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  1. #11
    Quote Originally Posted by 2e0poz View Post
    Here's the update so far, the config set up as 4.5:1 got me closer. over a distance of 150mm on screen the actual travel was 173.5. I've never set up belts before so what next? play with the ratio or the number of steps per mm? it seems a lot to play with the steps. Im using quality pulleys an belt.
    That's odd ... it implies the ratio is actually 3.8905:1
    You could just enter that ratio and see ... then check it with a DTI to get a more accurate value. There must be more to it though. Are you confident you have the pitch of the screw correct?

  2. #12
    What are you entering as steps per?
    Are you using microstepping ?
    John S -

  3. #13
    Also what pitch are your screws?
    It could be a combination of the microstepping and screw pitch causing it ... if it's just one of those then the factor would most likely be a more round number. The other possibility is the number of steps per rev. you used in the calculation is too low, causing the motor to move further and the step signal to the driver is poor making it 'loose' some of those steps. Pretty unlikely though. Is the distance consistent/repeatable?
    Last edited by Jonathan; 20-07-2011 at 10:13 PM.

  4. #14
    Jonathan,
    It's my take that he's using belt drive, no screws.
    John S -

  5. #15
    I played around with the ratio tonight and set it to 5.35 which brings it almost correct after some trial and error adjustment. I did this by measuring distance travelled etc. There is no screws on this axis just belts, i've set the drives at 16 microsteps (3200). definitely confident that it is not loosing steps as it will always return to point zero every time. Still managed to cut a few sample pieces which turned out rather nice in comparison to my old machine. I will spend some more time tomorrow playing with the ratio. I will rig up the DTI rather than judge by ruler which is what i did tonight. the belt is 5mm pitch, if you look at the pics it shows the end of the X axis. It runs with belt both sides powered by the single stepper (4amp bi parallel). Using PM542's on a Uniport V2 bob, kept to 5mm pitch screws on Y and Z. The Y has 24T pulleys 1:1 config and these axis are absolutely spot on
    If the nagging gets really bad......Get a bigger shed:naughty:

  6. #16
    Quote Originally Posted by John S View Post
    Jonathan,
    It's my take that he's using belt drive, no screws.
    I see, that makes the last picture make more sense. Since it is therefore the belt that is moving, not the pulley/stepper you need to use the circumference of the 24T pulley to work out the steps per unit distance. Since the belt is 5mm pitch, and 24T pulley, one revolution moves the axis 120mm ... so including the reduction that's effectively 26.66..mm pitch.

  7. #17
    Jesus H Christ this is like pulling teeth, we have all the details including what you had for dinner but not what was asked.

    HOW MANY STEPS PER ARE YOU SET TO ?
    John S -

  8. #18
    Quote Originally Posted by Jonathan View Post
    I see, that makes the last picture make more sense. Since it is therefore the belt that is moving, not the pulley/stepper you need to use the circumference of the 24T pulley to work out the steps per unit distance. Since the belt is 5mm pitch, and 24T pulley, one revolution moves the axis 120mm ... so including the reduction that's effectively 26.66..mm pitch.
    Nothing to do with the circumference.
    24 teeth, 5mm pitch 1 rev = 24 x5 = 120mm per rev
    can't be anything else.
    John S -

  9. #19
    200 as per the motor?
    If the nagging gets really bad......Get a bigger shed:naughty:

  10. #20
    [QUOTE=2e0poz;22816]I played around with the ratio tonight and set it to 5.35 which brings it almost correct after some trial and error adjustment.

    4.5*173.5/150=5.20 which is close to 5.35 ... doesn't make sense to me at this time of night though.

    With 3200 steps per rev, and using 26.66mm per revolution as worked out in my last post that's 120 steps per mm.

    Oh just notices, 5.35/4.5 is 1.188 ... i.e. very very close to 1.2, which is the factor the 24T pulley adds in. 1.2*4.5=5.4

    So in conclusion try 5.4 and I bet it will be right...I'm not going to bet much though as it's getting late

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