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So, I'm pretty new to 3D Printing, and to quote Spock from Wrath of Khan I would say "He is intelligent, but not experienced". Now everything I have been reading about Z-offset seems to talk about a 0.2 mm gap and using a piece of paper.

Wishing to be accurate, I have tried to use my 0.2 mm feeler gauges and this is too high.

However, the thickness of paper depends on the GSM (grams per square metre). A Google search tells me that the average thickness of paper is ~0.1 mm but how can we be accurate with this variation.

I tried using a 0.1 mm feeler gauge and even this seemed too high. Is this because of the lack of give in the metal? Anyway, I have now settled for a Lotto slip (UK Lottery) which has a thickness of 0.1 mm and seems to allow me to set a good offset.

However, I would welcome someone who can explain the science behind this.

0scar
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Byte Insight
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2 Answers2

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They are all generic guidelines. Don't count on them too much.

What you need is a reproducible offset to get the same value everywhere in the bed, then you can correct the overall offset via gcode at the beginning of your print.

You can also get an approximate Z-offset value, then print a solid 30x30x5 mm cube.

If, starting from the third-fourth layer, you see some over-extrusion, you need to adjust the extrusion multiplier or the E steps calibration and reprint.

Once the solid cube looks good starting from the third-fourth layer up, then you can tune the Z offset by printing a cube which is only 0.2 mm high (or 0.25 mm, or whatever your first layer height is).

If you see over-extrusion, the Z offset is too big. If you see visible gaps between extrusion lines, the Z offset is too small.

If unsure, better get some small remaining gaps rather than overextrusion and excess material.

The idea is that extrusion issues in the first layer can be caused either by the offset or by the multiplier, so you must adjust the multiplier first by looking at the print after about 1 mm height (the first layer issues tend to disappear after some layers). Once you know the extrusion is right, set properly the first layer.

Edit

For a good guide check Andrew Ellis' guide: set first the extrusion multiplier and then the first layer squish.

FarO
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Measuring a gap with paper is just a rule of thumb. Personally I didn't measure anything, I've just made sure my bed is level and adjusted z-offset bit by bit until I was satisfied with the results. I couldn't tell you how wide the gap is.

On the other note you might not have to reconfigure your Marlin. You might be able to configure your z-offset by adjusting it directly in your printer config menu or alternatively if you are using Cura you can download a plug-in that allows you to adjust z-offset. You just have to remember to reslice your model if you print on multiple surfaces with different thickness

Piotrekdoro
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