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  1. #1
    I plugged up my machine for the first time tonight. I'm running:

    4Nm Stepper Motor
    CW8060 6A Driver
    HG07 Breakout Board

    All connected to my PC running Mach3.

    I've just tested it with the Z-Axis motor and it does seem to work, however the motor is way too slow! It is also slower than the units/mm readout. So I assume I need to adjust settings somewhere. I tried 1/8 and 1/10 microstepping, both give a similar result. If I run the auto-tuning routine it gave me 6666.66 steps per unit (mm). However it then limited me on the maximum speed to around 400.

    Has anybody else got the same kit and can you tell me some good default settings?

    Thanks!

  2. #2
    6666.66*400/60=44.4kHz which implies you've set the kernel frequency (goto Config->Ports and pins->Port Setup and Axis Selection) to 45kHz. Exceptionally few parallel ports will manage that, so start with 25kHz.

    There is no need to use the auto-tuning since you know all the parameters - pitch of screw, microstepping setting and pulley raito, if any? Just work it out using the method Sean has suggested:

    Step/mm = 200*10/5=400 using 200 step/rev motor, 1/10 microstepping and 5mm pitch screw. At 25kHz kernel frequency you will be limited to 25000/400*60=3750mm/min which is passable but a bit slow, so you could change to 1/4 microstepping as that gives 200*4/5=160 step/mm and 25000/160*60=9375mm/min.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  3. #3
    Quote Originally Posted by CLaNZeR View Post
    Oh also remember on the CW8060 drivers that ON setting via the micro switch is actually OFF and ON= 0

    Sean.
    Lol, how can I remember what I never knew?

    Actually I had suspected that might be the case given just how many pulses it needed to move the motor. Thanks for confirming it. I'll have another go tomorrow.

    If my parallel port will do 45KHz is this preferable to 25KHz? It did seem to work.

  4. Quote Originally Posted by Tenson View Post
    Lol, how can I remember what I never knew?

    Actually I had suspected that might be the case given just how many pulses it needed to move the motor. Thanks for confirming it. I'll have another go tomorrow.

    If my parallel port will do 45KHz is this preferable to 25KHz? It did seem to work.
    Rule #1.. unless you need it, always go with the lowest usable option... 45kHz might well work, but it'll be more susceptible to noise, Windows glitches and other extraneous things... 25kHz will definitely be more robust. Missing 1 step pulse at 200steps/mm means losing .005mm - not that much but they all add up eventually... better to go with .00625mm resolution (in wood!?) and be safe...

  5. #5
    Quote Originally Posted by irving2008 View Post
    Rule #1.. unless you need it, always go with the lowest usable option... 45kHz might well work, but it'll be more susceptible to noise, Windows glitches and other extraneous things... 25kHz will definitely be more robust.
    Irving your correct about Rule 1# but here's a much better explanation to why from the main man ART Fennerty. It's an exert from a yahoo reply but it's worth the read.

    "
    Here's the deal with kernal speed.

    Lets say you select 25Khz, and then tune your motors. While tuning, you find
    you have the velocity slider up all the way, but would like to go faster than
    you can tune.. you then must select the next higher kernal speed, and retune all
    motors. If while tuning, you find you cannot go fast enough, repeat till the
    kernal speed is such that you CAN select the speed you need.

    The reason is this..

    In 25Khz mode, the computer interrupts every 40us.. in 35Khz, every 28.5us ,
    in 65Khz, every 15us , and for 100khz, every 10us.

    Now, the time-in-int is the amount of time spent servicing that interrupt. One
    of the secrets of the printer port driver, one Ive never discussed , is that
    all drivers in windows are told to do their thing fast, and get out. My driver
    breaks that rule..heck it breaks most rules. :) . SO it takes the time it needs
    to
    do 1 step pulse, read input, set outputs, unset the step pulse, jog if
    necessary, etc.. and then exits to wait for the next interrupt. The time-in-int
    is the time it takes to do all that.

    So lets say your in 25khz, every 40us an interrupt will come along, and your
    machin has a time-in-int of 15, that means your cpu has 40-15=25us to do its
    normal windows activity. Your computer is now 37% a pulse driver, and 63% a
    windows OS..

    Time-in-int doesnt vary from kernal speed to kernal speed, only computer to
    computer. Lets say yours is 11us. ( a bit high ), if your in 65Khz mode, your
    now interrupting every 15us.. , so Windows now has 3us every 15 to do its thing,
    its now a cpu that is 20%windows, and 80% pulse engine.

    The windows component runs Mach3, so you now have 20%Mach3 ( plus windows
    fucntions) , and 80% pulse engine. As the pulse engine % goes higher, the chance
    of lockup goes higher.

    So higher kernal speeds give you higher criticality, which can be defined as
    your sensitivity to random bad events affecting the computer. The lower the
    kernal speed, the higher your immunity. As youve noticed, your 45Khz machine
    doesnt lock up as much as your 65Khz machine. That follows the logic Im
    explaining. (Im almost willing to bet your machine at 25Khz will never lock up ,
    or would be very very rare, (Im assuming this from your statement about the two
    machines correlated to hundreds of very similar conversations over the years
    with lockup victims. Fully 80% of them didnt realize the connection, and tuning
    lower in kernal speed stopped the problem.

    Now sometimes you NEED higher kernal speeds, ( high step count machines
    typically), but fully 90% of people who have set high kernal speeds
    dont really need them, they do so simply as a result of the very human instinct
    to have the highest possible speed selected. ( "Yeah boys, my engine has triple
    hedenstock carbs with dual-hemi semi-octagonal rebuf cyclinder hose accessory
    packs!".. :)

    You may wonder..why the heck dont I tell people this more forcefully, since
    it will stop most lockups. Fact is, higher kernal speeds DO have a smoother
    motion just as a result of granularity, and Ive found the vast majority CAN use
    higher speeds with no problem. ( I am limited here to 65K ), I use 25K though
    for reliability. With over 25 thousand machines out there, the number of
    overall lockups is extremely small, and thats including the tendancy people have
    to select the higher speeds,so as a result, I try to keep my nose out of their
    selections, unless they have trouble.

    The final question you should be thinking about now is.. "Why didnt you ask
    me this when I complained about lockups.. :) ), the answer is that the
    subject comes up so infrequenctly now that even I forgot to ask this basic
    question about the kernal speed. I used to post it periodically on this group,
    but stopped quite a while back. In retirement I guess Im getting forgetful is
    my only excuse. Hopefully, youll find 25K never locks up.. Im suspecting this
    is true in your case. I hope so.

    For those that want maximum reliability, I suggest this, use as low a kernal
    frequency as you can live with. On many machines maximum cutting speed is easily
    achievable in 25Khz, the only sacrifice in using 25Khz is perhaps a slower rapid
    speed. Rapids are nice, but not as nice as perfect stability, so I tend to give
    up some rapids to put their power into stability. Look at kernal speed as a
    trade-off, you can go real fast, or real stable.. (This is only if you have a
    lockup problem, many can have both and use higher kernal speeds. )

    My own suspicion, again based on time and numbers, is that many people would
    have lockups, but most leave the kernal at the install speed of 25Khz.. I rarely
    hear form them. I hear most from 65Khz, and Ive heard quite a bit from 100Khz..
    this is because those that can run 100khz are a rare breed, very fast clean
    machines with extremely stable operating system installs. For 65Khz, you better
    have a nice fast computer. 45Khz isnt bad, lockups on those indicate a computer
    suffering some periodic problem that slows the time-in-int too much..

    None of this incidentally explains a random move. The driver is pretty much
    incapable of it, it canot move unless commanded, and it takes quite a sequence
    normally to command it. Youd have a better chance of winning a lottery than
    getting uncommanded motion.....unexpected..yes. :), that happens to all of us..
    usually at our unknown request, but uncommanded...near impossible in the drivers
    context.

    Let us know how 25Khz works.. do you have to sacrifice much speed ( or any )
    to use it? And what IS your time-in-int number?

    My average time-in-int is 5-7us by the way, which is pretty normal for a 2Ghz
    machines, by dual core is only 3-4us, meaning it will take much higher
    kernal speeds without reaching any high level of criticality. My 1.2Ghz was
    around 15us.. ( pretty bad, but ran fine..)

    Sorry for the ramble, I guess it was time for one anyway, for some reason there
    are some that actually like my rambles. lol

    Thanks,
    Art
    "Gearotic Motion Gear design Software"

  6. #6
    Today I put all the dip switches back-to-front and it goes nice and fast :)

    Another question though - how do I grease a ballnut?! I got mine from LinearMotion on eBay and I don't think they have any grease as it is. I know I need to put some in that nipple, but since grease is not a liquid, how can I get it in there? Do I need some form of syringe? EDIT: Ahh okay I should have searched for ballnut rather than ballscrew lubrication. I see Jonathan and Jazz use oil. Do you think 75W80 gear-box oil is okay?

    Also, my motors get very hot. Does the 'half current SW4' dip switch relate to the automatic reduction of current if the system doesn't do anything for a while? Should I just ignore them getting hot, or what?

    Thank you!
    Last edited by Tenson; 29-09-2012 at 03:50 PM.

  7. Define 'hot'.... sizzling if you put a drop of spit on them or just hot to touch? motors can run at 60 - 80degC if worked hard. Worth enabling the 'reduce current in standby' mode if you can. If they still seem to be too hot maybe you've got the current setting too high... confusing RMS and Peak values maybe?

  8. Quote Originally Posted by JAZZCNC View Post
    Irving your correct about Rule 1# but here's a much better explanation to why from the main man ART Fennerty. It's an exert from a yahoo reply but it's worth the read.

    "
    Here's the deal with kernal speed

    .. lots of words...


    Thanks,
    Art
    "Gearotic Motion Gear design Software"

    Yeah, I recall reading that some time back... its a longer, more detailed, but not necessarily better answer... :) saying the same thing... don't stress stuff unless you really need to...

  9. #9
    Quote Originally Posted by irving2008 View Post
    its a longer, more detailed, but not necessarily better answer... :) saying the same thing... don't stress stuff unless you really need to...
    Not to be pedantic here Irving but YES it is a far better "Explanation" and more accurate Answer because It shows has nothing to do with noise, windows glitch's etc like you suggested. It explains exactly what or why the kernal speed is important and explains the in's n out's of using it higher than 25K rather than just flat don't use it.!

  10. Quote Originally Posted by JAZZCNC View Post
    Not to be pedantic here Irving but YES it is a far better "Explanation" and more accurate Answer because It shows has nothing to do with noise, windows glitch's etc like you suggested. It explains exactly what or why the kernal speed is important and explains the in's n out's of using it higher than 25K rather than just flat don't use it.!
    When you've written a few hi-speed communications device drivers for windows you'll find that Windows (or to be more correct the underlying ancient-ish kernel) is often going off to service interrupts that are random and unexpected and have no purpose or indeed have no damn right to exist at all... call that noise/window's glitches/etc. but its a source of lockups that often have no easy explanation. As Art says, there's little time to play inside the interrupt and he breaks the rules to get things to work... trouble is, you can't be sure his driver is the only one breaking the rules... graphics drivers are pretty bad too sometimes, as are network drivers... and yes, i know ideally you don't want the machine on a network, but you can't do much about graphics drivers. So, I agree, his answer IS more detailed but its only down to certain level of accuracy as was mine... and for most people its moot anyway as they can't do much about it, and I stand by mine... if you don't need to do it, don't, and you gain reliability, and if you do, get a faster box... which is pretty much what Art says... :)

    but lets not argue :)

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