Massively Reduce Laser Etching Time

On any laser cutting job, an etch takes a long time. Thousands of passes back and forth across the job occupies a significant proportion of the job run time. For this reason I was pretty pleased this week when I worked out a way to cut a 29 minute and 25 second job down to a 14 minute 50 second job.

It’s rather obvious when you think about it, but since laser cutters are usually charged for by the minute, plus the material, knowing how to drastically reduce etch time is really rather valuable!

This really, really quick trick will only work on jobs that contain multiples of the same item. The secret? Rotate! The following picture is of the job that I was running, a run of 10 scout woggles for a website that Steve and I set up to make use of our laser cutter. I’ll use this job as an example of how simply rotating it saves so much time.

Laser Cutting Leather Scout Woggles

When designing an item like the woggles above, I design the outline in my favourite drawing (well… okay, CAD) package, Alibre then export as a dxf. The image I then add within the laser cutting software. It of course feels natural to start with the woggle so that the text and picture is the right way up as I view it. This is fine if just cutting one woggle. If I want to run off a batch of 10, I get all the settings right for one, then step and repeat it to fit the material I’m using. In this case it was easiest to have 2 columns and 5 rows. The diagram below illustrates the flaw in just accepting this, since with 2 columns and 5 rows the laser cutter head has to traverse the distance between the items being etched before it can etch the second item.

Bad Etching Demonstration Diagram

In the diagram above, the green circles represent the area being etched on each woggle. The red rectangles are the outer cuts of the woggle. The black arrow shows the direction of etch; I am yet to find an option on our laser cutter or in the software that allows me to etch along the y axis, I only get the choice to etch along the x axis. The large blue rectangle represents wasted time. It takes time to get from the end of one etch across to the start of the next etch. The laser cutter starts at the bottom left, etches a line left to right on the bottom left green circle, then moves across to the bottom right circle and etches that. This takes time to traverse. It then moves up a step (in this case 0.1mm) then repeats this until it’s etched all of the text and images.

By rotating the above 10 items by 90 degrees, a far more optimal etch can be performed, as demonstrated by the diagram below.

Optimised Etching Arrangement
This really simple rearrangement massively reduces the wasted travel time between etches. It could be further reduced by making the gap between the leather woggles smaller. I kept them at 1mm spacing rather than 0 since it stops the leather around them falling apart after being cut. This way I don’t have to pick up lots of small pieces from the bed of our laser cutter.

And here are some pictures of the job I was running, simply to plug our new website and because I’ve only used one photo so far:

Sample Laser Cut/Etched Leather Key Ring

Laser Cut/Etched Leather Scout Woggle

  1. Great idea for saving time. Seems so obvious once you explained it.

  2. Hackaday links: November 28, 2010 - Hack a Day - pingback on November 28, 2010 at 15:01
  3. Interesting, I used to write software for SMT (Surface Mount Technology) machines years ago and I’d always optimize. But with SMT I’d have to optimize for component location, rotation and feeder location. It’s kind of like this problem with a complexity X4!

  4. I think Epilog cutters do this automatically? They stop moving the head immediately after they engrave then move to the next area to engrave, then repeat for each line.

    How are you cleaning the residue off your leather?

  5. I don’t get any residue on the leather we cut. We use a low tack paper to cover it while it’s being etched/cut to stop the char coating the rest of the face of the leather.

    What do you mean about the Epilog lasers? What you described is the same way that our laser cutter does it, the process described in this blog post is done by the user though, to reduce the off time between etching on each line hence reducing the total distance traveled.

  6. Nice and detailed explanation, but nothing new here. When I was working in the sheet metal business 10 years ago we just drew a bunch of different shaped pieces of sheet metal, and the computer calculated the most effcicient way to cut those pieces out of a single sheet of metal.

    If you look at this example there still seems to be plenty opportunity for yet another 20% time optimisation by pacing every odd sign a little lower and making the total width smaller.

  7. @Paul: Yes, that would optimise the material usage but not the etch time. Since the material’s cheap and the machine’s time is expensive, we prefer to reduce the job time. It would be as you suggested if we were just cutting, since any two lines that are laid atop each other mean 1 less line to cut.

  8. How about rotating the pieces ~30 (or 60) degrees to stagger or nest them in a stair step fashion. You could save on material (yeah, just read you material vs. time post), but you might stil be able get optimal performance. Although, without knowing anything about the machine and the way it, I really wouldn’t know.

  9. Hackaday links: November 28, 2010 « Black Hat Security - pingback on December 1, 2010 at 02:22

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