Errors in initial 16 point calibration after power up
 

Errors in initial 16 point calibration after power up  

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willis.mj
(@willis-mj)
Active Member

On power on the printer does not know where it's extruder is. As it tries to calibrate the points run up against the end stop. Not only does this mean the points are in the wrong place but also causes mechanical stress. What is the correct way to start it. I assumed after switching it on it would home itself first before attempting the 16 point calibration, but it doesn't do this.

Posted : 15/07/2020 10:51 pm
gordon.w
(@gordon-w)
Estimable Member

You've posted in the section of the forum for the Mini, I suspect you are referring to the Mk 3, you may get a better response posting in the relevant section of the forum.

Good luck in finding a solution to the problem 😀 

 

Posted : 15/07/2020 11:01 pm
willis.mj
(@willis-mj)
Active Member

@gordon-w

No I am talking about the mini - that's why I posted here. The problem is only in X and Y mainly X axis. It's as if the printer thinks the head is to the left of the bed when it is to the right, where it left it after the last print.

This post was modified 3 weeks ago by willis.mj
Posted : 15/07/2020 11:04 pm
jaydubblazer
(@jaydubblazer)
Eminent Member

If you just assembled it it might be best to contact Prusa support.  You may have assembled it backwards, or wire might be backwards/crossed.  I’ve used their chat service write pretty good success.

JayDub
Weened on MK3's at work, FrakenMini at home....
Posted : 16/07/2020 3:26 am
willis.mj
(@willis-mj)
Active Member

@jaydubblazer

No I don't have any wiring wrong. It prints perfectly. This is apparently an initialisation problem. It happens because the printer does not automatically home correctly on power up and assumes the extruder is somewhere else than where it is, front right, where it left it after presenting the last print. If you do a second print all is fine. This happens only the first time after it is powered up. It mainly crashes the x-axis against the right hand X stop, sometimes Y. not thankfully the Z stop. I will repeat the main points in case I was not clear enough.

  • This appears to be a power on initialisation problem.
  • The x-axis crashes against the stop when performing the bed height calibration
  • The printer is a prusa mini and it is correctly assembled.
  • There are no calibration issues.
  • The axes are properly lubricated.  
  • Homing is correct on following prints without a power cycle.
  • Printing works well on second print attempt.
  • Yes I have done the calibrations and tests.
  • No I am not using the printer in a compromised environment.

The way I get around this is to abort the first print before it starts, but there is still the crash of the X or sometimes Y axis with unpleasent noise. The printer seems to fail to home on power up or on initialising the print. Most printers do this automatically. I am wondering if this is something to do with there being no proper limit switches (i.e. design fault) or some firmware issue (i.e. bug) or is because I am not doing what I am supposed to do.

 

Mike

Posted : 16/07/2020 7:42 am
gordon.w
(@gordon-w)
Estimable Member

@willis-mj

Apologies, your reference to 16 point calibration confused me. As far as I know, the mini only does 9 point (at least that's what mine does).

I'd suggest opening a chat with Prusa support, as they'll be able to help you track down the problem. Given that this doesn't appear to be a common issue it would suggest that either a fault has developed on your printer or that you are "not doing what you are supposed to do".

Posted : 16/07/2020 9:50 am
jaydubblazer
(@jaydubblazer)
Eminent Member

What version of firmware?  There was an earlier version that caused the xy to hit the z axis on occasion.

JayDub
Weened on MK3's at work, FrakenMini at home....
Posted : 16/07/2020 9:53 am
willis.mj
(@willis-mj)
Active Member

I am using the firmware it was supplied with when it arrived in mid June so whatever they were shipping with on 11th June. This is quite late in development so would have thought such issues in early version were ironed out by now. Do we know which version gave that problem and which one works?  I try to avoid firmware upgrades until things settle down so I have not installed any of the recent beta versions. 

Mike

Posted : 16/07/2020 11:26 am
bobcousins
(@bobcousins)
Estimable Member

The Mini firmware has never done a home at startup, it relies on a home command being in the gcode file. An easier way to manually home is select the Auto Home option from the Calibration menu.

I suspect this is another case of homing failure due to the Stallguard settings being too sensitive. Unfortunately the threshold values are hard coded in the firmware.

Posted : 16/07/2020 1:36 pm
crawlerin
(@crawlerin)
Honorable Member
Posted by: @gordon-w

@willis-mj

Apologies, your reference to 16 point calibration confused me. As far as I know, the mini only does 9 point (at least that's what mine does).

MINI has always had 4x4 point calibration. Other i3 printers have 3x3 or 7x7.

@bobcousins

I suspect so, I mentioned the same issue some time ago after upgrading to 4.0.5, and there were few issues for this on GitHub too, for all axes.

Posted : 16/07/2020 2:37 pm
zoltan
(@zoltan)
Member Moderator

.let us do few assumptions . it is not problem mini to remember the last position, unless you don't switch it off. When you do so you switch off also its electronics and motors. So any move o f the head, bed can change the coordinates without mini to know about it. To do homing at each start does not  make sense when not followed by print.

Before discussion with testing guys I had the same idea to home after switchon. But I realised - I can switch on just to unload a filament and should wait for homing?

Of course it makes significant sense when I want to print, so then the to find the home position of all axes  (not only x and y) as a part of MBL is crucial.

.

even an old man can learn new things 🙂
Standard I3 mk3s, FW 3.9.0, no closed box, sketchup , fusion 360, PrusaSlicer, Windows 10
PRUSA MINI FW 4.1.0, technical background...
Posted : 17/07/2020 8:48 pm
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