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  1. #11
    yes I did have a supply connected but in fact it isn't needed for the controller to communicate (that is USB powered). The external supply is for the isolated I/O.


    It's an Axminster ZX30M Mill
    I need 4 axis:
    X and Y at up to 43kHz to give me 2000mm/min rapids on 16 microsteps
    Z at up to 11kHz
    A doesn't really matter.

    Step, Direction and Enable opto isolation is provided at the stepper drivers. Polarity doesn't matter.

    Inputs should be opto isolated but if needed I can do this external to the controller.
    I already have signal conditioning for all inputs.
    I'd like plenty of inputs:
    4 for combined limit and home
    1 for a Z tool offset
    1 for an X, Y edge finder probe
    1 for Estop

    Outputs don't need to be isolated, as they will be external to controller.
    10v PWM for motor VFD
    1 for mist coolant
    2 for driver enables to allow staggered power up and to allow X,Y release without losing Z.
    (I can easily achieve this external to the controller if needed).

    In short nothing that just about every motion controller doesn't claim to offer. As said above "It doesn't need to be that difficult".

    The problem with good support is it tends to vanish once they have your money. That's why I mostly bought from UK suppliers but in fairness the Chinese made more of an effort to solve the problem than anyone else.

    As for 'Those that know', for every post from someone saying don't touch USB, there are others saying that it works fine. Same is true for every option! They can't all be right.


  2. #12
    Quote Originally Posted by ManicMetal View Post
    As for 'Those that know', for every post from someone saying don't touch USB, there are others saying that it works fine. Same is true for every option! They can't all be right.
    Well it's all about experience really and there lies the problem.? Most only have experience with one product or technology on one machine and if by some chance they don't have an issue they claim it's best thing since sliced bread and everybody should use it.!

    When I tell someone something is good it's because I've tried tested and fitted or used on multiple machines over period of time. Like wise if I call something Bad it's because I've had multiple bad experiences and trust me I've pulled my hair out with USB many times.

    Quote Originally Posted by ManicMetal View Post
    It's an Axminster ZX30M Mill
    I need 4 axis:
    X and Y at up to 43kHz to give me 2000mm/min rapids on 16 microsteps
    Z at up to 11kHz
    Ok well first your wasting your time really with 16ms because most steppers can't resolve to that degree if your chasing resolution, which isn't really resolution in true sense. Only other advantage then becomes slightly smoother running motor but will come at cost of torque.
    Then you have the fact some motors don't like running at those frequencys so could have issues in that department with them not playing nice with drives regards resonance etc. Again depends on quality of drives/motors.

    You'll have more stable machine with x8 ms or x10ms.
    If your wanting smoother running motors then I'd suggest looking at 3 phase steppers as they run much smoother

    I'm assuming that you must 2.5mm pitch screws if you have calculated 43khz.

    Now I'm going to suggest a card that I know will fit your needs perfectly for Mill and it probably has the Best Software in the business which as been developed over 30yrs and runs $$$$$ machines so is very well supported and rock solid.
    However this slightly breaks my rule on recommending because while I do have one of these cards here on test I've not actually fitted any to machines. But I do know plenty about them and have several contacts who like me are very experienced and have fitted to many machines.

    The card is Acorn from Centroid and you'll find it here. Again not cheap but it's the best in it's class when figure in the software/backup.
    http://www.centroidcnc.com/centroid_...ontroller.html
    Last edited by JAZZCNC; 23-02-2018 at 08:46 PM.

  3. #13
    You're right 2.5mm pitch screws.
    I've already had the X and Y drives running (from a signal gen) up to about 60kHz (2800mm/min on 16 ustep) Where the power supplies run out of voltage to drive the 2.8mH inductance. I loaded the bed with my heaviest vice, and angle plate.

    It isn't a matter of resolution 8 ustep would give me 1.5um resolution (way more than the tolerances of the machine) but 16 ustep does give a noticeably smoother motion than 8. There is hardly any reduction in torque (this is more a factor of adequate drive voltage). I've specified 2000mm/min at 16 ustep to stay within reasonable rpm for the motors while keeping to a frequency the motion controller should be capable of, I can always reduce this if needed (commissioning trials will prove the limits and determine the maximum ramp rates).

    I'll take a look at the Acorn system, seems a shame to abandon Mach3 and Mill Wizard, I like their simplicity.
    Last edited by ManicMetal; 23-02-2018 at 09:41 PM.

  4. #14
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 9-10 years. Has a total post count of 2,069. Received thanks 231 times, giving thanks to others 5 times.
    The accuracy gains between 8 and 16 microsteps will be marginal if any. The only time a stepper will produce full torque is when on a full step. In between those full steps, you're relying on two magnetic fields balancing the rotor over the magnetic detent. Stiction, friction, and cutting forces will all have an effect on the exact position the rotor ends up balancing.
    Motor torque is directly related to current, not voltage. The reason voltage comes into the equation, is because as motor speed increases, so does back EMF. The higher the available voltage, the faster the motor can spin before the back EMF becomes too high for the supply voltage to push enough current through the motor windings. Once you reach that point, the current flowing through the windings falls off resulting in reduced torque.


    Quote Originally Posted by ManicMetal View Post

    Step, Direction and Enable opto isolation is provided at the stepper drivers. Polarity doesn't matter.
    Maybe not electrically, but it does for the step/direction timing.


    I use USB on all my machines, but I'm well aware certain installations can be plagued with problems.
    The big problem is most USB motion controllers will cause Mach 3 to lockup if there is any kind of glitch/communication failure with the USB, at which point the only solution is a reboot, as there is no graceful timeout or failure.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  5. #15

    That's spot on m_c. I'm not concerned with the accuracy, it will be plenty good enough and other issues such as backlash, drive belt tooth engagement, quill bearing precision etc will all be significantly greater.

    There is very little, if any, torque reduction from 8 ustep to 16ustep it is just a bit smoother at low speeds. I could go down to 4 ustep, and it's still acceptable, if the operating frequency proves to be a problem. At high speeds the momentum of the rotor and load make the microstepping irrelevant and the driver reverts to full step to get a bit better torque.

    The stepper drivers are current regulated so they deliver what ever voltage is needed to achieve the desired current up to the maximum the power supply can give. The higher the rpm needed from the motor the higher the frequency from the drive and the higher the reactance from the motor stators. Higher reactance then requires a higher voltage to reach the desired current.

    The point about the step/direction/enable signals being opto isolated means I can wire them common anode or common cathode to suit the controller outputs, they will all be the same so no effect on timing.

    USB manages to communicate totally reliably for many other devices, other than poor EMC design, why should a motion controller fail to talk properly on USB?

    What motion controllers have you had least problems from?

  6. #16
    Quote Originally Posted by ManicMetal View Post
    I've already had the X and Y drives running (from a signal gen) up to about 60kHz (2800mm/min on 16 ustep) Where the power supplies run out of voltage to drive the 2.8mH inductance. I loaded the bed with my heaviest vice, and angle plate.

    It isn't a matter of resolution 8 ustep would give me 1.5um resolution (way more than the tolerances of the machine) but 16 ustep does give a noticeably smoother motion than 8.
    Time will tell on this because things change when chips start flying and resonance's start taking affect. Also are you 100% sure the motion is smoother or is it just the change in motor sound that makes you think this.?

    Quote Originally Posted by ManicMetal View Post
    I'll take a look at the Acorn system, seems a shame to abandon Mach3 and Mill Wizard, I like their simplicity.
    Doesn't get any easier than Acorns software and the built in Conversational Cam more than matches Mill wizzard. Another thing I can tell you with 100% certainty is that the motion is much smoother than Mach3. The motion planner is much more advanced and with the Smoothing feature enabled motion is noticably better.

    Only USB device I've had any success with is UC300 and even then didn't fully trust it due to odd unexplained happening on several machines. Gave it benefits of doubt thou because the machines that did occur on used the same Dell Pc's which I've had issues with regards USB.
    To be honest the PC is the biggest issue for USB and even when optimised in windows still get issues. Mostly I think quality of PC plays big part.

    With Ethernet never get any issues of any kind and I've got dozens of customer machines that use them. Some of them in some pretty noisy environments, ie: next to plasma machines. Try that with USB and your doomed.!

    My point being here I'm trying to help pass on my experience and not to slag off USB. If you or others choose to ignore this advice then that's fine by me, it's your money you waste it any way you like.

    The Frequency/Ms setting etc is irrelevant really because so many variables come into play and each motor/drive/controller/machine combo will be affected slightly differently. But my experience is that high Ms just stress's the controller for virtually no gains. What you gain in one area you loose another and to some degree depends on how your using the machine.! . . .Low down you'll see the smoother action but up high the motors/drives feel the pain and become open to resonances.

    However It's just flick of few switches to change so no Big deal provided you've got the frequency to start with and Most External controllers will have more than enough any way so again no Big deal.

  7. #17
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 7 Hours Ago Has been a member for 4-5 years. Has a total post count of 293. Received thanks 33 times, giving thanks to others 10 times.
    MM: I don't have the NVUM, but do have the NVEM (the ethernet variant), and can say that they are largely okay, but come with issues, the first one being that they have a fixed pulse width of 2.25us output to the stepper drivers, from memory (and that ain't great) negatively switched but capable of sourcing or sinking current. The default installation in the manual suggested switching the positive input to the stepper driver and grounding the negative input - with my cheap stepper drivers that lead to the LED in the optocoupler being "On" significantly longer than "Off", coupled with the low performance optocouplers (4n25) and saturation on the phototransistor meant that the stepper drivers were missing steps (scoping input vs output showed a grim transfer function). So, word of warning on the NVUMs (assuming the motion controller is largely the same) - check that you're not in a position described above, changing the arrangement above can help (as can better stepper drivers or replacing optocouplers.... but you're a way from that yet by the sounds of things).

    I've never tried USB on a CNC machine (only PPBoB and Ethernet). I did, however, once have a USB interface to a RepRap 3d printer. That was temperamental (occasional missed instructions which lead to offsets in the print space) and a shared view on the inter web pointed at the reliability of USB. Fortune smiled upon me and I managed to shear off the micro USB socket from the board by tripping over the cable - the easiest fix for me was tacking a bluetooth serial interface directly onto the Melzi board. Strangely, BT was infinitely more reliable than USB in that environment. I think USB and steppers and potentially disimilar grounds don't co-exist well.

    The NVUM ??? plugin buttons - I have those with the NVEM. Not figured out which button does what but again, from memory, there's only a couple of very basic options to play with on the config screen, so long as those "stick" then the two buttons are likely OK and CANCEL - press one and check the config sticks. The ddream driver - sounds about right - and I think indicates this is likely a rip-off controller, but works to a fashion for me on a NVEM.

    Open up the NVUM - you should find the inputs are Optocoupled already so external conditioning is not really needed. Just be aware that the ABS injection moulded case - the receptacle for the screws doesn't butt against the mating face on the other half of the case - so it's easy to overtighten and rip the plastic apart. Tighten to 0 white-knuckles loading.

    What exactly doesn't work for you with the NVUM? I guess you've tried jogging with no joy?, I know with the NVEM driver on first start-up I can find (though never really bottomed it) that I can't jog until I home the machine. Maybe a driver issue, but I usually have a 2 minute tussle persuading the machine to start moving - either a G1 X1 feed through the MDI or a home resolves and I then get distracted and never investigate further.
    Last edited by Doddy; 24-02-2018 at 09:15 AM.

  8. #18
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 15 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,148. Received thanks 202 times, giving thanks to others 5 times.
    Quote Originally Posted by Doddy View Post
    I know with the NVEM driver on first start-up I can find (though never really bottomed it) that I can't jog until I home the machine. Maybe a driver issue, but I usually have a 2 minute tussle persuading the machine to start moving - either a G1 X1 feed through the MDI or a home resolves and I then get distracted and never investigate further.
    Mach3 has the same "feature". A bit of a pain if you've parked the gantry at the far end of the machine at the end of the previous session as homing speed is slower than usual rapid speed. I found that it was because I have soft limits enabled - Mach3 errs on the side of caution and doesn't allow jogging until homed as it can't check soft limits otherwise. Don't know if it's the same on your controller. Just a thought.

  9. #19
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 7 Hours Ago Has been a member for 4-5 years. Has a total post count of 293. Received thanks 33 times, giving thanks to others 10 times.
    Quote Originally Posted by Neale View Post
    Mach3 has the same "feature". A bit of a pain if you've parked the gantry at the far end of the machine at the end of the previous session as homing speed is slower than usual rapid speed. I found that it was because I have soft limits enabled - Mach3 errs on the side of caution and doesn't allow jogging until homed as it can't check soft limits otherwise. Don't know if it's the same on your controller. Just a thought.
    Cheers - you might be right. I'm doing a lot of work on a plugin for my machine at the moment and learning an awful lot of the weirdness of M3 (like default feed rates on initialisation).

  10. #20
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 15 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,148. Received thanks 202 times, giving thanks to others 5 times.
    That one really narks me - first thing after startup these days I overwrite the feed rate to 3000. Initial jogging at 6mm/min is awfully tedious...

    Some time I'm going to be doing a CNC conversion on my own vertical mill, so I'm finding these discussions of various control options very interesting. One thing I know is that it's unlikely to be Mach3! Seems to be some good options available or close to available.

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