I’m hoping to use your laser cutting service to make a frame for holding electronics and sensors in some custom lab equipment. There are several references in your directions and examples to “tabs with small feet that snap into a smaller slot.” I understand such interlocking tabs wont be exact but I’m hoping to find examples of some tabs and slots that have worked well for other. I’m planning on using ABS as I understand this a good plastic for such designs. While my immediate concern is for the above mentioned lab equipment, I also enjoy building robots and would like to be able to use the same technique for these.
We are working on providing a library of useful laser cutting files, but unfortunately, we do not have any reference files for snap-together parts, yet.
You are correct that laser-cut snap-together parts (and other tight fits) are not going to necessarily turn our exactly as you plan; things will probably fit more tightly or more loosely than you want. Perhaps in your initial laser cutting file you can include some test parts to see what works better for your application.
It is good that you plan to use ABS, since ABS is better for snap-together designs since it has some “give”. Please note that ABS is smooth/glossy on one side, textured on the other side. The smooth side usually has some scratches and scuff marks since the plastic has no protective masking. You can read more about ABS at https://www.pololu.com/docs/0J24/3#abs.
Things to keep in mind when designing tight fits:
- Plastic thicknesses can vary by + or - 10% even within the same sheet.
- Plastic thicknesses we stock are actually in mm (1/8" plastic is actually 3mm + or - 10%)
- The laser cuts at a slight taper (1-2 degrees) since the laser beam is shaped like a cone (it gets focused from a larger spot to a small point).
- The Laser will center itself on the line you draw and will remove material from either side. Holes will be enlarged by roughly 0.005 - 0.01" in diameter, and parts falling out of the holes will be smaller by 0.005" - 0.01" in diameter. So, for a guaranteed fit, draw the male and female parts the same size. Otherwise, you can try accounting for the 0.005" - 0.01" and making one side bigger or smaller (depends on whether you prefer sanding or using shims).
- For a snap-together design (using tabs with small feet that snap into a smaller slot), we recommend making the tabs tapered so pushing them into the slots is easier. The tab itself should be about the thickness of the material (add 10%-15% if you want to be sure it will be long enough to fit through the female part in case the material happens to be on the thick side). The feet should probably stick out past the slot by 1-2 mm on either side.
I hope this helps; you might want to read more about laser cutting capbilities and limitations at https://www.pololu.com/docs/0J24/4.