Cutting & engraving leather

[Dubliner]

I got a few samples from a Leatherworker who does a lot of hand cut inlay & overlay work, so quite laborious. I 'm looking for tips as I 'm not having much success yet. I have a 100w CO2, air assist, great vacuum etc. but I'm getting wide burns at 75 w, on 2mm leather, another question? as the laser was set up when I got it the auto focus attachment is non functional. I need to make myself some gauge blocks to set the height. What do I need to know to determine the ideal height? Its a Weike 100watt and I have spare mirrors & lenses but not having aligned & assembled it myself I'm a little confused by the manual that came with it( when I say manual, I'm using lyrical liscence )tx Neville

[zax15uk]

As you've already discovered, leather is difficult to cut as it burns rather than cuts cleanly. Engraving tanned leather usually has good results but can also smell pretty bad. It will probably work better if you have the focus tuned.

To determine the focal length of your lens (likely 2.5" or 3") via trial and error you can use paper or Kapton tape and test different heights and determine the smallest spot size, then fine tune until you get the optimum result. A microscope or magnifying lens would help (100-150um is typical), the goal would be to minimize the heat affected zone (HAZ) and hole size, which indicates you've found the true focal length of the lens.

Alignment is critical to achieve the rated power output, placing a piece of masking tape carefully over the hole into the final mirror/lens housing and using a low power 'pulse' to create a small burn mark will indicate if you have the mirrors aligned - this needs to be done with the shortest and longest laser path. If you need to make adjustments (which can be tricky the first time) you would place a piece of cardboard or wood over the mirror and align each individually - several of the vendors have videos and instructions on this procedure.

Zax.

[MonoNeuron]

Zax is right about the leather smelling terrible. :-)
If you use tape over the mirrors and you burn through inadvertently to the mirror surface then you will get a whole heap of sticky crud on the surface that is hard to clean off. Much better using some thick (1-2mm) card and using the lowest power you can to just get a small light spot on the surface to find the right place for the beam.
If your lens is about 50mm focal length then it is relatively easy to get the right focus. Place a piece of thick card under the lens at an angle so it is about 2-3mm higher on one side with the length about 50mm long. Set the focus to about the average height of the card in the middle and engrave/cut a single line along the length of it at minimum power. You will see the char line start thick then go thin then go thick again. The thinnest part of the line is the focal length of the lens and is easily measured from a certain point of your choice on the lens assembly. make a mark or make a gauge to get the height, it's your choice. I just use a 6" rule and measure to a scribed line on my lens assembly that is 2" from the surface of the part to be cut/engraved.

[zoefie]

Just my 2 cents on alignment of your system.

To prevent your mirrors and lens from the residu of burning paper etc.
I use anodized aluminium business-cards. They are marked very easy with
CO2 laser, and you won't burn through them for sure.

Zoefie..........

[Dubliner]

I will try those ideas out, and thanks for the tips lads. I think the primary alignment is good as I cut .75 in acrylic (185mm) with it, slight bevel to it, but I'm cutting that stuff on my cnc all the time with a 5 hp spindle and its not exactly a piece of cake so it was awesome not to have to hold it down and get a polished edge when done. Awesome fun I'm having with this laser. I apologize in advance for a the dumb questions and really appreciate everyones advice. I will endeavour to find the "sweet spot" and see if I can get better results with leather, although I presume it will be difficult. I notice even when I do have the settings right, I get curling & shrinking being as organic as it is. So thank you all & bedankt Zoefie.

[Dubliner]

Just curious. I tried your setting method and it seems like 20 mm from the cone tip to material is the optimum. I was wondering about, freezing, wetting, masking leather to reduce burning. I tried some leather, probably .08mmand it cut reasonabluy well withouth too much charring. I'll have to experiment... Second question, is it better to set a slow move speed to cut thicker material or is it possible to run a second pass and set a new Z depth automatically in the software ( Lasercut5.3 ) Im so used to Aspire & toolpathing according to the material that I'm seeing Lasercut is rudimentary at best. I'm wondering if I should create 2 vectors ( or more) with different colours/settings to make more than one pass or is that possible within LC 5.3?

[zoefie]

It's easy to let lasercut cut the same layer multiple times, in the layercaontrol move the slide to the right of the screen, and you'll see a column " TIMES" this is the number of times the layer will be processed.

As far as i know it's not possible to adjust the Z-axis from within a lasercut "program" i've tried to find out but didn't succeed.