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My Robo3D upgrades (Smooth rod bed, z-axis stabilization, direct drive extruder)

Discussion in 'Mods and Upgrades' started by Stargrove1, Nov 1, 2014.

  1. Stargrove1

    Stargrove1 Member

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    You can calculate any step values by this formula:

    e_steps = (steps per rev * microsteps) * (big gear / small gear) / (effective diameter * Pi)

    or simplified for a direct drive extruder without gears:

    e_steps = (steps per rev * microsteps) / (effective diameter * Pi)

    In your case:

    e_steps = (200 * 16) / (10.5 * 3.14) // 10.5 mm from the internet since I don't have one, please double check the value
    e_steps = 97.058

    For details, see http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide#Calculate

    I also had issues with the extrusion, I found that the hotend was the root cause, when I tried to push the filament manually, the resistance was bigger than in the beginning. I exchanged the hotend and the extruder worked properly again.
     
    Galaxius and mark tomlinson like this.
  2. tonycstech

    tonycstech Active Member

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    I am far better to use a hammer then to calculate its trajectory, so thanks for crunching the numbers for me.
    I cleaned and even replaced heat breaker screw and nozzles with no results.
    Filament goes thru by hand same as before but i think my motor doesnt like direct drive setup and is worn out.
    I say this because before i was able to crank it up to 120mm/s or so with very little quality loss and absolutely no filament slip.
    It is lately i started to notice that it gets worse and worse.

    I can practically stop the extruder motor by my finger, i dont think thats normal.
     
    #62 tonycstech, May 24, 2015
    Last edited: May 24, 2015
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

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    Not. normal.
     
  4. tonycstech

    tonycstech Active Member

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    I have an extra motor. Will try to swap and see if it makes any difference.
    I had my motor with one loose wire at times and it would make impact like noise with no movement (slight jerk maybe).
    Perhaps there is internal damage ? Same sound can be reproduced when you simply hold the motor preventing it from spinning.
     
  5. Stargrove1

    Stargrove1 Member

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    Your welcome, you need to calibrate the calculated value by extruding a defined length and comparing it to the actual length.

    This is a good idea to find the main failure of the setup.

    Normally there is no deterioration of a stepper motor like the brushes of a dc motor, the magnet field gets changed around a permanent magnet. Only way would be to overheat, is your motor getting warm during extrusion?

    Another reason for less torque could be the electonics. Your ribbon cable solution looks quite nice, but there is a risk that wires may break inside of the cable which results in a higher resistance of the wires and providing less power to the motor. You may try to attach the motor directly to the RAMPS board and check if it runs normally then.
     
  6. tonycstech

    tonycstech Active Member

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    Ribbon cable is not the issue. It ran fine with it before. The only problem i had was heater lines were not thick enough causing cable to get warm. I ended up (as suggested) running same current thru 2 wires since i had 2 extra on the cable its self anyway and it solved the issue.
    thanks for good suggestions.
     
  7. Stargrove1

    Stargrove1 Member

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    It is possible that it worked well before, but it might have degraded now by bending it over and over again during the last months of use. You could also check that by attaching the extra motor directly to the board and then at the carriage with the ribbon cable.
     
  8. tonycstech

    tonycstech Active Member

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    Found the problem.
    It was the barrel cooling issue caused by my fan mount i designed for reversed version of direct drive.
    I plugged good old E3D shroud back on and problem almost went away (but not 100% because i use bad barrel with PTFE liner inside and it dies not have a heat brake area, its rather solid)

    So i ordered another barrel (cant find any E3D barrels) since i broke my old one messing with it too hard.
     

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