Hi Everyone,
So I know that regular Acrylic is not permitted in VEX robotics events because it can shatter but what about Shatterproof Acrylic?
I’m asking because we would like to have a material that can be precision cut with a laser cutter but many plastics including LEXAN are incredibly toxic. Acrylic is safe and cuts easily on the laser.
“Shatterproof” doesn’t exist, only “shatter resistant.” From the standpoint of safety, still not the same, which is why PMMA (plexiglass, acrylic, etc.) is specifically banned from compeition… Additionally, there is no way for an inspector to determine if the acrylic claimed by a team is “shatter resistant” or ordanary acrylic. Too much risk and uncertainty.
Huh, funny you should mention that, I have been looking for laser-safe VEX-legal plastics recently too. Here’s a table I put together on the topic:
(Disclaimer: the “laser cut” answers are based mostly on googling things, I haven’t actually tried to laser most of these materials yet. Consult with someone who knows what they’re doing before lasering unknown stuff, don’t just take my word for it.)
The “cost” is for a 12"x12"x1/16" sheet in the cheapest available color at McMaster-Carr.
PETG seems like the clear winner here to me, but I’m not 100% sure it’s legal - <R10> allows “PET” but it’s not clear whether that means all PET plastics or just PETE. Q&A682 will provide clarification when it’s answered. Otherwise, delrin and nylon both seem like good bets.
Maybe if PETG is ruled legal (I expect it will be), a place like robosource.net will start to carry it…they have some of the best prices on VEX plastic. Right now, they only have polycarbonate and ABS plastics.
Nylon is actually already available fairly cost effectively from places in McMaster Carr. link
I recommend https://www.boedeker.com in Texas, they have a variety of colors. Shipping is hard with the weight, but I get 20 sheets at a time and that makes it less painful.
Not to slam McMC, I go there first, figure out if what I want exists and get the right name for it. (They are a good translation from roboteer speak “finger size but really long spiral shiny” to a easier to find 5/8" x 24" lead screw. ). I then shop for that and can normally find it for 50% of the price. YMMV.
WOW! This is super helpful! thank you. Yeah I was talking to a laser cutter company and they were saying “why not use shatterproof acrylic” and I was thinking that sounded too good to be true. But it looks like there are some good options here!
I’m looking to buy a laser cutter for my shop so would I be able to cut something like Nylon with a 30W laser?
Thanks for sharing these links. Unfortunately I’m in B.C. Canada so I’ll need to find a local solution for getting these supplies. Shame that ABS isn’t laser friendly as it seems like one of the cheapest options that is VEX legal.
Is laser cut referring to can you cut it or is it referring to does it release noxious gas when laser cut. because I know for a fact that you can cut lexan with a laser cutter with relative ease assuming you have a fume hood or other vacuum chamber.
For the "no"s in that column, I mostly consulted one of my favorite PDFs:
It lists “thick (>1mm) polycarbonate” in the “NEVER CUT THESE MATERIALS” category, and has the following to say about it:
<1mm polycarbonate is listed under “safe to cut”, with some caveats:
Very thin polycarbonate can be cut, but tends to discolor badly. Extremely thin sheets (0.5mm and less) may cut with yellowed/discolored edges. Polycarbonate absorbs IR strongly, and is a poor material to use in the laser cutter. Watch for smoking/burning.
The maximum legal thickness for sheet plastic parts in VRC is 0.07", or about 1.8mm. As such, I’m not very confident about the prospect of laser-cutting polycarbonate.
But as I say, I’m by no means a laser cutter expert – maybe this document is wrong in some way.
I’m not too wild either about lasering materials that release nasty gasses but otherwise cut well, just on principle - even though our lab’s laser is fully enclosed and vented directly out a window.
The discoloration is definitely a thing but with the right power settings lexan can be cut with relative ease. The only thing that you have to worry about is pathing cuts close together too quickly. Because as the pdf says it absorbs the energy and holds the heat in longer than preferred. This can lead to melting and or disfiguration of the sheet. My org has cut plenty of lexan (yes we have the proper ventilation equipment) and has had good success.
We have laser cut quite a lot of 1.5mm polycarbonate for vex. It works fine, but…
Theres also some precautions you should take:
Make sure your polycarbonate sheet is fully covered with a removable protective layer on both sides.
Ensure you have excellent ventilation and do not breath in the fumes. Polycarbonate contains BPA which is a carcinogen. I’m not sure if this is released in the fumes but better to be safe.
supervise the laser cutter at all times, the polycarbonate can melt and burn along the cut lines, watch out for excessive flames and burning.
after cutting wear gloves when handing the parts and wash the parts under water while removing the protective layer.
Fun bonus fact:
You can also use “laser origami” to bend polycarbonate (or any plastic sheet). We used this to make very long, accurate bends in polycarbonate and it works great.
I found the same with polycarbonate, we had much cleaner cuts with ABS.
What I would like to know is how the stiffness and tensile strength compares between the plastics.
Our team will be using polycarbonate x-drive gussets cut on a ShopBot CNC router. We’ve only cut out one for testing so far, but we will be cutting 12 more next week. I recommend using double-sided tape to hold the plastic to a scrap piece of wood, and using a 0.25" or smaller endmill.
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