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[Dekan]

How do you remove laser cut burn marks from wood edges, Any ideas?

I have tried sanding... it just covers the glass paper with dirty streaks, which seem to find their way back on to the wood.

A Dremel sanding disc works but gives a slightly ripply edge even with very light pressure..

[Chuffy]

 Hi Dekan

I have used a small scraper in the past in a jig to keep it square to the laser cut edge and blow the residue away to prevent it being  forced back into the wood. All sanding does is to remove the soot and then deposit it back again into the grain of the timber, very frustrating.

Paul.

[Dekan]

Craft knife  blade?

[Boy From the Bay]

Stanley blade might give you better control.

[Chuffy]

Forgot to mention the blade, i use a block plane blade and put a slight burr on the edge with an oil stone or diamond hone. If you don't have a plane iron handy any piece of thin steel that you can raise a burred edge on will do, it's not as if it's got a lot of work to do. Also you can buy a ready made tool for the job but unlike paint scrapers they  have the burred edge but in this case it's a pre-formed one and is quite hard.

Do a google search to find out about the technique, as once you've got the hang of it, it's a very useful skill in boat building. A scraper can also be used on most materials for blending in and levelling work on my present build I have used it on GRP and brass.

Paul.

[steamboatmodel]

If you don't remove the burn marks will it interfere with gluing?
Regards,
Gerald.

[Dekan]

If you don't remove the burn marks will it interfere with gluing?
Regards,
Gerald.

Yes, Gluing through soot doesn't make for good joints..

[andrewh]

I have heard of soaking the parts in weak bleach to remove the charring - havn't tried it myself
andrew

[Dekan]

I tried cleaning mold off lite ply with bleach; it warped badly..

A club mate suggested Hydrogen Peroxide.... I have not tried it... the results might be similar to bleach  ...but it might work ok with balsa

[Colin Bishop]

Bleach might change the colour, it won't necessarily remove it. This is one of the drawbacks of laser cutting and why some manufacturers prefer to stick with CNC.

Colin

[HS93 (RIP)]

the problem is the Laser cooks the cellulose in the wood I have started playing CNC and have read and have done some reading on it , the reason it happens is that the Laser is not powerfull enough to cut the wood quickly the longer the Laser is on the wood the more it burns, big laser's are expensive, that is why some small company's use routers, the problem is the damage to the wood creates two problems one you cannot get a good fix to the charred surface and the damage goes a bit further than the dark are in that you can have problems with paint as around  the burn are is not as good at accepting paint.

sorry I have not been much help but it is sometimes handy to know what and why you are dealing with something, what is the kit or the parts.
high powered lasers leave just a pencil line of dark on the face and the end is clean or slightly dark that rubs of with a very light rub have a look at some plane kits.

Peter

[Martin (Admin)]

 
 Be careful with laser cut wood as it is quite accurately cut (usually), so over sanding or scraping may result in poor fitting joints etc....
 
http://www.modelboatmayhem.co.uk/forum/index.php?topic=2830.msg39305#msg39305

[Dekan]

Thanks Martin

Hmm... There doesn,t appear to be a simple solution.. It seems that laser cut kits maybe not be that good a solution, if you have to speed lots of time preparing the parts.
I haven't put the parts over the plan... so I have no idea how accurately they are cut out...

[Martin (Admin)]

It's not that bad. Just light sanding to get rid of the worst of it was all that was need with the Bismarck, that and a good PVA glue!

[Dekan]

I use aliphatic which seems to be struggling... I guess I need to get a little more soot off

[StarLocAdhesives/FiveStar]

When i bought our laser cutter i heard of the problems of bonding laser cut wood, But.... Ive had no problem gluing our laser cut wood with our ca glues, epoxy or aliphatics?

The cheaper grade of CA we sell as double glazing glue to window fitters wont bond it very well but the high grade CA we do in the model trade bonds to it fine with no removal of the black colour first

It must be down to the type of laser cutting , if the woods realy black then they havent got a clue how to cut it!

When we first got the laser cutter i was realy blackening the wood, that should never happen once set up just a thin dark layer of slightly browner wood should be there , but black will bond unless its falling apart black , it should be golden brown colour, its not down to size of laser as mines only fairly low power i think its 60w , cuts balsa no black burn marks on 10% power and high speed just golden brown `toast colour` wood

[Dekan]

The lite ply's edges are pretty black... this comes off easily when handled..

My Ca glue does not seem to glue lite ply very well without the extra handicap of the soot 

[StarLocAdhesives/FiveStar]

Liteply should bond well with CA, it takes about 30% longer set time than on balsa

To be burnt that much the liteply may have been the wrong grade for laser cutting , you get a special grade that the resin is better with the laser, to get round the burning on most things you can use an inert gas to blow onto the wood preventing any burn from the laser.

[Dekan]

MMI wood pack.....

[Dekan]

I tryed some Loctite industrial CA from work..... all I can say is what a difference ...No more cheap domestic product for me..

Mind you the cost is frightening.....