Pololu Robotics & Electronics
My account Comments or questions? About Pololu Contact Ordering information Distributors

Laser Cutting Query



I have a potential use for the laser cutting service. The design helps mention a draft angle that shows up on cutting thicker material. What is the average expected angle formed for 1/4 and 3/8 material?



The angle is not something we can control well; it’s typically within a few degrees of vertical. For instance, if you cut a small circle and rolled it on its edge, it would not roll straight. However, because the angle is not the same everywhere, the disk would also not roll in a circle with a constant radius, either.

- Jan


I’ve got a couple of questions along these lines. Assuming I’m getting parts cut from thinner stuff (say 1/8" to 1/16", so kerf angle doesn’t bug me), what’s the smallest cross-section part you’d recommend making?

Take the pterodactyl example off the web page… That same kind of keyed construction technique would work for bot frames as well, especially if the joints are backed up with CA or epoxy. But it’d be nice to spider parts out as much as possible to save weight.

Soooo… I was kinda thinking of a square cross-section for the spidered out bits and pieces:

I’m not asking so much from a material strength standpoint. I know that’s up to me to calculate and make sure I stay within bounds. I’m asking more from a machine setup standpoint. How thin and light can I go and not risk distortion, shifting, etc.?




In general, it starts getting risky when your feature size is smaller than the thickness of the material. By feature size, I mean anywhere you care about a measurement: if you have two cut lines closer together than then thickness of the material, things might not work out so well. However, it depends on the details; a 1/8" hole in 1/8" material, 1/8" away from the edge, will turn out better than a long, 1/8" wide strip (which will most likely get warped).

Also, for interlocking parts, we don’t have good control of the thickness of the material, so you can only count on two of four sides of a slot being close to tight. The SRS Workshop Robot is a nice example of what you can do with interlocking 2-D parts: http://www.seattlerobotics.org/WorkshopRobot/index.php.

- Jan