Delrin pulleys and gears


#1

my team just got access to a cnc laser. We were thinking for prototype we could cut delrin pulleys and maybe gears with the laser. Has anyone done this before and if so how well did it work?


#2

Yup.

Once you figure out the offsets if necessary for your laser, they work great.


#3

do you use these for your competition robot or just prototypes?


#4

We’ve done both.

We routinely use plastic pulleys and gears from sdp-si, so it’s really no different from that.


#5

so do you actually laser cut them yourself or do you just buy them from sdp


#6

We have done both.


#7

I know teams like 195 used a delrin gear for their turret this year, which they got laser cut.

Just my 3 cents


#8

We used delrin in our drivetrain a few years ago… The red traction wheel was made of a base of delrin with rough top attached to it. It’s pretty solid material. Also worth noting is that we machined it on our CNC.


#9

Having worked in a lab with a laser cutter, I can say that it’s one of the most useful (and underrated) tools out there. The workflow is extremely simple and there’s almost no overhead to make a part, which allows for very fast rapid prototyping and design iteration.

Also, delrin is plenty sturdy for most FRC parts (I’m pretty sure you’d be fine making nearly an entire robot out of the stuff, with the possible exception of the main chassis).


#10

I have zero experience with Delrin. Just how sturdy is it? Transmission gear sturdy?

We have a Epilog Mini 24 Laser (30 watt 12"X24" bed) that is almost never used for robot parts.

Give us a walk through of lazing delrin.


#11

Definitely not “transmission gear sturdy,” but it’s pretty durable stuff (I’d like to see this offseason if 1/4’’ delrin can hold up when used as drive transmission plates - I suspect it can).

The main concern with lasercut delrin is the kerf - your cut is *always *going to be at a bit of an angle, no matter how good your laser is. This is usually not a problem, but can be annoying for bearing holes and other things that need a press-fit or very tightly-toleranced hole. For these, I advise cutting a slightly-undersized hole and reaming it out to the desired dimension. For press-fitting into slots (often a very handy thing to do with delrin), you’ll have to figure out how much material the laser actually removes and offset your dimensions accordingly, which is not difficult but involves a bit of trial-and-error at first.

You might also notice that small holes (on the order of 1/4’’ or so) come out slightly distorted. Again, you can just undersize and then drill out (since the center of the hole will be accurately located), if you really want, but it’s usually not a problem.

The very nice thing about lasercutting is that it’s basically trivial to make a part once you figure out what settings cut well for a given material thickness (this will take some trial and error and depend on your specific cutter). You generally don’t have to clamp a workpiece, since there are no cutting forces (make sure that your cutter isn’t being vibrated by your compressor, though!), the cutting process is very fast, and (at least on the laser we used) going from CAD to part involved little more than opening a .dwg in CorelDraw, hitting “print,” and then selecting the proper settings in the cutter software.

On the settings that worked best for us, 1/8’’ delrin usually took two passes, and 1/4’’ delrin took three or four. High-speed, multi-pass cuts usually end up being much nicer than low-speed, single-pass cuts.


#12

Not to hijack this thread, but how much did you guys spend on a laser cutter? Also, where did you get yours?


#13

we were lucky enough that my work just made a maker space and gave the robotics team unlimited access. So we did not buy the laser however the price was around 70,000 not including the air filter. However i know a couple people with sub 5,000 laser and they are very happy with them


#14

You can just as easily water-jet Delrin Sheet as well. It can also be easily turned in a lathe. Our team has used it on occasion for some parts.

For a pulley cut a round blank with whichever center is needed, and then turn the “side” profile on a lathe.

For gearing, I’d recommend going with a 32 DP rather than the normal FRC 20 DP, and just use Delrin (or Nylon 66) plastic on metal. I wouldn’t recommend plastic on plastic gearing.

Delrin is the familiar material used in the white cutting boards. Delrin is a Dupont Trade Mark for Polyoxymethylene. It also sold under some other trade names.

I think one ideal use of Delrin Sheets or rounds is for tooling to repeatable machining complex parts. You can add drill bushings and side guides to consistently hand drill something like swerve side plates.


#15

Also if any of you guys have a Port Plastics around you they kindly donate and give us very discounted rates on Delrin and other Plastics for frc.


#16

I have used Delrin once and when compared to acrylic, is far more ductile, and, when compared to wood, is a far better approximation of a continuum. Delrin’s ductility makes it a good candidate for snap fits involving tabs and slots. Delrin has a reputation for its wear-resistance