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gerrymoore
21-09-2013, 10:58 AM
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!!!!!

JAZZCNC
21-09-2013, 12:06 PM
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.

Jonathan
21-09-2013, 12:07 PM
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.

Jonathan
21-09-2013, 12:17 PM
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...

JAZZCNC
21-09-2013, 12:25 PM
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.!!

gerrymoore
21-09-2013, 12:42 PM
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.

gerrymoore
21-09-2013, 12:48 PM
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?

JAZZCNC
21-09-2013, 12:55 PM
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 (http://www.zappautomation.co.uk/en/power-supplies/440-ps408-5-linear-power-supply.html)

Clive S
21-09-2013, 01:00 PM
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 (http://www.zappautomation.co.uk/en/power-supplies/440-ps408-5-linear-power-supply.html) ..Clive

Jonathan
21-09-2013, 01:01 PM
Lets all link to Zapp ;)

PS408-5 Linear power supply (http://www.zappautomation.co.uk/en/power-supplies/440-ps408-5-linear-power-supply.html)

JAZZCNC
21-09-2013, 01:29 PM
Lets all link to Zapp ;)

PS408-5 Linear power supply (http://www.zappautomation.co.uk/en/power-supplies/440-ps408-5-linear-power-supply.html)

That reminds me.!! .. . Need to throw a thread up for Gary.??

Gary
21-09-2013, 01:30 PM
Lets all link to Zapp ;)

PS408-5 Linear power supply (http://www.zappautomation.co.uk/en/power-supplies/440-ps408-5-linear-power-supply.html)

Thanks Jonathan, much appreciated.

m_c
21-09-2013, 01:45 PM
I did wonder if you'd managed to sort this problem or not.

One thing I never thought about on your last thread, is the shed earth good?
You could have all your grounds connected perfectly, but if the grounds aren't actually connected to anything, then they won't be doing much good. A quick and dirty way to test, is plug an RCD in, and try the test button. If the earth is bad, then it won't trip.
Even if it does test OK, and the shed doesn't have it's own ground rod, I'd still be inclined to add a ground rod.

gerrymoore
21-09-2013, 02:14 PM
Hi again! Yes, my workshop has a dedicated 30amp supply from the house meter with a full consumer unit and trips separate to the house.....just gone out now and tested the RCD and it works fine. Plus I am running the pc and drive electronics from a separate extension cable plugged into a different house ring main. I would be happy to add a ground rod though...anything that might get me up and running again!!

gerrymoore
21-09-2013, 02:50 PM
Here are the pics...they look worse than they are...I have lost my temper with it more than once 10184101851018610187101881018910190lately!!!

m_c
21-09-2013, 03:42 PM
Have you tried an RCD in the shed itself?
The RCD in the house will be connected to the house earth, which the shed will also likely be earthed to, but if there is anything wrong with the earth wire to the shed, then the shed itself may not be earthed. Trying an RCD, or one of those testers with the three neon lights that plugs into a 13A socket, will tell you if the earth is actually good.

Looking at your control box wiring, the main power supply to the drives should not be daisy chained. The diagram on the Gecko site at http://www.geckodrive.com/support/step-motor-basics/power-supply-basics.html shows how they should be connected. If connecting everything to the power supply is not practical, run short wires from the power supply to a star terminal, then run the wires to the drives from there. For the star terminals, a couple suitable mounted/insulated bolts are ideal and just use ring terminals to connect the wires.
Daisy chaining the logic (5V?) supply is probably ok, but I'd personally be inclined to add an electrolytic capacitor over the power terminals of each drive to ensure the drives get as clean a power supply as possible. Do that for both the logic, and the main power supply feeds at each drive.

What actually stops working on the BOBs?
It may give us some idea as to what is causing the problem.

gerrymoore
21-09-2013, 04:17 PM
Hi...there is a 30amp cable running from the house meter to a consumer unit in the shed. This is fitted with a main RCD and separate trip switches for the lights, shed ring main, and separate supply to the plasma cutter. The rcd in the shed works as it should. I am going to fit an earth rod as well.

The power supply to the drives is separated... not daisy chained. Two drives have a 36volt input the other has a 27 volt. I have a separate 5 volt psu... this is daisy chained to the three drives. The last thing I did before the BOB blew was to fit 4700uf caps across the main (not 5v) supply of each driver...I'm not sure if this actually killed the BOB..

I bought a spare BOB which I have just tried (without the plasma cutter) and all the drives are fine so the drivers have not blown. Looking at the new 'broken' BOB ...there is a small hole in one of the two 74HC245 chips ...a 3 state octal transceiver. How this has blown so quickly is probably the answer to my problems!! As I said....whenever I use the machine without the plasma to try out my codes and make sure of my material limits I never have a problem...only when the plasma 'fires up' and then this is intermittent...sometimes it's OK...but not very often!

I had already ordered 3 new drives from China but they wont be here for a week or two....they are HY-DIV268N-5amp microstepping drives.....not sure if any better than the ones I already have though....they are supplied with a breakout board that has a jog control fitted.

I am tempted to order the ZAPP toroidal supply (which has a 5volt tapping) and get shut of my other three psu's and the large filter unit which isn't helping. I've already removed the electrolytic caps in case they were to blame!!

I'm losing faith in ever getting this to work...I even suspect my RTech P40F plasma cutter could be the problem but just cannot afford another model at this moment.

JAZZCNC
21-09-2013, 04:31 PM
Couple of things I see.!!

Dump the daisy chaining it's bad news.

I see several shields going to chocolate block but don't see anything leaving it or going to ground.?

Coming from the torch I see thinner wire that looks like it runs and is taped to the same wire has the limit switch.? If so then try separating has noise could be travelling from torch to switch.!!

If that mass of wires hanging on wall are stepper cables or signal cables then shift them away from those power sockets.

Generally check and tidy up the wiring connections, all those straggler wire ends are potential aerials either fit ferrules or tin the wires. Again Separate the power and signal cables.

gerrymoore
22-09-2013, 09:23 AM
Thanks everyone for all the help....I have taken everyting on board. I have ordered a toroidal psu and will wait until I get my new drivers from China. I am going to rebuild my control box very carefully. I am even looking at a different plasma machine but it does depend on what I can get it for.

It's taken me almost 4 years to get the machine built and then build up paid work for it to do.....so I have to get it running again!!