Re: Rotary to linear translation
Posted by
Ron Ginger
on 2000-04-11 07:48:12 UTC
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
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