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I had a couple of recent nozzle/bed crashes, so I now frequently do a manual bed levelling. I do these while the bed is heated to allow for expansion.

Today i found, after levelling, a subsequent print could vary from having too much clearance (paper moves very freely) to less than no clearance (which left deep grooves in the bed as per the photo).

enter image description here

What are the possible causes? Is it just a dodgy Z-limit switch or something else? What solutions are available and at what cost? Obviously an ABL seems essential now, but requires a lot of hardware and setup.

Update

Just happened again so here are some more details.

Printing PLA this time. - Preheated bed. - Levelled bed all over and got a very good raft. - Print failed later so aborted. - Restarted the same print. - Nozzle gouged out a uniform depth trench around print perimeter.

The uniform depth of the gouge indicates a problem related to Z-axis only as bed remains flat and level, but height is out.

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  • $\begingroup$ I doubt it's the z-limit switch. I'd think two things: you aren't leveling your bed correctly; you've got some unaccounted for slop in your setup which allows the bed to come out of calibration after you've done your calibration. $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Nov 10 '18 at 13:27
  • $\begingroup$ How flat is the bed/sticker on the bed? Have you put a metal ruler on its side over the bed to check the level? $\endgroup$ – 0scar Nov 10 '18 at 13:31
  • $\begingroup$ did the physical switch moce? $\endgroup$ – Trish Nov 10 '18 at 13:36
  • $\begingroup$ @Paulster2: I have done over 100 successful prints, prior to this issue, so do have some clue about levelling the bed :) I am interested in what could cause such a large variation. Initially I thought it was temperature as I switched to ABS at the time, but it now varies from one print to the next. $\endgroup$ – Gone Coding Nov 10 '18 at 20:37
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    $\begingroup$ @filimonic I have the removal bed version and also a borosilicate glass bed. The glass is perfectly flat and the standard removable is dipped ever so slightly in the middle, but the difference is huge when it goes wrong. As you can see from the photo the trench it digs is quite uniform depth. That's why I keep coming back to the z-limit switch. I have a spare switch now so will try that next. $\endgroup$ – Gone Coding Nov 25 '18 at 18:30
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Similar issue happened to coworker's Maker Ultimate. I'm gonna go out on a limb and assume that your Z-stop is a little mechanical switch, and there's an M3 screw going through part of the Z carriage that pushes said switch. Check to see how much force it takes to rotate said screw. There's a lot of vibration happening in a 3d printer, and it takes surprisingly little vibration to make a threaded part do weird things, including making it back out against gravity if conditions are right. Redo your Z gap paper test, get everything lined up, and then slap a dab of blue loctite on the screw to make sure it doesn't move during your next print. See if that fixes your problem.

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I've just bought an Ender 3 Pro and as a guess I would look at the Z axis stepper motor to see if it is not holding position once it stops... the stepper motor has power on it all the time it is stopped to hold it in position.

I would check the plug that feeds power to see if it is damaged or not making good contact.

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This was killing me on mine. My problem wasn't the z-axis, it was the x-axis arm. On the right side, opposite the extruder gear, it had a lot of give (wobble). I could level my bed four times before starting a print and would still have problems, especially with the nozzle making deep grooves in the magnetic bed. The way it messed up was inconsistent as well, making it hard to troubleshoot.

I changed out the bedsprings, got a glass bed instead, changed out the extruder gear and Bowden tube; I was ready to give up.

How to fix the wobble, if that's your problem, if there's a lot of give / vertical movement on the right side of the arm:

You have to take the whole arm off. First, take the top bar off, remove the four screws. Second, disable steppers so you can take the x-axis off completely. I removed the cables once I had taken it off. Third, there's a plate with two holes to get to two screws - make sure these are tight! This is where the wobble was coming from. Four, reassemble and double-check. For me, the give was reduced drastically.

A video tutorial for help. There are English subtitles.

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  • $\begingroup$ Are you the original poster on a second account? $\endgroup$ – Davo Mar 20 '20 at 14:54
  • $\begingroup$ No, I just thought my issue was also my z-axis and came across this several times in trying to figure things out and figured I'd post my solution in case it helps anyone else. $\endgroup$ – Akexis Mar 21 '20 at 15:52

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