Recently, we needed to buy more so I looked at the website and became confused because I saw many different types of polycarbonate such as ABS and Acetal. We just bought some of both to experiment with.
However, when we tried to cut the Acetal, it kept on cracking and shattering along the cut lines and didn’t smoothly cut like normal polycarbonate.
Another question I have is what is the difference between Acetal, ABS, and regular polycarbonate as well as something called “smoke gray polycarbonate.” Is there a difference in performance?
These are not different kinds of “polycarbonate” but rather completely different kinds of plastics.
Polycarbonate is also know by the trade name Lexan, is the most popular clear plastic for VEX.
Acetal is often known by the trade name Delrin, a little stronger than polycarbonate, but as you have seen is more brittle.
ABS is a terpolymer of two plastics and a rubber: Acrylonitrile butadiene styrene. A good, tough, inexpensive plastic, but it isn’t clear.
The other popular clear plastic, illegal for VEX is PMMA, which goes by the brand names Acrylic or Plexiglas. This plastic is clear like polycarbonate, but can shatter which is why it is illegal.
A couple other legal plastics for VEX which you might consider: HDPE (high density Polyethylene) and Nylon, both are strong and tough, but they are not clear.
As for color (like “smoke grey”)…it’s just for appearance, it doesn’t affect performance.
Teams using Acetal (Delrin) are probably cutting it with a CNC router or laser. I understand that it cuts very smoothly with a CO2 laser. Are there any teams out that that are doing this? If so, what brand and model of laser cutter are you using?
If you are seeking you use delrin, and you’re just looking for ways to cut it, I would suggest a band saw, a laser table (as previously mentioned), a water jet cutter, or yes, a cnc table. The issue with shears is that the force is exerted laterally to the sheet, so it wants to crack and snap. Any saw should fix this, and in a pinch, it’s possible to cut delrin by taping out where you intend to cut, in the hopes that the tape will help prevent cracking, although this is mainly only significantly useful when drilling through it.
That said, I do recommend switching to Lexan or ABS, that’s what my team used for years without issue. It’s just easier to work with, and structural parts should be reinforced with metal anyways.