Notifications
Clear all

XYZ Calibration Failing.... im stumped....  

  RSS
Woodrow Collins
(@woodrow-collins)
Active Member
XYZ Calibration Failing.... im stumped....

Hello!

So I purchased a pre-assembled MK3 a while ago and it was printing great.  I decided to purchase a MMU2 kit and though I received the kit some time ago I just now am getting around to installing the thing (life happens).    I have successfully dis-assembled / assembled things according to the instructions and from what I can tell everything appears to be functioning.  I promptly have upgraded the firmware of the printer to the most recent firmware available and when I power the printer on it states the device needs to run through the calibration.  So when I walk through it, the printer seems to locate the first circle on the print bed and is fine but when it moves to the second it throws an error about not finding the location on the bed.

I've double check everything I can think of, all cabling etc.  The only thing I can find that may be an issue is possibly the tension on the belt for the X axis, though having been the same length of belt from before I started the install I doubt it's not cut to the proper length.  Watching the device it circles around the area of the bed containing the circle in the correct position.

 

What really throws me for a loop is if I choose to calibrate just the Z axis, that calibration succeeds.  Im also able to load and feed filament through the MMU2 so im somewhat stumped.  Does anyone have any suggestions on what steps can be taken to get the printer to calibrate the XYZ successfully?

This topic was modified 3 years ago by Woodrow Collins
Posted : 19/08/2019 11:48 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: XYZ Calibration Failing.... im stumped....

x axis far out of tram would cause that

try to use something rigid like a CD case and compare the height of the xaxis on both end to the bed - it should be the same

if the height is different on the 2 sides have a look at the z axis smooth rods and make sure the are both fully seated on both ends.

the z axis top brackets should be at the same height on the frame

 

 

Posted : 20/08/2019 12:46 am
Woodrow Collins
(@woodrow-collins)
Active Member
Topic starter answered:
RE: XYZ Calibration Failing.... im stumped....

Wow... truly amazing.  You were spot on.  For whatever reason the right side smooth rod had lifted maybe 1/8" .  After leveling the x and taking measurements with a tape measure and noticing a slight difference, twisting the rod dropped it back in place and the XYZ calibration steps are now making it further!

Now to see about possibly taking out the slack on the belt..... I don't recall how much slack was there to begin with but just watching the movement seems jagged.

Posted : 20/08/2019 1:25 am
Dave Avery
(@dave-avery)
Honorable Member
RE: XYZ Calibration Failing.... im stumped....

should be no slack but not too much tension - bates specs 8-20 lbs , motors are good for about 17 lbs. all it needs is enough tension that the carriage can't move if the motor pulley is locked in place 

Posted : 20/08/2019 2:26 am
--
 --
(@)
Illustrious Member
RE: XYZ Calibration Failing.... im stumped....

Actually - the LDO motors are closer to a 6 lbf radial limit 1/2" out the shaft.  The Gates GT2 belt is rated 2 lbf to >25 lbf (>100 lbf per inch).  So I use a target of 8 lbf initial, and let the belt stretch out down to 6 lbf.   17 lbf will probably damage the motor bearings. 

Push the axis to an end stop,  6 to 7 ounce lift on the lower mid belt should cause a 15/64" deflection on X, and a 12/64" deflection on Y.

200 grams yields about 6 lbf tension. The relationship is linear.

LDO spec: radial load limits decrease as you get closer to the motor (the loads are unevenly distributed to front bearing)

Gates GT2 Neoprene Belts:

And how you measure a belt tension:

Belt Tension Calculations

 

 

This post was modified 3 years ago by --
Posted : 20/08/2019 2:59 am
Share: