Saving Baby stepping value



  • I would like to request the option to have the baby stepping value saved. Right now it is reset for each print. I'm hoping that an option to have this value saved could be added so that we can enable or disable it in the printer config.g.

    I'm developing a printer that I hope to sell at some point and I want the user to be able to calibrate their z-offset from the printer and not have to edit config files. The printer I'm designing also has swappable hotend cartridges, so the z-offset may need to be adjusted when switching hotends.



  • @jckray That would kind of defeat the point of baby stepping which was introduced (at user request) as a means of making small adjustments to the first layer on a per print basis. That's why it gets reset every print. If the baby stepping value gets saved, then it is no longer a per print feature which is the reason it was introduced in the first place.



  • @deckingman The baby stepping feature could be disabled by default, but it would be nice if we had the option to enable it.

    Live z-adjust on the Prusa's works this way and for certain situations and setups like what I have, it is more desirable.

    I want the users of the printer I am developing to be able to calibrate their z-offset when they receive their printer and then have that value be saved. As I mentioned in my initial post, this printer also has the ability to change out hotends, which may require slight adjustments to the z-offset. It would be nice if when a hotend is changed, the z-offset could be adjusted and then that value would be saved, so the user would not have to use adjust it again until the switched hotends again.

    I know all this can be done through the config files, but that is not very user-friendly for the end user. I would like to have them be able to do all of this from the panel on the printer.

    If baby steeping needs to stay the way it is, maybe the ability to change the z-offset from the panel could be introduced?



  • @jckray That's one for DC42 then - but I know he's busy at the TCT show right now. Duet does have the functionality to do things like heater tuning and have the results saved to a config-overide.g file which kind of emulates writing to EEPROM. I guess doing the same for Z offset ought to be possible but only David could answer that.



  • @deckingman Okay, if you could pass this along to David, I would really appreciate it.

    Thanks for your quick response!



  • @jckray I'm just an end user like yourself so I don't have a direct line to DC42. He's very good at monitoring these forums so I'm sure he'll comment and/or add it to his "todo" list if he thinks it worth while and when he gets time.



  • @deckingman Oh for sure, something about the way you were responding made me think you might work with/for David.

    Yes, he has been great about responding to my post in the past!



  • @jckray said in Saving Baby stepping value:

    @deckingman Oh for sure, something about the way you were responding made me think you might work with/for David.

    Yes, he has been great about responding to my post in the past!

    I'm just an early adopter who had one of the first boards and who has been keeping the firmware up to date ever since. So I know the history of the firmware and the reasons why things were added or changed but that's all. Apologies if my post made you think otherwise.



  • @deckingman No worries! I appreciate your input/willingness to help.



  • @jckray Actually, something like what you are asking may already exist with mesh bed compensation. I don't use it myself so can't say for sure.



  • @deckingman Mesh compensation saves the topography of the bed and adjusts for it to keep z=0 consistent across the bed surface. Baby stepping is just another offset applied in addition.

    I think the best way to achieve what you're after might be a macro that could automate measuring the Z probe offset with G30 S-1 after a nozzle change and saving it to the config-override.g. I believe M500 already saves changes to G31 probe offset values. https://duet3d.dozuki.com/Wiki/GCode#Section_M500_Store_parameters

    So it may already be possible, though I don't normally use M500, so I'm not really sure.

    The bonus for this is that Z=0 is still Z=0 and any baby stepping applied after is still applied to that absolute value, which is more consistent. If you were to use baby stepping to set your new Z=0 it would actually be Z=0.2 or whatever for the nozzle to be touching the bed, which could be a bit confusing I think.

    Also, i'm not sure how relying on baby stepping would affect other processes like generating a new mesh grid. The real solution is to use G31 to set the real nozzle offset. Baby stepping is intended to be a minor temporary adjustment, using it as a cludge to set the Z offset permanently is just asking for unintended consequences down the road.


  • administrators

    @phaedrux said in Saving Baby stepping value:

    I believe M500 already saves changes to G31 probe offset values.

    In later firmware versions the G31 parameters are not written to config-override.g unless you use M500 P31 instead of just M500.



  • Is there a way for the user the set the z offset from the panel? If not would it be possible to add such a feature in the future?



  • @phaedrux said in Saving Baby stepping value:

    G30 S-1

    So I got around to taking a closer look at this, from what I can tell this would work if the z probe was attached to the removable cartridges and was a fixed distance from the tip of the nozzle.

    However, the z probe is attached to the tool head gantry and the tool cartridges mount to this gantry. I want to be able to have the user change the z value in the following line from the panel.

    G31 P500 X-25 Y25 Z.9

    Basically, I want the "live Z-adjust" feature from the Prusa mk2/mk3. This way the user can print a calibration file and adjust the z-offset until a desirable first layer is reached. This z-offset would then be saved until the user changed again. The distance between the nozzle and the z probe trigger height will likely change by 25-200um between tool cartridges.

    I hope I am explaining what I mean in a clear enough way. I attached a couple pictures of my set up to hopefully make what I'm trying to do more clear.

    ![alt text](2_1539468040878_IMG_0223.jpg 1_1539468040878_IMG_0222.jpg 0_1539468040878_IMG_0221.jpg image url)



  • @jckray Perhaps M500 could be modified to save the M290 babystepping value to config-override.g so it could be automatically applied at startup.

    Then you could just have a test print macro with an M291 S3 at the end asking if you'd like to save the current Z offset permanently.



  • @phaedrux yes something along those lines is what I'm looking for


  • administrators

    Suppose I add an option on the M290 command to shift the current babystep offset into the G31 Z parameter, clear babystepping and adjust the Z=0 position to compensate? Then you could set up a macro to run that command and then send M501 P31 to write the new G31 command to config-override.g.


 

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