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All my prints come out about 1 mm too short in the Z dimension. So for example a 20 mm cube comes out 19 mm high. A 10 mm cube comes out 9 mm high. The X and Y dimensions are fine. There's a little bit of visible elephant's foot at the bottom, so I assume whatever is happening is in the first couple of layers. The problem is fairly consistently around 1 mm even for larger prints.

10 mm test cube 20 mm test cube

The printer is an Ender 3 Pro with a glass bed and BLTouch for automatic leveling, but otherwise stock.

I had a similar issue with another Ender 3 Pro that was resolved thanks to a link to this question about problems in the first 3 mm. The solution was turning the eccentric nuts on the left and right to loosen the rollers that connect the X-axis gantry to the vertical posts. There the Z issue was not as pronounced, and I was getting really messy prints in the first few Z layers. Here that is not an issue; the first few layers look fine while they're printing. Loosening the rollers did not resolve it.

Things I've tried:

  • Tightening and loosening the gantry rollers using the eccentric nuts. They're currently just tight enough that turning them moves the gantry, but loose enough that I can turn them without moving the gantry if I hold it still.
  • Tightening and loosening the two little screws that attach the extruder mount to the Z-axis lead screw. Currently I made them just tight, then backed off 1/4 turn.
  • Adding a shim between the vertical post and the Z-axis lead screw. The lead screw is now pretty much parallel to the post.
  • Slowly turning the lead screw by hand to raise and lower the gantry. There's no noticeable catching or increased resistance anywhere.
  • Varying the brand and type of PLA filament.
  • Varying the temperature from 190 °C to 210 °C.
  • Obsessively leveling and re-leveling the bed. Manually leveling, auto leveling with the BLTouch, and adjusting the z-offset.

I'm using the stock Ender 3 Pro profile in Cura, and printing at 0.2 mm layer height. I've kind of run out of things to check. What else can cause Z height loss in the first few layers like this?

Robert
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    1 mm is a lot that is missed, certainly when you use a layer height with a multiple of full steps. Have you checked movement without printing? So measure the height after a move from Z0 to Z100. – 0scar Jul 05 '20 at 13:03
  • @0scar At your suggestion I did. I auto-homed, moved the head down to 0, measured the height of the top of the gantry, moved it up 100 mm, and measured again. It was dead-on 100 mm difference (as accurate as my ruler can be). So if that's working, what else should I look at? – Robert Jul 05 '20 at 21:00
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    Your question is very well formulated, but, to be honest, I've no clue at the moment. What I would do is write a script to generate G-code to move the printer from Z0 to Z100 in 0.2 mm steps to see if that makes a difference. I can't grasp why while printing it doesn't progress Z as a move. Look for play in the Z axis. Do you use Z-hop? – 0scar Jul 05 '20 at 22:14
  • @0scar I don't think so. "Z Hop When Retracted" is turned off in the (standard) Cura profile I'm using, so unless there's another setting somewhere I'm not using Z-hop. – Robert Jul 05 '20 at 22:37
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    Did you ever solve this? A new user without comment privileges just attempted to post such a question as an answer. I'm curious too, since I've had various Z-axis problems in the past on an Ender 3 and want to know what could cause such an awful one as you've experienced in case I encounter similar in the future. – R.. GitHub STOP HELPING ICE Sep 12 '20 at 13:53
  • If it's still a problem, are you sure the gantry is square with the Z-axis? It's possible to mount the roller brackets non-square and that makes lots of problems similar to this. – R.. GitHub STOP HELPING ICE Sep 12 '20 at 13:55
  • @R..GitHubSTOPHELPINGICE I haven't really solved it. I just avoid prints where the first 1 mm is critical (adding rafts or support helps). I have checked the gantry and it appears square - I rolled it to the top and measured the distance to the top extrusion, and it's less than 0.5 mm different between the left and right. I'd still appreciate any suggestions! – Robert Sep 12 '20 at 20:31
  • @Robert: Have you checked that the Z beams are parallel to each other (not closer at one end than the other, or bent somewhere in the middle)? – R.. GitHub STOP HELPING ICE Sep 12 '20 at 21:15
  • @R..GitHubSTOPHELPINGICE No bends that I can see. I just measured between the Z beams at the level of the build plate and at the top. The difference is within 0.5 mm. So not perfect but pretty close. Do you think that could be it with such a small difference? – Robert Sep 13 '20 at 11:02
  • @Robert: I wouldn't expect an error within 0.5 mm to be a problem especially if that's without the gantry at the height being measured; aside from being a very small difference I'm pretty sure it's within the amount the beams should be able to deflect under tension. If, even with the gantry positioned at the height where you're measuring, there's still a difference and it's not a measurement error, it might indicate something mechanically wrong, but I'm not sure what. – R.. GitHub STOP HELPING ICE Sep 13 '20 at 16:18
  • Is that elephant foot ? – Stefan Merfu May 24 '21 at 21:29
  • OP reports leveling the bed but no mention of adjusting the Zoffset height. The bed can be perfectly level but still too close to the nozzle. – Kezat Aug 09 '21 at 21:04
  • @Kezat That's part of the bed leveling process. I'll update the question to make that explicit. – Robert Aug 10 '21 at 03:18
  • Creality Ender 3 Pro-"Z" axis issues: Browsing through earlier comments I don't really see any clear, verified solution for errors in the Z dimension when printing. I don't have a solution, but I'm experiencing a pretty similar problem. To not "muddy the waters" with the specific observations of my problem I'll open a new question/topic, [Creality Ender 3 Pro: Problem with Z-axis inaccuracy (squashed layers?)](https://3dprinting.stackexchange.com/q/18781/4762). I leave this note here in the hope that perhaps somebody following this thread who has valuable info will be look at the new thread. – Peter X Jan 20 '22 at 17:04

2 Answers2

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Do you have any “slop” on the right side (non motor) of the gantry?

I’ve noticed that my gantry will settle on the right side and lag behind the motor driven - ever so slightly - when it starts to drive up. It will, after that first lag, move fine for the rest of the time. Z axis travel seems barely affected but all my prints are consistently about 0.5 mm short.

Greenonline
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j_q_m
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    N.B. "Slop" is a common term for looseness or play -- what machinists used to call "shake". In this context, it would mean the Xmax end of the gantry lags behind the Xmin end when the gantry starts to move up. – Zeiss Ikon Aug 09 '21 at 18:14
  • I think this is it. You've described what I see perfectly - a slight on the non-motor side. Is this something that's just endemic to the Ender 3? What can I do about it? – Robert Aug 10 '21 at 03:20
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    It's probably endemic to any single Z drive gantry type printer. The most reliable solution might be converting to some kind of dual Z drive -- I've seen single-stepper belt drive Z conversions with all printable parts (other than the belts). I hope that isn't what's needed, though; I have the same problem with an Ender 3 (the cheap one). – Zeiss Ikon Aug 10 '21 at 11:29
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I have the exact same issue on my Ender 3 V2, perfect bed level using a dial gauge, perfect first layer test prints (printing 9 squares all 1 layer high).

I can only get rid of it two ways:

  1. Using a Raft as you have said (annoying).
  2. Adjusting the Z-height Just exactly as the 1st layer finishes. I raise the height by 0.15-0.20 mm (in my case), and the resulting elephant foot is about 80-90 % better.

I recommend you follow Luke Hatfields guide on Ender 3 rework for The X-Gantry, as well as his other sections. Youtube channel "Edge Of Tech" does a decent job covering the rework in video form. Following most of these reworks I have made everything else in the print absolutely perfect, unfortunately EF remains.

Greenonline
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SwitchedMode
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  • I have edited your answer down to just the solution/workaround. The additional questions in the last two paragraphs could merit a new question. Please ask a new question, using the last two paragraphs as the contents, and refer back to this question, using the URL, as they are related. Hopefully someone will be able to provide you with a solution. – Greenonline Aug 11 '21 at 09:19