At Creative Mechanisms we have solidified a four step process for Prototype Injection Molding. Find them below.

1. Product Design

During the initial design phase, we have to be careful not to get too hung up on the details. The goal here is to quickly establish design feasibility and get to a “proof of function” model. We don’t want to spend too much time designing a product whose parts are logistically un-producible because then the entire essence of the design will have to be changed later. This is a waste of time, and so we work hard to strike a balance between speed and production feasibility.

The ability to strike this balances comes with experience. Knowing if the part, as designed, will be able to be engineered for production has become a sixth sense – an art form, even – for the seasoned engineers here at Creative Mechanisms.

We also have design experts and tool builders that will be collaborating with our engineers throughout this stage. No project moves forward without a unanimous agreement that the design is the best it can be for production.

2. Engineering for Production

When we move on to this step, it means that we have completed our design and proven its functionality. Now is the time to engineer the parts that are necessary for production. This must be done because the parts are going to be produced in a steel tool; they must be tapered so that they can be easily ejected from the tool. The parts must also have walls that are evenly thick and must have no undercuts to prevent the steel halves from opening or cause the part to be trapped in one half of the tool. We then need to determine where the plastic will be injected – also known as the gate – and then analyze how the material will flow into the part from the gate.

Our experienced engineers know that the wall thickness must be adjusted to allow the material to flow evenly throughout the part from the gate location. Trapped air causes problems, and our seasoned engineers call on their experience to look at the part, visualize the material flowing through it, and then to make adjustments to improve what they see.

3. Mold Design and Construction

The part has been designed and engineered; now we have to design and engineer the mold that will create the part. There are plates that need to be created with pins that will push the part out of one half of the mold and water lines need to be run in order to cool the part quickly once the cavities have been filled with the plastic. The tool will require additional pieces – more than just the two halves – if the part has a complicated geometric pattern of some sort.

Creative Mechanisms uses Mold Flow Analysis software that simulates the flow of specific materials through the mold, helping us determine gate locations and showing possible gas traps or areas that won't fill properly.

Here is a sample of a Mold Flow Analysis of a part:

4. Using the Injection Mold Machine

The mold is then put into our injection molding machine and “shot” for the first time. This means that molten plastic is injected – shot – into the mold. The mold’s halves are held together with extremely high pressure – usually hydraulic – while the molten plastic is forced inside. After the plastic is forced into the mold, it's cooled with water. The pressure is then released, the mold opens up, and the part drops out.

And an injection molded prototype has been made.