Odd AC servo motors - how to test

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01 Dec 2017 12:12 #102559 by tecno
Got my hands on a box with AC servo motors where I do not know if these are functional.

So my questions is can I use following to test these motors or will they be damaged?
goo.gl/HdPeiz

AC motors in question are these. 220VAC
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01 Dec 2017 16:11 #102568 by Todd Zuercher
I would think, if they spin freely, and the winding's arn't shorted and all have similar resistance, there is probably nothing wrong with them. I do not know a good way to test them short of connecting them to a proper drive.

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01 Dec 2017 17:21 #102570 by tecno
What I would like to 'hear' is the condition of the bearings, resistance and turning freely looks OK.
At the moment I do not have any proper drive only this test/lab VFD board but I assume it will destroy motors.

Maybe I dare to put these out for sale

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01 Dec 2017 23:30 #102576 by andypugh
What do you want to know about them? I am confident that they could be made to run with LinuxCNC without to much trouble.
Mesa 8i20 + 7i49 is one way, or the STMBL drive.

Do you have an application in mind for them?

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02 Dec 2017 10:21 #102591 by tecno
Well on a long time wanted list is a plasma table but it has been put on back-burner due to lack of space.
Much of the mechanic parts I already have but need to tinker how to build the table as it has to be fast/easy setup and tear down build. Main idea is to have a *cutting* frame easily manageable that I fix on material to be cut and store this frame hanging in garage roof when not in use. Size of this frame is still unknown but somewhere around a 1/4 plate (2000x1000 nominal size)

Is STMBL mature and what kind of cost are we looking at, assuming it has to be assembled by me?

The Mesa route is appealing as I have 7i90HD already but it is always a price tag on everything that I have to look for.

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02 Dec 2017 11:40 #102592 by andypugh

Main idea is to have a *cutting* frame easily manageable that I fix on material to be cut and store this frame hanging in garage roof when not in use.

Have you seen these?
wholesaler.alibaba.com/product-detail/ch...ter_60301320562.html
The design fits you requirements quite well.

Is STMBL mature and what kind of cost are we looking at, assuming it has to be assembled by me?

There are a number of machines running (and running well) with them. But building by hand (392 surface mount components) is not something I have managed to persuade myself to do. Component cost is about $100 and I think that someone is selling assembled ones for $250 (but I don't know how many he has). And you still ideally need a Mesa card to drive one (step and direction is an option, but smart-serial is a lot better). You would want to add a 7i44 to the 7i90 to connect the smart-serial.

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02 Dec 2017 11:58 #102593 by tecno
Yes I have been looking at that one but the total price landed here is way too much 4700US+import tax and fees + VAT.
Still pondering if I go that design route or if I make a frame for this, time will tell.

As I already have some Mesa boards that is the most economical for me, but it is still in planning stage.
Maybe I put these motors for sale and make my other projects ready up and running. Been off line again due to health reasons but now I need to get my lathe functional. Need to fix some relays between 7i76e and lathes original AC-coil relays and do some rewiring.

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04 Dec 2017 09:52 #102653 by rodw

Well on a long time wanted list is a plasma table but it has been put on back-burner due to lack of space.
Much of the mechanic parts I already have but need to tinker how to build the table as it has to be fast/easy setup and tear down build. Main idea is to have a *cutting* frame easily manageable that I fix on material to be cut and store this frame hanging in garage roof when not in use. Size of this frame is still unknown but somewhere around a 1/4 plate (2000x1000 nominal size)


There are some commercial vertical tables and I did think of building one like that as space is an issue for me. It would have just stood up against the wall. The material just needs to be on a bit of an angle (eg not quite perpendicular to the floor). One of the ones I saw tabbed parts so they did not fall out. That is actually supported in Sheetcam. For casual use, I think I'd sell your servos and invest in a 7i76e and a few stepper motors. I'm using 269 Oz NEMA 23's on the X and Z axis. I was going to use the same size on the joint axis (Y axis) but I found some nice NEMA 34 5:1 timing belt reduction drives so I upgraded to small NEMA 34's that I could still run with my 3.5 amp stepper drives. The drives I am using are Longs Motor DM542a from eBay and my steppers came from steppers online so they are nothing special. $35 for a stepper drive and $50 for a stepper motor vs $250 for a servo drive would make a big difference to the total cost. I am getting 21 m/min rapids and say 1.5 m/s/s acceleration with 20 x micro stepping. The 5mm/rev ball screw on the Z is good for about 5.5 m/min so there will be no constraints that will affect your plasma cutting.

If you did use a servo, Keep the smallest and put it on your Z axis to get maximum acceleration for torch height control. I think Dewey calculated that you needed 2219 mm/s/s acceleration to cut corrugated iron (if you want to show off). I did get that in testing but found in real cutting, it was too fast and I lost steps (I think - things happen very fast with plasma)

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