Noob question on scaling x,y, and z axis
I recently got a MK2.5. XYZ calibration is good (x/y is off by less than .06 degrees). The First layer calibration looks good. So now I print a calibration block. When I compare it to what the X,Y and Z sizes should be, it is off by a scaling factor. For example; X has a scaling factor of 1.015, Y has a scaling factor of .996 and Z has a scaling factor of 1.005. Is there a place where I can add these scale factors for this printer so that I don't have to prescale the STL model specifically for this printer? Ideally this should be part of the printer calibration and stored in the printer but I don't see anywhere to do that. Maybe I am missing it. I know on my milling machine I can use a g-code command G51 to provide different scaling on different axis but this only works if the g-code interpreter in the printer implements the G51 command. If it does support this then I could add it to the g-code generated in PrusaSlicer in the advanced/expert section. May there are scaling parameters in PrusaSlicer and I am am not seeing them. Any help would be appreciated.
RE: Noob question on scaling x,y, and z axis
it's stored as (micro)steps/mm with the M92 Gcode
i would print an extrusion width cal block to verify your extrusion width and check your y axis belt tension ( may be a bit loose allowing hysteresis in the y movements )
you Z is most likely first layer a bit high ( thick)
RE: Noob question on scaling x,y, and z axis
Are the M92 g-code changes made to the MK2.5 unit and saved in the eeprom using M500? and then a new XYZ cal performed? If the changes are only made in the slicer then will the offsets not match the cal on the unit?
RE: Noob question on scaling x,y, and z axis
yes, but i suspect most of the calibration error you see is overextrusion and Y hysteresis that should be fixed first
as this is additive machining any error in extrusion affects X-Y dimensions and any error in first layer thickness affects overall height
and hysteresis needs to dealt with differently than overall scaling error
RE: Noob question on scaling x,y, and z axis
hysteresis can be tested for by printing different sized test objects and seeing if scaling error is constant
extrusion error is tested by printing single wall cubes and measuring actual wall thickness vs programmed
first layer height is measured best by printing thin and thicker sheets and measuring thickness
RE: Noob question on scaling x,y, and z axis
Another factor is as the belts stretch, these factors need to be updated. What you might be seeing is the change from when you calibrated XYZ to now. I've seen as high as a millimeter (>1%) change in X accuracy when tightening my belts from loose to too tight. So I always recal after belt maintenance.
RE: Noob question on scaling x,y, and z axis
Thanks for all the help. I think I have isolated the problem. It appears to be hysteresis in the nozzle movement is caused by a loose nozzle. I am printing out a new extruder cover and extrudder body in ABS on another printer. The printer had been used to print a lot of PETG with a PETG extruder cover and body. It appears that these parts may have softened and the fit has loosened over time (1000+ hours).