Injection molding

I wanted to learn about Injection molding as well as recycle plastic and raise money for a good cause so I came up with a plan. I would injection mold reusable small cups, as well as other useful items, and sell them on campus to raise money for the Nature conservancy.

Small cup

The core:

The cavity:

The final product:

My first mold was for a small cup, I figured it would be an easy mold due to it having a built-in draft angle and only needing a two-part mold.

There were many factors I had to consider when making this mold including:

  • Draft angle

  • Vent holes

  • Sprue size

  • Shot size

  • Wall thickness

  • Radii

  • Machining resources

      • At this time I only had access to a small manual lathe

  • Stock material cost


This is the mold partially machined, I was still deciding my nozzle and sprue size. I made an ice proof of the cup to check my work, it worked shockingly well.

Here is a silicone proof (the flashing is because I didn't clamp the mold tight). you can pretty easily see the surface imperfections I plan to get rid of with sandpaper soon.

I used this collar method of locating the core and cavity rather than locating pins because it did not require precise machining from a mill that I did not have access to. My welding skills could use some work but it gets the job done.

-Work in progress-

I did a test injection with my injection molder (made from a kit by someone named buster beagle 3D on youtube) I was not able to get plastic to make it all the way down the mold and applied so much pressure plastic came out of places it was not supposed to, working on the cleanup to try again, this time at a higher temperature.