Problem with "Park Location"

[ThePoll100]

Hello, 

my machine works fine but I have one question. 

I have set a parking point after finishing work and the machine parks in this place. Unfortunately, the nozzle tips do not line up with the zero point. Is there a setting for this that I can't find? 

 What I mean is: I'm calibrating the nozzle and marking the zero point for the rotation of the nozzles. I start one job and finish it and the machine goes home but the nozzles are not at the 0 point of rotation. When I then click the "home" button, the machine sets these positions as 0 and is ready for a new job, which in turn gives the wrong rotation of the nozzle tips. 

 The only way is to manually click in the "park" program for each nozzle. 

 Regards.

Paweł M.

[mark maker]

As you can see on the Head, the park location only defines X and Y. 

It does not set the C rotation, nor does it set Z (except for going to Safe Z, but if your Safe Z zone has headroom, it might be above minimum Safe Z and stay there).

Note, this is "natural" in itself, as the head might have multiple nozzles (and actuators) attached, and each might have C and Z axes with potentially different potential "park" coordinates, which in turn could be constrained due to shared transformed Z axes, or restricted angular articulation.

https://github.com/openpnp/openpnp/wiki/Transformed-Axes

https://github.com/openpnp/openpnp/wiki/Nozzle-Rotation-Mode

As a consequence, it is not that easy to define a universal "park location" 😉

The Park Location also has nothing to do with the homing coordinate (on the axes!) per se, however that could be a way to define a more elaborate "park" location. I have to think about it.

> When I then click the "home" button, the machine sets these positions as 0 and is ready for a new job, which in turn gives the wrong rotation of the nozzle tips.

Relax, they do not need to be at 0 to start a new job. Both OpenPnP and the controller still keep track of the axis positions. But I guess you already know that.

Can you explain why you really need this? I hope this is not just a craving for excessive orderliness 😎

> The only way is to manually click in the "park" program for each nozzle.

If you press the P button in the center of the arrow buttons it will equally just park the X/Y axes. You would have to click on the bottom P for C too.

_Mark

 Regards.

Paweł M.

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[ThePoll100]

OK I understand.

 Then I will ask a different question.  

Do the nozzles reset to zero when you press the Home button?  According to my observations, no.  

 The program itself sets the zero angle after pressing the Home button, regardless of the position of the nozzles (without their rotation).  

This invalidates the nozzle calibration in my opinion. 

If the Home button set the nozzles to the angle consistent with the nozzle calibration then ok. Or after finishing work, parking set the zero angle that was used for nozzle calibration.  

Unless you have to calibrate the nozzle every time you start work, then everything is fine.

It is often the case that the machine ends its work with a nozzle angle of, for example, 90°. Then I click Home and this angle feeds but without rotation and I don't want to re-calibrate the nozzles. I would like the head to park after finishing work and set the angles 0 for both nozzles.

Regards

PM

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[Leoyu]

I think you can add some lines of gcode at the beginning of home command to rotate nozzles when homing machine.

Default> HOME_COMMAND : 

G1 A0 B0; Rotate A B nozzles to 0°

M400;
M114; Reporte position

...

...

Also, you can add the same lines above to the beginning of  Default> DISABLE_COMMAND, so nozzles will back to 0deg first when stopping machine.

At "Park Location", Openpnp know the angle of nozzles, can correctly move on to the next job.

[Leoyu]

Forget to consider that in the initial power-on state, each axis is not homed and the G1 command will be invalid or there is an incorrect extra rotation. I'll test it when I have time.

[mark maker]

> Then I will ask a different question. 

> Do the nozzles reset to zero when you press the Home button?  According to my observations, no. 

> This invalidates the nozzle calibration in my opinion.

As Leoyu already pointed out, the (rotation) axis position is unknown after the power was off or the controller reset, and most machines have no way of mechanically homing the rotation axes. Therefore, yes, nozzle calibration must be considered invalid in homing.

This means that the home command must make sure that the machine is in a known state, even after a power off. Even if there was no power off or controller reset since the last homing, it is prudent to assume everything invalid, as one of the reasons to press the home button could be lost steps or something else invalidating an assumed axis position.

This in turn means, that nozzle calibration should be a part of homing. Therefore, I recommend setting the Automatic Recalibration trigger to  MachineHome:

https://github.com/openpnp/openpnp/wiki/Nozzle-Tip-Calibration-Setup#automatic-recalibration

Note, Issues & Solutions will implicitly set this recalibration trigger, if you let it configure nozzle tip calibration:

https://youtu.be/Pxg6g3KI5_E?t=188

_Mark

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