Laser Marquetry

[TimSchubach]

Hi all,

I have access to an Axiom machine equipped with a laser, and I wanted to try doing some veneer marquetry. I understand about "laser kerf", and after talking with a few fellow CNC'ers, I thought I understood what I needed to do. Using Aspire, I took an outline image of a cross, cut it out on the line, and used that as my pocket. For the inlay, I took that same vector and enlarged it by 0.2mm, 0.15mm, and 0.1mm in all directions, assuming one of those would fit the pocket and tell me how large the kerf was. None of the four test pieces fit to the point where I think I'd be satisfied with the final project. The best I would do was to get the inlay to fit up/down, but there were gaps everywhere else..

I talked to my neighbor who has a laser ( not a laser attachment for a CNC ), and he did the same thing using Corel with the same results - nothing that I'd take the time to glue up due to gaps.

So, is there some trick to sizing the inlay so that it fits all the way around in the pocket? We tried the same thing using a simple circle, and with his laser, we got a very good fit making the inlay 0.2mm larger than the pocket. But we have no idea why that doesn't work using an irregular shape. Pointers to any documents or other posts I've missed are appreciated.

TIA,
Tim

[gkas]

I'm guessing that the pocket was cut with a bit, but the veneer was cut with a laser? If so, then the laser can make much finer cuts. It's like pocketing with a 1" mill, but cutting the veneer with a 1/8" bit. The profiles are never going to match.

https://docs.vectric.com/docs/V10.5/Asp ... index.html

[adze_cnc]

Rather than enlarging your vectors for the laser-cut pieces (risking deformation of irregular shapes) try offsetting your laser path as you would if you were cutting with a router bit.

[ger21]

If you have inside corners, you'll need to radius the corners of the inlay to match the tool radius.

[TimSchubach]

I'm guessing that the pocket was cut with a bit, but the veneer was cut with a laser? If so, then the laser can make much finer cuts. It's like pocketing with a 1" mill, but cutting the veneer with a 1/8" bit. The profiles are never going to match.

https://docs.vectric.com/docs/V10.5/Asp ... index.html

Sorry I did not provide enough detail. I'm using ONLY veneer, no solid wood. So the pocket and the inlay were cut with a laser. I've seen Marc Adams at the Marc Adams School of Woodworking do this same thing, but when I was there he did not go into details about how he created the toolpaths. And his laser will most likely have a different kerf than the one I use, although the process should be the same.

Thanks,
Tim

[TimSchubach]

Rather than enlarging your vectors for the laser-cut pieces (risking deformation of irregular shapes) try offsetting your laser path as you would if you were cutting with a router bit.

At the onset, the first thing I tried was Aspire's offset feature to create the inlay toolpath ( again, I'm using ONLY veneer, so both pockets and inlays are cut with the laser ). But depending on the shape, using the offset feature may not create an exact copy of the pocket toolpath, enlarged to fit the space.

The last thing I ended up doing was using Aspire's Set Selected Objects Size, trying to make the inlay just enough bigger that it would fit the pocket taking into account the laser kerf. This made a lot more sense to me than using the offset feature, but still isn't giving me the results I need. What I expected to see was a new vector that was "offset" by a specific measure all the way around the object. What I'm seeing is a new object that is longer and wider by a specific measure, but that offset isn't consistent all the way around, leaving gaps.

I'm betting my issue is user error, but I don't know where.

Thanks,
Tim

[gkas]

Using Aspire, I took an outline image of a cross, cut it out on the line, and used that as my pocket. For the inlay, I took that same vector and enlarged it by 0.2mm, 0.15mm, and 0.1mm in all directions, assuming one of those would fit the pocket and tell me how large the kerf was. None of the four test pieces fit to the point where I think I'd be satisfied with the final project. The best I would do was to get the inlay to fit up/down, but there were gaps everywhere else.

The problem could be cutting ON THE LINE. I'd try like a normal toolpath, inside for pocket, and outside for inlay. Remember, you will remove some material with the laser, especially the Axiom laser. The only way to control burn and cut is spindle speed. With all my use, I still have to run a LOT of test to make decent cuts. Try light cuts at a higher spindle speed. Or, you can jury-rig an air assist to keep the burn manageable. Cut out a small square, then a LOT of test patches. I inlaid a Scrabble board by cutting the pocket with a bit and inlaying painted pieces for the colored squares. I just made a grid of the squares and changed spindle speed and allowance offset. Every species of wood and thickness requires a new set of tests.

P.S. Have you tried the inlay toolpath?

[TReischl]

One thing you should NOT do is any operation that scales the workpiece. Scaling is NOT the same as offsetting.

When I laser cut veneer for marquetry I cut both pieces on the line. I figured out that the laser cuts about a .006 kerf. So that means theoretically there is a .006 gap all around the inset piece. That works for me.

If you want a smaller gap then you will need to offset the geometry of at least one of pieces, either inside or outside depending on which piece it is.

There is a problem with doing that. If you are creating complicated marquetry designs that offsetting will eventually throw the entire project out of kilter and drive you crazy and next thing you know you will be seen stumbling around in allies mumbling to yourself.

[TimSchubach]

One thing you should NOT do is any operation that scales the workpiece. Scaling is NOT the same as offsetting.

When I laser cut veneer for marquetry I cut both pieces on the line. I figured out that the laser cuts about a .006 kerf. So that means theoretically there is a .006 gap all around the inset piece. That works for me.

If you want a smaller gap then you will need to offset the geometry of at least one of pieces, either inside or outside depending on which piece it is.

There is a problem with doing that. If you are creating complicated marquetry designs that offsetting will eventually throw the entire project out of kilter and drive you crazy and next thing you know you will be seen stumbling around in allies mumbling to yourself.

Well, I don't think it'll take the laser to make me wonder allies and start talking to myself!

Let's start with what may be a more basic premise - that I'm using the right kind of toolpath. I'm using the Quick Engrave toolpath, which is what I'd been told I should use for the laser. So there is no inside/outside cut option. I have not tried using a profile toolpath, and cutting inside for the pocket and outside for the inlay, but that make even more sense than trying to scale pieces on the project I eventually want to cut. Now THAT would probably make we wonder around back allies after a while!

[TimSchubach]

Using Aspire, I took an outline image of a cross, cut it out on the line, and used that as my pocket. For the inlay, I took that same vector and enlarged it by 0.2mm, 0.15mm, and 0.1mm in all directions, assuming one of those would fit the pocket and tell me how large the kerf was. None of the four test pieces fit to the point where I think I'd be satisfied with the final project. The best I would do was to get the inlay to fit up/down, but there were gaps everywhere else.

The problem could be cutting ON THE LINE. I'd try like a normal toolpath, inside for pocket, and outside for inlay. Remember, you will remove some material with the laser, especially the Axiom laser. The only way to control burn and cut is spindle speed. With all my use, I still have to run a LOT of test to make decent cuts. Try light cuts at a higher spindle speed. Or, you can jury-rig an air assist to keep the burn manageable. Cut out a small square, then a LOT of test patches. I inlaid a Scrabble board by cutting the pocket with a bit and inlaying painted pieces for the colored squares. I just made a grid of the squares and changed spindle speed and allowance offset. Every species of wood and thickness requires a new set of tests.

P.S. Have you tried the inlay toolpath?

No, I have not tried the inlay toolpath. I was led to believe that when I use the laser I should be using the quick engrave toolpath, which may have been bad information. Cutting inside the line for the pocket, and then outside the line for the inlay makes more sense than trying to scale elements, especially on a large piece. So I'll definitely give both the profile and inlay toolpaths a look and see what kind of results I get. Thanks!

[TReischl]

::::shrug::::: I just use the profile toolpath. The way I see it, it is a profile, not an engraving. But hey, I see most everything as a profile, LOL.

Edit: one other thing. . . I do two things to control the burn. The first is that I have a vacuum tube mounted around where the laser beam goes. That keeps the wood from flaming on the top surface. The second is that I cut on a vac table. Nothing fancy there, just a thin box with a top drilled full of holes. Get a bit of burning on the backside but that is the part that is not going to show anyhow.

[TimSchubach]

Using Aspire, I took an outline image of a cross, cut it out on the line, and used that as my pocket. For the inlay, I took that same vector and enlarged it by 0.2mm, 0.15mm, and 0.1mm in all directions, assuming one of those would fit the pocket and tell me how large the kerf was. None of the four test pieces fit to the point where I think I'd be satisfied with the final project. The best I would do was to get the inlay to fit up/down, but there were gaps everywhere else.

The problem could be cutting ON THE LINE. I'd try like a normal toolpath, inside for pocket, and outside for inlay. Remember, you will remove some material with the laser, especially the Axiom laser. The only way to control burn and cut is spindle speed. With all my use, I still have to run a LOT of test to make decent cuts. Try light cuts at a higher spindle speed. Or, you can jury-rig an air assist to keep the burn manageable. Cut out a small square, then a LOT of test patches. I inlaid a Scrabble board by cutting the pocket with a bit and inlaying painted pieces for the colored squares. I just made a grid of the squares and changed spindle speed and allowance offset. Every species of wood and thickness requires a new set of tests.

P.S. Have you tried the inlay toolpath?

No, I have not tried the inlay toolpath. I was led to believe that when I use the laser I should be using the quick engrave toolpath, which may have been bad information. Cutting inside the line for the pocket, and then outside the line for the inlay makes more sense than trying to scale elements, especially on a large piece. So I'll definitely give both the profile and inlay toolpaths a look and see what kind of results I get. Thanks!

Well ... there may be one problem ... When I select the quick engrave toolpath, the laser appears to be the default tool. I can edit that tool, but I don't see anywhere where I can actually choose that tool. When I choose any other toolpath, I can't select the laser - I can't even see the laser as an option. Maybe that's why I was told to use the quick engrave toolpath ... ??

[TReischl]

Tim, the laser is a round tool. I have mine defined as an end mill with a .006 diameter. I name it as Laser Beam

There is a problem with that, almost impossible to see the preview. So what I do is increase the tool diameter to show me that I am not really goofing up and then reset it to .006. I suppose one of these days I will learn to double click the scrap so I can see the cutouts.

[TimSchubach]

Tim, the laser is a round tool. I have mine defined as an end mill with a .006 diameter. I name it as Laser Beam

There is a problem with that, almost impossible to see the preview. So what I do is increase the tool diameter to show me that I am not really goofing up and then reset it to .006. I suppose one of these days I will learn to double click the scrap so I can see the cutouts.

Good idea. I guess to determine the diameter to use, I could just cut a straight line and measure the gap left by the laser. Thanks for the tip!

[TReischl]

Good idea. I guess to determine the diameter to use, I could just cut a straight line and measure the gap left by the laser. Thanks for the tip!

That is a tough gap to measure accurately. What I finally did (this was before I had the microscope) was to cut 10 squares out, push them together and measure the length. Bit of arithmetic later and I had a pretty accurate idea of how wide the beam was.