Re: steppers or servo?

---for myself and many hobby machinist we are faced with a list of
compromises ranging from the cost to the weight we are prepared carry
down the basement.
I have used steppers on a home designed special purpose machine for
the last 2 years and I find steppers to be perfectly repeatable if
used within their range. If you can make one part that measures out
as designed on a stepper equipped machine you can make thousands.
Regarding servos. In my day job I chase tenths around on a surface
grinder that is equipped with a servo down feed. If the wrong
dimension is typed in and the wheel crashes into the piece, the servo
system does not recognise the new position with any accuracy!
There are 2 alternatives that I have tried to prevent lost steps and
that is larger motors or gearing down and they both work.
The greatest problem with a home built cnc machine is finding enough
work to keep it busy and for also for me it is the noise of high
speed cutters and dust which really worries me.
Terry

CAD_CAM_EDM_DRO@egroups.com, "Steve Carlisle" <quatsein@i...>
wrote:

> One reason people use closed loop servo system is because
> it does not loose it's position. A good stepper-servo theory
> source is listed below,
>
> www. linuxcnc.org
>
> and look under the Compumotor link.
>
> Steve
>
> ----------
> From: Terry Ackland <hexagon@o...>
> To: CAD_CAM_EDM_DRO@egroups.com
> Subject: [CAD_CAM_EDM_DRO] steppers or servo?
> Date: Saturday, July 08, 2000 6:14 AM
>
> Hi,
> Computer printers use stepper motors and they run forever with
> incredible accuracy. A hobby nc machine will also have the same
> repeatability as long the motors are not forced into missed steps,
> right?
> Servos can also be forced into missed steps so the advantage over
> steppers must just be the extra speed to return to the home
> position?
> Terry
>
>
>

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