Laser cut parts

[David Holland 2]

Evening all, 

does everyone sand away the discolouration from laser cut parts, does it affect the adhesion (I use mostly aliphatic)? I do on the areas that will be glued or if I’m using transparent film but am I wasting my time.

 

David

[Ron Gray]

If the parts are really burnt then I’ll clean them up first which stops it turning into a messy build! I don’t necessarily sand the parts but use a cloth to ‘dust’ them. I’ve not had a joint failure adopting this approach, I use aliphatic and pva.

[Denis Watkins]

There are two camps here David, as you suspect, to clean off, or not, the burnt cellulose.

In truth, it is not very deep, and a good quality adhesive will penetrate down to good timber and the joint will be sound.

A good glue joint is 1st made by " wetting ". The glue is spread evenly and wets both surfaces to penetrate and dry.

Heavily burnt surfaces are best wiped over with abrasive paper.

Edited February 3, 2023 by Denis Watkins

[kc]

As with all questions about glue trying a test piece from scrap material of the same type then testing to destruction after drying will get the answer!    If the wood grain comes apart then it's OK.     If the glue fails first then try a different glue or preparation method.

[Jason Channing]

if its cut well and is very light brown then that's fine, ifs its cut by someone blasting through then a light sand, if its cut very well then cyno is best I found.

[Andy Stephenson]

The problem I found with laser cut parts is that the dark edges tend to show through the covering.

[Paul De Tourtoulon]

19 minutes ago, Andy Stephenson said:

The problem I found with laser cut parts is that the dark edges tend to show through the covering.

They invented 'sandpaper' to get rid of that.

[David Holland 2]

I certainly don’t claim this to be the definitive answer, but I followed KC’s suggestion and the “brown to brown” joint failed at the glue line whereas, with the virgin balsa to balsa and the sanded laser cut, the wood failed before the joint. Sooooo….. I shall sand the glue areas as before, reasoning the peace of mind trumps a small time saving.

Thank for your replies,

David

[kc]

That's interesting David - what glue did you use?  

[David Holland 2]

Aliphatic Rapid Giant supplied by Rapid Rc Models, kc, used it for years and never had a problem, he said desperately touching wood!!

[PeterF]

Often the laser cut surface is dusty with charred particles / soot / carbon. Ifbyou ever get involved in powder processing you soon find that the finer the powder the harder it is to wet. A PVA or aliphatic type glue can sit on top of this layer and not wet the surface whereas cyano does wet through this layer more easily.