Re: [CAD_CAM_EDM_DRO] Re: Rotary to linear translation
Posted by
John Guenther
on 2000-04-11 08:16:00 UTC
Ron,
I agree, there is an old saying the goes something like Keep It Simple St____ (KISS) which I think really applies here,
especially for hobby use. Simple should equate to low cost which is what most hobbiest are looking for IMHO. I simple rolling
wheel on a flat surface is about as simple as you can get.
On the other hand, the idea presented earlier today about the cable being pulled out of the housing and returned by sprring
reminds me of the Starrett Digi-Tape which has the built digital display along with a 25 or 50 foot measuring tape. The
accuracy of the Digi-Tape is only to the 1/16" but I am sure the concept is the same.
John Guenther
Ron Ginger wrote:
I agree, there is an old saying the goes something like Keep It Simple St____ (KISS) which I think really applies here,
especially for hobby use. Simple should equate to low cost which is what most hobbiest are looking for IMHO. I simple rolling
wheel on a flat surface is about as simple as you can get.
On the other hand, the idea presented earlier today about the cable being pulled out of the housing and returned by sprring
reminds me of the Starrett Digi-Tape which has the built digital display along with a 25 or 50 foot measuring tape. The
accuracy of the Digi-Tape is only to the 1/16" but I am sure the concept is the same.
John Guenther
Ron Ginger wrote:
> I am a strong believer in keeping mechanical systems simple.
>
> TravaDial has made and sold 'rotary encoders' for many years. They
> happen to turn a pointer against a scale for a person to read, but for
> all practical purposes its an encoder.
>
> All they are is a rigid mounting for a hard wheel with a slight crown to
> the wheel. The wheel rolls on the edge of the table. No shim stock, no
> beairngs, no tensioning device, no rollers, just a wheel rolling on a
> flat surface. It doesnt get much simpler than that.
>
> The mounting box has a couple screws that cause it to tip slightly to
> adjust the wheel contact point, hence the effective curcumfernce.
>
> I have a TravaDial on my lathe and do not ever recall it having a
> problem with swarf or chips. It rides on the edge of the lathe bed, and
> is surrounded by a felt wiper.
>
> So, if you want a mechanical driven encoder I see no simpler way than a
> rolling wheel. Seems to me better than cables, shim strips, or racks and
> pinions.
>
> In practical numbers a wheel of 1" dia would have a 3.14" circumfrence,
> divided by a 2000 line rotary encoder and you have .00157 travel per
> count. Reduce the wheel to 1/2" and you get .00078 " per count. Let the
> electronics scale that.
>
> Or, if you made the wheel about .31830 dia it would have exactly .0005
> in per count.
>
> I still like my $700 Mitutoyo DRO, but if I was going to build one it
> would be a rotary enncoder on a wheel
>
> ron
>
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