Unofficial: <R7> f. Laser cutting plastic

VEX Robotics Competition Discussion VRC > Starstruck (16/17)
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In the official Starstruck Q&A, @Welshkiwi wrote:
Hi Karthik,

You previously answered a question regarding laser cutting here. In this instance the answer was that the laser cutting was illegal because it was being used to essentially try and double the area of the polycarbonate.

My questions relates more to cutting functional pieces of polycarbonate.

a) Does the answer to the linked Q&A also relate to laser cutting plastics in general, is it legal to have laser cut plastic on a robot?
b) Specifically, are we able to laser cut functional polycarbonate into the size we want?
c) If not, could we laser cut into functional polycarbonate that was cut by hand? In this instance it would be to engrave a team logo into the piece of plastic.

Relevant rule here would be <R7> f.

Thanks in advance.

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Unofficial answer:

They never ask how the platic is cut, they don’t test for how the plastic is cut, and the method by which it is cut would confer no advantage. So, you can cut it with a laser, or waterjet, or plasma, etc. What you cannot do is melt it to form some other shape from it, or to join two metal or plastic VEX parts together no matter how you apply that heat.

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@kypyro thank you for your input, however I’m seeking an official response as I believe it is something that probably should be examined. I’ve both competed and inspected at Worlds in the past, I know that ‘How did you cut your polycarb?’ is not exactly a standard question and I would hope it doesn’t become one in the future. I understand what you’re saying, but I feel the questions go deeper than your answer.

My question stems from the emergence of technology. Until this year, I never would have thought of a question like this, it’s only come up because I now have access to a laser cutter. Just like until a few years back no one was questioning why we couldn’t 3D print parts, yet now the Q&A is littered with questions about it. Example 1, Example 2, to name a couple.

If used correctly, you could cut custom shapes out of permitted plastics and build parts with them, with precision not seen until the emergence of laser cutters. My questions asks specifically about engraving, which is something fairly unique to machine cut plastic, I would not expect a student to scrape out the inside of some plastic, yet you could laser it in a couple of minutes without thinking. These could both potentially be used to give teams with access to one advantage over teams without.

Also, If we want to get into technical about it, the plastic is cut through melting, which as per the rule is illegal.

I feel these points alone justify the questions I’ve asked and hope that I’ve explained why I believe it’s a bit of a grey area. I know that if I was inspecting this year at worlds, and I saw a team when engravings in polycarbonate, I would question it. Maybe the ruling comes back that it’s fine, but maybe it doesn’t. That’s the point of asking the question.

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So I laser cut vex legal poly carb for some testing last year. It made it pretty brittle. Even at best settings it seemed to cook the entire sheet. It does not come out as well as acrylic.

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So, if I got a sheet of .25 delrin, could I legally use a laser to cut it down to <.07 inches if I only used one piece? Or would this violate commercially available? Could I use a mechanical cutter to do this instead?
Looking for a local of source delrin for worlds.

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@matterny there was a ruling against it i cant find it now

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The ruling I remember was cutting a sheet in half from .07 to 2 sheets of .035 thickness and use both sheets.

@matterny So if you are essentially laser cutting the sheet to a legal thickness and working from there it should be fine. I don’t see a reference to using a commercially available thickness. Just remember to stay within the “cut from a single 12” x 24" sheet" part of that rule in mind. You might still ask in the official Q&A, but I don’t see why there would be a problem.

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Are there special lasers for this? Because none of the ones I’ve used could have cut through a 12" sheet of plastic lengthwise.

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why so bloody tryhard and laser cut? just use a saw of some sort and ez pz.

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I missed this thread on its first go-round, but now that it has been “bumped”…

a) As stated, above, laser cutting plastic is legal, but…
Laser cutting Polycarbonate isn’t the best idea. It releases some very nasty gases that can damage your laser cutter. Epilog (one major manufacturer of laser cutters) goes so far as to say that cutting polycarb with their laser will void the warranty. (Yes, I know… voiding the warranty is part of the fun, but just not with my laser, please.) Yes, it will cut - not nicely, but it will cut. Yes, you can use it. But no, I don’t recommend it. Perhaps PETG, as far as the transparent polymers go, will be a better bet. Here’s a few other materials that might work… just remember to use the “non-shattering” ones for VEX. Pololu - 3. Pricing

b) See above

c) Feel free to hand cut whatever you want. Polycarb cuts beautifully in a water jet, and isn’t bad on a CNC router or mill, either. Cut away. Use a light saber if you’ve got one.

And let me add:
If you’re only cutting a Logo, for use as a non-functional decoration (and make sure you read the definition of non-functional) you can use acrylic, cardboard, hardboard or dilithium crystals. Well, okay, the crystals might be prohibited under safety rules. But non functional decorations do not count to your “plastic sheet” allowance. So long as they are 100% non-functional decorations. Heck, you can even 3D print your non-functional decorations.

As for using the laser to cut the sheet down to the correct thickness, the statement, above, that you can’t use the laser to cut through the piece is obvious… but you can use the laser to ablate the surface until you have material of the correct thickness. This strikes me as a slightly ridiculous approach, particularly when sheet of the correct thickness is commercially available… but in the event of the zombie apocalypse where you are trapped in a building and absolutely need a sheet of 0.070" thick plastic to avoid having your brain eaten. Yeah. It might work… might. That’s really not a great way to do it unless the zombies are coming for you, though. If you’re in the USA, then McMaster Carr is just as “local” as Amazon McMaster-Carr

And as for the immediately preceeding comment about using a saw… you aren’t wrong, but you haven’t used a laser cutter, have you? They are beautiful things.

Jason