Poor Quality Vector Results

[Frank Defert]

Hi Everyone,
New to the creek and this is my first post in this forum.
I am working on a project that includes both raster and vector functions on 0.8mm finnish birch plywood. The raster portion comes out good but the vector leaves a black char on the edges. I have tried all manner of speed / power / frequency combinations with no real results.
I have also learned since the purchase of this laser friendly plywood that it is actually three layers glued up which make it strong while remaining thin. This material would work excellent for my project if I can overcome the burning glue issue.
Any input to overcome the burning edge or a suggestion of another type of wood would be greatly appreciated.

Thanks .... Frank

[Mike Null]

Frank,

Welcome to SMC. Are you using the air assist feature? Have you tried transfer paper on the top and bottom of your wood?

How about lowering the power, increasing the speed and trying to use more than one pass.

[Todd Schwartz]

Frank - welcome.

I vector cut baltic birch without too much burning. You will always get a darkened edge where you cut, but can reduce it to the point where you can get it to be be a very dark brown vs black. Need to reduce the power, increase the speed a bit and significantly reduce the PPI and use air assist if you have it. With some experimenting, you should be able to get acceptable results.

Todd

[Rob Bosworth]

With a 35 watt Helix, you should be able to cut .8 mm plywood like butter.

If you use the settings in your Epilog manual, and you are not coming close to getting acceptible results, you are going to need to check some other things. Try each recommendation to see if one of them fixes your problem.
1.) Check and clean all of your optics with high quality optics cleaning supplies.
2.) Check your focus. I have seen a lot of variance in focusing optics lately. Put a piece of black anodized aluminum down on the table. Focus your system. Send over a file for raster engraving of a black rectangle at the power and speeds recommended in your owner's manual for anodized aluminum. Start engraving. While the machine is running, move your table up and down (focusing) until the "flash" is the brightest while the machine is running. That should be your true focus. Now, stop the machine and set your focus guage to that spot. Now that your guage is set, check to make sure that your autofocus is set for that same spot.
3.) Beam alignment - Make sure that your laser beam is traveling down the middle of each optic. If your beam is "clipping" anything in the beam path, you are losing lots of energy. I use masking tape to "burn" a spot to see where the beam is going into each otpic.
4.) Check to see if you have good air flow coming out of the air assist tube under your focusing lens.

You should be able to cut thin plywood fairly fast with very little edge discoloration.

I am sure that I have missed a few easier details to try or check, but the above should give you something to do and try. Good luck.

[Joe Pelonio]

Frank,

Welcome to SMC. Are you using the air assist feature? Have you tried transfer paper on the top and bottom of your wood?

How about lowering the power, increasing the speed and trying to use more than one pass.
Transfer paper on both sides then mist with water. Also, you might try basswood, it cuts cleaner and faster than ply. Some of that is the glues, though I've been able to cut it pretty cleanly with the wet transfer tape.

[Richard Rumancik]

I have some doubts that you can get rid of discoloration using air as an assist gas. I have cut baltic plywood and the edges are fairly black and sooty and I usually wipe and sand if possible. The adhesive to bond the layers is usually some type of thermoset which tends to burn when lasered. The wood itself will also tend to darken, some woods more than others.

Basswood tends to turn a goldish color (solid basswood). But solid wood tends to be much more fragile than baltic plywood. Depends on how intricate the part is.

The use of nitrogen (possibly argon) instead of air will reduce discoloration on wood, but I don't know if it will eliminate it because it depends on how much of it is caused by the adhesive. You would need to rent an N2 tank and get a gage/regulator for it, and connect it to your air assist system. It would be good to have an automatic shutoff valve so you don't waste gas when the laser is not cutting. I was going to try cutting with nitrogen myself but have not had a good enough reason to set it up. I know nitrogen gas it is more commonly used on industrial machines than laser engravers.

It would also depend on whether the added cost of nitrogen is feasible for your application.

Before went down this path I would get a sample made. You could try Synrad. I had them test some material for me and they were cooperative and did not charge. (Keep in mind their objective is to sell lasers.) Tell them the speed (inches per minute) and power (watts) you will be using, and ask them to test with N2 as you want to reduce charring. If you don't give the parameters they may put it on a fast high power laser and the results will be meaningless to you.

[Frank Defert]

Thanks everyone for the outpouring of information.

Richard your choice of words " edges are fairly black and sooty " is exactly what I am dealing with. I am however unable to sand or even wipe all the edges because of the design so I need to really get it to a quality level where this will not be required.

Joe can you tell me if transfer paper could also be refered to as white laser tape that is used as a laserable shield? Also I did soak a piece of this wood in a dish of water and the results were better but not good enough, maybe some tape will help.

Thanks .... Frank

P.S. Yes I am using air assist.

[Bill Cunningham]

I have a 35 watt TT, 1/8" wood turns a little brown, mostly where the vent blows the vapourized wood oil over the part, but using the settings from the Epilog Manual I get no black edges or charring.. Lines and cuts that are 'very' close together may suffer from some overburn, but other than that, I would check your focus as suggested, and also your vector frequency..
In the picture below, the disks are 1/8 x .75dia. they were 1/16" apart when cut, and you can see by the brown on one edge, thats where the vent was drawing the smoke over the piece from the cut.. A light sanding, or even a rub with steel wool takes it off.. But no black charring..

[Bill Cunningham]

Ooops sorry. I forgot to post the picture :rolleyes:

[Carol VanArnam]

Frank- I have a 60w helix... Tell me what settings you are using to do the vector cutting. Like it's been said- 1/8 baltic birch cuts like butter. I think it's your settings. Black dirty burnt edges means to me you may be going to slow on your speed or your power is to high. Let us see what you tried for settings.....

Are you using the vector cutting grid not the solid plate in your laser?

[Frank Defert]

Finally back into the shop today. Carol I have been playing around with settings, first I set the speed at 100 , power at 20 and frquency at 100. After a test run I began increasing the frequency until I achieved a solid cut line. Then gradually increased the power in increments of 10 up to 70 to cut completely through. Still have black sooty edges. I am using the vector cut table and air assist.
I do cut 1/8 baltic birch plywood like butter with only discoloured edges, no black and no soot. I also vector .042 - .040 Eastern Hard Maple strips that are cut on the table saw and they only have slightly orange edges.

Frank

[Joe Pelonio]

Possibly you just don't have enough power at 35 watts to go fast enough to avoid burning with that particular material.

The transfer tape that I use is meant for transfering vinyl lettering, it's a low tac adhesive, absorbs water but won't let it through. Wet transfer tape won't help as much as you soaking the wood in water though. You might consider sending a scrap of that wood to another member with 45 watts or more and see if they can cut it cleanly, maybe it's just a problem with the glues in it.

[Mike Null]

Frank

Is it possible that you're trying to cut 8mm material rather than .8mm as you indicated?

If that's the case then you would have to make 2 or even 3 passes and re-focus after each.