Laser cutting question from wood newbie!

[Phoebe Schaller]

Hi everyone!

I'm a designer so I've not worked with wood all that much before, nor have I had anything laser cut! Yesterday, however, I collected some mini trees (approx 14cm x 10cm) made out of 1.5mm ply I designed that had just been laser cut and they were covered in black smudges!

I understand from my research that the cut sides of the trees are charred as a result of the laser but I'm not painting the ply so I need to find a way to get rid of all the smudges from the surface of the wood because it looks horrid! The black from the sides comes off on my fingers so I don't want to touch it again unless I know what I'm doing because I don't want to make it worse.

What is the black? Why is it all over the wood and how do I get rid of it without ruining it?? I was thinking of using some turpentine and fine sand paper but I don't want the grain to lift as I really need the surfaces to be smooth and sleek.

Can anyone help me?? It cost a fortune!

Many thanks in advance!

[George M. Perzel]

Hi Phoebe;
The black substance is carbon residue caused by the cutting/burning action of the laser beam on the wood. Whoever did the cutting is using too much power and/or too high of a PPI setting and /or too slow of a speed. You can expect dark brown edges on cut wood but residue should be minimal.
Suggest you wipe each object to remove any loose material and then lightly sand to remove the smudges. You can try your turpentine/paint thinner as neither should raise the wood grain-water will. You might also try one of the citrus cleaners-spray on cloth and wipe.
Good Luck
Best regards;
George
LaserArts

[Michael Hunter]

Probably the wrong sort of plywood : ply comes in two basic types - exterior/waterproof which is held together with phenolic glue and interior grade which is glued with PVA or similar.
Phenolic glue is "laser-proof" and instead of ablating away, it bubbles up and makes lots of soot and char.
The glue in interior ply burns away cleanly with a minimum of smoke.

The very thin plywoods are often sold as "aircraft" ply with a quality stamp - this always has the bad sort of glue.

Even low powered lasers should be able to cut 1.5mm interior ply cleanly (so long as the settings are right), leaving a light brown edge.

Depending on the exhaust system efficiency and the type of cutting grid used, you will normally find some smoke marks on the faces of the ply right next to the cut lines. These marks should come off easily with fine sandpaper, or you could protect the surfaces with masking tape.

[Stuart Orrell]

I would lightly sand with fine grade paper. Be carefull if you have lots of fine detail that has been cut, the facing material on the ply may splinter....depends on the quality of ply.

Also to prevent the burn residue on the sides from smudging when handled, you could spray with shellac to seal it.

If you order a batch of laser cut in future, I would recommend approving the first off before having a batch produced. Also, you could ask your supplier to include clean up cost....ensuring that they deliver you the product that you need.

[Michael Hunter]

Having thought about the problem some more :

Talk of sanding all the edges sort of defeats the object of having the lasering done in the first place - might as well have got someone with a scroll-saw to do the job.

Have you complained to the laserist?


First thing is to find a new laserist.
It is totally unprofessional to deliver substandard goods : the laserist should have warned you that the "trees" were coming out dirty and asked what you wanted to do about it (assuming that you supplied or specified the type of ply to be used).
If the laserist supplied the material, then that makes it even worse!

Most people on this forum have lasered everything from laptops to cookies, with fruit and veg on the way. They might not be experts at every material, but will have a very good idea of what to expect (and know what is acceptable/achievable) for most common materials.

[Phoebe Schaller]

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Hey Everyone!

Thanks so much for your response!

They supplied the ply and as they are well-known for lasering, we trusted them about the specifics of the ply! We told them it was for a model of a set and they seemed to think everything would be fine.

The whole job has cost £210, which is a rather hefty sum for such a small job so I'll definitely be speaking to them tomorrow when they open (they've been closed all weekend), hopefully they'll give me a discount or redo the trees as the sides are completely BLACK and I can't do anything with smudged trees!

I don't know any other laserists!

All the best,

P.

[Mike Null]

I would coat the wood with a lacquer or clear acrylic before cutting them then scale back the power as others have suggested.

The coating will enable you to clean them. The edges will still be darker than the surface but should not be charred.

They should do the job over for free.

[Dee Gallo]

Phoebe,

Where are you located? There might be a Creeker near you, we have some great ones all over the place! I see you paid in pounds, so does that mean you're in Great Britain? If so, you need to hire Frank Corker!

cheers, dee

[Phoebe Schaller]

Hi again,

I'm based in Central London. I'm sure there must be many places that do it, but as I only need a maximum of about 60 pieces (and they are quite small) I think it might be hard finding people to do such a small job (?) cheaply. I also need it ASAP, the end of this week or next is too late so time-constraints really do factor into this.

I called the laserists today (for anyone in the UK or familiar with London I'm using 4D http://www.modelshop.co.uk (http://www.modelshop.co.uk/)) and they seemed to expect the problem but they mentioned that the "light ply" doesn't come thinner than 3.5mm or at least if it does, they didn't stock it. The guy said he would try covering the surface in tape to minimize charring and said he'd update me because apparently they can't use any other settings than the ones they have!

I'm not sure much is going to change with the other attempts by the sounds of things. If they are, why didn't he take the appropriate measures beforehand?

If anyone knows any alternative methods I could put forward in case this doesn't work, please let me know!

Again, thanks for all your help!

P.

[Michael Hunter]

Phoebe

Please look at your private messages.

Lite Ply (as used for model aircraft) is made from balsa wood and cuts very easily with no charring, soot or smoke marks at all (I know - I have done it. I think that the thickness I was cutting was 2mm, but it was a while ago so I might be wrong).

The thinnest "interior grade" birch ply readily available in the UK is 3mm (I just checked with my supplier). This cuts with a light golden-brown edge and minimal smoke marks on the faces (not normally objectionable). It is also very cheap.

[Mike Null]

Phoebe

Your original post says 1.5mm. Just curious about the thickness.

Hobby shops will probably have thinner material.

[Dan Hintz]

Phoebe,

Just so you're prepared for another failed run, covering the face with tape will not prevent the charring on the edges... as others have mentioned, that's caused by either improper settings for the material or improper materials. It will prevent smudges from the surface during handling, but one the tape comes off the edges will still have char on them, and any subsequent handling will continue to smudge.

[Michael Hunter]

Phoebe

Your original post says 1.5mm. Just curious about the thickness.

Hobby shops will probably have thinner material.

In the UK (and I imagine almost everywhere else) the very thin birch ply sold by hobby shops is "aircraft grade" (as in "light aircraft that people can get into and fly"; not models) which has the bad phenolic glue.
It is just not possible to get a clean edge with this stuff - even 1mm thick generates lots of char at the "best" settings.

Hobby shops do sell some good stuff - lite ply - which is made from balsa wood with a laserable glue. The results from this are astonishing - you can cut it at 100% speed, mid-power and still get absolutely clean edges.
Unfortuanely Phoebe's supplier only has this in 3.5mm or thicker.

[Dmitriy Kumets]

Orange pumice hand cleaner - put it on a very stiff brush and brush it in. The soot will come off easily

[John Lane]

Phoebe,

I use UK sourced lightweight Italian poplar plywood which cuts very easily with a 30 watt laser. There is no edge charring but if left unprotected there is some surface marking.

The plywood front face is protected by applying a transparent removable self-adhesive plastic film. The back face is wax polished. After face down vector cutting the film is removed.

This process eliminates any front face marks and disguises any back face marks.