Re: [CAD_CAM_EDM_DRO] Re: Can anyone advise me please?

On 02/17/2013 05:03 PM, snokket wrote:

> I have the timing pulleys from a heath robinson machine I built a few years ago ( Non cnc , all turning by hand ) I uses it to put barley twist onto miniature stems etc.these pulleys are all thats left of it so I would like to use them rather than buy new ones:-) if possible.
> I will look into it a bit more.
> Thanks again.
> Graham

As a point of interest, you will want two things, the basic drive and a
zero index pulse.

Using the 60 and the 12 tooth pulleys will give you 1,000 pulses per
revolution, resolving way under 1 degree. Microstepping MAY give you a
bit more resolution, but that is tricky. Half step is pretty good,
below that gets into motor design questions.

A zero indev pulse is simple, an optical LED/phototransistor pair and
some reticles (little slotted shields) with a tiny bit of logic will do
it. Basically it allows you to repeat settings. At 1,000 PPR, it is
simple, at higher resolutions it gets tricky. You can use an edge for
this with a little "smarts" in the logic and two detectors.

Usually, in woodworking, anything under 1/128" is invisible due to
grain, etc. For 1,000 PPR, that is around 2.5" in diameter, for 2,000
PPR, figure closer to 5" in diameter and it will be invisible, at 1,000
PPR and 5", you will see "stair stepping" errors of 1/64" or so, which
will be barely visible and can be corrected by sanding.

Dave 8{)
--


/"Among the many misdeeds of British rule in India, history will look
upon the Act of depriving a whole nation of arms as the blackest."/

Mohandus Ghandi, An Autobiography, Page 446.


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