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Z axis calibration  

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Rocket 3
(@rocket-3)
New Member
Z axis calibration

I have run the xyz calibration and for the majority of my prints I have no problem, however, I have made some simple tubular spacers where the overall length is not printing as desired. 
the spacers are designed in Fusion 360 and have a length of 113.5mm, outside diameter 35mm inside dia 21mm.

The tubes are printed using Prusa slicer, the length is aligned to the Z axis. The resulting printed part measures 113.70 ie 0.2mm oversize.  
Is there a simple remedy to achieve a more accurate overall length on the printed part?

thanks.....

 

Posted : 23/02/2021 4:05 pm
fuchsr
(@fuchsr)
Famed Member
RE: Z axis calibration

That’s 0.2% dimensional accuracy. Sounds pretty good to me, for a nonprofessional FDM machine. 

Here’s an article on dimensional accuracy and some suggestions for improvements:

https://m.all3dp.com/2/dimensional-accuracy-3d-printing-tips-tricks/

Posted : 23/02/2021 6:55 pm
chad.k
(@chad-k)
Eminent Member
RE: Z axis calibration

Z is often going to be the hardest to get perfect accuracy with, and often you'll just need to design around that rather than trying to get your printer to give perfect results.

The slicer itself might grow/shrink your object in the Z dimension and put you a couple tenths of a millimeter off.  For example, your 113.5mm tall object would be 113.6mm high after slicing if you use the default "0.30mm DRAFT" print settings, or 113.4mm high with "0.20mm QUALITY" setting.

Then there is just the fact the first layer has to be squished into the build surface somewhat in order to stick and that the top layer is going to be somewhat uneven.  That can easily be another source that alters your print by a fraction of a millimeter.

Posted : 23/02/2021 7:46 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Z axis calibration

What Chad says is true if you just use a normal layer. However as Prusa slicer is capable of variable layer height you can adjust the top few layers thickness to get a perfect multiple of your height if required.  For example if you change the top 2-3 layer to 0.1 instead of 0.2 you can get 113.5mm theoretically. You still have the first layer squish to take into account though. 

Posted : 23/02/2021 7:55 pm
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