Re: [CAD_CAM_EDM_DRO] Rack and Pinion

Dave, Any rack or gear pitch would work. Wouldn't it all be compensated for in the pulse steps per inch in the software config? Config for the unit of travel. If it be a pinion with a 3" pitch lead circumference, you'll need about 40 RPM of the motor to make one rev of the pinion using the same ratios as a mill to maintain torque. Then 40 times the resolution of the encoder or steps per rev., alot of room to fine tune the accuracy.

Ron

turbulatordude <dave_mucha@...> wrote:


Hi all,

I am probably missing something very simple in this.

A spur gear has a unit value as the rack with a pitch diameter
value of 1 inch. ie: a 12 pitch rack matches a 12 tooth gear when
the pitch diameter of the gear is 1 inch.

This then means the linear movement equals Pi for one revolution of
the gear.

Pi does not fit very well into any gear ratios or stepper or encoder
ranges.

How then, does one get a 4 foot axis without some accumulated error ?

I can understand accept the table and machine will probably be worse,
but theoretically, the best I get is a little over 1 thou over 72
inches. ( what did you say?? shut up and quit complaining over 1
thou ?)

I just don't want to use two jackshafts with 4 timing gears to get
this theoretical accuracy.

Am I missing something simple ?

I've been looking at 12 and 16 pitch as the rack and gear width seem
to be good. Higher pitch seems to be much thiner, maybe too thin ?
I do know the larger plasma table makers use much finer pitch, but
special order racks to get the wide face contact.


Dave








Addresses:
FAQ: http://www.ktmarketing.com/faq.html
FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com

Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@..., timg@...
Moderator: pentam@... indigo_red@... davemucha@... [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
List Mom
List Owner


Yahoo! Groups Links









[Non-text portions of this message have been removed]