Cutting rigid cast polyurethane resin



Would it be possible, but dangerous, or not, to cut/engrave small castings of rigid polyurethane resin ? The idea is to be able to modify identical castings, rather than have multiple moulds.


According to Google you can safely engrave it…it’s a little bit denser than acrylic, so you might not be able to cut through it as easily.

So…maybe, depending on how deep you needed to go? (Certainly worth experimenting with.)


When fully cured, the stuff is very brittle in thinner cross-sections. It chips almost exactly like glass. It would be interesting what happens in the laser. If you experiment with it be sure to report to all of us. - Rich


I had not thought to ask this myself, I’ll be waiting for the report as I could see myself making some nice knife sharpener handles out of Alumilite.


I got to thinking about the reverse. Creating a image mold out of a soft material, doing a silicone mold and casing from that. I see that you don’t want several molds, but won’t that allow cheap replaceable forms.

That would allow creating various sizes of the style, but different sizes. Since you would have the saved pattern and not have to deal with density changes and possible imperfections on the final product, you would deal with throw away silicone and not resin casings.

I am interested in working with polyurethane, but it looks more temperamental to lasering than molding.


What had a bearing on thinking about this approach is that the cost of silicone rubbers used to be about x20 the cost of polyester resins.
Since they started to produce rigid pu’s with much less sensitivity to water vapour, I’ve started to use them instead, but I expect the price differential might be similar.


I think it depends on the level of variation. For instance if the only thing I was changing was a number for serialization. I would have to create a unique mold for each one. I would much rather try to engrave the number into the part after the fact.


Thanks for the heads up on that product. Looks like a bigger range than the one I have been using.


Are you using a pressure pot? If so, home made?


No, but if I did, it almost certainly would be !
I made my own degassing pot about thirty years ago, and I’ve still got it.


I dont have any useful information but there’s so many formulations of polyurethane resins out there, I dont think you could say they all behave the same under a laser without testing them all to verify.

I use Smooth On materials mostly for my castings and just the number of formulations in the TASK series alone is a lot to experiment with. I use a lot of their Crystal Clear and Smooth Cast series… and I mean enough volume that Smooth On sent reps to my house to see how I used their materials! :slight_smile:

I cant wait to try using the GF with castings too.


Hi mpipes,
By coincidence I also use Smooth On, but as I’ve just popped back to UK for 8 weeks, I can’t access which of their products I’m using for my current experiments.
With my luck, I expect to get THE email when I’m over here, and have it delivered into the hands of SWMBO instead of mine. So it looks as though I might have to get it delayed to fit my schedule, and how bad is that ?



I dont think you’ll have to worry about getting the shipping email from glowforge within your 8 week window in the UK.


Ah, I should have explained that I’m going back and forth, between UK and USA, every two months, while I wait for my green card application to be approved !!
So I suppose I’ve a 50/50 chance of being present when it arrives.


If it makes you feel any better, when they send the email asking for your address, you can choose to wait to give it to them. That way, you can make sure you are in the US when it’s delivered.


Yes, but can you imagine my panic if something were to go wrong :frowning:
I’ll take a chance and assume that fate is on my side :slight_smile: