Re: [CAD_CAM_EDM_DRO] cnc mill project

Generally stepper controlled machines are open loop. That does not
mean that you couldn't attempt to use a stepper in a closed loop
system. Selection of encoder and motor would have to be done
carefully. Due to the stepping nature of a stepper you may end up
with a system that is unstable due to the step size of the motor.

AS I mentioned, with the TIAG there is no reason why you couldn't
configure the machine to use either at a reasonable cost. With both a
stepper drive and a servo drive you would have a great deal of
capability with respect to algorithm development.

There are good web resource out there, I've personally viewed a few,
unfortunately I did not book mark them at all. What I can suggest is
to go to www.linuxcnc.org and look in the links section. There you
should find links to people associated with the NIST, I believe one of
these guys then had links to a university in the midwest that had an
excellent site. At least that is how I remember it, its been some
time now. In any event linuxcnc.org is interesting in and of
itself. It does sound like you need a book that covers motor
technology more than control systems technology and CNC is another ball
game all together. At the moment I have nothing to reccomend book wise.

With respect to your question about the mill and the use of steppers,
I'm going to go out on a limb here and say no. There will be people
that will attempt to saw that limb off but from my perspective you are
talking Apples and Oranges. People will argue about this but I do not
consider STEPPERS to be motors at all. A motor itself may be a motor
or it may be a servo or more strictly a part of a servo, it is not a
stepper. Servos simply have capabilities that steppers don't. It is
interesting that way back (we are talking way back) when I covered
motors in college the stepper never came up in class. Thankfully I
was able to drain much of what was passed off in that class from my mind
and only save the usefull bits ;)

Thanks
dave

John D. Bussema wrote:

>Thats exactly why we only considered servos. As I understand them, stepper
>systems are typically open-loop. On the other hand, I have seen some stuff
>on the internet about hybid stepper systems, but it is pretty undetailed.
>Consider for instance, a stepper contolled mill system with linear encoders
>mounted on the knee. Would this system not be capable of closed loop control
>in every manner that servo systems are? I'm having trouble finding good
>literature on control systems specific to servos/steppers. Typical contol
>books are very general in topic and geared more towards specific industries
>rather than CNC's. Does anyone have a good web resource on the topic?
>
>-John
>
>----- Original Message -----
>From: "David A. Frantz" <wizard@...>
>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>Sent: Thursday, May 13, 2004 7:44 PM
>Subject: Re: [CAD_CAM_EDM_DRO] cnc mill project
>
>
>
>
>>To add another perspective depending on what you intend to do with your
>>study of adaptive controls a true servo system may be more useful and
>>flexible. By true servo I mean a system that closes the loop through
>>the processor running the control code. This would allow information
>>that can not be had with step and direction controls to be feed directly
>>into your algorithms.
>>
>>Obviously there are a number of things that you could be interested in
>>under the guise of adaptive controls that could very well be attacked
>>with step / direction electronics. The use of a Taig though indicates
>>that you probally could implement a number of differrent systems
>>relatively cheaply.
>>
>>Thanks
>>Dave
>>
>>
>>
>>>>>>>>>>>>>>>>>>>>>>>.snipped a great deal of material.
>
>
>