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  1. 200 steps per revolution will move the axis 10mm if using screw xx20 and if 1:2 as Dean suggested. so for 1mm -20 steps. But as you will use 1/8 microstepping, then 160 steps per mm. So 1/160=0.00625 resolution.
    project 1 , 2, Dust Shoe ...

  2. The Following User Says Thank You to Boyan Silyavski For This Useful Post:


  3. Hello !
    okay that's clear thanks..

  4. #23
    Quote Originally Posted by Boyan Silyavski View Post
    200 steps per revolution will move the axis 10mm if using screw xx20 and if 1:2 as Dean suggested. so for 1mm -20 steps. But as you will use 1/8 microstepping, then 160 steps per mm. So 1/160=0.00625 resolution.
    Boyan is correct that what I suggested gives same 10 movement per rev like 10mm pitch because of the ratio but don't be fooled by the micro step numbers because they are unrealistic in real world use.
    Micro stepping is best thought of as way to increase smoothness not resolution. Yes the resolution is increased to some degree but not anything like the numbers suggested.

    If you take it that Full step 200 is the minimum resolution then it's safer bet. What you actually get will be better but how much does depend on several factors like motor quality etc. If you work on calcualting using half the micro step used this will probably be more realistic figure.

    Now if your going to use 2:1 ratio on the RM1610 ( I didn't realise you was doing this!) then whip won't be problem because the same apply's. Your screw will be spinning at half the speed than if 1:1 which is when whip occurs on 10mm pitch. Down side is that Max speed is halfed and with 10mm pitch this means for materials that require higher feeds you could struggle.

    There are other factors that come into play which will dictate which way is best for you. The relation ship between Motors, drives, psu and Controller will greatly affect the kind of performance you'll get from machine.
    Just saying I'm using 4nm motors (even if low inductance) isn't enough to determine overall performance.

    For instance same 10mm pitch with 4nm High inductance motors with only 45v using Analog drives controlled by the parallel port with 25khz will perform much much slower than same size motors with Low inductance using 65v with Digital drives and Ethernet controller at 125khz. Upto half the speed.!!
    Even if motors are low inductance the remaining factors still play big part in overall performance.

    So this relationship between components affects how you go about it.

    However I can safely tell you that on machine like yours if using 4nm motors with 65v with 80v digital drives and good motion controller, ideally Ethernet based that you will, provided build quality is to decent standard with good alignment of rails ballscrews etc with 2:1 ratio on 10mm pitch achieve 7500mm/min without too much trouble.


    If using 2:1 on 10mm pitch gives what you require in speed terms then I'd go with 16mm.

  5. Quote Originally Posted by JAZZCNC View Post
    Boyan is correct that what I suggested gives same 10 movement per rev like 10mm pitch because of the ratio but don't be fooled by the micro step numbers because they are unrealistic in real world use.
    Micro stepping is best thought of as way to increase smoothness not resolution. Yes the resolution is increased to some degree but not anything like the numbers suggested.

    If you take it that Full step 200 is the minimum resolution then it's safer bet. What you actually get will be better but how much does depend on several factors like motor quality etc. If you work on calcualting using half the micro step used this will probably be more realistic figure.

    Now if your going to use 2:1 ratio on the RM1610 ( I didn't realise you was doing this!) then whip won't be problem because the same apply's. Your screw will be spinning at half the speed than if 1:1 which is when whip occurs on 10mm pitch. Down side is that Max speed is halfed and with 10mm pitch this means for materials that require higher feeds you could struggle.

    There are other factors that come into play which will dictate which way is best for you. The relation ship between Motors, drives, psu and Controller will greatly affect the kind of performance you'll get from machine.
    Just saying I'm using 4nm motors (even if low inductance) isn't enough to determine overall performance.

    For instance same 10mm pitch with 4nm High inductance motors with only 45v using Analog drives controlled by the parallel port with 25khz will perform much much slower than same size motors with Low inductance using 65v with Digital drives and Ethernet controller at 125khz. Upto half the speed.!!
    Even if motors are low inductance the remaining factors still play big part in overall performance.

    So this relationship between components affects how you go about it.

    However I can safely tell you that on machine like yours if using 4nm motors with 65v with 80v digital drives and good motion controller, ideally Ethernet based that you will, provided build quality is to decent standard with good alignment of rails ballscrews etc with 2:1 ratio on 10mm pitch achieve 7500mm/min without too much trouble.


    If using 2:1 on 10mm pitch gives what you require in speed terms then I'd go with 16mm.
    Really thanks for your complete answer !

  6. to resume for everyone from slower to faster if i'm right...
    rm1610 with 2:1 pulley ratio 7.5m/min feedrate
    rm1620 with 2:1 pulley ratio 15m/min feedrate
    rm2020 with 1:1 pulley ratio maybe 30m/min

    for information
    stepper : 4nm cnc4u
    controller : MESA 5i25 + 7i76
    driver : AM882 Leadshine@70V

    and for resolution : 200 steps with 2:1 ratio and 10mm pitch -> 400 steps for 10mm -> 40steps/mm ->25 microns resolution (more with the micro step effect...)
    Last edited by pierantoine; 12-01-2017 at 09:45 PM.

  7. I believe ~10m.min is very good for a DIY machine, not servo driven. i would not trust steppers for faster speeds. Also there is that thing that the machine to benefit from the fastest speeds it must be big. See the formula at the bottom of that page http://www.prusaprinters.org/calculator/

    My machine is servo driven and as snappy as a bullet , acceleration 3000mm/s2 and at >15000mm/min looks bloody dangerous and i am very very careful not to make a mistake. Stepper driven machine i am not sure that could achieve that. Think more 1000mm/s2, if i am wrong sb correct me.

    What i am saying is you need distance to achieve that theoretical speed. Your aim should be to achieve higher acceleration, than speed.

    PS Plus all must be perfectly rigid, especially Z to benefit from that speeds
    Last edited by Boyan Silyavski; 13-01-2017 at 10:52 PM.
    project 1 , 2, Dust Shoe ...

  8. #27
    Quote Originally Posted by Boyan Silyavski View Post
    I believe ~10m.min is very good for a DIY machine, not servo driven. i would not trust steppers for faster speeds. Also there is that thing that the machine to benefit from the fastest speeds it must be big. See the formula at the bottom of that page
    Fact using stepper doesn't mean can't have higher feeds. The feeds depends on pitch. Could have 50,000mtr/min quite easily and still have acceptable acceleration with the right pitch.
    What stepper does restrict is having High Feeds and High Resolution. The price you pay to achieve high speed is Low resolution.

    Also To answer your question if Stepper can achieve 3000mm/s/s and 15,000mm is yes.!! . . . . . . Could it do this and hold the same resolution at your size/weight of machine then No.!! . . . Hence why you wouldn't fit steppers.

    However on smaller machine with lighter gantry then yes it's possible with careful selection of pitch and motors etc.

    Good machine will have nice balance of speed and Acceleration. IME for Medium machine size which this is, 10,000mm/min and 1500mm/s/s is all thats required.
    Last edited by JAZZCNC; 13-01-2017 at 11:57 PM.

  9. Quote Originally Posted by JAZZCNC View Post

    Good machine will have nice balance of speed and Acceleration. IME for Medium machine size which this is, 10,000mm/min and 1500mm/s/s is all thats required.

    I think also that one should be very happy he found this forum and all information here. I will give a reward if sb finds me commercial machine that is not servo driven that could actually achieve that, speaking about cheap Chinese knockoffs and other ebay style machines.


    Actually for intricate carvings on aluminum i lower the acceleration to 1000-1500 for better results. Its difficult to have all in one. Its not a big deal, just change one number in the controller. For wood i could push it even higher than that 3000 but not a real need.
    project 1 , 2, Dust Shoe ...

  10. #29
    Quote Originally Posted by Boyan Silyavski View Post
    I will give a reward if sb finds me commercial machine that is not servo driven that could actually achieve that, speaking about cheap Chinese knockoffs and other ebay style machines.
    Not quite sure what your saying here Boyan.? . . . . Are you trying to say this isn't achievable with steppers.? Because if so then your very wrong.!
    Just about every machine I build will or should say is designed to achieve these speeds or very close to them. Some Smaller machines will achieve well in excess of 10mtr/min and 1500mm/s/s.
    Don't actually run them or tune them at those speeds for reliabilty reasons but they will do it if required.

    I find above 2000/s/s gives negative affect to machine as it's far too jerky on short moves leading to poorer surface finishes.

  11. Quote Originally Posted by Boyan Silyavski View Post
    Your aim should be to achieve higher acceleration, than speed.
    This is the vital fact, I have found the negative side of this equation - low accel/high speed and what it does with Mach3 is give terrible contour following because of the constant velocity engine Mach uses. Its not just a little bad, it's the difference between turning out scrap and turning out parts.

    I have retuned with lower speed as higher acceleration was too jerky on my old Bridgeport conversion and its all working nicely now.

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