Skew Correction, Belt Tension and XY Alignment
Having upgraded to the Kit Core One from a Mini I figure it would be a good time to reprint all the components of the mini is a colour the missus likes then she can use it for PLA in her craft room. I downloaded the Califlower from Printables and used that to check things. Initially the results were carried out in Overture Matte Black PLA as the PETG was drying, not looking to dial in dimensional accuracy, just practice.
After the initial flower I figured I'd tweak the belt tension as I followed the Prusa instructions to so the alignment is 'true' and the belt tension is unequal and wanted to see what happened if I dropped the difference (ie tuned the belts to have the same frequency, rather than maintain alignment.:
Filament: Overture Matte Black PLA, Nozzle: 0.4mm SiC Phaetus Nozzle.
Slicer Settings: 0.2mm Structural, Prusa PLA, Prusa Core One 0.4 Nozzle.
Flower One: As above, no changes to slicer settings. Left Hand Belt 83Hz, RH 89Hz. Core XY aligned as per Core One Belt Tuning Guide, alignment compensated by unequal belt tension. Result: 0.21° Skew (90.21). -0.2% error on on X and Y Axis.
Flower Two: 0.2% Shrinkage Correction in Slicer. Left Hand Belt 83Hz, RH 87 Hz. Core XY will no longer be Aligned (didn't check, but the gap will be on RHS) Result: 0.15° Skew. X axis -.02%, Y Axis 0.04% Error.
Flower Three: 0.2% Shrinkage Correction in Slicer. Left Hand belt 86Hz, RH 87Hz. Core XY will no longer be Aligned. Result: -0.05° Skew, -0.1% Error X, -0.05% Error in Y.
I've printed one flower in the PETG using the 86/86Hz tension and got 0.06% error (which for me confirms the skew). I'll point out that I thought I had landed flower 3 and the PETG flower at 85/85Hz but had missed it. I've tuned it to 85/85 after the last flower. Will need to do another check to see if the skew is reduced further (logically you would assume it has). Also, I didn't check the carriage alignment after equalizing the belt tuning because from experience of tuning I know it will no longer be aligned.
For me this raises some questions regarding the alignment/belt tensioning phase of the assembly as the results would seem to indicate that the alignment check I carried out was not in fact aligning the printer. Is it possible that something was not aligned correctly /dimensionally accurate in the Core One parts that caused the carriage to appear unaligned?
RE: Skew Correction, Belt Tension and XY Alignment
It is best to start by loosening the belts and then moving the portal all the way forward.
Now check whether both ends are against the stop or whether there is a gap on one side.
If both are on at the same time, the portal is correctly aligned.
However, if there is a gap on one side, place something in between on the opposite side so that you can carefully but firmly pull the other side forwards.
Then move the portal forwards again and check whether the gap has narrowed.
Repeat this until both stops are in contact.
Then tighten the belts alternately until you have reached 85hz.
Now check the portal again.
When both sides have no more air, the alignment is complete.
Don't worry, the bracket with which the X axis is attached allows such corrections without any problems.
RE: Skew Correction, Belt Tension and XY Alignment
It is best to start by loosening the belts and then moving the portal all the way forward.
Now check whether both ends are against the stop or whether there is a gap on one side.
If both are on at the same time, the portal is correctly aligned.
However, if there is a gap on one side, place something in between on the opposite side so that you can carefully but firmly pull the other side forwards.
Then move the portal forwards again and check whether the gap has narrowed.
Repeat this until both stops are in contact.
Then tighten the belts alternately until you have reached 85hz.
Now check the portal again.
When both sides have no more air, the alignment is complete.
Don't worry, the bracket with which the X axis is attached allows such corrections without any problems.
I think i will leave it for the moment. The skew is pretty much gone for my prints. My concern would be that the carriage is aligned with the front but the xy remains skewed as having them aligned gave me skew.