Head overdriven because of cuts at 19 inches to right

I have a wide design with some little marks that my GF may be thinking are some sort of bar code at the 19 inch mark. The inital “print” works great. I have a second “print” that needs to align with the first. For some reason the GF runs to the right and overshoots a bit. The drive makes a curious sound and skips about 1/8 inch and therefore my second “print” is off by that amount. This took some time for me to discover the issue of the head being overdriven to the right side during the scan pre-cut.

This crops up in on the forums from time to time. Mostly, the units get replaced. Usually support will ask you to print gift of good measure on the right hand side in the position where you had trouble before. And then you’ll need to post pictures and times of operation so they can look up the logs. They usually want it done on Proofgrade, so you may want to wait for them to ask you before you burn up your material.


So sorry your print did not turn out beautifully. So we can investigate further, could you please do the following for me?

  • Turn off your Glowforge (this is important to avoid damage to your unit)
  • Open the lid and, using both hands, gently move the laser arm to the center of the bed
  • Gently move the head under the lid camera
  • Turn your Glowforge back on
  • We included an extra piece of Proofgrade Draftboard with your materials shipment for troubleshooting. Please print the Gift of Good Measure on Proofgrade Draftboard in the lower right hand corner of the bed
  • Let us know the result. If the print looks incorrect, please include a photo

Thank you in advance!

Sorry, this is a software bug I am reporting in the driver for the cutting head. The scanner is located to the left of the cutting optics and the scanner will try to read stuff beyond the physical limits of the head mechanics. This little bug could cause a lot of needless returns. Here is my test to duplicate the error.

  1. cut some marks at the 19" point near the front of the honeycomb. I used three staggered horizontal lines and one vertical line.

  2. re-position the material so the marks are near the back of the honeycomb.

  3. load another file.

  4. start the cut. The GF will see the marks on the left an attempt to scan them. you will hear the mechanism hit the mechanical stops.

If GF detects marks beyond the 18 7/8 inch mark on the GF cutting bed; the GF thinks the witness marks are bar codes from proofgrade materials. The GF then moves the cutter head so that the integral scanner can “read” the witness marks. Problem is GF overdrives the head beyond its limits and the horizontal drive skips a tooth. This results in the GF cutting everything about 1/8 inch left of accurate.

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The lid camera reads the Proofgrade barcode, not the head camera.

The “scanning” step is the head using its internal laser diode to measure the height of the material. The location it chooses is a point where it will later cut/engrave (any stray marks on the material are ignored and do not figure into the decision).

The problem is not a software bug in the head driver. It is likely with the calibration of your unit - It thinks it has more room to travel in the lower right area than it actually does.

Support is asking you to confirm that by printing the ruler in the lower right corner. If it is confirmed, then they likely will replace your unit as there is no way to re-calibrate it remotely.


Where does the red laser strike the bed relative to the CO2 laser?

To the left, pretty close to the middle, or to the right - depending.

Since the laser diode is fired at a 45 degree angle, it varies with the material height. It also may always be slightly above or below depending on the individual unit.

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I am using the feed through with my own technique for alignment to cut larger “prints”. That is why I have been cutting a lot of items at the 19 in mark. The only time the GF does its slam to the left thing is if a cut at the 19" mark is visible to the camera. If there are no marks over there, no problems.

The second cuts are perfect, just translated to the right about 1/8" after the slam, that is why I am assuming the head is skipping a tooth. It makes lining up the next cut on a pass through a bit of a challenge.

This scan, whatever it is, seems to happen at places where there are marks. Most of the time it seems to be on the right side of the GF. Sometimes near the front and sometimes near the back on blank material, but never slams to the right.

If it skips a tooth that would be 2mm, not 3.175mm. A slam is more likely to skip motor steps unless the belt is loose.

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I’m sorry for my slow reply.

@gmallard, Did you get to try the test print?

If not, could you take a video of your print that shows the slam you’re describing?

It’s been a little while since I’ve seen any replies on this thread so I’m going to close it. If you still need help with this please either start a new thread or email support@glowforge.com.