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I have two printers, one is an Anet A8 and the other one is a CreatBot DX plus. On both of them I installed a BLTouch, firstly on the DX and today on the A8. I have never had a problem with the probe, but today I am experiencing some problems. I just set the offset, by doing the procedure, and I found to that the Z0 is -0.8 mm.

Problem is, when I start to print (I use Cura as a Slicer and OctoPrint), I run G28 and G29, everything is fine and the bed gets mapped. When the print starts, something weird occurs: the nozzle goes down for the regions where the bed is higher! So, the layer that is put down, is very thin and the nozzle actually dives into the bed! It is like a Z0 too low, so the nozzle crashes into the bed, but it is not because in X100 Y100 it is perfectly fine! Could you have any idea why this occurs?

What have I tried?

Changing bed springs
Because I was curious, and impatient I changed the springs with the Ender ones I bought online. The problem is still here! I can see the bed closer to the nozzle during bed leveling, compared to the left side. So I screwed the right side, to see any difference. However, the nozzle seems to be always closer on the right side! I checked the X rods, they are leveled.

Searched online
I checked almost everywhere online and I found out that it could be a problem related to the bilinear bed leveling. So I changed to linear, and apparently now I can print! I believe it is something related to the mesh the firmware creates after the leveling, which is avoided for the linear. <I will let you know tomorrow, after I change the frame whether the bilinear will work or not! I can still see that the left-side part of the print is closer to the bed, but now I can print at least. Will let you know! Bye!>

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  • $\begingroup$ Welcome to 3DPrinting.SE! Is the bed flat or is there a bump that is not mapped by G29? $\endgroup$
    – 0scar ♦
    Jan 30 '20 at 19:01
  • $\begingroup$ Do you have a Z offset stored for the head somewhere? $\endgroup$
    – Davo
    Jan 30 '20 at 19:49
  • $\begingroup$ ZO already stored and no bumps on the bed :/ $\endgroup$
    – Giovanni
    Feb 1 '20 at 7:55
  • $\begingroup$ Did any of the posted answers solve your issue? If so, please mark it as the accepted answer. If not, then either refine your question or please post an answer if you found the solution yourself and then mark it as accepted in 48 hours, in order to remove your question from the unanswered queue (it will be popping up once in a while then). Thanks! $\endgroup$
    – 0scar ♦
    Apr 2 '20 at 10:59
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Check and potentially replace your bed springs as this is a common cause with cheap bed springs. An immediate workaround is redoing your Z-offset but most likely after a while you have to repeat it until you replace the bed springs with stronger ones.

After replacing springs you have to redo Z-offset again.

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  • $\begingroup$ Hi thank you! I will do it once I will change the whole frame, so in 2 days. Hope it will solve the problem! $\endgroup$
    – Giovanni
    Feb 1 '20 at 8:16
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In my opinion, you should check if you get consistent value every time you G29.

If you didn't do anything and the value keeps changing that means your bed is not durable which could be due to bad bed springs.

Now if you do get the same value, again and again, that means your bed is okay.

This means you need to see your Cura. You may have something set in the Start G-code that might be causing it to move further down.

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  • $\begingroup$ Hi thank you! Because I am waiting for the metallic frame, I will change the springs once it arrives, on Monday. In the meanwhile I will do some G29, because I can feel the bed a bit loose when I touch it! But I don’t get how the bed could move so much just after a G29. It is super weird, I do G29 then the print start and the nozzle goes down only on the right side of the bed! I can clearly see it, because from left to right the printed lines disappear! $\endgroup$
    – Giovanni
    Feb 1 '20 at 8:00

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