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Hello Hood,

Those are some powerful motors for CNC if I'm not mistaken !

We use 18 N.m motors at work to move tonnage up and down, counterweighted yes, but running at 2m/s or so she picks up a fair bit of momentum ;) There are large safety factors involved in what I do also

In the meantime I'm learning slowly what I need and come up with a slightly better specification:


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') or mach3 if that proves troublesome

Second application:

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

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) 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

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.


Any thoughts ?

heh, more images from the website:

Do you think the XL motor (blue line) has enough torque for a mill/drill CNC conversion ? (ballscrews will be used) - I'm guessing it does, but how does it compare to a proper servo, especially at the higher RPM ?  It weighs 5Kg by the way   :o

If I decide to keep its speed range from 0 - 1500 RPM then my minimum torque is around 6 N.m (850 oz.in) - I can 2:1 gear it for double speed and still be 425 oz.inch - and the resolution of steps is still not too jerky once the encoder P/R specs are looked into. Is this logic sound ?

In general I'm finding this whole servo/stepper/drive decision very hard - so many opinions, so many ebay listing telling you their way is the best etc... I figured that buying a driver and motor combo would at least ensure I'm getting the most out of both, no wasted specification either way.

What is an equivalent servo set up ? I understand Gecko have servo drives, but then I'm stuck with the question of what are appropriate motors to go with them ...

Thanks for you reply,

Two immediate thoughts:

isn't that the same issue for any servo ?

Interesting point re. the two axes - do people ever use rotary tables to get around using two axes for off axis cuts ?  i.e. rotate piece to X or Y - cut - rotate again - cut - etc... Circles easy also - I guess arc's would have the issue of two axes (X or Y moves with rotary movement) -  I have a rotary table and am keen for four axis  ;)

As for the benefits of the fastech - I was looking at the front page of that link I posted - stuff like this:

and so on...

marketing hoohah or ?


I'm Iooking at these Korean servo stepper/drive units:


Particularly the NEMA34 '86' series steppers - specifications below ... They can go up to 32,000P/R res which can be divided down to 500 - They also claim some impressive advantages over standard stepper drive system, or so they have led me to believe - maybe as a beginner I have been bamboozled by jargon ?  :P

I'd use them firstly in a mill/drill CNC conversion, where they may be over specced (?) - and over priced (?) -  but I will end up using them in other projects also, I'm mainly concerned with what I don't know about the extra costs involved - I imagine a breakout board would be required, which might be cheap enough, but what about 40~70v power supply per axis for 4 axes ?

They'd run open loop with respect to mach3 ? but closed loop internal to themselves ?

Any chestnuts of experience would be greatly appreciated -  Maybe they really are a nice piece of kit ?

Kind Regards,

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