Calibration Questions
I don't want to make assumptions with complex machinery.
1) Under what conditions should I recalibrate x, y, and z? For instance, when I am peeling off my test print from my first layer print calibration, I tend to move the bed in the Y direction. Does the system record this with some absolute or relative opticoder? If so, what about when the power is off?
2) If I re-run calibration for one system (ie: xyz), is it necessary to go through other calibrations in sequence? For instance, running the xyz calibration might zero out the first layer offset. In this case I would need to know that I need to re-run the first layer offset. I would like to know what calibrations require what other calibrations to be run afterwards.
3) My request would be to automatically retract the z-axis much more after a first layer calibration. I have scratched my PLE sheet because the nozzle is so close to the sheet when I try to remove it.
The first layer calibration results in lines that are difficult to peel, and it would be good if I could more easily remove the steel sheet. This could help me avoid moving the heatbed while removing the lines.
Thank you!
Re: Calibration Questions
The Prusa printers, like all consumer/hobby FDM printers, dont' keep track of actual positions with any kind of sensor. They rely on aligning each axis against a reference "stop" and then keep track of position by counting steps that are sent to the stepper motors. So if something happens to mechanically disturb the position, they have no way to know or compensate.
That said, Prusa printers normally go through a zeroing or "homing" process for all three axes at the beginning of each print; that's built into the G-code created by the slicing routines used with the printers.
If you find that the Y axis (or X axis) moves easily when you are removing a print, that means the printer control firmware has turned off current to the motor that drives that axis. In that case, the printer is absolutely dependent on the normal "homing" maneuver before starting the next print, which is perfectly normal behavior.
Re: Calibration Questions
for further information, the Z motors are powered at all times when the i3 is operational, to prevent the X axis drooping to one side or the other...
if this does get disturbed when power is off,
You can easily move the Z axis by pressing the lcd control for three seconds, whilst the printer is powered but idle, and the XZ level adjustment screen becomes visible... rotate the knob to drive the X axis up to the top where one side will stall until the other side reaches the Z axis endstop on the other side.
you can access the Z height adjustment in the same way, after doing first layer adjustment, to make filament removal easier.
to my understanding XYZ calibration is only needed after assembly to prove that the frame is as 'square' as possible
it shouldn't need doing again unless the printer is handled roughly.
similarly Z axis calibration is to confirm full movement is available after building
Live Z adjustment should be don after initial build, or whenever a nozzle is changed, or if bed adhesion reduces and cleaning with detergent and water, IPA and acetone fail to restore adhesion... {nozzles do wear!)
the first layer calibration print, is quick, but not very easy to use... try Jeff Jordan's 'Life Adjust My way', the version 6.1 files are at the bottom of the first page
.(note mesh bed levelling does a reasonable job, but sometimes the perimeter of the bed is a bit out of synch with the centre, so there is an LCD menu for Bed level correction, which allows you to adjust the left, right, front and back edges of the heatbed to gain better all over adhesion...)
there is also a PINDA temperature stability option on the LCD menu's to help address sensitivity varience at different bed temperatures hotter bed temps change the pinda sensitivity
auto home and mesh bed levelling are normally part of the pre print G code, to be run on every print
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Calibration Questions
Thanks to both retireeJay and joan.t. Knowing about the automatic homing and the way the motors are positioned helps me a lot.