rE:Re:RE: programming by hand

>Another thing about electronic files..there isn't any

guarantee

>they'll anymore right than a paper drawing. Just had one

today, the

>dimension on the drawing said one thing and the inherent

dimension in

>the drawing file was different?? Every see CAD files where

the

>entities that would represent a tool path are not

connected? They

>appear connected on the screen and on paper, but they might

have

>larger end gaps than the CAM program can automatically

compensate

>for. I see that one all the time.

I work almost exclusively with ProE files and ProE generated
iges files for machining mostly 2.5 D parts. I machine parts
directly from the geometry files provided, usually before
prints are even generated.The biggest problem I had in the
beginning was convincing the 10 or so mechanical engineers
that the geometry they were creating needed to represent the
actual part they wanted me to machine. this meant that the
model file needed to have all the geometry set to the
nominal of whatever tolerance they wanted. Typically, they
would draw something at 3 inches and then they would
manually dimension the print with a 3 inch plus 0 minus .010
tolerance While some will say that this is not a problem, it
is when you are machining the parts from the model files
sometimes weeks before drawing files are actually created.

I have been able to convince them to provide proper files
for parts machined in house but unfortunately I still see
some parts being sent to outside shops where the electronic
files we provide are not representative of what we want
according to the print. I see the purchasing guys arguing
with the shops over NRE (Non Recurring Engineering) costs
because "well we sent you the IGES files, why should we have
to pay you to redraw the part."And in case where the vendor
simply uses the geometry files we sent to machine the parts
in the same manner I do in house, our inspection department
rejects the parts because they do not match the paper
drawing. In these cases, its up to the vendor to either fix
the parts or he doesn't get paid.

Bill Griffin
www.grifftek.com/links.htm