just another plasma build and then some :)

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23 Apr 2020 14:32 #165265 by machinedude
Tom i think i figured out what they mean by 2 phase wiring of the stepper motor to make it into a servo motor from the white paper i was reading. bipolar stepper motors have to set of winding's in them. phase A+ A- and phase B+ B- which is each of the 4 wires on a bi-polar stepper. is it something so simple as taking the positives from each phase and tying those two wires together and taking the negatives and tying those two together to convert the stepper into a DC motor for hook ups on the two motor connections on the servo drive from gecko?

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23 Apr 2020 14:47 #165266 by tommylight

machinedude wrote: Tom i think i figured out what they mean by 2 phase wiring of the stepper motor to make it into a servo motor from the white paper i was reading. bipolar stepper motors have to set of winding's in them. phase A+ A- and phase B+ B- which is each of the 4 wires on a bi-polar stepper. is it something so simple as taking the positives from each phase and tying those two wires together and taking the negatives and tying those two together to convert the stepper into a DC motor for hook ups on the two motor connections on the servo drive from gecko?

That will not work! DC motors use brushes to do the commutation between magnetic poles, steppers do not have them
Doing that will just get you a stiff motor shaft and to much current will make short work of burning those windings.
Where did you find such erroneous info ? As i've said before, the internet has become a mine field of bad info,

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23 Apr 2020 19:05 #165288 by rodw
If you were going to blow anything up I'd prefer to see you blow up your crappy drives than a perfectly good stepper motor. I can't believe how a certain manufacturer has got away with such poor products for so long. All in the name of made in USA I guess.

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23 Apr 2020 19:14 #165290 by tommylight
When i got my first G540, it came with 100gr of Hawaii coffee ! :)
Just to be clear, Marious ( or similar, the owner ) is very good at electronics, for sure, just some design decisions should have been made with some feedback from users, not just " i can get get the servo drives to spin fast with a parallel port ", "oh i will add a divider by 10".
For what it is worth, in full step mode, none of the drives can work with less vibrations than his, and that shows that he really knows a lot.
Interestingly, the price has not gone down a lot.

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23 Apr 2020 19:34 #165296 by rodw
My first stepper driver was a G251X but user error let the magic smoke out. For about what I paid for it I replaced it with 4 Longs Motor DM542A which I am using in the Spaceship and what Syil chose for their CNC machine my mate has. I have tried to let the magic smoke out of them but have failed totally!

Aside from a significant size advantage, there is no perceptible difference I could determine except that I can run now much higher microstepping which the Mesa card handles with ease. From memory, I think I am running at up to 90-100kHZ vs about 25kHz. Does it make a difference? I dunno but they just work!
The following user(s) said Thank You: tommylight, thefabricator03

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23 Apr 2020 19:52 #165300 by tommylight

rodw wrote: Aside from a significant size advantage, there is no perceptible difference I could determine except that I can run now much higher microstepping which the Mesa card handles with ease. From memory, I think I am running at up to 90-100kHZ vs about 25kHz. Does it make a difference? I dunno but they just work!

It does, the motors work much quieter and with less vibrations when using microstepping. They do loose some torque, but in plasma machines torque is not that important to a certain extent.
Personally, i have several stepper drives i have made over time, form 4 Darlington transistors or MosFet's and some resistors, to Linisteppers with PIC uC, and plenty of salvaged ones modified to work with step/dir or quadrature ( have some that can be pushed to 15A ), etc etc, but i rarely use them due to full stepping and vibrations they cause. For experimenting i always have some TB64109 or TB6600 and some Leadshine, but for bigger machines i always use Lam Technologies DS1044 or DS1076 or some others when needed. For Italian products, they are extremely good, and i did try to blow one up by miss wiring the motor and by reversing the power ! Nothing! Just a blinking red LED. Fix the wiring and they happily continue to work. The only downside is the price, for the same price of a single drive i can get a servo motor and drive from China (now with CCP ! :) ).

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23 Apr 2020 21:21 #165307 by machinedude
i was just trying to understand better how it would even be possible to use a stepper motor as a two pole brushless servo motor? i can't seem to find to much on the subject? from the looks of it it's not worth wasting more time on. it would be easier cheaper to just use something better suited.

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23 Apr 2020 21:53 #165311 by rodw
Bevins has had good results with ST80 servos and a Mesa 7i77

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23 Apr 2020 22:05 #165312 by tommylight
3 phase ones might work with 3 phase servo drive, but instead of the normal 120 degree angle it would have 0.6 !
I do have some here, but i never thought of trying that, no use in it. I also have some 5 phase ones.
As general info, almost all 3 phase servo drives for cnc use hal sensors or similar for commutation.

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23 Apr 2020 22:09 #165313 by rodw

tommylight wrote: It does, the motors work much quieter and with less vibrations when using microstepping. They do loose some torque, but in plasma machines torque is not that important to a certain extent.


I'm not convinced that torque loss is an issue any longer. With a decent stepper control as most morph back to a native step at higher speeds (eg drop the microsteps).

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