Re: CNC Lathes, follow rests, and mass production...

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jeff Albro <jeff@a...> wrote:

> (Thanks everyone who responded....)
>
> Okay... follow rest bad for production, (_maybe_ a three point

system)

> bar puller good.... got it : )
>
> Two follow on questions:
>
> 1) Are there cnc controlled chucks out there for less than the

cost of a

> first born child?

No. There are three components to power chuck cost:

1) Design $ Plenty of designs around to copy using air or
hydraulics
2) Production $$ Many close fitting, sliding fits, usually hand
lapped
3) Liability $$$

> 2) Don't you have to support the other end sticking out of the
> tailstock? Or do you just keep it short?

You absolutely must support the bar end , and preferably have a
tubing enclosure all along the extended length. Many CNC machines
with power chucks have a CNC controlled "Bar Feeder". This can be
an air or hydraulic pusher system that pushes the bar against a CNC
positioned stop if front of the opened chuck. One that I admired
used steel cable attached to a counterweight with a pulley system.

The programming for a bar puller is more complex than a bar feeder
as the bar feeder will exert constant pressure, or have an external
M code controlled release. The programmed process( in G-code) is
move stop to position, open chuck, close chuck.

With a puller the CNC program steps are change to ipm feed, grab
bar, open chuck, pull, close chuck, release bar, change to ipr feed.
Grab bar, pull, and release bar are G01 type motion commands with
associated tool offsets for the bar puller.


Fred Smith - IMService
http://www.cadcamcadcam.com/hobby