Injection Mold Making Process

anatomy-of-a-mold manufacturingMold Design

Mold design is the first step to make an injection mold, no one can make a mold without a mold design. Since the mold design process is a little bit complicated, so it’s hard to explain how a mold is exactly designed.

However there are some basic rules and terms that you must know it.

  1. You should never design a mold without any basic information the part, like the part material, color, total usage of the mold, part function, etc.
  2. Make the mold design to adapt for customer requirements in cost, quality, and timeline.
  3. You should confirm with your customer if any information you are not sure, otherwise it’s risk to make mistakes.
  4. Before mold making, you should send the mold design drawing to your customer for confirmation.
  5. Document all the design drawing, BOM, and sketches, since those information might be traceable for future’s modification.

Here below are some critical concerns that a mold design should consider:

  1. What is the mold life?
  2. Number of cavity for the mold?
  3. How to design the parting line?
  4. What way does the sliders deploy?
  5. How about the gate system?
  6. What is the estimated injection cycle?
  7. How to make the mold running at automatic system?
  8. What will be potential defect if we design the mold in this way?

Preparation of mold steel, mold base, and other accessories

After the finalization of mold design, we should get all of material prepared to mold making, because a mold factory can never produce raw steel, mold base, and other mold accessories. Here below are the main list of all outsourcing components:

  1. Mold Base
  2. Mold steel of core
  3. Ejection Pin
  4. Copper for EMD machining
  5. Sleeve Pin
  6. Ejection Spring
  7. Screws
  8. Cylinder for sliders(if have)

Rough Machining

When we get all of the mold material on site, we are about for rough machining for mold cavity and mold core. At this stage, most of work will be done by milling machine and CNC machining. Because it’s a rough process, we will leave about 0.3~0.5mm extra material on the part so as to make the precision process at next step.

If for some high volume production mold, we will have to harden the mold steel after rough machining. This is only to obtain high better duration when injection molding process. But after hardening of mold steel, it’s hard for machining.

However if a mold life doesn’t require high volume, we don’t need to harden the mold steel. Certainly the manufacturing cost and lead-time will be much different. Therefore you should always tell your mold manufacturers on your mold life.

Precision Machining

Normally we have to make precision manufacturing for a mold, so that we can obtain better surface and precision dimension of the part. The EMD, CNC, wire cutting machines are most commonly used for precision mold manufacturing. As the manufacturing time is very slow, so these process makes high quality mold, surely the cost is much higher.

In China, we operate those machines by workers. However in some advanced countries(Like Germany, Japan, USA), they can make the mold by automatic system, instead of labor cost facility. This is why people think Western countries can produce better injection molds than China.

Mold Assembly and Fitting

After every mold components are manufactured based on our design, it’s the time to get them assembled and fitted together. The mold assemble and fitting time takes about hours to complete, however a skillful mold maker can even make it quicker, because they have rich experience on how to fit the mold, however the beginner might take much longer to get it ready. Otherwise the mold tool will need to be fixed again after the first of mold trial.

Mold Trial

When mold fitting is done, we need to get the mold for a trail(we call T0), so that we will know if any problem with our mold making. At this stage, we should keep some sample for inspection or measurement.  For the first trial sample, there will exist some injection defects, like flash, flowing marks, deformation. But these defects can be fixed by mold improvement.

Actually mold trial is an important process to verify a new mold. During the mold trial, our mold trial technician, QC, and project engineers should follow up it until the mold is running normally.