[AT] Transmission oil, 90-wt? Now: drawings

[Larry D. Goss]

The difficulty with dimensioned drawings is that there are companies
that routinely treat the dimensioned drawing as the official document
for the design (which it used to be, historically) rather than letting
the electronic database have precedence.  I even caught the author of a
major drawing textbook trying to inject information about how to make
hand corrections to the plotted output from a CAD package.  That is
plain and simply an ethical and legal No-No.  The database and the
drawings have to agree with each other.  The plotted or printed output
(drawing) from a CAD package is nothing more than refrigerator art.  All
of us know what refrigerator art is -- Johnny or Susie brings a paper
home from school, shows it to their parents, and it gets posted on the
refrigerator until the next piece of paper is brought home.  But you
don't correct it, preserve it, or otherwise treat it as anything except
a "check print".  In the case of an engineering drawing, you most
certainly don't take dimensions off of it or scale the drawing directly
to determine any measurements.  If a company doesn't have the capability
of going directly from the 3D model information to a tool path without
referring to the drawing, they're in trouble.  They're likely to find
fewer and fewer contracts coming their way.

A local company was a vendor for parts to a major appliance
manufacturer.  They called me in for help on a contract they had where
the company had given them the database and a complete set of annotated
CAD drawings.  The vendor proceeded to redraw the parts from the CAD
drawings and converted it as they went to the procedures and the units
of manufacture they were used to.  And then they wondered why their
parts didn't pass the parent company's inspection.

But the parent company was not exactly blameless.  They were attempting
to use geometric tolerancing on flexible items such as rubber gaskets
and vacuum-formed plastic sheets.  That's not appropriate practice,
either.

But here's the bottom line: the local vendor lost the contract and
eventually closed its doors after an association of more than 20 years
with the parent company.  The parent company sold the whole line
(including all the production equipment) to a company in China, and you
can now buy the same appliance under a different imported brand name at
either Lowes or Home Depot.

Larry

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of John Hall
Sent: Tuesday, September 05, 2006 8:33 PM
To: Antique tractor email discussion group
Subject: Re: [AT] Transmission oil, 90-wt? Now: drawings

I'm a little confused when you said you're in favor of getting rid of 
dimensioned drawings. Do you mean paper drawings or cad drawings with no

dimensions? We are seeing more and more solid models with literally no 
dimensions. We either charge for dimensioning or have the customer
dimension 
them before we start. Heck, they even want us to quote parts lately
without 
having dimesions on the print. My high school drafting teacher would go 
beserk on the junk some of these "engineers" put out. Our easiest to
work 
for customers are the ones who put out "textbook" drawings. Even their 
prototypes bolt together and work teh first time. Revisions with these
guys 
are generally minor.