Parametric open-face mold generator for OpenSCAD
by jasonwebb, published
A pair of OpenSCAD scripts that can be used to generate either positive and negative open-face molds from arbitrary STL models.
The positive open-face mold generator script takes your external STL model and combines it with a solid, flat base with or without walls.
The negative open-face mold generator script takes your model and subtracts it from a solid base, leaving an indentation in the form of your model. You can use this script to create ice-cube trays by arranging multiple models in a single STL input file!
I have included sample input and output files that you can use for inspiration, but there is much more you could do that I haven't documented. If you come up with a new use for these scripts, please post a photo and/or make a derivative!
I've provided some more information on my blog at: http://jason-webb.info/2012/11/making-3d-printable-open-face-molds-with-openscad-casting-experiments/
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Prepare a model to create a mold from
To create an open-face mold using these scripts, you first need to prepare an STL model of your choice. OpenSCAD has some performance limitations when it comes to loading external STL files, so keep your polygon counts as low as you can. I like to use Meshlab's "Quadric Edge Collapse Decimation" filter (under the "Remeshing, Simplification and Reconstruction" section) to reduce the number of faces in more complex models to get them to load in OpenSCAD.
Avoid undercuts and overhangs in your model, as this mold-making process doesn't really allow for that.
Using the scripts
- Download one of the .scad files and open it in OpenSCAD.
- Update the parameters in the script to point to your model, as well as transform it to be suitable for printing.
- Compile and Render (F6) the script with your updated parameters.
- Grab an STL using the "Design > Export as STL" tool.
Guide to parameters
- Model parameters - external STL model to build mold around. Use the rotation, translation and scale parameters to orient your model relative to the mold.
- Mold parameters - attributes of the mold itself. Make it any size you want, and turn on or off rounded corners to help with printability.
- Wall parameters - toggle walls and alter thickness and height of all walls
- Removable wall parameters - make one wall of the mold removable by adding a slot and separate wall to slide in. Be sure to use adequate wall thickness for this to work.
Using the removable wall
Though I did include the option to make one wall of the mold removable in the "positive" script, you should consider whether you need it or not. I intended it as a way to make the demolding process easier, especially for tall molds or stubborn casting material. If you decide to use a removable wall, you may want to beef up the walls a bit. I recommend using modelling clay on the outside of the mold to secure the wall in place and prevent leaking.