RE: [CAD_CAM_EDM_DRO] Re: Why is the push to such high step rates (Grex and Arc100)?

A couple of notes on resolution.

One machine type that does use better than 2.5 micron of resolution and from
ball screws are wire edm machines. With a normal mill you have backlash,
cutter load, and cutter bite error to contend with.

Wire erosion machines are a bit like a band saw with a wire, and teeth that
are electrical sparks. The wire is continuously fed from a reel, and since
the spark wears both it and the work piece the wire is drawn away with belts
and dumped. wire that is used. There is no load on the wire, any backlash
could be taken up with a simple spring. They can move the wire through the
work piece with paths controlled for parts of a micron, though most older
machines have resolution to about 0.5 micron. At these sorts of resolution
temperature is a real critical issue.

As a note on mills and the like. Most commercial mills of the 80's and 90's
have a resolution of 0.2 thou, or 5 micron and expect a cutting accuracy to
about 0.5 thou. I am Mach3ing my mill and I have chosen 0.1 thou, 2.5 micron
to give the servo a measurable error to work with or a few counts during
which I won't be able to see an error.

Some more useless information



Regs Mark



_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of turbulatordude
Sent: 18 December 2006 18:14
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Why is the push to such high step rates (Grex
and Arc100)?

> As for resolution and precision, in machine tools, it's pretty hard
> to find anything with a resolution better than .0001" or .001MM.
> Beyond that is very impractical without taking some very special
> steps to insure the mechanicals can deal with any more resolution.
>

0.0001 inch = 0.0025mm
so 0.001mm = 0.000039 inch

The only thing you can really get with those resolutions is distance
between cuts or holes. I don't think there are many machines that
have drives that are that accuarate across the axis. Certainly not
our home brew stuff.

I can see high step counts on some devices that are using movement
like rotations, a telescope following a star ? no discernable step
motions, and not trying to stop and hold.

There is a HUGE ammount of uses beyond what we discuss.

Dave





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