RE: [CAD_CAM_EDM_DRO] "lost steps", what is it and how do you know you lost 'em?

Step and direction servos are open loop between the computer and the
drive and closed loop from the drive to the motor. Yes they can loose
steps. The way you know it is you measure the table travel with an
indicator and see if it compares to the commanded motion. You can also
see it when cutting pockets if the cut levels shift. Another way it
turns up is when after the program finishes and you go to a know
reference point and it is not where it should be.

Tim
[Denver, CO]
Sherline products at Deep Discount
Mach1 & DeskCNC with credit card ordering
www.KTMarketing.com/Sherline

> -----Original Message-----
>
>
> I think I know what the term "lost steps" is describing, but how do
> you know that you lost them? Is it a stepper motor thing only? I'm
> putting together a Taig mill with servo's, Gecko 320's (Camtronics
> kit, if it matters, but I don't think it does) and demoing Mach1 (I
> don't think that matters either, could be any step and dir
> controller program). I've read about servos and the encoders sending
> feedback "back to the computer", but in this sort of setup the
> encoder feedback isn't going "back to the computer", is it?
>
> The control program is feeding step and dir to the drivers. Are the
> drivers making sure that no steps are lost? Is this a true "closed
> loop" system, or just a way to use a step and dir controller program
> with servo motors, but still with the possible problem of lost steps?
>
> Monte (electronics almost done, waiting for mill, reading too much)
>
>
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