Laser cutting Question

[Alex Morefield]

Hello all, I've been a lurker now but had a quick question for you all.

I recently received a Boss laser LS3655 100W. I have had this for right at two weeks now so I am still learning. The problem I have ran into is one of the first order requests I received locally (most sales our online for us) is for a 24" 1/2" birch three letter monogram. Up until this order, I had been cutting basic 1/4" wooden christmas ornaments basically as something small to practice on. With the ornaments, I have had no trouble at all.

I decided to cut a test monogram first from the 1/2" to make sure my settings were good to go. However, using 95-100% speed and a speed as low as 2mm, I was unable to cut through the wood completely. To test this a little further, off of some advice I cut a basic 2" circle from the 1/2". I was able to do this at a speed of 6mm. I then attempted to cut the same circle in all four corners of the 36x55 table. The top and bottom left cut through fine. The top right had to be pushed through, and the bottom right didn't go through at all. I have still been unable to cut the monogram or even a simple letter A in the monogram font at the 5-6mm speed range in any area of the laser. Does anyone have any suggestions as to what could be going on here?

Yes, I have tried a different 1/2" piece of wood, which also had the same results.

[Bill George]

Hello all, I've been a lurker now but had a quick question for you all.

I recently received a Boss laser LS3655 100W. I have had this for right at two weeks now so I am still learning. The problem I have ran into is one of the first order requests I received locally (most sales our online for us) is for a 24" 1/2" birch three letter monogram. Up until this order, I had been cutting basic 1/4" wooden christmas ornaments basically as something small to practice on. With the ornaments, I have had no trouble at all.

I decided to cut a test monogram first from the 1/2" to make sure my settings were good to go. However, using 95-100% speed and a speed as low as 2mm, I was unable to cut through the wood completely. To test this a little further, off of some advice I cut a basic 2" circle from the 1/2". I was able to do this at a speed of 6mm. I then attempted to cut the same circle in all four corners of the 36x55 table. The top and bottom left cut through fine. The top right had to be pushed through, and the bottom right didn't go through at all. I have still been unable to cut the monogram or even a simple letter A in the monogram font at the 5-6mm speed range in any area of the laser. Does anyone have any suggestions as to what could be going on here?

Yes, I have tried a different 1/2" piece of wood, which also had the same results.

Interesting. Well the not cutting the same on differant areas could be as simple as mirror and lens alinement. Is this plywood or solid wood? Or it could be a not up to power tube?
Do you have a mA meter on the machine, that can tell you a lot.

[Scott Shepherd]

As a general rule, you aren’t going to cut 1/2” thick wood with a 100w laser. The focal band of a 2” lens is 1/8”. When you try and cut 1/2”, the beam goes out of focus and the power density drops drastically. The beam diameter exiting is probably .060”-.090” wide.

Not on a good thing to do. You can take cuts, move the focus down into the work and cut again.

[Dave Sheldrake]

Scotty is right, 1/2 inch is well over the sensible capacity of a 100 watt tube'd DC laser, with a longer focal length lens (you would need an 8 inch) the power density will be so low you won't be able to cut it anyways.

1/2 inch anything is router materials

(I'm sure there will be a few posts saying "But I cut 3 foot thick stone with my 20 watt etc etc) and they are true, but the quality will be dreadful and will take hours

[Gary Hair]

Scotty is right, 1/2 inch is well over the sensible capacity of a 100 watt tube'd DC laser, with a longer focal length lens (you would need an 8 inch) the power density will be so low you won't be able to cut it anyways.

1/2 inch anything is router materials

(I'm sure there will be a few posts saying "But I cut 3 foot thick stone with my 20 watt etc etc) and they are true, but the quality will be dreadful and will take hours

Absolutely correct. I did cut some 1/2" mdf with my 80 watt Trotec but only because the pieces I needed to cut took less time than it would have to drive home and cut them on the tablesaw... The edges were pretty charred but for this application, fixtures for my fiber, it didn't matter, and I had to have them asap.

[Guy Hilliard]

Alex;

It will be slow but you should be able to cut 1/2" plywood with your 100w laser.

The issue you are having could be one (or both) of two issues;
Misaligned optics - this was mentioned earlier. If the optics are correctly aligned then the power delivered should be consistent over the entire bed of the laser.

Laser bed is not flat - if the laser bed is not flat then the laser will go out of focus as it travels across the bed and the cut will be inconsistent.

Check both and fix as required.


Hello all, I've been a lurker now but had a quick question for you all.

I recently received a Boss laser LS3655 100W. I have had this for right at two weeks now so I am still learning. The problem I have ran into is one of the first order requests I received locally (most sales our online for us) is for a 24" 1/2" birch three letter monogram. Up until this order, I had been cutting basic 1/4" wooden christmas ornaments basically as something small to practice on. With the ornaments, I have had no trouble at all.

I decided to cut a test monogram first from the 1/2" to make sure my settings were good to go. However, using 95-100% speed and a speed as low as 2mm, I was unable to cut through the wood completely. To test this a little further, off of some advice I cut a basic 2" circle from the 1/2". I was able to do this at a speed of 6mm. I then attempted to cut the same circle in all four corners of the 36x55 table. The top and bottom left cut through fine. The top right had to be pushed through, and the bottom right didn't go through at all. I have still been unable to cut the monogram or even a simple letter A in the monogram font at the 5-6mm speed range in any area of the laser. Does anyone have any suggestions as to what could be going on here?

Yes, I have tried a different 1/2" piece of wood, which also had the same results.

[John Lifer]

Maybe 3/8" wood will cut fairly decently. My 80 watt will cut that thick but barely. And it won't look pretty. Sorry, I agree with Scott, Gary and Dave, 100 watt isn't that much higher and while it might cut some, it won't be consistent, nor good. Fergit if you have anything with ANY knots.

[David Sharp02]

Maybe 3/8" wood will cut fairly decently. My 80 watt will cut that thick but barely. And it won't look pretty. Sorry, I agree with Scott, Gary and Dave, 100 watt isn't that much higher and while it might cut some, it won't be consistent, nor good. Fergit if you have anything with ANY knots.
That explains a few things for me. No matter what I try, I haven't been able to cut 1/2" MDF on my 45w Epilog 24TT. If a 100W is underpowered for 1/2" wood, then it's no wonder.

Home Depot 1/4" MDF though cuts beautifully, almost like it was made for lasering.

[Joseph Shawa]

Do test your height from table to cutting tip in all 4 corners. I found that by running my table up (Z) and having it be stopped by the head or whatever that the level get off a bit.

[Robert Bonenfant]

Like others have stated 1/2" is To much for a 100 watt laser to cut consistently. We have found that 1/4" is the economic cut off for our 100 watt machines - Anything thicker isnt worth the extra cut time and error rate. You can cut 1/2" hardwood and plywood but it will require very slow speeds and/or multiple cuts and normally it leaves poor edge and surface quality.

Plywood: Different grades of plywood will laser cut differently. We use baltic birch BB Grade plywood and it works great. If you try some big box store plywood you will find the cut can be very inconsistently because of Hard spots created by inconsistent glue levels and core materiel, knots.

[Bill George]

He said that it cut a test circle and then it cut 2 inch circles in some of the corners. So that was impossible?

From above: To test this a little further, off of some advice I cut a basic 2" circle from the 1/2". I was able to do this at a speed of 6mm. I then attempted to cut the same circle in all four corners of the 36x55 table. The top and bottom left cut through fine. The top right had to be pushed through, and the bottom right didn't go through at all.

[Brian Lamb]

There is something to be said for what type of cut you are doing as to wether it will get all the way through. I find my ULS cuts at a slower feed rate in curves and angles than in straight line cuts, so I have to slow down for the worst condition and go from there.

[Alex Morefield]

So today I double checked the alignment, and confirmed everything is level. Yes it is 1/2 birch plywood coming from lowes. I see that several people here and other sites use 9mm/10mm instead of 1/2", where is the best place to purchase that? Attached is the four circles I cut from the corners, as well as the monogram (prior to knocking it off and breaking it) the outer perimeter of it cut fine. As you can see the center pieces is where the trouble began.

[Dave Sheldrake]

The black spots are hard spots in the cores, usually wood filler and an absolute bug bear to try and cut no matter how much power you have available

[Alex Morefield]

Could be attributed to being low grade Lowe's plywood?

[Robert Bonenfant]

Lowes and Homedepot offer builder grade plywood, great for the every day contractor but not so great for lasers. Also if you check the thickness its not true 1/2" plywood. I would talk to a few lumber yards and see what they have instock and what they can order.
As I stated above, a go to plywood for Lasers and Routers is Baltic Birch - Its offered in a verity of Thicknesses and is available through out the US. We go through pallets of it each month and it always cuts well, We get a few hard spots every so often but what do you expect its from Russian :-)

Monograms are a pain to cut, make sure you cutout the middles first and then make the second order the outside.

[Bert Kemp]

like everyone has said 100 watts is really not enough power for 1/2 inch big box store plywood. this plywood is not designed for lasers. Go online and find some good BB grade baltic birch from Woodworkers source, woodcrafters, Rocklers and try that.
Why does it have to be 1/2 inch? If I were doing that I'd cut 2 pieces from 1/4 and glue them together. JMO

[Bill George]

Could be attributed to being low grade Lowe's plywood?

I would try to switch over to 3/8 and plain wood not plywood if you can. I dont think anything 1/2 inch is going to be something you can realiably do. Like Dave said, its the glue. So many good suggestions here!

[Mike Null]

Read again what Steve says:


As a general rule, you aren’t going to cut 1/2” thick wood with a 100w laser. The focal band of a 2” lens is 1/8”. When you try and cut 1/2”, the beam goes out of focus and the power density drops drastically. The beam diameter exiting is probably .060”-.090” wide.

You need to understand the capabilities of your equipment.

[John Lifer]

I'll speak to the grades of ply. DO NOT by underlayment from ANY of the big box stores. It has very hard and a LOT of glue that is probably an epoxy based. I can cut great and then hit a spot and laser won't even dent it at power needed to cut thru the clean areas. I've found my local HD to have decent Baltic Birch (marked as such) at 3 and 5mm thickness that is flat and easy to cut. Three layers. Thick center ply and two thin veneers. Not 5 layers, nor 3 that are roughly same thickness. Look for thick center and thin surface veneers. Those will cut well and Yes, double to triple the cheap ply costs...... But well worth it.

And Half inch MDF is impossible with my 80watt. Charred Mess. I have a bunch of 6"x96" pieces I create as scrap from my other projects and it just sits. Guess I could engrave rather than cut couldn't I? Anyone have project that uses 6" x MDF in half inch? :) Just ends up as jigs when I can use it.

[John Blazy]

Lowe's 1/2" ply could be glued with exterior grade glue which resists cutting, might not be tho. Baltic Birch (buy through cabinetmakers supply plywood companies) is generally regarded as best for laser, and some specialty laser grade birch is available.
Although 1/2" is maxing out practicality, just figure in two passes with the laser, and it should be fine, but plan on ordering a mini saw blade for your dremel to cut the uncut areas. I cut 1/4" BB all the time, and have gotten pretty good at cutting the uncut areas with my dremel fitted with a 1" DIA blade.

Now the reason you need to check mirror alignment is this: When the laser cutting head is closest to the laser (usually deep left corner) and say your beam is visually dead center on the mirror, but maybe .030" off center (which you can't tell by eye), then when the laser is cutting close right corner (farthest from actual laser tube), then that .030" is magnified to maybe .120" off center. Hope you get the picture here. My bed is 36 x 48, so alignment is important all across whole bed. So check beam center with tape at all four corners and adjust accordingly.

Another unique issue on large bed lasers is that there is such thing as beam spread. I removed the cover and the first mirror on my laser to shoot it into my shop for cross cutting 4 x 8 sheets of acrylic (long story, mounted a mirror / lens assbly cantilevered off wooden arm - look for my thread on it), and tested the beam DIA across ten ft, then twenty feet, and the spot grew to 1-1/2" DIA at 20 feet. This is why laser mirrors are larger in DIA than the effective beam spot, to catch all the photons when farther away.
When my laser hit the mirror dead center on my cantilevered arm, the whole black housing got really hot, proving that residual beam spread photons were hitting the mirror mount armature.