Turn Your 3D Printer Into an Injection Molder

3D Printing & Imaging
Turn Your 3D Printer Into an Injection Molder


One of the issues with using FDM/FFF 3D printers is the ability to print small objects. The extrusion widths of the deposited plastic are just too large to capture the fine details in a miniature print.

Molds, on the other hand, can capture every detail of an item they are trying to create. The professional world uses injection molding when they want to create small detailed parts.

Now, Instructables user BFK (Bruce Kinsey) has created a great guide on how you can do the same with the help of your 3D printer.

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This process is done by creating a mold of the item to be duplicated, in this case the holder for a small cannon to be used in a museum display. That mold is then injected with hot plastic coming from the 3D printer.

To ensure there is a proper path for the plastic to flow into the mold, Bruce used round plastic toy construction bricks that were ground into a point to create a channel known as a sprue. (I can’t help but wonder though why he chose to grind his toys when he could have just 3D printed his sprue.)

Bruce then followed traditional mold making techniques to create a two part mold of the item out of silicone, which would be resistant to the heat applied to it from the extruder. Pressing this mold onto his extruder nozzle and then turning on the printer’s filament load function for roughly 30 seconds, he filled his mold with hot plastic and formed his object.

This process was successful thanks to the small size of the object. With injection molding, you must keep all the plastic hot inside the mold until the process is complete. A larger part would have cooled before all of the mold was filled in, and would have likely resulted in an incomplete or brittle part.

This is just an initial experiment by Bruce, but we hope that he and others will continue this research and perfect the technique. Adding this to the list of useful functions for our 3D Printers helps make these even more productive desktop factories.

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Matt is a community organizer and founder of 3DPPVD, Ocean State Maker Mill, and HackPittsburgh. He is Make's digital fabrication and reviews editor.

View more articles by Matt Stultz