What has gone wrong????

Ok as many of you will know I have been eagerly awaiting the delivery of my new plasma torch, while waiting I have been extensively testing and debugging my new DIY CNC table and it was all going very nicely.

The torch came this morning so I moved the table into my test area, connected up the ground clamp and powered the system up.

All went ok, Mach3 was happy, so I placed a bit of test metal on the table, moved to position for a test fire and triggered a quick pierce signal, no cut just a quick pierce at half power.

That went ok so i went to move the torch back to start position for a cut test, the torch would not move so i pressed the e-stop and restarted, z axis started moving and partial x axis but not Y.

Killed the plasma supply and reloaded Mach.

Now it was jumping about randomly as i turned the MPG knob on the pendant and kept throwing "e-stop requested" errors.

Thinking it might be my cheapo crap pendant, i unplugged it, turned off "run macro-pump" and disabled support for modbus/mpg, I think that was all that is needed to return to normal?

Then i reloaded Mach and tried again, now it sort of moves but the DRO's are moving like 20mm for every physical mm moved, its very jerky too.

Pressing home-all, would bring the axes to home but then back off at 1% speed or very slow at least.

It would also still throw the e-stop requested errors.



Now, having spent a lot of effort hardening the table against RF, I cant believe I have fried it with a two second pierce?http://machsupport.com/forum/Smileys/default/huh.gif

No other PC's in the area showed any sign of problem and there was no radio interference.
This was just a quick pierce at half power.

Any suggestions at all?
I'm desperate.

It sounds like a a bad connection between the PC and your machine so that it's loosing various signals, check the cable and make sure it's secure at both ends.
Maybe you have a bad connection on the emergency stop circuit that is going on and off fast, check all connections but it may be the switch contacts themselves. To confirm this you could link out the E/Stop right at the bob but be careful it could be dangerous.

What you using for the BOB.?
I always turn to the BOB first when having troubles like this has often it's the weakist link in the system due to wrongly thinking it does a simple job so cheap will work.!

Can you try another PC to see if it's frazzled the PP.?

The BOb was one of cnc4you.uk's items.

It has been running fine with a pen in the tool holder for weeks, all I did was move it 10' test it and the fire the torch for two seconds.

i don't see how it can be the bob as that would not affect the dro's which are running way too fast.

the e-stop circuit is relay isolated so the only thing that could be bouncing is the relay and that's doubtful. It's not the same as an e-stop, that just displays emergency stop button pressed I think, this displays emergency stop requested.?

its baffling and if it is related to the torch firing then I am at a loss as to what I can do, I spent a lot of effort rewiring it with cup screened cables, star earthing, ferrite blocks and so on, I was thinking it would be impregnable, don't see what more I can do.

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Originally Posted by JAZZCNC

Can you try another PC to see if it's frazzled the PP.?

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Thats the odd bit, it boots fine, runs fine, loads mach ok, and passes the mach driver test easily still.

i would expect the BSOD or software load errors/graphics corruption.

Check the parallel cable from the PC to the bob, is the inner shieldings fubar, even letting it cross the power cables will do that. Its sounds like your problems are to random for it to be a physical interference problem. but interference on the parallel cable would do all of the above.

you can test this by keeping the cable as far away from the others, but if its the actual connector ends of the cable, it might not show. then place it across some see if its worse.

If not, ( i suspect it is the above ). check the PC to see if anything is on the same IRQ or interrupt as the parallel port.

I say the above from experience.....

Is your electrical system on the end of a long extension ? maybe your earthing arrangements are not adequate.

I will check the cables out in the morning.

as it happens, I am running the PC and bob on a 20' extension, I will check the earth as well on that, the plasma is running on a temporary short extension to a wall mounted isolator that is at 180 deg from the PC supply, the two do not cross.

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Originally Posted by Davek0974

I will check the cables out in the morning.

as it happens, I am running the PC and bob on a 20' extension, I will check the earth as well on that, the plasma is running on a temporary short extension to a wall mounted isolator that is at 180 deg from the PC supply, the two do not cross.

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I'm thinking there could be a voltage difference between both 'grounds' at the ends. In a bathroom for example all metal parts are connected together with a decent size earth wire which is then connected to the earth terminal of a ring main for example, I think you could do the same with your setup where all the earths are connected to a 'star point' on your machine frame. However there is a risk of creating a complex circuit, it would be better if all the equipment could be fed locally from the same supply so that the earth wires between them are very short.

I can arrange that pretty easily, the plasma is running off one leg of a TP&N isolator, I can easily run the controls from the same point, same phase of course.

is the work lead of a plasma connected to supply CPC?

if not then there is no connection between systems so it should have been ok?

edit

just checked and and the ground return clamp is not connected to supply CPC.

It's just a theory and I still suspect the PC to bob cable.

your sort of thinking the wrong way round with this.

You may have a problem with interference from many things in the workshop, and isolating them all would not be possible.

Its the data lines between PC>BOB and sometimes BOB>MOTORS that you need to make sure is insulated from everything else, swap out that parallel for another one.

Its also the only place apart from the BOB, that you can interfare with the motor timings and estops and motor direction at the same time.

Let me add this though, i have never worked with plasma gear so i dont understand what fields that creates, or what extra current/dump loads it uses. So there may be something obvious am missing

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Originally Posted by Davek0974

i don't see how it can be the bob as that would not affect the dro's which are running way too fast.

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Bob's are sneaky bastards they trick you into thinking they are fine so you go round in circles chasing other things but then you end up back at the BOb and soon has you change them out every thing works fine.!!

Also if you have noise it won't affect the software or the DRO's it will only affect I/O's so causing trips or lost signals. When you say DRO's are running fast what exactly do you mean.?
Mach's DRO's only show the pulses sent out the parallel port so could be that they are sending the correct pulses for the speed but motors/drives are not getting them.? This could be BOB or PP and if you say driver test shows it's fine then BOB would be my first port of call. Thou changing the PP cable is always good place to start.

My first cause of action would be going over all the wiring and connections again with a fine tooth comb. Then trying another PC and PP cable if available or very least re-installing Mach and creating a new XML. Then if no differant go straight for the BOB.

If still no differant After that lot then I'd be concerned and scratching my head.!!

Just been messing about again and noticed that there is an LED on the BOB, this is on normally, but after running the axes up and down manually a bit, the LED flashed off then on and Mach threw the "e-stop requested" error, after that the torch relay will not trigger and the axes start messing about.

I really can't believe I've fried a BOB or the PC surely?

If that is the case then there is little hope of success as I have done almost everything I can to shield this stuff, I have not driven a ground rod yet as its in the factory at work and i doubt the landlord would appreciate that :)

I could understand it if I hadn't connected the plasma ground lead or something else stupid but I even checked it with a meter to the work-piece first!

I will need to order a parallel cable as they are not standard ones and have two DB connectors whereas a parallel lead has a centronics on one end, got boxes full of them :(

I will disconnect the motor drives and watch that LED for a test. I'll also ring cnc4you and see exactly what that LED indicates.

I might be able to pinch another PC but even if that works, I wouldn't risk another test without discovering the point of destruction.

Spoke to the BOB suppliers, seems the BOB is fried 100%. (:

They also said it was wired wrongly, I had the BOB supply fed from the Z-axis output of the main PSU, apparently that is bad and must be a separate regulated supply for the BOB only.

Anyone know anything about this?

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Originally Posted by Davek0974

Spoke to the BOB suppliers, seems the BOB is fried 100%. (:

They also said it was wired wrongly, I had the BOB supply fed from the Z-axis output of the main PSU, apparently that is bad and must be a separate regulated supply for the BOB only.

Anyone know anything about this?

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Dave It would be helpful for you to give the model number of the BOB and the type of power supply, Voltage and a wiring diagram of how you have connected it up. Then you might be able to get the correct advise from here. It is difficult for people to have vague information and give proper advise. ..Clive

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Originally Posted by Clive S

Dave It would be helpful for you to give the model number of the BOB and the type of power supply, Voltage and a wiring diagram of how you have connected it up. Then you might be able to get the correct advise from here. It is difficult for people to have vague information and give proper advise. ..Clive

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I can fully understand that, but the diagram is in my head, however its currently like this basically...

1 - I have an 11A smps connected to the three motor drives,

2 - a smaller 24v smps connected to the BOB,

3 - The BOB is a cnc4you.co.uk HG07 unit - Breakout board CNC Stepper Motor 5 Axis Spindle Relay HG08

4 - Another small 24v psu is running the relays for e-stop and limits / torch trigger.

5 - I have used screened cable for all motor leads, this is connected at one end only inside the cabinet to a star ground.

6 - I have connected the Z-axis to the X-axis carriage and then back to the star point.

7 - I have connected the Y-axis gantry to the star point.

8 - The case of the PC is connected to the star point.

9 - All PC leads are fitted with ferrite chokes.

10 - The mains is now filtered at the plug.

11 - The plasma ground lead is clamped to the cutting bed.

12 - The frame of the table (and therefore the cutting bed) is not connected directly to my star point, I am guessing this is catered for by having the cabinet bolted direct?

The whole lot is mounted in a steel cabinet bolted to the machine frame.

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I can fully understand that, but the diagram is in my head, however its currently like this basically...

1 - I have an 11A smps connected to the three motor drives,

2 - a smaller 24v smps connected to the BOB,

3 - The BOB is a cnc4you.co.uk HG07 unit - Breakout board CNC Stepper Motor 5 Axis Spindle Relay HG08

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Ok Dave what is the o/p voltage from the 11A p/s. It states on their data sheet that when using a plasma you have to use a separate p/s for the BOB (that is normal anyway).
re this (They also said it was wired wrongly, I had the BOB supply fed from the Z-axis output of the main PSU) if that is the case what is the purpose of the smaller 24V p/s connect to the BOB

In my humble opinion smps are crap for motors and you would have been better off with a toroidal type none regulated.


Don't get despondent there are enough people on here to help out if you give the information that is required ..Clive

It's a 36v unit.

The leaflet i have with the bob states "you can use your regulated DC motor PSU if not exceeding 55v" no mention of plasma warnings etc so they must have updated the data, this is why i originally had it wired to the motor PSU.

Will look into a linear toroidal type psu.

Dave You also stated that you had a 24V p/s was this connected at the same time if so how? ..Clive

The 36v psu is connected to the motor drive boards, the 24v one is connected to the BOB.

Previously I only had the 36v psu connected to the motor drives AND the BOB.


I have just tested it again with a different 24v PSU connected to the BOB, this one is a PLC supply so pretty good quality.

It worked ok with the torch off, ran a cut program 10 times in succession and all worked ok.

Connected up the plasma and did a quick test pierce and down it goes again, no movement on the motors.

This now confuses me as it seems the BOB is OK still but i have serious issues elsewhere, trouble is i dont where or how to test them????

Following a reboot, normal control is returned.

The PC showed no signs of a crash, no lock-up or BSOD etc.

Not sure which way to go now but clearly i have issues.

Its random, tried a reboot again, this time no control is regained.

As soon as i triggered the torch, the power led on the bob went out, the y-axis jumps 5mm and that's it, no more action.

Its also holding the motors locked despite being told to disable the drives, this point indicates the fried BOB but I cant risk another BOB until I know what went wrong or it can get expensive quickly.

Well the BOB is not fried so that is good news. When you say after a reboot and also say the PC shows no signs of a crash!! Does that mean that Mach3 locked up and could not be reset? It does sound like RF problems though I have never used a plasma before so can't help you there. Some pictures of you setup might help others glean some info.
..Clive

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Originally Posted by Davek0974

8 - The case of the PC is connected to the star point.

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Would take this away as the PC should have it's own path to earth you could be creating a Earth loop here.?

After this I can only suggest you triple check all the wiring and then replace BOB and try again.

One thing you could do is try running the machine then moving the torch away from machine fire it from a distance and see what happens.?

FULL MARKS TO JAZZCNC, read on...

i had a chat with the plasma supplier, told them of my woes and the only suggestion they had was to rive an earth rod, connect the terminal on the cutter to that and then connect the CNC table likewise. Unfortunately I couldn't drill a hole through the factory floor so I just connected the terminal to the table frame.

I tried that and managed three pierce tests this time but then locked up again.

Then I disconnected the earth from star point to PC case and it worked! Passed repeated pierce tests, then I run a simple cut-line test of six 70mm lines at reducing speeds, table was still responding so I ran another test pass followed by a more detailed test and it still responded afterwards!

here's the results...
Attachment 11783
numbers are mm/min at 30A.

i like the result at 4000mm/min, it's very fine and about 0.75mm kerf, this is 1.5mm sheet so very thin.

i gather the point where it closes up at the end is due to deceleration?

anyway, it was getting late so I quickly dialled in 4000mm to my next test in sheetcam and compiled the g-code.

Attachment 11784
It looked ok, showed up some signs of serious axis wobble but ok. However on turning it over it appears not to be cut very well. ...
Attachment 11785
Now, I'm not too worried as I did rush the test and the changes to sheetcam so I may have bodged it up. The main thing for this thread is that it's working and surviving extended cuts.

many thanks to all for the helpful suggestions, but it appears JAZZCNC wins :)

Excellent pleased your working and sure helps when you have more details to work with. If we'd have known this sooner you'd probably have been sorted because it jumped straight out at me.
I'm sure you'll soon have it dialed in to give nice clean cuts. .:applouse: (Oh it's obligatory you cut the Road runner for testing with Mach3 so lets see it. .:hysterical:)

Dave Glad you got it sorted. Just goes to show that you have to give correct info to get good results.:barbershop_quartet_.. Clive

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Originally Posted by Clive S

Dave Glad you got it sorted. Just goes to show that you have to give correct info to get good results.:barbershop_quartet_.. Clive

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Ye does help loads Clive but you know what I find funny.? . . There'll be loads of others with routers who have been getting away with it now going "Oh shite" I better disconnect it on mine. . .:hysterical:

Just goes to show thou how Bad Earthing can send a machine mental and really Dave I think you have been lucky not to fry the PP or PC because effectively running the Earth like that you bypassed some of the Isolation of the BOB.!!

Yes, I was lucky there, not normal for me ;)

hopefully as as it has put up with that abuse, and the fact that I was cutting with the panel door open too, it shows that the rest of my efforts re shielding and grounding were all beneficial and good ones :)

my original plan was to strip the guts out of the PC and fit it all in the cabinet but it was not big enough, that would likely have worked ok too, oh well live and learn;)

thanks again for all the help.

Dave, you have 3 power supplies, the 36 volt and 2x 24volt, are the negatives of these connected together ? and are they connected to earth ?

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Originally Posted by EddyCurrent

Dave, you have 3 power supplies, the 36 volt and 2x 24volt, are the negatives of these connected together ? and are they connected to earth ?

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Ed Have you not noticed he's got it sorted.?

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Originally Posted by JAZZCNC

Ed Have you not noticed he's got it sorted.?

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Yes but I'd like to understand it more.

Quote:

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Originally Posted by EddyCurrent

Yes but I'd like to understand it more.

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Ok well don't see there's much to understand really.? He had an earth loop because of PC case earth and the High frequency and voltage of the Plasma sent the PP mental. . . . . .Simpliz really.!!!

What you looking for or thinking.??

Yes there are three psu's, an 11A 36v for the motors and drive boards, a small 24v 1/2A one for the safety and control circuits, and a 24V 3A unit for the bob.

none of the negatives are grounded or commoned, unless done internally but I checked them with a meter from 0v to mains earth and all were isolated it seemed.

the bob is not commoned to the PC as the screen on the cable does not connect, the screen on the db25 plug is not connected to the 0v rail on the bob either, it has full opto isolated PC inputs.

the outputs are also fully opto isolated to the drive boards so no common needed there either.

the safety inputs are also opto but I threw in the relays as an extra measure to keep the low voltages inside the cabinet.

the safety circuit psu is just a little wall-wart that I threw in when I pinched the good psu for the bob, I could try using the bob psu but that would likely bridge the noisy circuit direct to the bob power supply lines and defeat the object of isolation. I will get another small psu and ditch the wall-wart now it's working.

cant think of much else to offer really, please do ask if you need more.

dave

From what I've read so far, it's a bit like milling, the jet prefers to cut one way rather than the other, I'm trying to find the post again because I can't remember if it was clockwise around the outside or anti clockwise, easy to test though.

its connected with the way the plasma swirls as it exits the nozzle.

once the first part of the cut passes a bed slat, it's pretty much tack welded down so the contact should be good.

Oops, wrong thread..

Well, all is still not well.

I had some more play time today, tried some 30A test cuts and it's messing about, stopping cut motion midway, throwing e-stops, losing co-ordination etc.

It will be even worse if i plug the PC into the same extension as the system, I have to run two extension leads back to the wall socket just to get a partial success.

If it was 100% because i have no ground rod then i would stop testing until I take the machine home where I can fit one, but I'm not totally convinced it is that.

The system has a filtered plug fitted and the pc has an in-line filter fitted.

Not sure where to focus my efforts now????

Have a read at this, lower down the page.

CNC Router Kit | Low Cost CNC Milling Machine | Cheap homemade CNC Conversion | Floating Z axis drive Plasma Cutter - DIY, x2, x3, bf20

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Originally Posted by EddyCurrent

Have a read at this, lower down the page.

CNC Router Kit | Low Cost CNC Milling Machine | Cheap homemade CNC Conversion | Floating Z axis drive Plasma Cutter - DIY, x2, x3, bf20

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Hmm, if i got the chinglish right, I really do need a ground rod, ground the lot to it with the shortest thickest cable I can find and keep my fingers crossed?

Just had a chat with the suppliers and they feel the generator is not switching to full power i.e. I am cutting (or trying to) with pilot arc power which is about 20A on this model http://bbs.homeshopmachinist.net/ima...lies/frown.png

They are sending me a new (tested good) hand-held torch for test purposes and while waiting they have advised me to try upping the air pressure to 75psi just for a test.

But basically at 30A and 1.5mm sheet, it should practically vaporise the damn thing at the slow speeds I have been trying!!

Will know more tomorrow.