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?