Confused as heck about microstepping configuration



  • So.. I'm a newbie to a lot of this jargon. I've tried to read through as much as I can on the forum and RepRapWiki, etc to figure out what I 'really' should have configured in my DuetWifi - but I'm just not sure. The threads have been great - I'm just not sure I understand it all.

    So.. I have a CORE XY printer I've built (D-Bot) .. which seems to be working pretty good - but I'm really wanted to fine tune the accuracy/speed, etc.
    Chimera w/2 Titan Extruders

    I'm running Nema 17s for the XY and 2 Z motors (https://goo.gl/djfM2Q)
    1.8 deg steps / 1.5A current
    using 20 tooth pully on XY
    driving direct on Z motors

    Nema 17 pancake (2) for 2 - Titan Extruders (https://goo.gl/RmaKOs)
    1.8 deg step / 1.0 A current

    I can push the speed faster .. 60mm to 90mm, but it seems the extruders can't keep up - so, I don't know if that's the microstepping, current or just inherent with the motor/titan setup.

    I don't have anything defined for setting microsetting (I don't think) - so I assume it defaults to 16X

    I would like to get good accuracy + good speed (the best combination of both)

    I'm currently running the 1.17.c Firmware

    This is the current config for Machine Movement - any help to improve/fix would ge greatly appreciated!

    ; ************* Machine Movement configuration  *****************
    ;M569 P0 S0 ; Drive 0 goes forwards (change to S0 to reverse it) //X or Y
    M569 P0 S0
    M569 P1 S1 ; Drive 1 goes forwards //X or Y
    M569 P2 S0 ; Drive 2 goes forwards //Z Motor
    M569 P3 S1 ; Drive 3 goes forwards
    M569 P4 S1 ; Drive 4 goes forwards
    ; If you use an endstop switch for Z homing, change Z0 to Z1 in the following line, and see also M558 command later in this file
    ;M574 X1 Y1 Z1 S0 ; set endstop configuration
    M574 X1 Y2 Z1 S0
    ;M574 X2 Y1 Z1 S0
    M667 S1 ; set CoreXY mode
    M92 X100 Y100 Z400 ; Set axis steps/mm
    M906 X1000 Y1000 Z1000 E850:850 ; Set motor currents (mA)
    M201 X2000 Y2000 Z100 E4000 ; Accelerations (mm/s^2)
    M203 X30000 Y30000 Z500 E1500 ; Maximum speeds (mm/min)
    M566 X600 Y600 Z24 E300 ; Maximum jerk speeds mm/minute
    M208 X530 Y460 Z430 ; set axis maxima (adjust to suit your machine)
    M208 X0 Y0 Z0 S1 ; set axis minima (adjust to make X=0 and Y=0 the edges of the bed)
    
    

  • administrators

    Is the extruder motor skipping steps when you try to extrude faster? If so, you need either more torque from the extruder motor or a hotter extrusion temperature to make the filament easier to push.

    You are using lightweight low torque Extruder motors (13Ncm) and that may be part of the problem. I use motors with nearly double that torque in my extruders, which have a similar gear ratio. You are running them at their 1A rated current already. However, the rated current is specified with both phases energised, and the current set in firmware is with one phase energised. So if the motors are not already getting hot, you could increase the current by 20%.

    The microstepping setting won't make any significant difference to the ability of the extruder to push the filament.



  • Thank you - that helps with the extruder … I'm using the pancake because of weight - they are on the X axis - but I have some others I can try.
    It's not really 'skipping' .. when I push it faster than 70mms - it just seems like not enough filament is getting pushed through. I do have .6 nozzles - but - if 'Tom' can push enough for Volcano nozzles - I figured I could on a .6

    What about the X, Y, Z microstepping .. are those correct in my config?

    Can I improve those?


  • administrators

    If not enough filament is getting pushed through but the motor is not skipping, does that mean that the extruder is losing its grip on the filament?

    You haven't set the microstepping (M350) in the configuration that you posted, so you will get x16 with interpolation. That works well for most people.



  • X Y And Z Microstepping are fixed by the design of your system however I don't actually see a M92 to set the Extruder Steps/mm. I use one of those Pancake motors on a Titan with no issues.

    Also bare in mind that the Volcano has a much longer heat zone than a std V6 so you will probably need to increase your temps.

    I think I have my Steps/mm for the titan at around 406 but you will have to calibrate yours but that should give you a good starting point.

    HTH

    Doug



  • I do have the extruder steps/mm set lower in my config as:
    M92 E400:400
    However - that was based on a 'cold' calibration - just pushing 100mm of filament before I added the nozzles .. so that really could be off. I'll do another calibration actually pushing hot filament.

    So .. apparently the steps of:
    M92 X100 Y100 Z400 ; Set axis steps/mm
    in my config is ok .. I've just seen so many others with different or fractional steps - so I didn't know if it should be fine tuned to something else.

    Thanks all for your time.


  • administrators

    The fractional steps/mm are mostly needed on machines that use MXL belts instead of GT2 belts.



  • While doing a calibration test - I found that if I tried to push the filament anything over 5mm/s from the Duet Web Interface - it was like the filament just couldn't push through the nozzles.

    The extruder wasn't really skipping - more like the it was pushing hard, but just would grind on the filament.

    Once I turned it down to 5mm/s - it was just fine and I could calibrate. I don't know at what speed between 5mm/s & 10mm/s is the limit but I know 10mm/s didn't work.

    I ended up with:
    M92 E430:412

    Unless there is something else I can do - I suppose my speed is really limited to how fast the nozzles will allow filament through.

    This is on E3D Chimeras with Titan Extruders with ~50mm of bowden tube from the bottom of the extruder to the Chimeras. Both nozzles are .6



  • The 5 (or 10) mm/sec you're referencing is how many millimeters of filament is passing through the hotend per second. 5-10mm/sec is a normal flowrate.

    Print speeds are measured in how fast the hotend passes over the print. That is called feedrate. Since the nozzle is a lot smaller than the filament, the print head moves a lot faster than the filament does. 40-100mm/sec is typical for feedrate.



  • thank you for that clairification.


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