Baltic Birch - Possible to not have burned edges?

[Glenn Chua]

Hello all,

I have been reading through the engraving forum on and off for a couple years now and have just recently started to tinker around again with the laser machines I have access to.

I used a 45-Watt Epilog (Vector Settings: 15 Speed, 100% Power) to make the finger joint baby block (date of birth, weight, length, etc...) in the attached picture. It came out really well, buy my wife doesn't really like the burned edges. I myself like the look (even like the look of the left-over kinda sticky residue), but was wondering if anyone has been able to vector baltic birch plywood (1/8") without the burned edges?

I realize that I could just move away from the finger joints and miter the edges to resolve the burned edges on this specific item, but am working on a few different ideas/items where I would not have that option.

I have access to a 150W Kern HSE laser, but haven't given baltic birch on that machine a try yet... I was going to try this weekend, but if the experts here say it isn't possible then I won't bother tinkering with it?

I wanted to thank everyone here for all their posts as I have learned SO much by reading through the threads. I really enjoy projects on the laser and am considering giving it a try as a side business.

[Larry Bratton]

Glenn,
One thing you can do to eliminate some of that look, is to make the finger just a little bit longer and then sand it down flush with the face. I just got in a shipment of baltic birch. Although I am into my 3rd year with my 40 watt EXT I have never cut any baltic birch, so I'll let you know my results. I have cut other plywood and it is somewhat difficult because of the different plys. I am going to try 1/8" with a slow speed, high power and a 500 frequency, I'll let you know how it comes out.

[Glenn Chua]

Thanks. I just found a post submitted not too long ago on the same topic (I should have searched before I posted to prevent double work). Lee DeRaud did mention that it may be possible with higher power lasers so I'm going to give it a try with the 150W and post my results.

[Mike Null]

I think Larry's on the right track. I have never been able to cut without some burning of the edges. I would suggest cutting, assembling, sanding then engraving.

I doubt that 150 watts is going to solve the problem but maybe that faster speed will help.

[Robert Alexander]

One idea to get rid of the burn marks is to laser out just the box pieces not photos ect. and assemble and glue your boxes together as shown in your photo. Then lightly sand with a palm sander each of the sides. Then put on a few coats of finish. Make a jig (matte board works great for this)or cutout the size of your box to help locate the box on the laser bed, and laser away. Then just clean off the burn marks with some window cleaner.
You could also make your tabs on the box .01"-.02" higher if you are worried about sanding into the plywood

[Martin Boekers]

If you are looking at just doing these "baby blocks" you might consider searching the internet under wood blocks, I'm sure there are many suppliers of pre-finished blocks.

We used to do these on base when someone had a child.

Marty

[Michael Hunter]

Baltic birch ply always gives me brown edges, but the brown I get on 1/8" is much lighter than in Glenn's photo.
In the photo it looks as though there is more power than needed and it is bringing the resin - try reducing the frequency.

I have a bit more power, so these settings are not immediately usable, but might give a guide -
For 1/8 ply I use Speed 25, Power 25 to 35 and Frequency 300.

I'n jealous of the Kern - with 150W you should be able to cut 3/8 - 1/2" ply without charring.

[Michael Kowalczyk]

Glenn,
Put a clear coat on both sides first. Then use double odd steel wool on the best (football free) side, clean off with either a tack cloth or blow it off with compressed air. Then give the best side another light coat. This will either help prevent the residue on the surface or make it simple to clean off with a damp towel.

Your edges are darker than normal. I am not sure what your settings would be but for my 60 watt Trotec I use 100% power 1.18% speed and 5000 hz. Also make sure you have really good exhaust. I just installed a pin table and am working on the setting to prevent flash back but having air pulled from under the part also helps reduce smoke residue on top.

Also the type of Baltic Birch can make a difference. You should use interior grade because the glue for exterior grade is harder to cut for most lasers.

Hope this helps and ...

[Lee DeRaud]

Thanks. I just found a post submitted not too long ago on the same topic (I should have searched before I posted to prevent double work). Lee DeRaud did mention that it may be possible with higher power lasers so I'm going to give it a try with the 150W and post my results.

For solid wood, possibly (probably?). But the glue in the plywood will probably come out dark brown or black no matter what you hit it with.

[Lee DeRaud]

One thing you can do to eliminate some of that look, is to make the finger just a little bit longer and then sand it down flush with the face.

If you're using my 'fingerbox' macro to lay it out, there's an option in there to do exactly that...IIRC it defaults to 0.03". I usually use a router with a flush-trim bit rather than sandpaper, especially if there is any engraving or inlay on the faces.

[Stuart Orrell]

Hi Glenn,

I cut some Baltic Birch last year with my 40W laser. The glue definitely makes a difference.

If you buy laser grade baltic birch, it should have the better glue. It didn't leave the cut completely residue free but much less than the regular plywood from the hardware store.

For a single pass cut, I used speed = 12 mm/s, power = 50%. This needed sanding to clean up.
Alternatively, for a better finish, I tried 3 passes at 50 mm/s, 100% power. This just left a slight residue, so much less or no clean up, if your ok with a light tan finish.

Let us know how you go on with the 150W kern. It would be good to see some pictures to compare with your other piece.

[Robert Walters]

I just installed a pin table and am working on the setting to prevent flash back but having air pulled from under the part also helps reduce smoke residue on top.

Hi Michael,

Which pin table did you get and how do you like it?

[Glenn Chua]

Lee,

I will have to look for your 'fingerbox' macro. I initially started laying out the finger joints in Corel manually, but 1/2 way through found the rahulbotics box maker online and it worked well. I just took a closer look at the options and I guess I can just over-state the material thickness to achieve the same results...

If for some reason I end up doing more finger boxes I will take your advice on the flush-trim bit.

Thanks

[Larry Bratton]

Lee,

I will have to look for your 'fingerbox' macro. I initially started laying out the finger joints in Corel manually, but 1/2 way through found the rahulbotics box maker online and it worked well. I just took a closer look at the options and I guess I can just over-state the material thickness to achieve the same results...

If for some reason I end up doing more finger boxes I will take your advice on the flush-trim bit.

Thanks

Glenn:
As I originally advised. I do use Lee's macro and the default of .003. Sometimes though I don't sand it back because we like the look of the contrasting edges.

[Bill Cunningham]

Usually a lower frequency will burn less.. For 1/8" on 'good' baltic birch I generally use a freq. of 150, speed about 12-15% and power 100% and get light brown edges.. The edges will always have some brown..after all..you 'are' dealing with a machine that does cut by vapourizing the wood..