Re: [CAD_CAM_EDM_DRO] Losing steps...

Patrick wrote:

>I've recently discovered my machine is losing steps, as steppers do,
>and so I'm trying to figure out if some (small) amount of missed
>steps is "normal." The resolution on my machine is quite small
>(.000098"), and I'm wondering if it's just too much to ask to expect
>it not to lose any steps at all. I can usually re-home the machine
>after a fairly long program and get less than .0003" "homing error",
>(measured with the homing switches, which are purported to be
>repeatable to .000039" when new). I'm really not getting wrapped
>around the axle with meaninglessly small numbers, but I would like to
>know if a properly working stepper system can be expected to miss no
>steps? At what point do I declare a problem? 3 missed steps or 10
>missed steps?
>
>

If you don't restart the CNC program, or power off the drives, then you
should not miss a step, ever. You don't say what software you are using,
or over what time period this error develops. Some software is known
to accumulate mathematical errors from the finite precision of the
computer's number system. This is pretty old stuff, however. If you
are using a DOS program on a Windows machine in the DOS emulator
window, the periodic handling of background tasks by Windows will
cause an abrupt halt in the step pulses, and this may cause lost steps.

It is also possible that electrical noise is being picked up as false
step pulses
by the motor driver. Some drivers are also sensitive to when a direction
reversal is done, and may step in the wrong direction if the direction is
changed just before or after a step pulse is given. Again, you don't
tell us
what stepper drivers you are using.

Jon