Re: retrofitting an older CNC

Peter - You sound just like I was right after I bought my project
machine. Congratulations, it appears to be immaculate! Hopefully
you'll have as much fun retrofitting it as I'm having with mine.

To answer some of your questions, generally there isn't any
feedback to the controller when using step and direction drives. (I
know, there are a few programs that support it, but it's not as
common.) The controller assumes the drives will maintain the
commanded position, if not, they will error out, hopefully tripping
the controller. (depends on the controller, and how you wire things.)

For a machine like yours, you pretty much have two choices: Use EMC,
a servo interface card of some sort, and keep the rest of your
electronics as is. (Getting the spindle speed controlled with EMC
might take some work, but I believe it's possible ??) Otherwise,
your best bet would be to replace your servo amps with step and
driection drives. This opens your possibilites for controller
software considerably.

I haven't actually actually finished my machine, so the following
opionions are my impression from two years of lurking: EMC with your
current servo amps and a Servo To Go board, or Jon Elson's parallel
port setup will probably provide the smoothest motion, with the best
response from your current motors. The downside is that you are
pretty much stuck with EMC. It appears to be pretty powerful, but not
always easy to setup, and some of the features appear to be works in
progress. If you go with rutex or gecko drives, you will probably
give up a little torque and speed, but you will have a bunch more
options in the control software. I really don't know which is more
important to you.

I hope this helps some, and I'm sure you will get plenty of input
from everyone else.

Good luck with your new machine.

- Cameron




--- In CAD_CAM_EDM_DRO@yahoogroups.com, no falloff <nofalloff@y...>
wrote:

>
> After using CNC mills both at a friends shop, and as school, I

decided I just had to have a machine of my own. After saving for the
better part of a year, I just bought a CNC Shizuoka mill with a
Dynapath Delta 20 controller (pics at: www.cyclegarage.net/mill). I'm
not sure if the controller is any good. It seems to work but I'm
getting a fault on the Z axis. I bought the machine figuring that the
controler wasn't working, and had planed to replace it (of course
only knowing enough to be a danger to myself and others :-) ). It
seems retrofit controller systems by Centroid, and Anilam etc. are
way too expensive for my current budget. I was hoping to use as much
of the existing hardware (servos, servo amps and electronics) as
possible, and just use a PC as the controller. The mill is currently
fitted with Baldor permanent magnet servos. The book for the servo
drives (the only documentation I have) mentions that the drives are
looking for PWM signals from the controller. I know that

> one could probably write a book in response to my questions, but I

just need a general bit of clarification.

>
>
>
> 1. Systems that use gecko drives don't have absolute feed back?

That is, the computer sends motion signals (step and direction) to
the drive but has no way of knowing if the servo is in the position
it is supposed to be in? How does this compare to the positional
accuracy as compared to the current system?

>
>
>
> 2. Does the fact that mach 1 uses step and direction commands mean

that it can't be used with the existing servo boards in this machine?
If not what controller software (EMC?) would work?

>
>
>
> 3. How do I interface it with the existing hardware? If the servo

amps don't except step and direction signals, then I assume that a
simple breakout board such as those used with gecko systems won't
work. Likewise anyone have suggestions as to what will?

>
>
>
> 4. These servos are rated a 120v and 10A (continuous) 39A (peak).

It is my understanding that these can be used with gecko 320 drives,
but will not achieve their maximum rated torque or reach their
2500RPM max rated speed. Is this correct? Will the tachometer need to
be replaced with encoders in order work with this system? Rutex
drives seem a better choice, true?

>
>
>
> Lastly. How hard would it be to include the stepper motor

controlled spindle speed, and tach into the new controller? Could
this be done by defining it as say a 4th axis?

>
>
>
> I've been searching and reading as much as I can, and have royally

succeeded in confusing myself. Any links and information I get I plan
on including on a page on my web site covering everything I do to get
this machine running. I hope to document everything I go through, as
other who have done so are what inspired me to try this crazy stunt.

>:-)
>
>
>
> Thanks in advance for your help.
>
>
>
> Peter-
>
> pdh@k...
>
> (remove knowspam to reply)
>