Re: Measuring accuracy

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Gregory Kamysz
<smsupply@a...> wrote:

> I just found out that the accuracy of my setup won't be defined my

the

> mill but by the software I'm using. I've looked at all of the sub-

1k$

> software and they all seem to work the same. There is always some
> rounding in the numbers. Much more tolerance than accuracy in the

mill

> would cause. If I write the G-code, it's not a concern but if I

use a

> software to generate G-code I'll be lucky to get +/-.05mm before I

even

> start the spindle.
>
> The error I'm talking about is when using a .25mm step over and my

part

> edge falls somewhere in between a step. Sure, I can cut parts

at .01mm

> stepover but who is going to wait weeks for a part to run on the

mill?

> If I want something pretty to look at, it's not a concern, but if

I want

> to use the part in an assembly, it's unreasonable.
>
> Am I missing something?
>
> Greg
>

Huh??????? Yeah, you're missing something.

CAM software does not limit the accuracy of your parts. The
software will make a partial step over on the last pass, but never
going past the part profile. Actually, it depends on the software.
For instance, if you're removing material up to the part profile and
it's done in two step overs. Lets say 1/4" has to be removed and
you specify a step over of 3/16". The software could do it several
ways, take a 3/16" step plus a 1/16" step. Or it could take two
1/8" steps. Which ever way I've never seen software that would go
past the part profile because of specified step over amount.

Getting back to accuracy testing....there are all sorts of ways. I
prefer cutting rather than testing with indicators with no load on
the machine. The load on the machine is what will determine play or
lack of rigidity in the machine.