MU Project 2006

Rapid Injection Molding Using RP Mould (M4)


Manufacturing Stage


1. Grinding


It is used to parallel plans on a working piece.







Product involved: Sliding table, principle bar, side bar, vise, support blocks, space blocks, rails.

The work was fixed on the worktable by the electromagnetic chuck, the cutting coolant have to be added through the grinding process. This photo shows that the coolant is not added efficiently, the spark was form during the grinding. It would let the heat accumulating on the work and affect the flatness of the grinded surface after a long time operation.

The special vices were used for holding the work vertically to grind the perpendicular surfaces. The pair of surfaces would become the datum plates for the other machining process such as milling and drilling.

The upper one is grinded by the normal grinding wheel with the good operating condition; shining surface would be formed after the process. However, the lower one, the black machined marking was generated after the grinding. It caused by the wear of the grinding wheel and shows that the wheel have to be cleared up by the diamond head for the better preferment.



2. Milling


It is used to cut a deep surface and drill holes.








Product involved: Sliding table, principle bar, side bar, vise, support blocks, space blocks, rails.

The carbine face-milling cutter was used for reducing the size of the work-piece into the desired dimensions. Because the material we chosen are relatively harder than the normal used, large amount of steel spark was generated during the cutting process.

Sometimes because of the size of the parts are greater than the capacity of the normal vise used in the workshop, the special clamp have to be used for mounting the parts tight into the position. The alignment would also be done for getting the reference datum; we used the dual indicator during the alignment process and controlled the variation within 0.03mm.

The flat end mill can be used on making the slat or the step on the work-piece. However, the cutting coolant has to be added for function of cooling. In the milling process, the slow spindle speed and the slow table feed was chosen because of the hardness the P20 steel and the longer tooling service life.



3. Turning

It is used to make circular parts.









Product involved: Bearings, bearing spacers, guide pins and bushes.

The brass was used for making the rollers and the bushes on the sliding unit of the design, because of relatively easier on machining comparing with the P20 steel and good on wear resistance. The photo shown on the left hand side is our products make by the turning operation.

The work-piece clamped on the three jaw universal chuck is the M12 screw thread beam. It is difficult for us to hold it tight because we don’t want to damage the thread during cutting, a optimum clamping force would be required fixing the special work-piece for the turning operation. The slat was machined at the free end of work-piece shown on the photo.


4. CNC Machining

The CNC is different with the manual machine. The program has to be written before the machining operation no matter turning and milling. G-code is one of the common languages interpreted on the CNC machine interface. The operation procedure such as the too using and the tool path needs well designed before the manufacturing.

CNC machine is designed for the mass production, to raise the efficiency; normally the machine has the automatic tooling changing system. The cutting tools can be changed within the whole operation many times. Therefore, during the per-processing, the tools have to assign well on the tooling cells for the operation used.

The slated plate was manufactured by the CNC machining technique. Comparing the working hours, CNC machining is faster than the manual operation with the complex profile. In this case, the CNC milling machine finished the whole part within 2 days. However for the case of small batch with the simple profile, the manual operation would be preferred for the less preparation on the per-processing.


5. Measurement

The Vernier caliper is the most using trough the project. The photo shows that is the caliper with the dual indicated; the resolution is about 0.01mm and the accuracy about 0.02mm. It can measure the width, height, inter diameter, etc. For having the accurate reading, the holding methods would be a great knowledge for us to learn.

The main function of the dual indicator in this project is to measure the small differences on the work-piece. It is a accurate device the measure the things within 0.01mm. The other function is to make the alignment on the parts and the tuning the machine such as the spindle head of the milling machine.



The micrometer is accurate on measuring the outer diameter and the inter diameter. The accuracy can be 0.001mm for some derive. The clamping force of the gauge is a affective issue on measuring, normally the hold torque is regulate by the ratchet stop attached on the end of the screw handle.


6. Check tolerance

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First of all, the checking process have to carry out on the injection machine, because we want to have a consistence result with the correct alignment, also we want to neglect the error when we check the system in other place rather then inside the machine.

We use Vernier caliper to find out the height of the rail plus the height of the bush, that is the height H1 show in the lower picture.

We find out this height is to use it as a reference for the later diameter of the upper bush and the other bushes for this space block.

We did the same procedure for the other space block

After the installation of the second lower bush, we have to check the height again, we did that is to ensure the two lower bushes together with rail have the same height along the travel, otherwise the rail can not give us smooth sliding motion, also will give difficulties to later installment of other components.

If the bush is not fit for the height, we will make a new one.

Just using the Vernier caliper to check for two specific points of height to ensure the whole rail is at the same level is not enough, we use another apparatus to help us, that is the Dial Indicator, we use it to slide along the installed slide to observe the actual tolerance along the whole slide, in our observation, the tolerance is in 0.1 mm.

The photo on the left hand side is the measured result of the eight bushes height and diameter; we combined time into a table for later reference that will make later maintenance and modification become easier.

For the other need to have tolerance checking, we also make a table for easy reference.

The photo on the left shows the fine tuned rail system.


If you have any questions, please feel free to email us.