Z offset calibration print

Nothing more than a square, 0.2mm high so it prints a single layer. I use this for setting the Z offset. The printer's own Z offset calibration is a good start, but it can be a challenge to get the height just right if you haven't done it a bunch of times already. I find using a solid infill test part helps immensely.

Start with the printer's own Z offset test if you haven't already, you want to be in the right general area. Load up this model and start the print. The skirt and the two outer perimeters should print well, but what we're really looking for is how the infill behaves.

• Gaps or low spots between the lines? Drop your Z height.
• Plastic “smooshing” up between lines? Raise your Z height.

Note that your Z height will likely be a negative number so dropping your Z height means increasing the Z height, eg: -1.100 to -1.150 will get the nozzle closer to the print bed.

Your goal is to get the top surface flat - but remember if it was too low and was smooshing up a bit of plastic, it can take a couple passes before an adjustment is seen, as that extra plastic throws off subsequent lines. If you were getting a bunch of smooshing, you can raise it a bit for a line, then back it down to where you thought it should be.

Ultimately, you're looking to get the top layer as smooth as you can. Once you get it where it runs several adjacent lines and doesn't have any valleys or ridges, that's your Z offset. Once you're happy, you can cancel the print.

Three sizes - 100mm, 75mm and 50mm. Only difference is how long it'll take to print and how long you'll have between each subsequent line to make adjustments and see how they affect the print quality. Start with the 50mm and if you feel like you need more time to make adjustments.

Update 3 May 23: I added a 100x50 shape rotated at 45 degrees. With the normally rotated squares, it takes a while printing in the corner before the lines are visible enough to start making adjustments. By rotating the part 45 degrees the infill is now parallel to the short end and you can start seeing results immediately. Another option is to set the infill angle to 0 degrees in the slicer, but this is just marginally faster and easier, so I'll always take that route.

How to make your own

This is what I usually do unless I already have a good model saved on my Octoprint.

• Load up PrusaSlicer with an empty print bed.
• In the white box on the right of the window, right click, you should see “Add shape…”
• Choose “Box” and you will get a box on the print bed, most likely 18x18x18mm
• Click the lock icon next to “Scale factors” so it turns orange and shows unlocked
• Enter the X/Y/Z dimensions you want, with Z being 0.2mm
• Position the rectangle on the print bed as you wish
• Slice it and send that to the printer!