Apparent layer shifting but...strange

Support & Troubleshooting Form 3/3+
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I have been unable to print anything in Castable Wax 40, even though it is a brand new tank and resin cartridge. Also I have printed this material with success before. However, now all my prints fail, with a very weird characteristic. It looks like the print shifts over about 5-10mm after a couple layers. You can see in the photo. The bottom layer (or few layers) seem shifted over from the upper layers. When I go to remove the failed print, the top layers separate relatively easily. That bottom layer is really tight on the build platform, and needs to be scrapped off.

Note that the top layers actually hang off the edge of the build platform a bit, whereas the bottom layers seem to match where the print was supposed to be printed.

The only thing I can think of is that after some couple hundred layers, the entire print “slid” just above those bottom layers. For example, maybe when layer 200 is being printed (or separated), layer 3 “slid over” about 5-10mm on top of layer 2. Notice the direction of sliding is directly towards the mixer side. I don’t know how or why this would happen, but after that point the next layer would not line up with the supports, and everything would start failing.

Anybody seen this? Any idea how to prevent it. I am stuck, this happens on EVERY print now.

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2

Something wrong with the LPU jack screw assembly. You need to open a ticket with FL and have them take a look. It’s not something that you’re causing.

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Hello @Gringotuerto,

Randy is right that you should open a ticket with our Support Team; they will be able to check the logs for your printer and help to identify and troubleshoot the cause.

4

All,
I think the problem has been resolved, so I wanted to report back. I did file a support ticket, and Formlabs quickly helped out. After some diagnosis, I was basically advised to take two steps, clean the optical window and clean/lube x-axis:

When I went to clean/lube the x-axis rod, I was surprised to find very visible contamination. In retrospect, I should have just opened the printer and looked around with a flashlight, it would have been obvious something there was abnormal. Attached are a few pictures showing segments of the x-axis with what little “shavings” of black junk that have fallen on the floor of the printer under the x-axis rod (see arrows pointing to specific location in the photos). I could even see some accumulating around the hole where the x-axis enters the LPU.

So I just vacuumed out the shavings, cleaned the rod with a clean rag, and applied some white lithium lubricant. I have white lithium grease that I use on all my printers…FDM, SLA, SLS, etc. they all have positioning rods. After that you just move the x-axis back and forth a few times to spread it around. I also cleaned the top of the optical glass per the instructions above (PEC PADs).

Next three prints were all successful, no problems. Given that I had about 5 failed attempts in a row before that, I think it is safe to say that cleaning the x-axis rod really helped. Since I cleaned the optics at the same time as the rod, I cannot say with certainty which made the difference; but given the visible evidence of problems with the x-axis, I’m going to speculate that was the key issue.

Anyway, if anybody else has this problem, I would advise: (1) remove the tank and look around with a flashlight. Do you see this kind of junk under and on the x-axis? (2) If so, remove it and grease the rod. It took about 2 minutes of work.

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1 Like
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Hi @Gringotuerto,

I am glad to hear that Support was able to help, and thank you so much for sharing your experience on the forums! I hope this post will help some others uncover the cause of any print issues sooner and reduce downtime and frustration. Take care!

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Not like I like to cause trouble… but that seems like an excessive amount of wear for what needs to be a very precise positioning system. All that material that was vacuumed up and wiped away had to come from someplace, and the friction bearing surfaces of the ball-screw assembly are, I think, the only possible source. Material removed from those surfaces increases backlash and loosens tolerances. It might be that the ball-screw design can tolerate some wear without a loss of precision (some ball-screws are designed this way), but geeze, that sure looks like a lot of “swarf”. Hard to imagine the assembly could wear that much and still work accurately…

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Is it worn material or dried up lubricant?

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If it’s dried up lubricant, FL needs to spend a little more on their grease. :slight_smile:

Looks metallic to me.

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Sorry I vacuumed it and didn’t examine it. Could be dirt & lubricant, or something else. The support person asked “have you noticed any black (or another color) gunk in your printer cavity?” which prompted me to look.

My main advice would be, whenever you are changing resin trays, don’t be shy about shining a flashlight in there and looking around. It only takes a moment, and I could have seen this a long time ago, I’m guessing.

1 Like