"Return to Home" after mid-print material change

[CTotten 18]

I recently had an issue with an X/Y axis shift after changing material on my S5 mid-print.  When the S5 detects the material runs out, it pauses the print and moves the print-head to the center/front position.  It stays here during the material change.  When you resume the print, the print-head goes directly to the X/Y position it left off prior to the pause.  My general practice is that I clean off the print-head prior to each print.  Since adding the S5 (with active material detection) to our line-up, I also cleaned the print-head during the material change process.  My assumption is that I slightly moved the print-head while cleaning of the nozzle. 

 

I recommend that following at material change pause, the "Resume" command starts with a return to the Home position before resuming the print.  This would eliminate any possible error introduced by moving the print-head during a material change.

[fbrc8-erin 296]

The motors should already be locked in place during the change process so the head shouldn't be moving. Is it possible the glass is shifting/being touched when you go to wipe the head?

[CTotten 18]

While I can't rule out that the glass moved, it is highly unlikely.  The glass on my S5 fits very tight (my 3E is another story).  And I don't know if keeping the stepper motors energized really functions as a true lock, or if the steppers really stay energized the entire time after a pause from running out of filament.  Yes, this "return to home" will not correct movement of the plate, but it seems like a logical step to zero out any potentially introduced offset in the print-head following an intrusive procedure like changing filament mid-print.  And it is a 5 second process that can be added into the resume command.

 

Once I finish my production runs mid-week, maybe I will test this again to see if casual contact with the print-head does cause movement in this condition.

[CarloK 204]

We decided against the homing before resuming because the switches do have a small tolerance. The accuracy is good enough for homing but was never intended to be used as an absolute accurate position calibration.

 

A shift problem after a material change during a print is rare. The motors remain engaged to keep the position locked and it requires considerable force to move the head but it is possible. As suggested, another cause for the shift could be a glass plate shift, this can't be detected or fixed.

 

I'll keep an open eye for more problem reports of this type.