Coplanar Datum Not Quite Coplanar
Coplanar Datum Not Quite Coplanar
(OP)
I have a customer-generated drawing in which the product has a datum that is really key to the functionality of the product, so virtually every other dimension comes off of this datum. The datum is formed by 4 different surfaces that are located of 3 different sides of the part, but are obviously interrupted. We have some parts that are failing to fit up with the mating part. The problem is that, of the 4 datum surfaces, there are 2 small ones that are not planar with the other 2 surfaces. There is no profile callout for these datum surfaces. Is there some sort of implicit profile tolerance? Would a profile tolerance be the long-term solution to control this unacceptable condition?
Richard McInteer
www.class-vi-o-rings.com





RE: Coplanar Datum Not Quite Coplanar
RE: Coplanar Datum Not Quite Coplanar
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Coplanar Datum Not Quite Coplanar
I am just wondering... If you use Continuous Feature modifier instead of profile of surface, how much coplanarity error will be available?
In my opinion the notification <CF> itself is not enough, there still has to be a tolerance controlling the coplanarity.
Side question: assuming <CF> was used, like shown in fig. 7-45, could flatness control be used instead of profile of surface since 2 surfaces would be treated as a single datum feature?
RE: Coplanar Datum Not Quite Coplanar
SeasonLee
RE: Coplanar Datum Not Quite Coplanar
We had a debate on CF applied to non-FOS some time ago. Look also at fig. 7-45.
RE: Coplanar Datum Not Quite Coplanar
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Coplanar Datum Not Quite Coplanar
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Coplanar Datum Not Quite Coplanar
Pmarc, flatness on the <CF> would control the coplanar features as Profile would have.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Coplanar Datum Not Quite Coplanar
Also -- the flatness tolerance with the <CF> would take care of the coplanarity. Would that be an extension of principles? :)
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Coplanar Datum Not Quite Coplanar
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Coplanar Datum Not Quite Coplanar
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Coplanar Datum Not Quite Coplanar
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Coplanar Datum Not Quite Coplanar
Powerhound, I think you're misunderstanding. Simplistically I was imagining maybe a flat, square surface with a 'cross' shape relieved in the middles leaving the 4 corners to create the effective surface.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Coplanar Datum Not Quite Coplanar
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II