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Thread: Tell me about drivers and steppers

  1. #13
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    Mad Welder has given some sound advice there.

    When I made the selection of going with the G540, it was for the reasons that Mad Welder described (capacity was well within my goals using 381 oz/in motors), but also the reputation of the G540's being virtually bulletproof/indestructable, and Gecko having top notch support. Plus, for ~$250 for a 4-axis driver w/breakout board, it just seemed like a no-brainer. I bought a power supply that could handle 4 motors simultaneously (48v, 12.5A), so now when I decide to add a 4th axis all I have to do is purchase a motor and I'm done.

    Take your time and do enough research that you feel totally comfortable with your choice before pulling the trigger. Let us know what you decide though!



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    another thing to between the Keling and the G540 is microstepping selection.

    What are your resolution requirements?
    The G540 is locked into 10 microstepping. (this seems to be the most commonly used)
    But the keling drives are adjustable. In the jewelry industry higher resolution is required to be able to fit so much detail in a small area. I have also done this with the G540 and high pitched lead screws.

    I have also needed the higher microstepping in cutting demo parts ffor the micro-fluidics and medical fields. I have seen recessed features so small that they can line up blood cells in single file.

    Now I know that for your mill, this means nothing, but it falls into the question that you asked...... what is the difference.

    Another difference is design. I can configure the keling box (standard BOB and drives) to suit a specific need. You have more inputs and the ability to add more devices to the package where the G540 is what it is but gives you alot of what is popular but there is a trade off. One example is the 3 inputs. For what I do, 4 inputs is great but I can get by with putting home switches in series on a single input.

    The G540 is a GREAT drive and I recommend them all the time. I own both the keling (both the older and the new digitals) and G540 drives.



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    steppers are a specially trained horse.

    High stepping elegant Hackney horses - YouTube

    drivers herd cattle





  4. #16
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    Quote Originally Posted by MrWild View Post
    steppers are a specially trained horse.

    High stepping elegant Hackney horses - YouTube

    drivers herd cattle





  5. #17
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    Quote Originally Posted by Fixittt View Post
    another thing to between the Keling and the G540 is microstepping selection..........But the keling drives are adjustable.........
    Sorry there SwampDonkey I didn't realise that the Gecko was locked into 10 Microstepping cheers Fixittt

    Quote Originally Posted by Fixittt View Post
    .......I have also needed the higher microstepping in cutting demo parts ffor the micro-fluidics and medical fields. I have seen recessed features so small that they can line up blood cells in single file..........
    Mercyful Heavens.....WOW....I had read in the Keling Digital Driver specs for Microstepping upto 25,000 but I never really took in the reason for it….I’d say at times your job gets extremely interesting…..


    Quote Originally Posted by Fixittt View Post
    Now I know that for your mill, this means nothing, but it falls into the question that you asked...... what is the difference........ Another difference is design. I can configure the keling box (standard BOB and drives) to suit a specific need. You have more inputs and the ability to add more devices to the package where the G540 is what it is but gives you alot of what is popular but there is a trade off. One example is the 3 inputs. For what I do, 4 inputs is great but I can get by with putting home switches in series on a single input.

    The G540 is a GREAT drive and I recommend them all the time. I own both the keling (both the older and the new digitals) and G540 drives..
    Thanks for the info Fixittt

    Eoin


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    Quote Originally Posted by Fixittt View Post
    another thing to between the Keling and the G540 is microstepping selection.

    What are your resolution requirements?
    The G540 is locked into 10 microstepping. (this seems to be the most commonly used)
    But the keling drives are adjustable. In the jewelry industry higher resolution is required to be able to fit so much detail in a small area. I have also done this with the G540 and high pitched lead screws.

    I have also needed the higher microstepping in cutting demo parts ffor the micro-fluidics and medical fields. I have seen recessed features so small that they can line up blood cells in single file.

    Now I know that for your mill, this means nothing, but it falls into the question that you asked...... what is the difference.

    Another difference is design. I can configure the keling box (standard BOB and drives) to suit a specific need. You have more inputs and the ability to add more devices to the package where the G540 is what it is but gives you alot of what is popular but there is a trade off. One example is the 3 inputs. For what I do, 4 inputs is great but I can get by with putting home switches in series on a single input.

    The G540 is a GREAT drive and I recommend them all the time. I own both the keling (both the older and the new digitals) and G540 drives.
    Good stuff! Thanks.
    I plan on making miniature internal combustion engines and need fairly tight tolerances. Im guessing the higher the microstep count, the higher the resolution/ accuracy? I'd like to get to .0005 if possible. I will be using 5/8" ballscrews with .2 pitch.



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    "Im guessing the higher the microstep count, the higher the resolution/ accuracy?" - No, that is not correct. Microstepping beyond 10X is of virtually no value. First, no benchtop machine is going to benefit from more than 10X micro-stepping, because it's already far beyond the mechanical resolution of the machine itself. If you're running direct drive steppers with 5-pitch screws, 10X microstepping gives a nominal (NOT actual) step size of 0.0001". Flex and vibration in the machine will FAR exceed that. Second, micro-stepping does not produce equal-sized steps, and the higher the ratio, the greater the % error will be, so microstepping beyond a relatively low ratio does absolutely nothing to increase resolution or accuracy.

    Regards,
    Ray L.



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    Quote Originally Posted by HimyKabibble View Post
    "Im guessing the higher the microstep count, the higher the resolution/ accuracy?" - No, that is not correct. Microstepping beyond 10X is of virtually no value. First, no benchtop machine is going to benefit from more than 10X micro-stepping, because it's already far beyond the mechanical resolution of the machine itself. If you're running direct drive steppers with 5-pitch screws, 10X microstepping gives a nominal (NOT actual) step size of 0.0001". Flex and vibration in the machine will FAR exceed that. Second, micro-stepping does not produce equal-sized steps, and the higher the ratio, the greater the % error will be, so microstepping beyond a relatively low ratio does absolutely nothing to increase resolution or accuracy.

    Regards,
    Ray L.
    Then what is the point of microstepping if it does nothing? Im a bit confused. Are you saying it can potentially increase resolution, but wont due to the limitations of my machine?
    So with my .2 pitch screws, what resolution will 10X microstepping give me?

    Thanks,



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    The primary function of microstepping is to provide smoother motion, NOT to increase resolution. The ultimate resolution, and accuracy, of any CNC machine is FAR more a function of the mechanical characteristics of the machine than it is the drive system. In the real world, it is quire difficult, and VERY expensive, to even get close to +/-0.001" true accuracy and resolution. It is done on large commercial machine by FAR more expensive components, a FAR more massive (stiffer, with better damping) machine structure, and more complex software, which compensates for some of the many remaining sources of error and inaccuracy. Having a drive that is theoretically capable of high resolution will do nothing to improve the overall system accuracy or resolution, unless the many errors contributed by the many other parts of the machine are all already below the error contributed by that drive. On these machines, you typically have ballscrews with an accuracy of perhaps +/-0.003" per foot. Flex of the machine itself can be several thousandths of an inch. Thermal expansion can contribute that much more. You always have stiction, and backlash, which can completely consume small movements. So what does reducing the step size from 0.0001" to 0.00001" actually accomplish? Now, you can try to address all these deficiencies, but a single high-precision ballscrew will cost more than you paid for the whole the machine, and the other parts you'd need to swap out won't be much cheaper.



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    Quote Originally Posted by asifjahmed View Post
    I just did an SX2 conversion (see my photos thread) and used the Keling 381 oz/in NEMA 23s from Keling. They are working out great! I got the package with the G540, but opted for the 48v/12.5A power supply so that I can add a 4th axis in the near future by simply adding another motor (gecko and power supply are already up to the task).

    I also got a smoothstepper board, and am very pleased with it.

    If you have any more specific questions, feel free to ask. I literally JUST got done doing one of these conversions.
    Awesome! So how accurate are your cuts? Did you have to tram and adjust the mill significantly?

    Thanks



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    So far my machine looks to be within +/- .005" for the X/Y axis, and somewhat better than that for the Z axis. However, with the Z axis I experimented with different size balls in the ballnut, and was able to stuff .1257" balls in there, where the X and Y axis have .1250" balls. I have of course placed an order for more .1257" balls for the other axes.

    See my build thread for a ton of pics - http://www.cnczone.com/forums/bencht...uild_lots.html

    As for tramming, I honestly have not even gotten around to doing a full tram yet. I did adjust the column/table tram by placing some shims between the column and base (I have the solid column version of the SX2), and it was then trammed to within a thou. However I have since discovered that there are more adjustments in the head that I should have checked first. I can tell when face milling that my tram is not 100% perfect (seems like 1 of the 2 cutters on my indexable mill wears faster than the other). I will have to take the plunge and tear down the mill and adjust everything. I also want to make some slightly oversized brass gibs to replace the stockers. I am hoping that this will help with repeatability.



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    HK is correct, you have to have a machine that is capable of utilizing the increase in microstepping. 99.9% of desktop and benchtops only benefit from high microstepping to smooth out the motion if need be. My bench top mill on the other hand costs more then my some new cars, so it can utilize the increased microstepping to its advantage. There is a % of loss but its umm.............very small LOLOLOL most wont get that, but its ok.......

    Just for the record, my jewelry mill with THK ballscrews and .9 degree steppers runs at 10 micrstepping with the keling non digital drives.

    My granite based desktop (difference between desktop and bench top is size.... think the size of a X1) its THK everything its tight and solid so it can use it.....




    Quote Originally Posted by HimyKabibble View Post
    The primary function of microstepping is to provide smoother motion, NOT to increase resolution. The ultimate resolution, and accuracy, of any CNC machine is FAR more a function of the mechanical characteristics of the machine than it is the drive system. In the real world, it is quire difficult, and VERY expensive, to even get close to +/-0.001" true accuracy and resolution. It is done on large commercial machine by FAR more expensive components, a FAR more massive (stiffer, with better damping) machine structure, and more complex software, which compensates for some of the many remaining sources of error and inaccuracy. Having a drive that is theoretically capable of high resolution will do nothing to improve the overall system accuracy or resolution, unless the many errors contributed by the many other parts of the machine are all already below the error contributed by that drive. On these machines, you typically have ballscrews with an accuracy of perhaps +/-0.003" per foot. Flex of the machine itself can be several thousandths of an inch. Thermal expansion can contribute that much more. You always have stiction, and backlash, which can completely consume small movements. So what does reducing the step size from 0.0001" to 0.00001" actually accomplish? Now, you can try to address all these deficiencies, but a single high-precision ballscrew will cost more than you paid for the whole the machine, and the other parts you'd need to swap out won't be much cheaper.




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