Parametric open-face mold generator for OpenSCAD

by jasonwebb, published

Parametric open-face mold generator for OpenSCAD by jasonwebb Nov 26, 2012
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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/


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

  1. Download one of the .scad files and open it in OpenSCAD.
  2. Update the parameters in the script to point to your model, as well as transform it to be suitable for printing.
  3. Compile and Render (F6) the script with your updated parameters.
  4. 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.

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Hi, thanks for the scripts they are awesome. Did you do a tutorial for this one like the one for the two mold part? It really helped me to get the mold right, and this one it been a bit trick for me to get the file right, I tried to modified the length on the mold but i could not find. thanks

Hi! I am trying to make a negative mold from this http://www.thingiverse.com/thing:201773http://www.thingiverse.com/thi... but I cant. It just shows the cube without any mold in it. Can anyone help me and point for the paramaters in this model?

Thank you.

Mario front
by ojaneri

Check out the "Instructions" tab for this thing for some basic help. You will need to verify that your model is 3D-printable outside of OpenSCAD, then make sure you know it's size and orientation. You can try manually importing the STL with a separate OpenSCAD script just to make sure it works, then bring it into this script to make your mold. OpenSCAD can be tricky for beginners, so if you haven't used it before I recommend trying out some simpler scripts to get a feel for what is going on.

Thank you for your help. I already printed the part, and it works, but I need a solid mold. I can import with import("filenam.stl"); and it appears on openscad fine, even if I make a union with some cube, for example. But using difference cube - imported filenamed, just shows the cube. Maybe it is my stl problem?
Thank you!

Did you manage to solve this out ? Got the same problem..

Could be the STL - keep an eye out for errors in the console. Repair the model using Meshmixer or netfabb, and possibility decimate the faces in Meshlab if it is a very detailed model with curves. If you hit F11 in OpenSCAD (after you've done a full "Compile and Render" with F6), you will get a wireframe view. Perhaps the model is being subtracted, but is hidden inside the cube.

THANK YOU!! I have been experimenting with the home made form of Sugru - Oogoo (100% silicon caulk + corn starch) and was trying to make molds from my models. Your positive open face mold worked perfectly!

Glad you find it useful! Check out the work that cerebus333 is doing with using similar molds to cast objects using Oogoo, he's been having some good success: http://www.thingiverse.com/cerberus333/collections/cerbys-crawlershttp://www.thingiverse.com/cer...

Looking good, but I'm trying to create a silicon mold for casting ice and chocolate items ;-)

Right, I was just pointing out that cerebus333 has been using Oogoo with molds too and has some good tips about how he's prepared his molds and mixing ratios he's used for his Oogoo. I'd love to see some photos if you get it working for you!

Can this be combined with the new customizer feature of Thingiverse?

Once we add ability to import STL files into Customizer, yes. Right now, no.

This is a really awesome idea. Nice work!

awesome idea generating a script for this.
deserve as Feature