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  1. I am having all sorts of trouble with my plasma cnc electronics. I am using 3 x SD2H044MA 4.2 amp drivers and have two psu's one 27volt 13amp and 1 36 volt 10amp....Nema23's that run cold and very well - when the drivers are working!

    Loads of problems with one or another axis 'freezing' when the plasma fires...sometimes it can cut 20 holes without problem others just one stops an axis with the red fault light showing. Tried everything regarding caps, earths, filters...you name it.

    Last week it fried the BOB so I bought a new different type. Fitted it yesterday and the first plasma cut fried the new BOB.

    I need to get it working as I have work coming in (at last)...so thinking of getting the Gecko 540 4 axis (only really need 3) drive from the USA. Costs less than 200 delivered.

    Don't want to waste more time and money...anyone used these or can recommend anything better??

    Grateful for any help on this as I am tearing my hair out!!!!!

  2. #2
    I've used G540 and they are ok and very neat thing's but If your frying BOB's then something fundamentally wrong in the control box or machine wiring and changing to better drives won't stop anything. Plus Gecko's are not the strongest drives and you will fry them easy enough. I've killed x2 of the supposedly UN-killable 203V's and that was in normal router use not wiring error, the Only plus here is they do a good replacement warranty.

    I wouldn't be connecting anything until you have gone thru the control box and machine wiring. All grounds back to same point (Star grounding) and all signal cables using shielded cables and shielded at one end only. Rout all cables carrying power in different trunking to signal and keep separate has much possible.

    Your problem sounds more to do with signal interruption and noise/EMF than dodgy drives so I'd concentrate on improving this area.

    Think about changing the PSU's to a single toroidal supply because the capacitors handle back EMF better, this would be my first component change if I couldn't find any wiring faults.
    I'm no electrickery expert but have experience of similiar things and it could be high EMF getting introduced on the drive power line and because your using linear psu's they protect them selfs from returning currant. The drives will try to pass any extra currant back but if can't go anywhere they will protect them self and fault. (Or blow up if too high)
    The caps in toroidal supply will absorb any EMF, either created by the motor/drives them self or outside influences, so they are much preferred for steppers anyway. . . . Also Very easy to build your own and if you want to go that route then PM me and I'll tell you whats needed or browse the forum there's plenty of debate to how it's done.!

    If you really want change drives then I'd recommend going Digital and the AM882's are my preferred choice (thou never had them on Plasma yet)

    Hope this helps and you get sorted quick.
    Last edited by JAZZCNC; 21-09-2013 at 11:16 AM.

  3. #3
    It sounds like your problem isn't the stepper drivers, it's getting the signals to the stepper drivers that's the problem.

    Plasma cutters are well known for emitting a lot of emi, so you have to make sure all the signal cables are shielded with the ends properly terminated and earthed...but it sounds like you've already done that?

    Perhaps post some pictures of your control box so we can see what you've got and if there's anything obvious?

    What motors are you using? You might be able to run them all from the 36V PSU.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  4. #4
    Quote Originally Posted by JAZZCNC View Post
    I'm no electrickery expert but have experience of similiar things and it could be high EMF getting introduced on the drive power line and because your using linear psu's they protect them selfs from returning currant. The drives will try to pass any extra currant back but if can't go anywhere they will protect them self and fault. (Or blow up if too high)
    At worst electromagnetic interference is only going to add well under a volt to improperly shielded cables. That's not enough to damage the drivers due to overvoltage, since the voltage they output is substantially greater. Also, the drivers are optically isolated, so no matter what you do to the motor side it's not going to harm the breakout board.

    Having said that, it's a bit strange that a red fault light is showing. Assuming that's on one of the drivers it's most likely caused by a dodgy connection somewhere on the motor. That or it could be that the power supply you're using isn't regulating the output properly, since these drivers do apparently have protection against over and under-voltage. I tend to agree that if you want to start buying things, getting or making a better power supply would be your best bet. But check the wiring first as that's more likely...
    Last edited by Jonathan; 21-09-2013 at 11:18 AM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  5. #5
    Quote Originally Posted by Jonathan View Post
    Having said that, it's a bit strange that a red fault light is showing. Assuming that's on one of the drivers it's most likely caused by a dodgy connection somewhere on the motor.
    Yep it's the Red fault light that makes me think it's power related more than signal error and that's why I said " this would be my first component change if I couldn't find any wiring faults."

    I agree thou it's more likely to be a wiring issue.!!

  6. Thank you both for your replies....I am grateful for any help on this! I do seem to be going backwards!! I started with just the 27volt 13 amp supply..I only run my motors at 2amps...but when my freezing problems started I added the extra supply....made no difference...possibly worse??

    My machine has worked quite well for a long while with just the odd axis freeze but of late it has become almost unusable. I added a massive mains filter unit...didn't help. Rewired everything with new shielded cables and earthed one end...no good. Put the whole caboodle in a pc tower case with a cooling fan...not that anything was getting hot! I've had the plasma cutter checked out and also use a different torch...this has given me much better quality cuts...when the mchine actually works! Re routed the plasma supply cables up and over the machine well away from the steppers.

    I can run it forever without a problem until I start the plasma so don't think I have a wiring problem...then, with the plasma it's just pot luck how long before a freeze. Sometimes I can cut out a whole profile without a hitch, then it will start freezing on nearly every plasma fire up.

    I run the PC through a UPS via a separate mains supply to the plasma....the wife isn't too happy that we have an extension cable across the lawn to the shed!

    I did try earthing the plasma unit to the CNC table but that seemed to make things worse rather than better......

    The BOB problem started last week...the plasma 'stuttered' badly as it re-fired over a precut 'hole' ...the axis froze and I reset everything but the three axis would only go in one direction...using the Mach3 jog control forward or back they went the same way. Bought a new, different make, BOB and fitted it. Everything was working fine again until I started the plasma....first fire up the Y axis has gone completely and I suspect the driver unit has been damaged...the Z axis was OK but the X is only going one way again. I tried the X and Y on the Z BOB output.....the X was OK but the Y doesn't move at all.

    It's driving me potty!! I was a TV engineer so I do understand electronics but as I said, everything new I do seems to make matters worse rather than better.

    I would be happy to go to a toroidal PSU (did a quick EBAY search but couldn't see anything ready made) and even pay out for new digital drivers...if I thought it might cure my problems. BTW, when you say 'control box' what do you mean....the tower case I have with my drives, psu and BOB in I presume...if so yes I can post a photo.

  7. Just a quick one as just seen your other responses. The red light fault can be on any oif the three drives so can't be a wiring problem....sometimes both the red and the green lights go out..so that does point to the psu's?

  8. #8
    Quote Originally Posted by gerrymoore View Post
    I would be happy to go to a toroidal PSU (did a quick EBAY search but couldn't see anything ready made) and even pay out for new digital drivers...if I thought it might cure my problems. BTW, when you say 'control box' what do you mean....the tower case I have with my drives, psu and BOB in I presume...if so yes I can post a photo.
    Yes inside the box and if possible around the machine were wiring routes.

    Gary at Zapp sells ready made toroidal supply. PS408-5 Linear power supply

  9. #9
    Quote :I would be happy to go to a toroidal PSU
    This sort of thing but it does depend on the motor and drives used.
    PS408-5 Linear power supply ..Clive

  10. #10
    Lets all link to Zapp ;)

    PS408-5 Linear power supply
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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