Spec servo system for EMC2 & another app - hard!

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01 Oct 2010 23:26 #4484 by 1:1
Hello all,

I have two applications that I'd like to purchase motion control gear for - I'd like to try to get gear that can be used in both applications (there maybe a little adaptation involved in one or more of the cases):

First application:
A 4 axis mill/drill CNC conversion using EMC2 as the controller (the 'loop')


Second application:
A generic 4 axis machine in which the purchased drives can handle being fed simple feed step/dir pulses (from an arbitrary source) with the drives doing their own PID control internally (no more PC attached!) :whistle:


Consequences I've discovered that will likely need addressing:
-I will likely need some sort of USB or parallel I/O card to free me up of on board parallel port restrictions in EMC2 (I'd prefer not PCI bus) - Mesa gear looks interesting here as it is EMC2 ready
-Once the above point is taken care of its looks like I can have high resolution (incremental) encoders - I'd like them for obvious reasons
-The motor drives would be good if they were able to be hijacked or switched to allow the encoders to go to EMC2 directly (or indirectly) for the CNC, the motors would then run 'dumb'. (If this is impossible within the spec I give then I can run EMC2 (or mach3 even) open loop with the drive running the loop.)
-Assuming the last factor can be addressed I need ALSO to be able to split the encoder stream for the second application, one stream to the drive for its internal PID loop again ('smart' mode), the other split to the arbitrary 'brain' for other purposes (non real time, non control).

Limiting factors:
-I'd prefer brushless servos for the motor, but standard servos are fine also
-COST - I'd like as high torque as I can get (NEMA34 likely?) but don't want to be spending more than around $600~$700 per axis - factor in eventual power supply cost into this also
-I live in single phase 230-240V/50Hz land - thats 10A per circuit ... 2400W max available per circuit

Notes:
I would emphasis the ability to function relatively unhindered or adapted under the second application as more pertinent than the EMC2 CNC application - that can run adapted/converted if need be...
The motors will probably be over spec for the CNC application, excess torque however will be used in the second application.

Does anyone have any suggestions of suppliers I could approach ?

I am in contact with Mesa, Pico systems so far ... but am interested in higher torque/higher power DC motor and drive suppliers also

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10 Oct 2010 21:38 #4611 by PKM
Hello!
Consider this www.dmm-tech.com/Products.html
I am going to use it in step/dir mode first and then upgrade to closed loop system using built-in encoders.

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10 Oct 2010 22:39 #4613 by 1:1
PKM07 wrote:

Hello!
Consider this www.dmm-tech.com/Products.html
I am going to use it in step/dir mode first and then upgrade to closed loop system using built-in encoders.


You'll have to swap out the absolute encoders for incremental ones for EMC2 to be able to run the loop... :side:

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11 Oct 2010 01:03 #4614 by PCW
Are you sure thats possible? The absolute encoders are probably used for drive commutation...

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11 Oct 2010 02:07 #4615 by 1:1
PCW wrote:

Are you sure thats possible? The absolute encoders are probably used for drive commutation...


I read somewhere (maybe here?) that someone was going to experiment with it ...

Yes, being BLDC motors the encoders are probably essential for the drives - maybe they meant attaching an incremental on top of the absolute, or decoding the absolute to incremental ... or maybe just EMC2 getting an encoder of sorts so it knows where it is at least ... or nested loops, or ... shucks! heh heh

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11 Oct 2010 05:38 - 11 Oct 2010 05:46 #4616 by PKM

1:1 wrote:
You'll have to swap out the absolute encoders for incremental ones for EMC2 to be able to run the loop... :side:

Well, I did not think much about it, but I guess that absolute position data can be easily transformed to incremental data... not vice versa. I.e., vice versa is not so easy )
Last edit: 11 Oct 2010 05:46 by PKM.

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