Gaps in vector cutting problem

[Larry Robinson]

I have been practicing cutting 1/4" Baltic Birch Plywoood with my newly purchased GWeike 80 Watt laser with Lasercut 5.3 software. For the most part the laser cuts very nicely. However, I am getting some random areas where the laser does not cut all the way through the wood. I have cut the same project 4 times and the gaps seem to show up in different areas along the cut path. Most of the gaps are smaller than a pin head. The attached pic shows a gap of about 3/8".

Any help to solve this mystery would be appriciated.

Larry

[Zsolt Paul]

Cutting wood is not always an exact science. The grain, density, even moisture content within the SAME board can vary. Therefore different parts of the wood requires varying amounts of energy to get through. When you cut plywood, its even worse. You have to factor in the glue which can be really difficult to get through. So, before we know if its the wood itself or something else, I'd recommend making the same cut in acrylic or some medium that would give the laser as consistent resistance as possible. Generally plastics are best for this b/c moisture content is non existent and the material is pretty consistent. If you get through plastic / acrylic evenly, then we know its not your file or machine, its the wood. This could be perfectly normal given the varying parameters in wood. You might just have to increase your power or slow the speed. Of course, you always want to make sure your alignment is correct and lenses, mirrors are clean.

[Anthony Scira]

Thats the laser not firing at all....not just a wood density problem. Does it happen in the same place on the table or random spots ?

[Larry Robinson]

Paul,

I did crank up the power a little bit on one of the last trys. Maybe it just needs even more power or a slower speed as you suggest. Will give it a try. I guess I am just in awe watching the laser cut so precisely and then fined those gaps dissapoints. But your point of wood being inconsistent is quite valid.

Anthony,

The picture is of the back side of the board (sorry for not being clear on that). The laser is cutting the complete top side.

Thanks
Larry

[Richard Rumancik]

. . . The picture is of the back side of the board (sorry for not being clear on that). The laser is cutting the complete top side.


I would suggest that you examine the section that did not cut through, by manually breaking it and looking at the edge under magnification. Chances are, you will see blackened (charred) material which may be a result of a knot in an internal layer of the plywood.

Or it could be caused by filler used on an internal layer. Sometimes the internal layers of "baltic birch" are quite inferior to the outer layers, and so there may be numerous defects in that layer. You don't see the defect, but it may mean that the laser can't get through it. I assume your 1/4" material is at least 5 layers.

It is almost impossible to salvage a piece like that. You either have to accept a certain % of rejects or look for a higher quality plywood and see if you can get the yield you need.

Reducing speed may help, but you will probably end up over-burning the "good" areas which are probably >95% of the perimeter. I would probably take the hit on rejects rather than a hit on speed which might not help much overall.

[Mike Null]

You may be able to salvage it with a utility knife and a steel ruler.

[Joe Pelonio]

Is that picture of the bottom side? I hope so, because when my first tube went out, that's just what the top side looked like.

[Larry Robinson]

Quote from Richard:
"I would suggest that you examine the section that did not cut through, by manually breaking it and looking at the edge under magnification. Chances are, you will see blackened (charred) material which may be a result of a knot in an internal layer of the plywood. "


Richard,

I did break off a piece and took a look at it. (The part is too small to post a picture.) The uncut area is at the point between the 4th and 5th layers and I did not notice any knots or fill.

Not sure if the extra humidity today has any effect on the cuts.

Mike,

Cutting with a knife may work, but the parts are small and some of the gaps are in the corners.

Joe,

The pic is of the back side.

Thanks
Larry

[AL Ursich]

Could be a dirty mirror...

AL

[Michael Hunter]

I was doing some 6mm ply today and sure enough, had the same problem.
Every time I do ply, I up the power and lower the speed compared to the previous time, and still the problem doesn't go away!
Ply is HORRIBLE (but it's cheap so you just gotta use it).

[Nancy Laird]

Larry, we cut a LOT of 1/8" birch ply, and we have that problem occasionally. Hubby says that sometimes the the laser just hits a spot in the middle of the plywood that just doesn't want to cut, for some reason. We cut our 1/8" ply at about 1.2 max, and still have the problem once in a while. It's just the plywood. Don't start blaming your laser.

[Bruce Dorworth]

I have had this problem several times and learned that it is a speed issue. No, it's not that you can't cut all the way through at a given speed. It is just an issue with Laser Cut I guess. Slow the speed down and lower the power setting and see if that doesn't help.

Bruce

[Richard Rumancik]

Just to point out, this thread is two years old.