Re: confused?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cadcamclub"
<cadcamclub@y...> wrote:

> Good day everyone,
>
> Trying to understand an article from the Techno-Isel site where

they

> described configuration of a mill needed to machine a wing 105'x21'
> ____________________________________________
> http://www.techno-isel.com/Tie/Boeing_5.html
>
> In theory, wing spars and wing skins made in one continuous
> piece..... require metal measuring up to 105 feet by 21 feet. ... A
> standard CNC mill has a fixed length arm extending over a table...
> the spindle would have to hang over 12 feet from the column, losing
> precision and strength.

Think a Bridgport with a table large enough to mill the far side of a
21 foot wide part. the arm extending over the part and table would
need to be 21 foot long. A single column mill of that nature will
flex with the tinyest of cutters.

By using a gantry mill, the gantry is supported on 2 columns thereby
reducing the overhang by half, immeadiatly increasing strenght and
ridigity. but also, by attaching the far end of such beam, even more
ridigity occurs.

Compare a Bridgeport where the table would have to move 21 into and
out of the throat. that means the Y axis would need to be 42 feet
for a fixed head machine.

> ____________________________________________
> It appear to me that a spindle overhanging 12' from the column (12'
> throat) have a work envelope of only 12' in that direction? So, is
> Techno-Isel confused or is it me who is confused?

It is the writer who got you confused. I'm not sure why they talk
about a 21 foot spar, and a 12 foot skin. Seems they jumped from one
part to the other without telling us. That is the point to recheck.
A 12 ft overhang would do the skin, but not the spar. and of course,
it is quite possible the 12 is 21 in reverse and the editor missed it.

Dave

I'd like to see a finished part and know just how many lines of code
they use per part.

>
> A1