Paul,
 It looks like Jon from Pico contacted you. He works alot with EMC and

has a nice setup. Go to http://www.usdigital.com/products/e5/  look over these to see if this may fit the bill, 500 count differental encoder. This will replace the resolver. Another direct hookup is www.camsoft.com, a little more pricey. I know you do not like Windows,

but the other option is www.artofcnc.ca  . You might check with the guys on http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/ to see if there

is anyone close to you, this is the EMC group. Richard

www.camsoft.com There appears to be something wrong with this one.
Perhaps it is misspelled.

www.artofcnc.ca this one seems to be stepper only. It is not just because I
am not fond of Windows it is because Windows is not a real time operating
system while Linux RT is. You don't want Windows stopping in the middle of
circular interpolation and going off and doing something else. Makes nasty
marks in the part.

Paul Lamar ...No rotor no motor.


I converted a mini lathe to CNC and I bought the Mach 3 software from
Artofcnc. The software installs low level drivers that control the parallel
port hardware before Windows get ahold of it, and it works very smooth once
properly set up. You will have to disable some Windows stuff like the
automatic screensaver and sleep modes. You would want to use a PC dedicated
to the mill anyway so that should not be a problem. The
Mach3 software is free to try out to see if you like it.

A year ago, I converted a Cincinnati mill that had resolvers and SCR motor
controls. We had to replace the resolvers with encoders which required
machining some parts to adapt, but the encoders are cheap and work
excellent. We retained the Getty motor controller and used  a Rutex drive to
go between the PC parallel port and the Getty drive. It took a while to get
everything tuned up but finally got it working great. If I wasn't so busy at
work I would come help you Paul. It's a fun project, almost as fun as
building and flying a rotary.

Chuck Dunlap

I did not know you did this kind of stuff Chuck. You are multi talented guy.

My resolvers are mounted on the back of the servos geared off the servo
shaft. Any tips for finding encoders that will fit?
Here are a couple of pictures. It would be easier if I could find a resolver
to count box.

BTW have you decided what you are going to do with your airplane?

Paul Lamar ...No rotor no motor.



Paul,

I strongly suggest you put the encoders on the ball screws.   That way you
are reading directly from them vs. reading via a gearbox or other mechanics
with backlash.

Even better get some linear encoders and put them on the ways.  Almost all
of them can output the quadrature you need for the controller.  The closer
you put the linear scale the better.

I have done a little work myself in the wild and wacky world of CNC
machining.  Even retrofitted a few machines along the way.

Here is an article I wrote for Modern Machine Shop magazine regarding
corrections to the control to achieve maximum accuracy.

http://mmsonline.com/articles/029710.html

Back in those days about 12 years ago we had to write our own software to
control that machine.

-Ben

That is kind of hard to do Ben. The gears shown are split, spring loaded,
anti back lash gears. The linear encoders sound good and maybe easier to
implement. Any brand you can recommend?

Paul Lamar ...No rotor no motor.


It's been awhile since I've been involved in machine tool retrofits.
Heidenhain, Mitutoya, Acu-rite and Sony come to mind because I've used them
in the past however, probably everyone who makes a rotary encoder now also
makes a linear encoder.

For your application .0005" is probably going to work.  I was dealing (and
still do) with work on the order of 1 micron (.000040)over 3 meters.  When
you get down to those tolerances it's a different world.  We can't even rely
on the linear encoders but instead track the part in real time with lasers.

The key is to get a signal out of those encoders that is compatible with the
control.  The control reads the position of the cutter via those encoders
and sends either a voltage or digital command to the driver board to move
the motors.  Any decent control will have a means of correcting linear
errors and that will allow you to hold very close tolerances with a
relatively sloppy machine.   Rotary encoders are too far away from the
workpiece to give you if the machine tool is the least bit out of whack.

-Ben

I think that is a great idea Ben and I am going to go with linear.
Actually easier to install  on my mill. Thanks.