Re: Re: Cheap Encoders

Re the cable drive toan encoder-

There is a commercial unit on the Australian market with a spring tensioned
pulley system and a stainless wire attached to a point on the moving machine
element.

I was considering a scheme using a system I used on a servo driven chart
recorder when I was with NASA. This had a drum on the (shaft type) encoder
about 1" dia. with a coarse thread on it. The wire was clamped to the mid
point of the drum thread, and wound round the thread equally both ways. As
the cariage moved, the wire fed in on one end and off at the other, lying in
the thread groove, so stacking was eliminated, and the wire was clamped to
the drum so it could not slip.

Obviously there needs to be enough turns of thread on the drum to accomodate
twice the machine travel of wire with this arrangement.

By the way two Aust. electronics journals are running construction articles
on CNC machines - one a plotter/engraver, using a printer carriage mechanism
as the Y axis drive, and the other a printed circuit coordinate drilling rig
-2.5 or 3 axis.

Jim Gregg
W. Australia

At 21:05 15/07/99 -0400, you wrote:

>From: Scott Acorn <sacorn@...>
>
>hi everyone,
>my name is scott acorn i`m new to this so please bear with me.
>i have been a tool maker for 40 yr.
>the last 20 yr. i have had my own small shop.
>i`m also a tinkering type,and have my hands into a lot of projects.
>i`ve designed and bult a number of things that might be of interist to
>all of you. thay include a e.d.m,and also a dro.
>so-----now that i`ve blown my own horn--------
>maybe i can answer some of your questions and provide some help.
>i don`t always have time to respond rightaway but i will try.
>
>Scott Acorn
>sacorn@...
>mike grady wrote:
>
>> From: mike grady <mgrady@...>
>>
>> I have been thinking about doing this
>> and using small prec, timing belts
>> mike
>> Matt Shaver wrote:
>>
>> > From: "Matt Shaver" <mshaver@...>
>> >
>> > > From: "Dan Mauch" <dmauch@...>
>> > >
>> > > Yes it has been done before. Steve Stallings had a good idea using a wire
>> > > set up like a radio dial connected to a encoder. The mechanical part

worked

>> > > fine but there were problems finds a pc lpt card that would work

well. The

>> > > linear encoders are much simpler and more positve.
>> >
>> > I think this should be Steve Lindsay, see:
>> >
>> > http://www.angelfire.com/biz3/handengraving/dro.html
>> >
>> > I want to build this to see how well it works, especially whether the wire
>> > will slip on the pulley when wet and oily. This, and the US Digital linear
>> > strip, seem the only alternatives to commercial glass or capacitive scales
>> > (Shooting Star's rack and pinion setup perhaps being a third).
>> >
>> > Matt
>> >
>> > P.S. I've met Steve Stallings at some meetings of the Chesapeake Area
>> > Metalworking Society:
>> >
>> > http://www.cams-club.org
>> >
>> > He is a real nice guy and is the fellow responsible for the "Drop Box" at:
>> >
>> > http://www.metalworking.com
>> >
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>Welcome to CAD_CAM_EDM_DRO@...,an unmodulated list for the

discussion of shop built systems in the above catagories.

>To Unsubscribe, read archives, change to or from digest.
>Go to: http://www.onelist.com/isregistered.cgi
>Log on, and you will go to Member Center, and you can make changes there.
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