Re: [CAD_CAM_EDM_DRO] Losing steps...

>-----Original Message-----
>From: Patrick [mailto:alleven@...]
>Sent: Monday, July 12, 2004 8:28 PM
>To: CAD_CAM_EDM_DRO@yahoogroups.com
>Subject: [CAD_CAM_EDM_DRO] <sigh> Losing steps...
>
>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?
>
>

One other comment: If you are really quibbling over 0.0003" change, you may
be experiencing thermal expansion of the entire machine, or just the
leadscrew,
during the run of the program. The "big CNC" guys have warm-up programs
that run the axes back and forth for a half-hour or so to bring them up to
more stable temperatures before aligning the workpieces and beginning to
cut metal.

Jon