Material Thickness Error Nov 2022

Hi all,
There doesn’t seem to have been a post about material thickness errors in quite a while.

I am trying to cut card stock. Which I last cut one month ago (and it has only been a week since I last cut some cherry). The Glowforge seems to go through the ‘Set Focus’ routine, but when I go to print, I get an error that says "Material Thickness Error… The material was not measured correctly… ".

I had not thought that anything had changed since my last cut, but just in case, I have…

  • Turned it off and back on several times.
  • Cleaned all the lenses
  • Cleaned the crumb tray, including making sure that the divots it sits in are clear
  • And… I threw in a scrap of wood, set the focus on that, and did not get the error. So it does seem to be focussing, or at least going through the focus routine, without problems.

The material is 0.27mm/0.0105in, but I have never set the material thickness with anything except ‘Set Focus’ (I got the GlowForge back in early 2020). And… strangely, If I restart the laser, set a thickness in the “use uncertified material” and then press print… it cycles through an “Autofocus” and then gives me the same error.

Any thoughts or suggestions?

Have you tried cleaning the two lenses windows on the bottom of the head? Might be smudge and throwing off the red dot.

Otherwise might need to lift your material with a sacrificial surface to make it happy.

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There is only one lens in the head.

There are, however, two small windows on either side.

I have cleaned the little windows and the lens. I had even hoped doing a second wipe-down would help (no luck). Whatever the issue is, it may also be why I’ve noticed in the last month that cuts haven’t always gone through. I’d thought it was because the lenses needed a wipe, but maybe not. Maybe the laser focus is a tiny bit out.

Thanks for the reminder about cutting on a sacrificial piece [I’ve used that technique for veneers so often; you would have thought I’d go to that first].

I may try adding sheets of cardstock layer by layer, see where Glowey thinks minimum height now is. If I get to that, I will post results.

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OK… That experiment didn’t take long. The answer is one. After a couple of hours of messing about with it, I cut my part on a piece of sacrificial draft board. Then went to try to see how many sheets of card stock on their own, without the draft board, we needed… and Yes, the laser did focus on one sheet and was prepared to print.

So the solution seems to have been “Cut something thicker then then try again with the card stock”.

Thanks, elfguy and wesleyjames for the suggestions!

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Just use a piece of MDF. It will also have the benefit of reducing flashback on the underside.

You sir are technically correct. The best kind of current.

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