I am looking to engrave individual pieces of a life-size human skull model. Some 42+ pieces (32 of which are individual teeth). It is made of the same plastic as standard car or airplane models. Is this safe for the gf and are there any recommendations for settings for producing a clear etched image?
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You need to know the composition of the material before engraving it. Some models are resin, which should not be engraved. No one can assure you that engraving your model will be safe without knowing what the material is.
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According to the listing … High Impact Polystyrene. As already stated: the same thing used in most model car or airplane kits. I have heard bad things about the foam version, but nothing about the mix used for hobby models.
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The short answer is absolutely not.
While HIPS is a fantastic material for 3D printing or vacuum forming, putting it under a CO2 laser like a Glowforge is a recipe for a toxic, melty disaster. Here is the breakdown of why you should keep it far away from your machine:
- It’s a Chemical Hazard
HIPS stands for High Impact Polystyrene. When a laser hits that “styrene,” it releases styrene gas. Not only is it a known respiratory irritant and a suspected carcinogen, but it also smells like a chemical fire. Even with a high-end filtration system, the fumes are incredibly invasive and difficult to fully neutralize.
- It’s a Literal Fire Hazard
Unlike acrylic, which vaporizes cleanly, HIPS has a very low melting point and high flammability. Instead of engraving, it tends to:
• Catch fire: It burns easily and aggressively.
• Create “Laser Soot”: It produces a thick, black, oily smoke that will quickly coat your mirrors and lens. This soot can “bake” onto your optics, leading to a very expensive repair bill.
• Melt into a mess: The plastic often melts back into the cuts, leaving you with a gooey, warped blob rather than a crisp engrave.
- It Ruins Your Bed
The “slag” (melted residue) left behind by HIPS is notoriously sticky and difficult to remove from the honeycomb crumb tray. You’ll likely spend more time scrubbing your machine than you did on the actual project.
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Under the circumstances, you might be better off making Mylar stencils instead. Mylar is polyester and safe to cut in your Glowforge.
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Would still have to engrave by hand and given no 2 designs are the same it would just be an extra step. I am only looking at using my gf because I have cracked or exploded a few skulls using the hand tool. Thanks though.
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Another option would be to cut what you were hoping to engrave out of 3M tape & leather or veneer and attaching them that way.
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@dwardio is being sensible, working with unknown materials can be risky. That said, I’ll chime in on the “absolutely not”, my take is more of an “absolutely, maybe”.
Quick disclaimer: I’m just a guy with a laser and just enough knowledge to be dangerous. Take my and anyone else’s safety recommendations with that in mind — it’s up to you to decide what risks you are comfortable with.
It’s a chemical hazard
Nearly everything you laser produces gases or smoke that you should avoid. If you have good ventilation I don’t think this is particularly worrisome compared to other plastics. I’d need to check an MSDS to be sure, but that’s my gut feeling.
It’s a Literal Fire Hazard
Any material and especially any plastic is a fire hazard. Fire risk is a broad topic but to me has a lot more do with your design and your settings; pretty much any organic material can be made to ignite if you use the wrong settings and/or the wrong design.
As for it burning aggressively, I’m not sure if this particular form of styrene does or not. As most of us probably know fire requires fuel, heat,and oxygen in the right ratios. Expanded styrene, like polystyrene foam, has air built into it and burns quite aggressively, as would especially thin sheets of higher density styrene — the thin material has greater access to oxygen. For a thicker piece that you might use in a model? I’m not sure how aggressively that would burn. I’d use caution but I would think it would be manageable.
Heck I’d probably take a small piece or scrap outside with a lighter and give it a whirl to just see how it burns in a safe test.
And just to be clear, @dwardio is right: fires with plastics are serious, they produce more energy per pound than most other fires with laserable materials like wood. Caution is warranted whenever working with plastics, even ones that behave well like acrylics should be watched carefully when lasering.
It Ruins Your Bed
I’d qualify that with a it *might* ruin your bed. If you’re using the right settings you shouldn’t turn your plastic into slag. If you’re being particularly cautious you could line the tray with aluminum foil while you’re testing, if you happen to melt the plastic it would drip onto your aluminum foil and save you a messy cleanup.
Nor will you make excessive smoke and/or soot, especially if your settings are correct and your ventilation is working properly to evacuate the gases as they’re created. I would find it surprising if this was any messier than say MDF or laser rubber stamping material: both notoriously dirty, both will catch fire if you’re not careful, and both emit noxious gases when lasered that you should not breathe… and yet we don’t say you should absolutely not use them.
Do I think that the skull will laser OK? I don’t really know, @dwardio and others are right, styrene isn’t always the best target for lasering but there are many formulations and lots of different settings to try. If it were me, I would start with high speeds and low power and work my way up to see if you can get a good engrave without excessive melting or any hint of fire. Luckily it sounds like you probably have spare material to try it on in the form of ruined previous models or even the leftover bits that aren’t part of the model itself.
It may be that there’s no good combination settings that will get you the result you’re looking for. You may need enough power to get it to be sufficiently deep but that amount of power might be enough to also melt it or discolor it in a way that you’re not happy with. Multiple passes at lower power might be a good option, it’s just really hard to say without trying it.
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A lot of the sentiment about material safety that I’m expressing here is previously written up in number four on my FAQ. Here’s the link in case you want to see a more general write up of my thoughts.
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+💯 I’m more adventurous myself so I’m in your camp. But I’m also not the one who might be harmed if it turns out badly so I don’t recommend anything to anyone that I haven’t done myself. By and large though I think we tend to over worry about some dangers and totally disregard other more likely dangerous things. Risk analysis isn’t something most of us are taught though so it’s probably to be expected.
(I had one student once who was super worried about the exhaust from doing some leather work in the laser and what it was doing to his lungs - it was exhausted outside but he thought it was bad to be in the atmosphere. But then he’d go outside for a cigarette break 
.)
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Same answer I gave cynd11: It would just be an extra step since I would have to still engrave by hand anyway.
I should clarify that the designs are not too difficult for me to by hand, just time consuming. Plus, I have had several skulls crack or even shatter from use of the hand tool. Stencils of any sort are just an unneeded extra step and extra effort with NO benefit to the project. I was hoping that using the gf would reduce the time and be less likely to damage the skull. Apparently this isn’t the case so how do I get rid of this otherwise unproductive thread now that I have an answer?
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You can’t get rid of it, this thread is permanent. Things a good thing, you never know who will come along later with a similar question; they’ll benefit from the time you took to ask about it. Also, lots of people have contributed their efforts now and it wouldn’t be fair to delete their contributions. Calling it “unproductive” feels like you’re downplaying the time people have given to your cause.
You can choose to not follow the thread by clicking on the bell icon and selecting “muted”. It’s is a bit unusual to do with your own threads, but we all manage our alerts and attention differently. I can empathize, I’ve muted threads I’ve created in the past as well.
As for me I wouldn’t mute it just yet if I were you — it’s still relatively new and you never know, someone may show up tomorrow with first hand experience, pictures, settings, the whole works. Unless there’s some sort of negative to keeping the thread in your feed I wouldn’t take action in your shoes.
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Besides, you never know when someone else will come along with the same question and then this post will become quite productive.
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