Laser Cutting Materials - Stencil Board & Foam?

#1

Many thanks to @Jonathan for a really informative laser induction the other day. I’m working on some projects in CAD that I’ll hopefully come down and try out cutting next week. Two projects I’m interested in making are details for architectural models, and storage cases for models: I’ve got two questions about materials for @lasertechs

“Stencil Board” - also known as “Oiled Manilla” or “Oiled Board” etc - https://www.londongraphics.co.uk/daler-rowney-oiled-manilla-stencil-card I’ve seen this recommended elsewhere as a good laser safe alternative to styrene board (traditionally used in model making) which is obviously banned. Can I check it would be OK to use this board in the Trotec laser?

Polyethylene Foam - I understand that polyurethane foam is banned, but is polyethylene foam allowed for cutting? I found an old thread that seemed to suggest polyethylene is allowed, but it doesn’t cut well. The little Trotec sample box looked very neatly cut itself though. I wonder if a closed cell polyethylene like this would work better than open cell? https://www.efoam.co.uk/zotefoam-plastazote.php I’d be looking at about 12 or 15mm thickness. The alternative for my project would be to make boxes with ply dividers and line the compartments with thin self adhesive foam sheet - more work, but perhaps less grief?

Many thanks!

Justin

#2

‘Plastazote’ cuts, but it’s not brilliant. Leaves melty edges

#3

https://www.troteclaser.com/en-gb/applications/foam-filter-mats/

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#4

Thanks @Jonathan it looks like it should do the job perfectly. I can’t find any on the Trotec UK web shop though, but it looks like the Plastazote should be worth a try, at least.

Any objections to trying the stencil board\oiled board?

#5

I’ve grabbed Plastazote from here before if that helps :slight_smile:

#6

So it took me a few months to actually getting around to trying this. Luckily @petra was around last night and gave me a few pointers for settings to try. The foam I bought was Plastazote (PE) LD33, 20mm thick, in black, from the link above.

I tried some saved settings for 20mm foam that @Calum_Nicoll had saved (100 power, 2.3 speed, 1000Hz frequency), but found that it burned right through and made a molten sticky mess of the reverse side of the foam I have.

I didn’t really have much idea of how to go about adjusting the settings yet, but guided by https://www.troteclaser.com/en-gb/knowledge/tips-for-laser-users/definition-of-laser-parameters/ I had a fiddle and did a load of tests. I figured I needed a higher speed to counter the melting, and the Trotec page suggests wood needs 1000Hz but acrylic 5000Hz or more to get a clean cut, so I went to the higher end for that.

But I couldn’t seem to get a cut that went all the way through without making a mess of the bottom surface. I ended up with a setting of speed 14, frequency 5000, and 4 passes - this cut 80-90 of the way through, and I finished off with a scalpel.

Any tips on which parameters to focus on tweaking to get a good clean cut all the way through?

#7

If depth is an issue, I would offset the focus by raising the bed a couple millimetres in job control. There is a setting for this in the material settings. (May be called z offset or something like that.)

#8

I’m interested in cutting foam for organised tool storage.

Somebody has been cutting some sort of dark grey foam which looks perfect for the job.

I’m not sure what type it is or if it’s allowed?

It didn’t look like the link above. It was more foamy, airy and quite like the normal stuff found in some tool boxes or fragile equipment storage.

#9

Thanks @Jonathan

According to this https://www.troteclaser.com/en-gb/knowledge/tips-for-laser-users/definition-of-laser-parameters/ its called Z-offset and it works between -5mm (bed higher) and +127mm (bed lower).

So you’re saying if I’m being left with say 3mm of uncut foam at the bottom, I should set the Z-offset to -3 to move the focus point of the laser down below the surface of the foam?

#10

Yes, if the focus is set to the top surface the beam loses a lot of power by the time it has travelled 20mm through material or not. So, by offsetting the focus plane down you will slightly increase your chances of success

#11

Just a reminder – if adjusting settings always return them to the defaults afterwards

Trying to diagnose why the laser isn’t cutting properly can waste hours…only to find the z-offset is wrong, for example

#12

I was adjusting all the settings within a new material profile, inside my own folder in the materials window of JobControl. Each new job seemed to default back to a default material profile (Petra - 9mm ply), so I don’t imagine my fiddling would have affected anyone else? Hope I’ve got that right!

#13

Hey Justin - just seen your message but replying here for more visibility. Yeah I’ve cut a lot of foam recently and it’s alright when you figure out the quirks.

Jonathan’s right - the focus point needs to be lower for thick foam cutting or the beam spreads too much and you get melting and potentially flame which makes the melting worse on the bottom side. I do it manually but didn’t realise z offset jobcontrol would also do it.

For 20mm foam I’d be about 3mm below.

I’ve also got a longer focusing lens that I got to do thick foam but have found the standard lens OK so haven’t tried that yet.

Foam is quite flammable so I’d keep a very close eye on it when cutting, especially thicker bits - when the beam spreads out at the bottom of the cut it can sometimes melt/burn. Definitely would avoid trying to cut it in one pass at 20mm thickness or it will get flamey.

I use https://www.flightcasehardware.co.uk/index.php?route=product/category&path=61_108_151 my standard is 20mm but have also used the 10mm and 15mm with great results too.

#14

Also weigh your foam down if it’s not level - often foam comes slightly curved or can warp as you cut it and a slight shift will make a massive different to cut quality - I use steel flat bar offcuts which are usually around laser but obviously you can’t run laser over them so make sure you put them in the right place!