Injection Mold — Corativly

-students guide to injection molding Using High Density Foam CNC

while working for the workshop at school, i had the opportunity to learn how to operate our cnc. i decide to intertwine projects from class’s i was taking into a design challenge and a learning experience. i modeled a mold assembly in solidworks for injection molding a midsole, which i designed in my footwear class. the midsole was designed around a air-cushion system that can be placed in once mold is cured.

Getting to know the CNC

First Cut

practicing on pink foam. programmed in Vetric Aspire, cut with CNC Shark

High Density Urethane Foam

Cutting on HDU to see more details

Cutting Two Faces

lower piece is a jig to hold bottom cut midsole for top cutting

Making the Mold

Reviewing 3D Model

initially modeled in Solidworks then brought into Rhino for complex surfaces

Integrated Forefoot Air-Cushion

modeled a section in the midole to include this cushion

3D Printed ABS

component for cushion piece of two part mold

Vacuum Forming

testing vacuum forming on styrene for potential mold improvement

Inner Piece of Mold

this piece fits in bottom portion of mold, machined separately due to intricacy

Top and Bottom of Mold

Checking Accuracy

although i modeled guide pins, i wanted to make sure the seam was aligned

Parting Line

Filling Pores

first phase of finishing the mold using PVA glue to reduce porosity of foam

Epoxy Coating

For ease of release of midsole, a self leaving epoxy is coated

Mold is Ready

Foam tape in between for tight seal

Injection Molding With Silicone Caulking

Injection Port

using homemade oogoo(proto-putty), silicone + corn starch, the injection port is made. i used this method to reduce the amount of bleed once pressure is applied.

Applying Mold Release

finding a applicable mold release agent was tricky due to the nature of silicon caulking. but after numerous trial and error, Vasoline did the trick.

Injection Mold Ready

here comes the fun part!

Injection Molding Silicone Recipe

after trial and error of finding a material that can be injection molded, silicone + dish soap was the answer. the soap acts as a catalyst to accelerate curing.

Pressurizing the Mold

next tricky task was to find a way to do the actual injection porition and sometimes the anwer is right in front of you. i will be using the caulk tube to inject the casting material.

Getting the Casting Material Ready

this is a very quick process because once the silicone mixes with the dish soap, it starts curing. in this picture, i am kneading the silicone, eliminating as much water as possible.

Filling in The Caulking Tube

Purging

and Injecting

Let it Cure

The Results + Conclusion

Success

Trial and Error

sorry mother nature

reference midsole

concluding this experiment, resourcing the supplies obtainable as a student and making a diy injection molding process, was very informative. i learned to maximize the use cases of everyday materials and think outside the box of what is possible.