Re: [CAD_CAM_EDM_DRO] EMC Real world

Ethan Vos wrote:

> OK, I have everything set up to do what I want, now I need to connect to my
> machine.
>
> How do I change the parallel port pin-out for XZA instead of XYZ? The .ini
> file is set up for 4 axis so the A will work properly. I know I'll probably
> need to add a parallel port.

The pinout is pretty much fixed in the software. The easiest thing is to
make up a cable that has the right wire connections in it.

> And I noticed something odd. The A axis move very slowly when a G00 is
> commanded, but will move very quickly if the G00 is combined with either
> the X or Z axis.

This may be a transient condition. I have noticed that after switching
from auto to manual, some axes will manually move at the rate programmed
in the RS-274 program until you do something, like hit a feedrate override
button, that resets that axis to the manual jog feedrate.

> In terms of stepper drives, am I better to use the existing Compumotor Zeta
> drives or change to something like the Gecko? I need the stepper to receive
> 5,000 steps/rev and 5 rev/inch so 25,000 steps/inch. My target is 10 inches
> per second so I need 250,000 steps/sec.

You may have a real problem, here. Unless you have very special motors
and/or drives, you will not be able to get any standard steppers to go to
250,000 full or half steps/second. This would be 1250 RPS on a 200 step/rev
motor. That's 75,000 RPM! I think i can tell you that you can't run a
stepper
that fast, or you'll be wearing pieces of it! Are you sure you haven't made a

mistake here? Duo you really need to do 600 IPM = 50 Feet/minute?
I would talk with Mariss before ordering Gecko drives, as he may
have some suggestions. I think Oriental Motor VEXTA drives might be able
to do better with a high-end 5-phase stepper motor. I have run their motors
to 20,000 Steps/sec with no problem, but I don't know how much torque is
left at that speed.

This may be a servo application. You can talk to Mariss about his Gecko
servo drives, which should be able to handle this kind of step rate.
But, then you run into the computer limitations. You will need a very fast
Pentium CPU to generate 200,000 steps/sec on up to several axes at once.
I have a parallel port device that generates step pulses, and can handle
these rates without problem. Depending on the need for setup time or hold
time
on the direction change, even that can become a problem, ie. if the step
driver
needs a 100 uS setup time before a direction change, then you could be
limited to 10,000 steps/sec. You can fudge that, as direction won't change
at the high speed end. But, I think there must be a mistake in your numbers.
If there's no mistake in the calculations, then you will have to forget
steppers,
and go to VERY expensive, ultra high performance servos, and change
your gearing. By the way, if you try to spin a leadscrew (or other shaft) at
75000 RPM, it will turn into a flail.

Jon