First, I want to say that I’ve open-sourced LcAlg, my program for generating laser-cut polygonal sculptures from 3d models. There’s a link a little bit farther down on the page if that’s what you came here for.
Second, the majority of this post will be about an interesting method of connecting coroplast sheets using acrylic connectors that I’ve developed.
Source Code
svn co https://lcalg.svn.sourceforge.net/svnroot/lcalg lcalg
https://sourceforge.net/projects/lcalg/files/
- Check out the code. Download either of the two obj files and put them in the input folder.
- Adjust constants in util.constants.py to change most values in the program. Currently it’s set to use 2.5mm acrylic and ~3.5mm coroplast.
- Run LcAlg by running LcAlg.py. You’ll need python 2.7.
- Watch for updates. This is an early beta that I’ll be updating regularly.
Connectors
Coroplast is essentially plastic cardboard. It is lightweight and flexible, and bends rather than breaking. I now use it for the triangles, or faces, in my models.
I used to use acrylic plates for both the faces and the connectors. It was shatter-prone, heavy and expensive. I secured the faces to the connectors with first solvent glue and then cotter pins. This worked, but was labor intensive and in some cases fragile.
The solution is to use acrylic connectors and coroplast sheets. This leverages the strength of both materials. Because the coroplast is flexible, I use retaining tabs - the coroplast deforms around the rigid acrylic tabs and is locked into place
This forms a very strong connection. I have to pull very hard to force the pieces apart. However, I can easily remove a connector by slipping the retaining tabs over the coroplast retainer. Think zip ties - all it takes is a small piece of metal to jimmy one open but brute force will get you nowhere.
(By vector-cut I mean vector-etched)
Unfortunately, sharp angles lead to an issue that can be seen in this diagram: if angle A increases much more, distance B will decrease until there is not enough material there to hold the connector together
Unfortunately, sharp angles lead to an issue that can be seen in this diagram: if angle A increases much more, distance B will decrease until there is not enough material there to hold the connector together
Large angle A’s can also lead to intersecting faces: In the diagram below, imagine if angle A were to increase. The two coroplast panels would quickly be intersecting. LcAlg solves this issue by calculating an offset and then removing that much material from the relevant edge.
Faces
A face is a flat coroplast triangle with 3 pairs of two mounting points for the acrylic connectors.
They’re cut out as below, to save laser time and material.