When making custom pieces on 1/4" Aluminum 6061 -with a CNC machine- could the part be substituted for Delrin? Examples for this piece would be intake mechanisms that go outside of the robot, or plates that incur a lot of vibration, such as a shooter plate.
No. Delrin will be weaker but lighter. Whether that still works depends on your system.
While Delrin and polycarbonate are pretty great plastics for robot building, it really depends on application and thicknesses. I would necessarily want to use delrin on a shooter plate, but would consider polycarbonate. Delrin has great wear characteristics, and makes more sense for applications where there will be something spinning or sliding on it. Neither plastic will ever hold up as well as aluminum, but polycarbonate can be great for things going over the bumper. It’s lighter weight than aluminum and cheaper at greater thicknesses, but you may have to step up the thickness to survive your application. As always, every robot and application is different and your results may very.
Is Delrin a direct substitute for aluminum? No. Delrin is not nearly as strong.
Can Delrin be used in applications where some teams use aluminum? Totally. Delrin is still somewhat strong and is lighter than aluminum.
If you are going over the bumper, I would generally not recommend Delrin as it is somewhat brittle and not extremely strong. Polycarbonate is a much better choice as it is very tough which helps absorb impacts without failure.
I’ve used Delrin for shooter plates in the past with some success - the important thing is that you ensure your shooter is still sufficiently rigid.
I teach my team that any material can substitute for another, but you’ll have to use more or less to take the same load.
Bikes used to be steel, but now most have aluminum frames and they’re thicker. You could make a Delrin bike, but it would be thicker yet.
For instance with gears, to carry the same load, you increase the face width. Tensile strength for Delrin I looked up to be 11,000 psi, while 6063-T5 aluminum (extrusion) is 27,000 psi. Or with gears, you might use compression-strength.
I teach a materials class to our kids and with that I hand out a materials spread sheet that includes strength, hardness, elasticity. I try to focus on the materials that might end up on an FRC robot.
Here’s a link. https://docs.google.com/spreadsheets/d/16L_TRL0uBW6pIdMmRnKncthF9C6B7lwjf53mF30vzLI/edit#gid=1368262860
The data comes from multiple sources so for strength, I have columns of ‘high’ and ‘low’ which also addresses anisotropy for example in wood.
Reference, it is in English units because most sources still use them.
If you see things you don’t think are right or you can fill in empty boxes, tell me and I’ll change them. It’s hard research to pull this together.
The nice thing about Delrin is that it can be lasercut quite nicely, and it mills like butter. However, tapped threads in it are not particularly strong, and hot motors mounted to it can be an issue. When used for a gearbox, plates can flex (and sometimes are not totally flat to begin with) leading to gear tooth wear.
Just to add a little dissent here, I made a gearbox out of Delrin my senior year in high school. It’s still running, to this day. That’s 8 years of survival.
Delrin is just another material. Material choice isn’t a simple response, and varies SO much based on location, use, intended and unintended forces, impact potential, load capability, potential for compression, cost, budget, tooling, and so on.
CAN you use Delrin in the place of some Aluminum? Sure. But the list of materials you CAN use is insanely long.