Paul wrote:

The big problem is the software that reads the G & M codes off the

hard

disk, sends the proper commands to the motion control card and

generates

the user interface on the LCD and PC keyboard. Do you have something

in

mind for

that. Seems that software would be custom for each motion control card
design.  Can that be bought off the shelf for some motion control
chips set?

Mark Wrathall wrote:
That's why it is cheaper to dump the motion control cards on Ebay, and

buy

Gecko's. Both the Stepper (G210)and Servo (G320)  geckos accept step and
direction input from a parallel port. There are about a dozen software

which

convert G and M code to step and direction conmmands. TurboCNC (DOS),

MACH2

(WIN XP) and EMC are the three best choices (from the CAD_CAM_EDM_DRO
group).

EMC can also be set up with the servo-to-go cards if you want true

closed

loop control. In practice the G320 version is fine (PC sends open loop
STEP/Dir commands - Gecko controls the servo's closed loop to acheive

that -

Gecko's fault out and report to the PC if the command can't be met (not
likely).

Note the G & M code is not really standardized. The 1974 RS-274 (?)

standard

is not adhered to. Obviously EG, on a Rapid (G00) one controller might

clear

Z first, and then do a coordinated X, Y move, another controller (like
TurboCNC) might do a coordinated move in all three axis, and a third
controller might send all axis off at their own topspeed. Whatever
Controller SW you end up with you need to be sure that your CAM program

has

a Post processor to output your dialect of G code.

The PC based controller mentioned above are generally better at sticking

to

the mainstream defacto standard (FANUC) then many OEM controllers.

Regards,
Mark

Something I still don't understand Mark. My servo amps require +/- 10 Volt
analog control signals. How do you get that out of a parallel port?

Paul Lamar

You don't. You either use a $808 ISA servo-to-go card which puts out +/-10V
http://www.servotogo.com/
This ties you to Linux EMC, which supports this card.

The easiest option is to drop the whole controller system on ebay, and use
the proceeds to buy Gecko G320's. PC sends step and dir through two
dedicated LPT pins for each axis Gecko. By convention pins 3and 2 for X
axis, 5 and 4 for Y etc. The Gecko is fed 5V for it's logic, ~70V muscle
power, and the encoder feedback from the motors. It decides what to do with
the motors to achieve and hold the position/motion.

The Geckos are good for 80V and 20A, but if motors need more the australian
Rutex drives are also step/dir and go as high as 200V/40A. Considering you
are likely to be running shorter production runs, Gecko's will likely
provide enough muscle to get the job done plenty fast enough. Many of these
machines are pretty massively over powered.

Regards,
Mark

So the Gecko is both motion card and servo amp?
It inputs a step rate and outputs the analog voltage for the servo
motors?

Sounds like DOS would be the best OS to use as it comes closest to 
to being real time OS.

Paul Lamar
 
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