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Stepper motors dampening ?

Discussion in 'Off Topic' started by tonycstech, Feb 14, 2014.

  1. tonycstech

    tonycstech Active Member

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    I look at the code and i find (at the current state of 3d printing code execution behavior) that:
    For example:
    G1 X100.00 Y100.00 E1.00
    Move in X Y and extrude some material.
    So.....
    What i see is nozzle moves from point A to point B at a constant speed.

    Problem:
    Its all good and dandy for as long as your printer parts can take a beating traveling too fast. Printing fast will wear your bearings down quickly as well as shaking the crap out of your printer while doing so.

    I thought that MAYBE the "G1 X100.00 Y100.00 E2.00" could be cut in 3 or more lines to gradually slow it down or speed up.


    For example:
    Instead of "G1 X100.00 Y100.00 E2.00"
    i would get
    Code:
    M220 S20 ;Slow down to 20% speed
    G1 X10.00 Y10.00 E0.10
    M220 S100 ;Speed up to 100% speed
    G1 X80.00 Y80.00 E0.80
    M220 S20 ;Slow down to 20% speed
    G1 X10.00 Y10.00 E0.10
    M220 S100 ;Speed up back to 100% speed for next move 
    Doing this, i slow down the nozzle move as well as extrusion down to 20% at its take off and at its landing. Middle is printed at normal speed.
    This is a loss of 20% print time, but it will dampen the motion so its not as hard going back and forth.

    Does anyone here have some extensive knowledge of G-code who can suggest how would i go about breaking 1 move into 3 or more parts to create dampening effect ?

    The way G-code is executed (as a script one line at the time) it is not possible without breaking the each move into parts. Or am i totally wrong ?

    Can reprap 1.4 read multiple lines at once or not ? Because if it can, it changes the game but i dont think it can.

    Or maybe all i need is a stepper motors with dampers ?
     
  2. polylac

    polylac New Member

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    i thought there's an acceleration setting?
     
  3. sjreggel

    sjreggel New Member

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    I was also thinking about this, Slic3R 1.0.0RC2 has in the speed tab acceleration control (advanced), i don't know if it generates the exact code that you want, but i guess it should. I am though curious what the acceleration limits of the robo3d printer are, and if this (i.e. good/correct acceleration settings) lead to better prints.
     
  4. tonycstech

    tonycstech Active Member

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    My LCD does show those settings. I dont know if thats what it is but i am more then willing to mess with them if someone give me more info on what they do.
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I tweaked mine to 900 across the board. Seemed to help somewhat. If you went too slow it would just suck, but not be fatal :) You could easily bump it back up.
     
  6. tonycstech

    tonycstech Active Member

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    Tweaked where, in slic3r or the firmware ?
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    In Slic3r settings
     
  8. tonycstech

    tonycstech Active Member

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    Sucks CURA does not have those settings.
    What about changing them in firmware ?
    I assume it wont be the same.

    Does anybody know exactly how does acceleration settings in slicer work and those that changed in slic3r ?
    What about jerk settings ?
     
  9. tonycstech

    tonycstech Active Member

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    Ok here is what i found.
    Changing Acceleration using LCD is not good idea, because once REPETIER or CURA is connected to the printer, all changes are reset back to default.
    So in CURA in the start code section i added M201 X500 Y500
    I noticed that motors are gradually speeding up and slowing down. This create a time increase but hardly noticeable.

    To compare 10x10x10 cube with M201 X500 Y500 its done in 3:14 minutes
    with default X3000 Y3000 its done in 2:31 minutes but its much louder and breaking your bearings due to harder impact on reverse direction.
    2:50 minutes at M201 X1000 Y1000

    Few other problems also went away as i used the M201 X500 Y500 command.
    Blubs on corners and slightly warped corners of first few layers.
     
  10. SteveC

    SteveC Well-Known Member

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    I tried the M201 X500 Y500 command in the Slic3r start code and it is worth the increase in print time. It's worth it because my wife says the printer sounds much nicer.
     
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  11. tonycstech

    tonycstech Active Member

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    Hey happy wife happy life ha ? :)

    Another thing i noticed is:
    If you have LCD, there are options in the motion control for acceleration and jerk.
    1st 2 effect both X and Y so i tried to tweak it as it prints.

    You better increase your XY jerk too, by about 2 times, or you will start to get this:
    DSC06535.JPG


    At this point i struggle to eliminate bulging at where next layer starts as show below:
    DSC06537.JPG
    This is the point where each layer ends/sizes/starts a new one.
    If i set it to random start, this problem will be allover the print and not just one point.
     
  12. SteveC

    SteveC Well-Known Member

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    I have a bit of the layer start bulge. I was going to mess with retraction I have it set to 1.5mm now and maybe that is too small. It may be very filament dependent.

    The XY Jerk default is 20 I think. So you set it to 40? This blog post (July 12th 2012) http://blog.lincomatic.com/?p=773 discusses Jerk and suggest that a lower value should stop the "ringing" between two segments. He uses a value of 15. Perhaps if the value is too low you get different effect.
     
  13. tonycstech

    tonycstech Active Member

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    Lowering your jerk will effect your acceleration and vice-verse.
    Jerk is a strange parameter that can be observed by printing a cylinder.
    Try printing a hollow small cylinder about 20mm accross with 16 sides.
    If your jerk is low (1-5), you will hear your printer almost stopping at the end of each side while printing no matter what acceleration you have.
    If your jerk is high (10-20) you will see that head moves very smooth laying nice wall.

    None of these 2 changes will bulging of filament that i observed in my second picture above.

    Another thing to keep in mind that if u mess with accell and jerk, u have to mess with extruder acceleration as well, or you will end up having too much filament at each turn of fill, extruder need to be slowed down about same as XY do. I changed my extruder jerk to 20, seem to work fine so far.

    Will do few small test prints and post my final results.
     
  14. tonycstech

    tonycstech Active Member

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    Ok here is what i learned after testing to print cylinders and cubes hollow and filled.
    I ended up being happy with XY Acceleration at 500 and default XY jerk at 20. I needed to lower extruder jerk down to 1 to make it quiet as well when it retracts.

    All those factors slowed the print speed but made me happier. I can now sleep in the room with printer running.

    None of LCD available controls had any effect on corner bulging or bulging at each layer start point, so i am clueless on how to fix that. Print speeds did not effect that as well, nor temperatures.

    Does anybody else have 1 corner having extra filament or am i the only one here ?
     

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