RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION

Where else could you get great info like this !!

This is what this group is all about.

Rgds

Dave Fisher

-----Original Message-----
From: R Rogers [mailto:rogersmach@...]
Sent: 24 January 2005 19:10
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION


Manel.

You can use those with a higher reduction between the screw and the servo.
Typically, there is a 2 or3:1 reduction with a .200 or 5mm per revolution
screw. You would need approximately 4 times that reduction to retain the
servo resolution per rev. I would go with like an 8-10:1 reduction then use
a 200 or 250 quadrature encoder and a Gecko320. The reduction would
undoubtedly need to be a two stage arrangement. Two belts running in
parallel, each one with a 4 or 5:1 reduction. The belt on the servo could be
half the size of the belt on the screw. Lets see, 20 mm/8:1 reduction=2.5mm
traverse per servo rev. 2.5mm/1000 servo counts per rev (250 encoder
quadrature)=.0025mm traverse per pulse step. 1mm/.0025 =400 steps per unit
in perhaps Mach2 "motor tuning" menu to calibrate the axies. This
represents units selected as millimeters. This is basically the same as a
mill with 2000 steps per unit in inch units having a .200" lead ballscrew.
.0001" traverse per step. 8:1 reduction, Gecko320 and a 250 count encoder
1000 steps per rev. would work well.

Ron


mfmiranda <mfmiranda@...> wrote:



I'm older to this list but this is my first question to the forum.
I'm looking at putting together my own CNC mill. I already have two superb
40" german x/y linear assemblies and the servo motors (54V, 7A, 3000 RPM),
everything saved from junk. I intend to use Gecko 340 and Mach2.

The question I have regards to the TPIs of my ballscrews -they are 20mm -
(0.8") - per revolution. This seems very large to my purpose.

I would like to know if some of you kind folk would take a moment to figure
the way I can use it with a minimum of acurracy, say 0,01mm, using belt
reduction, I guess.

Thanks very much,

Manel Miranda
Braga, Portugal









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[Moderators] URL to this group:
http://groups.yahoo.com/group/CAD_CAM_EDM_DRO

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
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