students are very helpful. Since every machine is new to me, I have to learn how to use the machine and the safety precaution from the beginning. With the help of the students and the instructor, I can finish my work in a short time. Otherwise, I believe that I cannot finish my job in time and the whole progress of the project will be delayed because of me. It leads to a terrible result.  Thanks to the IC instructor about teaching me so much. After reached so many workshops in the industrial centre, I am really glad that I have entered the engineering subject of the Hong Kong Polytechnic University. It is because it provides a very awesome environment for the students to learn different manufactory process.

Self-Refection

YIP Yan Wing         09525299D

Times flies, and the IC 349 Manufacturing Projects comes to an end. These five months training which started from March and ended at July was a remarkable experience and simply helped me to get prepared for the upcoming final year project in the next semester. This training was total different from the previous IC 348, from which we need a good time-scheduling, creativity, and job specializations for every teammate.

 

A good time management is the key to the success of the project. We found out time is a constraint and the most challenging problem in this project during the project design stage. From March to May, we are scheduled with tones of tests, presentations, journals and examinations, but we still squeezed our leisure time to do research on how to fabricate an automatic machine which we are not familiar. Our efforts and hard works had rewarded us quite a lot of innovative ideas and designs such as the “Crank and Shaft” which are mentioned in this report.

 

Creativity is the most important soft skill that I learnt in this training. Not only does creativity help us to generate new ideas and design, it can make our lives better. Our automatic plastic bending machine is a GREEN product because it reused wasted materials such as the plastic wheels and roller slide. The four plastic wheels (bottom of the trolley) and the two roller slides (in parallel to the heater for smooth vertical motion) were collected from a computer desk in garbage. Besides, we solved our low budgeting and mobility problem with the idea of FUSION. The whole machine was mainly made with wood and plastic except the parts which need to endure heat and stresses.

 

The job specialization technique had helped us a lot during the fabrication stage. We are allocated to different sections in accordance to our specialties. For instances, some are good at Cad drawing and stimulations, others are good at programming and circuit design, while the rest are responsible for fabricating and assemble the automatic bending mechanism. We worked as a team and always communicated with the items tolerance and latest amendments. It is a challenging job because the whole project would be suspended if misunderstanding and defect occurs in any sections.

 

Lastly, I would like to express my thanks to all IC staffs and our project supervisor Pete Wong who gave us valuable guidance and support during the IC349 training.

Self-Refection

YUEN Tsz Wai           09229142D

I have found so much fun in the project although dealing with the turning machine all day long is really tired. However, it is really interesting to make the parts from the raw material to the real parts according to the drawings. This makes me proud of making my own product. I have been wondered by the high accuracy of the machine and the history of the milling machine. Many years ago, the milling machine had already exists. I am also wondered by and technique of the technician in many years ago. It is because they can think of a way to produce a machine with so high accuracy. They had also high technique to control the machine. Every one of them is making the world in a better and more modern way. I am pleasant that I can have the chance to reach this are of knowledge and I am getting familiar with it. It is not a easy task and it also needs high level of concentration. It makes me tired and exhausted after every working day. However, when I put the product on my palm and look at it, it is worth to put so much time and mind into it. This is the masterpiece of mine! I have learned so many techniques and I know that there are more to learn. Experience is really important! I hope that I can have the techniques and knowledge like the IC instructor.


 

Appendix

User Manual

There are total of four steps in the bending processes, including clamping, heating, folding and cooling. User needs to input some data into the initial setting, and clamp the plastic sheet only. Other bending processes will be automatically worked by the PLC program.

 

Normal steps (Standby Mode)

 

1.      First, user needs to switch on the on-off switch, and adjust the heating time of the timer to the value according to different thicknesses of plastic sheet. The table of heating time is shown in the following table:

Heating Time Table for Acrylic Plastic Sheet

Thickness

Heating Time

2mm

120s

3mm

180s

4mm

240s

5mm

300s

 

2.      Then, user needs to clamp the plastic sheet in which the folding center of the plastic sheet should be placed above the marked line on the folding plate. And, user needs to insert the Bending Angle Plate into the rectangle hole to preset the bending angle.

 

*If the indicating lamp placed in front of the Marble Box is already turned red, then skip the step 3 and directly move to step 4.

 

3.      User needs to press on the dimmer and adjust the dimmer to the marked value. The indicated lamp placed in front of the Marble Box will be turned on from dark to red. Now, user needs to wait for 3 minutes to pre-heat the heat wire.

 

4.      User now can press the “Start” button to start the automatic processes. All the bending processes including heating, folding and cooling will be worked in sequence.

Heating:     The platform moves away, and the heater moves up. And, the Timer will start counting until achieving the preset heating time. During this process, the red indicating lamp will be turned on.

 

Folding:      The platform moves to standby position, and the heater moves down. Then, the folding plate will rotate anti-clockwise to process the bending movement until it touches the preset bending angle.

 

Cooling:     The mechanical system will be stopped for 50s to cool the plastic sheet. Then, after the 50s, the folding plate will rotate back to the standby position. And, the buzzer will sound on to let the user know all the bending processes are completed.

 

5.      To turn off the buzzer, user needs to press the “End” button. Then, user can release the clamp and take out the bended plastic sheet. That’s all the bending processes.

 

 

 

Accident or Special Case

*If there is any accident happened, user can press the Emergency Stop to stop the bender in any time. Then, the bender will be stopped and the electrical circuit will be also cut off. Then, user needs to follow the guideline of Special Steps.

 

Special Steps (Not in the Standby Mode)

 

1.      If the Emergency Stop is pressed, please release the Emergency stop first. And, user needs to switch on the on-off button.

 

2.      If the bender is not in the standby position, please press the “Start” button. The bender will move back to the standby mode.

 

3.      Then, user can take away the plastic sheet or re-start the bending processes. If user wants to re-start the bending processes, please follow all the steps in the Normal Steps.


 

Appendix

(a) PLC connection diagram


 

Appendix

(b) Relay connection diagram

(c) 25P D-type connector – Control box

 

Number

Description

Number

Description

1

 

14

 

2

 

15

Timer 2 <-> N, 220VAC

3

Lamp R <-> Y5

16

 

4

 

17

 

5

 

18

Lamp R, G, Y, Buzzer, Timer 7 <-> L, 220VAC

6

Lamp G <-> Y6

19

Timer 1 <-> Y3

7

 

20

Timer 3 <-> PLC output COM

8

Lamp Y <-> Y7

21

 

9

 

22

Timer 6 <-> X4

10

Start NO <-> X3

23

Start COM, End COM, Timer 8 <-> PLC Input COM

11

 

24

 

12

End NO <-> X5

25

Buzzer <-> Y4

13

 

 

 

Appendix

(d) 9P D-type connector – Limit switches

 

Number

Description

Number

Description

1

Limit switch 3 NC <-> X16

6

Limit switch 4 NC <-> X17

2

 

7

 

3

Limit switch 2 NC <-> X15

8

 

4

 

9

Limit switch 1,2,3,4 COM <-> PLC Input COM

5

Limit switch 1 NC <-> X14

 

 

 

 

(e) 9P D-type connector – Motors

 

Number

Description

Number

Description

1

Relay 1-9, Relay 2-6 <-> Motor 1 +

6

 

2

 

7

Relay 3-9, Relay 4-6 <-> Motor 2 +

3

 

8

 

4

Relay 1-6, Relay 2-9 <-> Motor 1 -

9

Relay 3-6, Relay 4-9 <-> Motor 2 -

5

 

 

 

 


Appendix

Initial Design Data


Appendix

Initial Design Data


Appendix

Initial Design Data


Appendix

Initial Design Data

 

 


Appendix

Initial Design Data

 

 


Appendix

Initial Design Data

 

 


Appendix

Initial Design Data

 

 


Appendix

Initial Design Data

 

 


Appendix

Initial Design Data

 

 

 


Appendix

Initial Design Data

 

 


Appendix

Initial Design Data


Appendix

Initial Design Data


Appendix

Initial Design Data


Appendix

Initial Design Data

 

 


Appendix

Initial Design Data

 


Appendix

Initial Design Data

 


Appendix

Initial Design Data

 


 

Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches

               


Appendix

Sketches


Appendix

Sketches

 


Appendix

Sketches


Appendix

Sketches

 


Appendix

Sketches


Appendix

Sketches


Appendix

Sketches


Appendix

Financial Statement

 Appendix

Bill of Material

 


 

Appendix

Bill of Material


 

Appendix

Gantt Chart