CAD CAM EDM DRO - Yahoo Group Archive

RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION

on 2005-01-24 12:37:12 UTC
Ron,

Why would a 8:1 or 10:1 need to be a 2 step reduction? Is it to reduce
belt friction (more belt wrap on the large gear) or is it a moment of
inertia concern (large diameter gear = geometrically larger I). I'm
guessing the latter but just looking for confirmation.

Regards,

Adrien

-----Original Message-----
From: R Rogers [mailto:rogersmach@...]
Sent: Monday, January 24, 2005 2:10 PM
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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if you have trouble.
http://www.metalworking.com/news_servers.html

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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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Discussion Thread

mfmiranda 2005-01-24 10:13:58 UTC BALLSCREWS QUESTION Henrik Olsson 2005-01-24 10:46:46 UTC Re: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION R Rogers 2005-01-24 11:10:34 UTC Re: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION Terrenoire, Adrien L 2005-01-24 12:37:12 UTC RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION Dave Fisher 2005-01-24 12:39:03 UTC RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION Andy Wander 2005-01-24 12:51:55 UTC RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION A. G. Eckstein 2005-01-24 14:01:42 UTC Re: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION manuel miranda 2005-01-24 14:12:51 UTC RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION R Rogers 2005-01-24 16:51:32 UTC RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION R Rogers 2005-01-24 17:37:40 UTC RE: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION Terrenoire, Adrien L 2005-01-24 20:18:45 UTC Re: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION