On 2010-03-06, F George McDuffee wrote:
On Thu, 4 Mar 2010 14:31:33 -0500, "Buerste"
wrote:
snip
The only problem I have is that the gears over-run and feed too much wire.
I've considered lightening the gears by drilling a bunch of holes.
snip
Lots of good observations and suggestions so far on what appears
to be a very interesting project.

Do you really need intermittent feed or is some sort of
continuous wire feed with a "flying cutoff" possible, with the
length adjustable when the extruded/extended wire trips a
proximity or optical switch.

Hmm ... I've thought of another possible approach.

Are you familiar with "Geneva gears"? Input is a constant
rotational speed. Output is a precise 1/4 turn (or 1/5th turn or 1/6th
turn depending on the particular gear set involved). There should be no
overshoot on the output of this. Rotate the input gear with a constant
velocity motor, trigger cutoff just a little after the output rotational
position locks, and repeat until out of wire.

Here is an example of a Genevia Gear:

http://www.tangendrives.com/

Never dealt with them -- and there are other makers of Genevia
gears, they were just the first web search hit which looked fairly
reasonable.

The Genevia gears even have the advantage that the output
rotation accelerates for about half of its revolution, and decelerates
for the other half.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---