Re: [CAD_CAM_EDM_DRO] How does one adjust Ballscrews on a Bridgeport

Ballscrews are like that. They feel spongy when they have no backlash at all. I ran a manual machine with ballscrews and it was exactly like what you are describing. I dont know why they are that way. They feel much different than an acme leadscrew which feels very solid. But, with a servo or stepper belted to them they will hold perfect position. I can't explain it.

Ron

Stephen Wille Padnos <spadnos@...> wrote:

Hi, all.

Both myself and a friend are having the same issue with our Bridgeport
milling machines. We're both converting manual machines to CNC. I
installed new ballscrews (his machine came with ballscrews), and they
feel "springy". If I lock the table and push the handwheel, it turns a
little (around 8-10 mils, according to the dials). If I let go, it will
spring back to where it started. It gets harder to push (like a
spring), until eventually I overcome the table lock friction, and the
table moves.

I'm using the same bearings that were used for the leadscrews I
replaced. They are dual opposing Fafnir 204KT4 on one side, and a
single SKF 6204 on the other side (the single bearing on my friend's
machine is a Fafnir 204KTT).

We're not quite sure how to proceed. We have thought of putting shims
in various places - between the inner races of the two angle bearings or
between the outer race and the bearing bracket. It seems like a preload
problem, we're just not sure what needs to be preloaded.

The odd thing is that I don't remember the leadscrew doing this (though
it was one of the first things I pulled out of the machine for the
retrofit :), and my friend is pretty sure his didn't do this when he
bought it (the table had to be removed for shipping, so he did take his
machine apart and put it back together).

Any ideas?

Thanks
- Steve



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









---------------------------------
Do you Yahoo!?
Yahoo! Mail Address AutoComplete - You start. We finish.

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