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Re: Encoder Basics

Posted: Fri Jan 05, 2018 1:03 am
by BigWillieStyle
Question

Lead, Pitch, TPI all refer to different things but numerically are all equivalent?

*Note in below example TPI is actually 5.08 according to my arithmetic.

5mm Lead = 5mm Pitch = 5 TPI*

Is this correct?

Re: Encoder Basics

Posted: Fri Jan 05, 2018 7:12 am
by frijoli
woffler wrote:
Tue Jan 02, 2018 2:11 pm
Hi all ,i have a 16 bit encoder differential driver receiver it says on my servo motor for my spindle ,with A+A-,B+B-,Z+Z- it is a 1.8kw servo motor from DMM tech that i use on my lathe .
I was wondering if it would interface with the Acorn board ?
The DMM servo encoder out will work with Acorn.

Clay

Re: Encoder Basics

Posted: Fri Jan 05, 2018 4:00 pm
by woffler
Thanks for the reply Clay

Re: Encoder Basics

Posted: Fri Jan 05, 2018 4:39 pm
by tblough
BigWillieStyle wrote:
Fri Jan 05, 2018 1:03 am
Question

Lead, Pitch, TPI all refer to different things but numerically are all equivalent?

*Note in below example TPI is actually 5.08 according to my arithmetic.

5mm Lead = 5mm Pitch = 5 TPI*

Is this correct?
BigWillie, lead and pitch are the same. TPI is not - it is the inverse of the others. A 0.2" pitch is 1/0.2 = 5 TPI.

Pitch is how far a screw advances in one turn. TPI is turns per inch. So if one turn moves 0.2 inches then 5 turns move one inch. Metric screws are normally specified based on pitches. Imperial screws are classified on turns per inch.

Your example gives the false impression they are equivalent only because 5mm is close to 0.2" but not exactly. 5/25.4 = 0.19685“. 1/0.19685 = 5.08 turns per inch.

Re: Encoder Basics

Posted: Sun Jan 07, 2018 9:41 am
by DICKEYBIRD
woffler wrote:
Tue Jan 02, 2018 2:11 pm
Hi all ,i have a 16 bit encoder differential driver receiver it says on my servo motor for my spindle ,with A+A-,B+B-,Z+Z- it is a 1.8kw servo motor from DMM tech that i use on my lathe .
I was wondering if it would interface with the Acorn board ?
Remember that the servo motor must drive your spindle at a 1:1 ratio...no belt reduction.

Re: Encoder Basics

Posted: Sat Jan 13, 2018 8:00 pm
by cncsnw
tblough wrote:lead and pitch are the same. ...
Pitch is how far a screw advances in one turn.
Just to be pedantic here:
- Lead is how far a screw advances in one turn.
- Pitch is the distance between successive thread crests.
- They are the same for a single-start thread (the vast majority of threads you will encounter).
- They are different for multi-start threads: lead = pitch * number of starts.

Re: Encoder Basics

Posted: Sat Jan 20, 2018 3:00 pm
by BigWillieStyle
Thanks tb, I appreciate the clarification. Also with regard to encoders, through some additional reading I found a diagram via Dynapar as being a helpful tool for those less familiar, like myself, to delineate the semantics of encoder classification.

http://www.dynapar.com/uploadedFiles/_S ... _29_13.pdf

Image

To the experts, please confirm or correct my assertation with regard to the correct encoder type.