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I'm trying to print a lithophane with my Ender 3, but the nozzle gets closer and closer to the previous layer, layer after layer.

I thought that what was causing the problem was perhaps a gear lock due to the fact that the Z rod wasn't parallel to the vertical axis, but after fixing it the problem remains.

The bed is super planar and perfectly levelled and, in fact, the first layer comes out perfectly. Extrusion is also okay. The printer seems fine in all aspects.

It seems like the seriousness of the problem is proportional to the number of layers, just like the printer is losing a fixed height by each layer.

I've ruled out the possibility of wrong calibration of Z steps because after measuring a cube of 12 cm of height and telling the printer to raise 12 cm the cube fits perfectly under the nozzle with the levelling gap (so perfect calibration).

What do you think may be the problem?

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    $\begingroup$ Could you please add an image of a print? Calibration cubes are excellent for this. $\endgroup$
    – 0scar ♦
    Apr 7, 2020 at 10:33
  • $\begingroup$ Yes I could, but there's nothing wrong with the print except the fact that after few layers the nozzle is practically in touch with the print and after few more layers the print fails completely because the nozzle rams agains the edges of the print. If I manually increase the gap by rotating all bed screws thne it prints fine for few more layers but I have to keep compensating throughout the print. It's a pain! $\endgroup$
    – Fredo Corleone
    Apr 7, 2020 at 10:54
  • $\begingroup$ What layer size are you printing? This must be an issue with missing steps as a result of insufficient torque or something. But strange that it goes to the correct height without printing. $\endgroup$
    – 0scar ♦
    Apr 7, 2020 at 11:50
  • $\begingroup$ Layer height of 0.12 mm, the torque is good I suppose (I find hard to block the Z rod with my hand). Can it be that the printer is skipping steps due to high resolution? I have not printed rough models yet. $\endgroup$
    – Fredo Corleone
    Apr 7, 2020 at 13:05
  • $\begingroup$ Could you include your settings? I'm not an expert, but wondering if you are putting down a .12 mm height of material, but you are only incrementing upwards of .1 mm at a time. Don't know how this would happen, but seems logical in my pea brain. $\endgroup$
    – Pᴀᴜʟsᴛᴇʀ2
    Apr 7, 2020 at 13:08

1 Answer 1

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Finally I've found the damn problem: Adjustable rollers of all axes were flat on one point making layers to shift in all directions.

The effect was less visible on the X and Y axes but it was more notable in the Z axis as the flat part was right from the start of the print. I think that flat part was making difficult for the Z axis to move upward, and making my prints fail when printing at higher resolutions (I guess the finer the displacement the weaker the torque).

It seemed to me that the nozzle was getting closer to the previous layer but instead it was resting (or barely moving) on the flat part of the Z right adjustable roller first and then on the other adjustable roller of the same axis.

To diagnose the problem disable the steppers and moved the axes manually and feel if there are notches, so to speak, in various spots on every axis.

The solution is to replace the rollers with new ones and to not close them too tight otherwise they'll deform over time.

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