Z offset! Arrgghh!!!

[great white]

Usually, setting z offset is easy on my rig. I run a custom marlin build and it has a z offset wizard. Run it, adjust the clearance and good to go. Has worked wonderfully for the last couple years.

A couple days ago, I changed nozzles and did an offset calibration.

First print bottom):

What the heck? Fooled around with some settings that all seemed to check out. It seemed like the nozzle wasn't lifting engouh and plowing through the previous layers, creating the "balling" and lines you see in the print. the top object is a second attempt. Still a mess but better.

What it seemed to be is the Z offset wasn't set right, even though I did it several times. I had to go into the firmware and manually raise the nozzle, which this firmware allows for as running changes while printing.

Finally go tit to this point:

Better, but still some roughness and unexplained lining.

It's a housing fo r a light on the Argo in case anyone is wondering:

3d printing can blow my mind sometimes. It will often do things that I just don't understand and often the solution is something you never would think would have been the problem.....

 

[WobblyHand]

Having ported someone's code recently to a processor that used a stricter compiler, I have found that there's lots of sloppy code out there, such as ints in one place and uints in another for basically the same variable. It works sometimes and is wonky at others, seemingly at the phase of the moon. You can get silent casts and unpredictable math results. I have been burned by it before, myself. Perhaps you should compile with -Wall or something stricter to find these potential issues. Yes, its a pain in the behind to fix all the warnings, but the result is usually much better and predictable code. Might not fix this particular problem, but is a very good thing to do.

That first print is pretty ugly, indeed. I'm not smart enough, nor experienced enough to fool with custom firmware for my printer just yet, so I can't help you there. Maybe someday, I'll get to the point where custom firmware makes sense. I do think it has merit, especially with tuning out resonances in the printer. That is seriously neat stuff. Those phantom lines could be resonance, perhaps your belts are too tight or loose? Or a default setting changed in the firmware? Can you do a diff on the firmware with the previous version?

 

[great white]

To be fair, I did expect some "lining" as that is being printed with a 0.8 nozzle and in ABS. The blobs and trails are the problem.

Abs is notoriously difficult to print with, but it's actually my prefered filiment. Mostly for it's mechanical properties, but especially for how it reacts to post print processing.