advanced motion control servo drive choice

24 May 2014 10:35 #47275 by edscrane1
I have a beaver turret mill, originally nc5 with Anilam GXM.
The control is now Linux using MESA 5I25 and 7I77 boards, set up with invaluable help from this forum.
The original servo amplifiers ( Anilam type 415 ) are starting to be problematic , mainly slow to power on, and the Y axis card is awaiting a repair estimate as it stopped output during a cut, with no fault lights.

As an alternative to the original servo amps, I am looking at advanced motion controls 25A20I and 50A20I drives.
The motors are SEM 140 volt dc brushed with tacho feedback 3Nm 30amp.
Would the 25A20I drive be sufficient as the machine will not need to be pushed hard commercially, or should I spend more on the 50A20I and limit the current output ?

Any comments or advice would be appreciated


24 May 2014 20:16 #47282 by emcPT
I use with success several Argon drives from Granite Devices.
24 May 2014 20:50 #47284 by tenaja
I have not used those you mentioned, but I have had pretty good success with servos. I used them in a non LCNC project, but they would work well there also. A friend of mine repairs machines, and he recommends them to all of his clients.
27 May 2014 20:48 #47396 by green751
I've used the AMC servo drives for a few things... mostly testing and experiments.

They seem to be pretty solid, if basic drives. They do have the necessary power to do what you want.

If you buy the lower current model, you'll be missing the top end torque your servos can generate, which is actually more important for accurate milling *if* you use that range of power than full voltage.

Torque lets you do sharp stops and turns, and fast acceleration. I'd consider carefully what you're doing with the mill before you decide whether you can get along without that top bit of power. If it's only running programs for things like a grid of holes that's one thing, but if you're making accurate 3d parts with it, that's another..

The AMC drives are quality stuff, either way. Depending on what voltage/current your old drives output you may even see a performance increase with the new AMC.

27 May 2014 21:27 #47397 by andypugh

edscrane1 wrote: Would the 25A20I drive be sufficient as the machine will not need to be pushed hard commercially

One way to tell would be to see what the typical output peak is of the 7i77 in the current setup. If you never see more than 8V drive voltage then you aren't using more than 25A at the moment, and you don't need that extra 5A.
13 Aug 2017 07:13 #97406 by nkp
Can AMC PWM servo drive (eg 30A8) brake as described here:
"The same technique can be used to brake the motor very quickly and is called “reverse braking.” Instead of using the motor’s energy to re-charge the battery, it is used to quickly stop the motor, and will stop the motor even faster than dynamic braking. To reverse brake, just directly change the H-bridge to the other driving direction. In this case, all the BEMF will add to VM total. The motor’s current will counter with the driving current and decay rapidly. The motor will also stop suddenly and try to run the other direction. If you just want a quick stop and don’t care about the big VM overshoot, just give several tens of milliseconds of reverse braking and then dynamic braking to zero speed. The below picture show a large overshoot on VM (pink) when applying reverse braking."
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