index table was Re: Bridgeport MDI update

Hello,

There are "indexing tables" made to extend the operating envelope of
a cnc machine (or manual mill). Anyone on this list could probably
cobble one up quite handily. They are essentially a single axis
manually shifted table. The process is similar to shifting the part
on the machine table itself, but much faster and more easily
repeatable.

They consist of a support surface (sub base) sized to fit the
available table of the machine. Then there are linear bearings which
are run parallel to the intended "short" axis. On top of this is a
larger table upon which the work is mounted. Now here is the key:

There is a very repeatable indexing pin or lever system which allows
locking the movement of the top table at some specific offset (10 and
20 inches are typical).

In this way the part with the 32 inch keyway is fastened to the top
indexing table, and the index position is set to allow the first part
(18 inches available, prob'ly use 17 or so) of the operation to be
done. Then the tool is lifted and the table is indexed (shifted) to
again make use of the cnc machines' available travel, but now on a
different part of the work. This allows long parts to be accurately
made on machines with limited travel.

Obviously, the linear bearings of the index table need to be in
alignment with the machine axis (and are "dialed" in when the index
table is mounted), and the precision of the index table needs to be
equal to the expected accuracy of the finished part(s).

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., machines@n... wrote:
<snip>The 12" Y shouldn't be a problem but the 18" X could well be.
> It just means I'll have to pick jobs for it. Some of the keyways
> can be up to 32" long.
> I wasn't actually moaning just passing a comment. When I was first
> looking for a CNC I passed over a couple of Series 1's as not being
> suitable for my job and went for the long bed Beaver. As a second
> machine these limitations aren't as great.