What has gone wrong????

[Davek0974]

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.

[Davek0974]

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.

[Clive S]

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

[JAZZCNC]

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

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.?

[Davek0974]

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...

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.


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. ...

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 :)

[JAZZCNC]

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. . (Oh it's obligatory you cut the Road runner for testing with Mach3 so lets see it. .)

[Clive S]

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

[JAZZCNC]

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

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. . .

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.!!

[Davek0974]

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.

[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 ?