Re: [CAD_CAM_EDM_DRO] Re: DRO encoders- Rotary or Linear?

Chain and sprockets are non-linear.


At 09:34 AM 10/29/02 -0500, you wrote:

>This may be a stupid question, but why not to use a normal bicycle
>chain\sprocket combination for driving an encoder?
>Is it a backlash issue?
>Alex
>
>----- Original Message -----
>From: jcc3inc <jccinc@...>
>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>Sent: Tuesday, October 29, 2002 9:44 AM
>Subject: [CAD_CAM_EDM_DRO] Re: DRO encoders- Rotary or Linear?
>
>
>> --- In CAD_CAM_EDM_DRO@y..., "Roger Linscheid" <r.linscheid@a...>
>> wrote:
>> > Hi, I am ready to begin adding a DRO to my G4003 lathe. What is
>> the
>> > current thought on the best method to accomplish my goal?
>> >
>> > IIRC, when I was looking into this before, the linear strips from
>> > U.S. Digital were only available in 250 CPI and this was not
>> > considered high enough to provide the necessary resolution. Using
>> > rotary encoders meant the possibility of losing counts if the drive
>> > cable slipped or stretched.
>> >
>> > Now U.S. Digital has linear strips in 300 and 360 CPI. Will these
>> > provide a resolution of 0.0005 or better?
>> >
>> Roger:
>> Since you seem interested in accuracy, why not use rack and pinion
>> for rotary encoder drive. A 1/10 inch circular pitch rack with a 20
>> tooth pinion requires a 500 count encoder to read .001". Precision
>> rack is available from PIC Instruments, Berg, and Allied Devices.
>> They can also provide you the pinions. Less expensive rack is
>> available elsewhere.
>>
>> Linear encoders eliminate backlash and encoder mounting errors and
>> are probably the better of the two approaches. A 250 line scale will
>> give you (with 4x multiplication) a .001" resolution. A 360 line
>> scale yields 1440 steps per inch or .6944 mils per step.
>>
>> Good luck,
>> Jack C.
>>
>>
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>Addresses:
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>FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
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>OFF Topic POSTS: General Machining
>If you wish to post on unlimited OT subjects goto:

aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.

>http://www.metalworking.com/news_servers.html
>
>http://groups.yahoo.com/group/jobshophomeshop I consider this to be a

sister site to the CCED group, as many of the same members are there, for
OT subjects, that are not allowed on the CCED list.

>
>NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.

DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........

>bill
>List Mom
>List Owner
>
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
>

Regards, Hoyt McKagen

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