Hi everyone,
I received my A250 ten days ago, and I’m so into it. Already printed a book holder when cooking, CNCed and laser engraved a clock, only great moment.
Nevertheless, I have a question for you guys.
When printing, I have to set a Z offset of 0.3 to 0. 4mm, otherwise the first layer create chunks of plastic (see the attached picture). The first part is with no Z offset, the second with 0.2 and the clean part is with 0.3.
I did recalibrate the bed, and the machine passes succesfully its auto leveling at the start of each printing. It does it with PLA and PETG.
Any idea?
Hey, first of all, i see just one picture but I understand.
The nozzle was too close to the bed at the bubble parts. The problem is, if you print on a other area of the bed/printsheet there would be a other offset in my case.
The bubbles will disappear if printing more than one layer. Printing closer (not too close) to the bed means better adhesion to the bed.
It’s better to print a bit closer than too far away.
Your offset with 0.3mm is good.
You could try to recalibrate the bed and set the offset at the final point a bit less tight than now.
BTW your print sticks, that is good 
Thanks for the fast answer.
That’s what I thought. If I leave with no offset, the nozzle can catch the buble from the previous layer, and then… disaster. It pulls the bed off its magnets, and all the print get shifted, total mess.
If I leave too close, with 0.1 or 0.2, it is super sticky. I ruined one side of the bed trying to unstick it. So I will keep moving to 0.3 or 0.4 at the beginning, and see.
I tryed to recalibrate the bed 3 time, and it does the same effect.
You should start printing a calibration sheet or something else, maybe the area where you print is not optimal.
I wonder, if you give it a greater offset after fast calibration, it should work.
The z offset is used to find the proper height for the nozzle, and the printer would use that height to start the print I guess. The auto-leveling should only be able to create a virtual flat surface that use to print, but it is not able to set a proper height to start the print.
You’ve done a good job to find the proper height for your machine, 0.3mm.
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Ok, it is clear for me now. Thank you for your help. Time for printing again 
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