I’ve wondered for a while whether the custom designed ISA slot brackets used by lo-tech PCBs would be any good made with 3D printing. The technology is obviously progressing rapidly, with the price of home machines tumbling and commercial services now offering a variety materials and processes (including some metals).
The first step was to create a 3D model of the brackets from the simple sketches, for which I opted for OpenSCAD. It’s a kind-of programming language that allows the design to be described precisely in code, for example a bit of code looks like this:
union() {
linear_extrude(height=z) {
roundedRect([x,y],0,0,3,3);
}
translate([(x/2),holepos,-2]) linear_extrude(height=(z+2))
circle((thread/2)+0.5,$fn=20);
}
Once the shape has been defined, the software then renders it on-screen and produces a bunch of stats about the object generated. Here’s the rendered shape of the lo-tech type 3 bracket:
This can then be exported to a suitable format for manufacturing, like STL. Two things I learnt:
- The 3D shapes are unit-less, that is to say that the fabricator needs to know what a measurement of 1 means. Most online quoting tools allow the selection of inches or mm.
- When rendered, OpenSCAD produces some stats. To be made successfully, a shape must be simple and have 2 volumes.
With that sorted and an order for both FDM and SLA processed brackets placed, a few weeks later the first prototypes dropped through the door. The FDM process had a great textured finish and was quite stiff, but was too brittle at least at the specified 1mm thickness, and the M3 screw threads couldn’t be printed. The SLA process produces a way more flexible and high-resolution product accurate enough to have working M3 threads. This is therefore the chosen process for the brackets now available for the lo-tech EMS, RAM and soon-to-be-released 8-bit IDE PCBs:
3D Printed brackets for lo-tech EMS and RAM boards are available in the store now.