ESAB Ultrarex UXD-P 2500 retrofit with Linuxcnc and Proma THC

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08 Feb 2020 16:47 #156768 by alexandrub
Hi, i have the same esab plasmacutter to retrofit. I ask you why do you change the z servo motor with a stepper?

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08 Feb 2020 18:12 #156771 by tommylight
Z axis has a DC motor with simple feedback, not a usable servo motor.

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08 Feb 2020 22:12 - 08 Feb 2020 22:18 #156785 by alexandrub
In this case you use the computer paralel port to command the z stepper driver and 6i25 to command the mesa 7i77? The control panel from esab is working now or is just for design? You assign all the key?

Can I use a doughter card from mesa to comand the z stepper motor?
Last edit: 08 Feb 2020 22:18 by alexandrub. Reason: I forgot a question

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08 Feb 2020 22:43 #156786 by tommylight

alexandrub wrote: In this case you use the computer paralel port to command the z stepper driver and 6i25 to command the mesa 7i77?

Yes.

alexandrub wrote: The control panel from esab is working now or is just for design? You assign all the key?

The client was not interested in using the control panel at all, i was since i already have 2 of 7i73 boards. He won ! :)

alexandrub wrote: Can I use a doughter card from mesa to comand the z stepper motor?

You can use the other port on the 6i25 to drive the stepper, but you would need to flash the 6i25 with different firmware. You should use a BOB to protect the 6i25, just in case.

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08 Feb 2020 23:05 #156789 by alexandrub

alexandrub wrote: Can I use a doughter card from mesa to comand the z stepper motor?

You can use the other port on the 6i25 to drive the stepper, but you would need to flash the 6i25 with different firmware. You should use a BOB to protect the 6i25, just in case.[/quote]

What is a bob? Can you give me an model?

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09 Feb 2020 00:14 #156792 by tommylight
BOB = break out board
They cost from 7 to 40$.

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09 Feb 2020 01:56 - 09 Feb 2020 01:56 #156808 by rodw
If it was possible to add an encoder to the Lifter mechanism, you might be able to use the 7i77 or a Linuxcnc PID component to control the lifter. You need position feedback so you can set pierce height and starting cut height positions.
Last edit: 09 Feb 2020 01:56 by rodw.

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09 Feb 2020 07:01 #156835 by alexandrub
From your experience, if i use a stepper, what is the minim torq i need to use for lift z axis? I need closed loop ?
Can you tell me what breakoutboard do you use for retrofit the esab plasmacuter?

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09 Feb 2020 07:56 - 09 Feb 2020 07:56 #156843 by rodw
thefabricator03 shared a spreadsheet that could work this out for you recently. I used a very unscientific approach and used a 269 oz/inch NEMA 23 stepper on a 5mm pitch ball screw becasue I had one on hand. I think Tommy uses NEMA 17 motors.

You don't need a closed loop stepper motor. Any error from missed steps will be corrected on the next touch off.
Because you are using a 7i77 which supports 6 servo drives, you might also look at using a small servo motor which is probably going to give you better velocities and accelerations which is desirable for plasma....

Regarding breakout boards, thats not my forte, so I'll let someone else answer but there are heaps on ebay.
Last edit: 09 Feb 2020 07:56 by rodw.

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09 Feb 2020 08:42 #156847 by tommylight
As Rod said, you can add an encoder to the existing DC motor and use a servo drive for Z axis.
On that machine i just piggy-backed a Nema23 stpper on top of the existing DC motor, so they are both mounted there.

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