Parametric Two-Piece O-Ring Mold

Sometimes a printed gasket or o-ring won't do and one has to be molded out of a particular material, such as rubber or silicone.  Print the mold, put your molding material in the groove (use release agent for sticky materials), and press the two parts of the mold together very firmly.  Once the part has set up, pull apart the two pieces to reveal the o-ring, and remove carefully. 

This mold generator allows you to input the outside diameter and cross-section diameter of your desired o-ring and it will generate a two-piece printable model suitable for casting your own gaskets.  You may optionally have it remove the center of the mold to reduce the amount of plastic needed to print it.

You will want to print this out of a tougher material such as PETG or ABS as you will likely need to apply a good amount of force to it to squeeze out excess material when molding.  Using a press or vise for larger o-rings wouldn't be a bad idea.

The overmold will get larger as the o-ring gets larger so use your discretion in terms of infill and layer thickness.  For the small molds (15.6 x 2 mm) that I have printed, I used 100% infill and 0.08mm layers, but less infill and thicker layers should be suitable for larger molds.  Please share your settings if you post a make!

This mold works particularly well when using silicone and can be made tougher and easier to work with if you use a catalyzed silicone mixture such as The King of Random's "Proto-Putty" (search on YouTube) or any commercially available two-part molding silicone.

Pictured is a 22 OD x 3.5 mm o-ring and mold made for the Marimo Labs water rocket (https://www.printables.com/model/86434-water-rocket-launcher) made using GE Silicone I accelerated with just food coloring.