Re: [CAD_CAM_EDM_DRO] Re: Measuring backlash with a ohm meter

The Sherlines have anodized aluminum parts. The
anodize layer is an insulator.

Greg

R Rogers wrote:

> Pete,
>
> I guess I should do a little more reading and a little less thinking..lol. I re-read his post and now I see what he meant. Thats another version of an electronic edge-finder of sorts. I agree, that wouldnt work for most mills. I'm surprised that it does read different resistance.
>
> Ron
>
> vavaroutsos <pete@...> wrote:
>
>
> Ron, I may have mis-understood what Chuck was saying, but I think he
> is measuring the electrical resistance from the work to the spindle,
> not the resistance to movement on the axis. This would require that
> the work be electrically isolated from the mill or the probe be
> electrically isolated. Things may have worked ok in Chucks case due
> to the construcion of the mill not providing much electrical
> conductivity from the spindle to the table, but I don't think this is
> a valid assumption for all mills.
>
> ~petev
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers
> wrote:
>
>>Interesting concept. However what may seem absolute is often not.
>
> Measuring resistance upon contact is measuring the effects of a slow
> minute crash. Contacting a surface to the point the drive begins to
> struggle would not be touching off on an edge. Due to deflection. I'm
> not ruling out that this would be accurate. It would require testing
> involving the method you perscribed versus a conventional edge
> finder. If the results parallel that would be a great edge-finding
> technique. Design into a machine control software to enter a setup
> screen that when resistance is sensed upon a drive it would
> automatically zero that axis, spindle rotating as this is more
> accurate. Would need to be able to distinguish between touching and
> fast jog resistance measured. Could even have a compensation preset
> for the radius of the stylus. None for Z obviuosly. Possibly an
> extremely stiff die spring in the shank of the edge finder to prevent
> damage on over-travel. This would be alot faster than present
>
>>method. Sometimes when I'm in a hurry I just use the end-mill for
>
> the cut as an edge finder, step-jog to touch and then add the radius.
>
>>For measuring backlash, a good dial indicator is pretty tough to
>
> beat. It's not something that is measured all the time.
>
>>Ron
>>