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  1. #1
    Hi looking for some advice, build a DIY laser cutter, as you now there in no load on the x axis, so they swing fast,

    Using 10mm belt 20tooth pulley nema 23 189nm wired parallel giving 4.2 amps, now I've seen some lasers running 500mm second and looks very fast, mine can 800mm second but does not look fast,

    Now I can only set steps to 3200 any lower stalls and can only move at about 4mm second, so would changing the motor to smaller nema23 say 2amps 4 wire be better, or should I wire these in series, I used these as they where for a cnc but never used them so were spares,

    Thanks for any help guys. Kev

  2. #2
    Why did you open a second thread with the same question?

    If you want to get some feedback here, try to write/explain better and more detailed what you have.

    What means 189nm? nm is the symbol for nanometre. You wanted to say Nm? Then I doubt there are 189...
    What steps have you set to 3200? Are you talking about microstepping? Are you setting them in a drive unit? Has this drive unit a name/model number?
    Your 800 mm/sec does not look fast... What software are you using? have you set the unit correctly? What is your acceleration?

    You are asking about changing the motor but you did not tell us what drives you have (current and voltage ratings) and what is your supply voltage. Stepper torque at high rpm highly depends on the voltage and drive quality.

  3. #3
    Quote Originally Posted by paulus.v View Post
    Why did you open a second thread with the same question?

    If you want to get some feedback here, try to write/explain better and more detailed what you have.

    What means 189nm? nm is the symbol for nanometre. You wanted to say Nm? Then I doubt there are 189...
    What steps have you set to 3200? Are you talking about microstepping? Are you setting them in a drive unit? Has this drive unit a name/model number?
    Your 800 mm/sec does not look fast... What software are you using? have you set the unit correctly? What is your acceleration?

    You are asking about changing the motor but you did not tell us what drives you have (current and voltage ratings) and what is your supply voltage. Stepper torque at high rpm highly depends on the voltage and drive quality.
    Thanks for reply, sorry about 2 threads was not sure if first was sent,

    Motor 2amp series 4amp parallel 1.89Nm holding torque,
    Driver. M542t. 24 to 50vdc 1.5amp to 4.5amp
    Awc608 control with laser cad software
    36 Volt switching power supply running drivers,
    24 Volt switching power supply running Awc608
    3200 is micro stepping

    First this software as calibration like mach3, cut square 100mmx100mm till your steps are right,
    Cuts ok 4mm ply as 10mms is needed, but engraving uses faster speeds, and I notice 20 minute job is about 50 minutes

    Thanks again for reply kev

  4. #4
    What is the output power of your 36V PSU? How many motors and how long are they? Do you know their voltage and inductance?

    I doubt that the steppers are the problem.
    You have a 20 tooth pulley with 10 mm pitch? This means you are moving 200 mm with one motor rotation. At 800 mm/sec your motor has 240 RPM which isn't that high.

    At high speeds acceleration is important. Unless you are cutting very large parts, you will hardly get to your max speed. Better the acceleration, quicker you'll finish the job with the same feedrate.

  5. #5
    Quote Originally Posted by paulus.v View Post
    What is the output power of your 36V PSU? How many motors and how long are they? Do you know their voltage and inductance?

    I doubt that the steppers are the problem.
    You have a 20 tooth pulley with 10 mm pitch? This means you are moving 200 mm with one motor rotation. At 800 mm/sec your motor has 240 RPM which isn't that high.

    At high speeds acceleration is important. Unless you are cutting very large parts, you will hardly get to your max speed. Better the acceleration, quicker you'll finish the job with the same feedrate.
    thanks for replying again, thought I put belt size, 10mm wide t5 belt so 5mm pitch

    psu 36 volt, 300w, 9.5 amps
    3 motors, only 2 for x and y axis, 3rd runs table up and down, Size 76mmx56mm


    General specifications motors

    Step Angle 1.8 Rated Voltage (V) 2.6
    Temperature Rise (℃) 80 Max (Max 2 phase on) Rated Current in Sereis (A) 2.0
    Ambient Temperature -20~+50 Rated Current in Parallel (A) 4.0
    Number of Phase 4 Resistance Per Phase in Series(+/- 10%) 2.2 (Ohm)
    Insulation Resistance (MΩ) 100 Min (500VDC) Resistance Per Phase in parallel(+/- 10%) 0.55 (Ohm)
    Insulation Class Class B Inductance Per Phase in Series (+/- 20% mH) 7.16
    Max.radial force (N) 28 (20mm from the flange) Inductance Per Phase in parallel (+/- 20% mH) 1.79
    Max.axial force (N) 10 Unipolar Holding Torque (N.cm) 1.4
    Rotor inertia (gcm2) 480 Bipolar Holding Torque (N.cm) 1.89
    Mass (Kg) 1.0

    hope this helps a little thanks again kev

  6. #6
    Quote Originally Posted by kev20009 View Post
    belt size, 10mm wide t5 belt so 5mm pitch
    That's what I did, but it was wrong.
    I bought T5 belt, tooth width 2.5mm
    I bought T5 pulleys, tooth width 3mm
    I stared at them in disbelief for 30 seconds then gave up an did something else. Couldn't believe it. What a rip.
    If you have better luck let me know so I can resurrect it

  7. #7
    From the HPC gears website...

    Approx. belt flank play backlash are as follows:
    T5 - 0.6mm
    T10 - 1.1mm
    AT5 - 0.2mm
    AT10 - 0.4mm
    AT20 - 0.8mm

    Wonder if I could turn a 5.08mm pitch pulley down a tadge. The 5mm tooth seems a pretty good fit in that.
    24t * .08mm / Pi = 0.61mm off the diameter. Might work. Or am I completely getting the sum wrong?

  8. #8
    You can go with the voltage higher and you will want to do that for better torque at high speeds.
    According to the rated inductance you can go up to 32*sqrt(inductance)=43 volt.
    Or if you take the rated voltage you have a max. of 20*2.6V=52 volt.

    First calc. is more accurate but you have +/-20% inductance accuracy.
    Personally I would try with 45-46 volt, but I don't know how would the drives tolerate that voltage. Maybe there are others here with more experience in these drives.
    Have you tried wirh the drives set to the maximum amps rating? (SW1, SW2 and SW3 off)

    It is possible to be able to improve your speeds in other ways as well. How easy are your axes sliding on their guides? The quality of the belts and pulleys, the weight of the gantry, reducing the inertia of the rotational loads, etc
    Last edited by paulus.v; 29-01-2017 at 09:07 AM.

  9. #9
    Quote Originally Posted by Robin Hewitt View Post
    Wonder if I could turn a 5.08mm pitch pulley down a tadge. The 5mm tooth seems a pretty good fit in that.
    24t * .08mm / Pi = 0.61mm off the diameter. Might work. Or am I completely getting the sum wrong?
    It is not that simple to get the pulley tooth size. You have the pitch line, which corresponds to the belt insertion, where the belt bends. From there you calculate the gap between the teeth to correspond to the belt teeth dimension. The teeth on a smaller diameter pulley are narrower than those on a bigger diameter...

    If you tension enough the belt you'll have no backlash even with a smooth belt. The teeth are there for timing ... at times

  10. #10
    Quote Originally Posted by paulus.v View Post
    You can go with the voltage higher and you will want to do that for better torque at high speeds.
    According to the rated torque you can go up to 32*sqrt(inductance)=43 volt.
    Or if you take the rated voltage you have a max. of 20*2.6V=52 volt.

    First calc. is more accurate but you have +/-20% inductance accuracy.
    Personally I would try with 45-46 volt, but I don't know how would the drives tolerate that voltage. Maybe there are others here with more experience in these drives.
    Have you tried wirh the drives set to the maximum amps rating? (SW1, SW2 and SW3 off)

    It is possible to be able to improve your speeds in other ways as well. How easy are your axes sliding on their guides? The quality of the belts and pulleys, the weight of the gantry, reducing the inertia of the rotational loads, etc
    Paul thanks for that advice, I got a 48 volt switching psu that can be turned down so will give it a go,

    Axis all run on hirwin rails, will add photo today for you to see,
    Thanks again you been big help. Kev

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