profile and MMC
profile and MMC
(OP)
[.005][(B) mmc] applied to inside wall of the rectangular shaped can (cover). B is a hole at the can bottom. the hole has +.002/-.000 on its diameter. how can i apply MMC to this bilateral profile? bump .005 to .007 or else?thanks.





RE: profile and MMC
That said, there is sort of a back-door effect onto the profile tolerance, and it depends on the actual size that the hole at the bottom is made. BTW, does the hole at the bottom have any GD&T applied to it?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: profile and MMC
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: profile and MMC
Does the profile callout control inside rectangle all around?
RE: profile and MMC
RE: profile and MMC
the profile tolerance is specified BILATERAL.
what M does to the profile tolerance? MMC, or MMB, bilateral becomes uneven bilateral? which side get the "benefit"? will the other side lose the "benefit"?
thanks to all helping me.
RE: profile and MMC
RE: profile and MMC
RE: profile and MMC
You may think of it in following way [let's say the basic rectangle (defined by basic dimensions) is 5" long and 2.5" wide and the datum feature hole is 1" +.002/-.000)]:
Imagine a wireframe containing following elemets:
1. Circle of dia. 1" simulating datum feature hole at MMB
2. Two rectangles - 5.05"x2.55" and 4.95"x2.45" simulating profile tolerance zone. The rectangles are perfectly centered to each other and to the circle defined in point 1.
Now, take your part and try to fit it - by rotating and sliding - inside the wireframe, so that the surface of datum feature hole does not violate circle from point 1 and the outline of the rectangle fully fits inside a space between two rectangles from point 2. If you weren't able to fit it, the part is out-of-spec.
So what is the benefit of (M) modifier in profile FCF? It is hidden behind a type of movement you did when trying to fit the part inside the wireframe. If you were able to slide and rotate the part that means the diameter of datum feature hole was bigger than 1.000 and smaller than 1.002. If you were only able to rotate the part, the diameter of datum feature hole was exactly 1.000. Rotation would be also only type of movement available if the profile FCF was [.005][B].
Having said all of that, notice that (M) modifier does not enlarge profile tolerance zone - it is always 0.005 wide. Instead of it you gain a possibiliy of shifting the part to fit it inside profile tolerance zone, if datum feature hole is not at its MMB = 1.000.
I hope you picture what I tried to say.
RE: profile and MMC
If you attach something, make it .pdf, .jpeg, .png, .doc or something similar. Thanks.
RE: profile and MMC
in pdf
RE: profile and MMC
My explanation about interpretation of profile FCF applies to this drawing too. The geometry is slightly more complicated, but you will still have a possibility of shifting the part to fit the inner contour inside profile tolerance zone if the datum feature hole is not at MMB = 1.000.
Positional tolerance applied to that hole has no impact on what I said, since profile FCF does not use A as datum reference. If A was referenced in profile FCF, you would have more shift available, because circle described by me in point 1 would be. dia. .188, and not .190.
Side note: I assume the true profile of inner contour is described somewhere by basic dimensions - in CAD file for example.
RE: profile and MMC
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: profile and MMC
thanks.
RE: profile and MMC
Did I understand your response correct? Are you saying that profile FCF's with and without (M) result in the same geometrcial requirements?
RE: profile and MMC
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: profile and MMC
http://files.engineering.com/getfile.aspx?folder=5...
RE: profile and MMC
thanks.
see attached.
RE: profile and MMC
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: profile and MMC
Here is what would happen if tolerance zone was enlarged:
You added .1 (half of maximum datum feature shift available) to profile tolerance and made it +.35/-.25 all around. But notice, that by doing it you changed the requirement for maximum height and width of rectangle. Using your logic maximum actual size of outline could be 2.70 x 3.70. My example is showing the rectangle that cannot be bigger than 2.50 x 3.50.
RE: profile and MMC
[prof][.5][B(M)] = [prof][.6(U).25][B(S)]
RE: profile and MMC
These are not equivalent callouts (even if you correct the second one to [prof][.6(U).35][B(S)]).
Like I suggested, think of minimum and maximum size of rectangle allowed by the callouts.
For [prof][.5][B(M)]:
- min. size of rectangle would be 1.50 x 2.50;
- max. size of rectangle would be 2.50 x 3.50;
For [prof][.6(U).35][B(S)])"
- min. size of rectangle would be 1.50 x 2.50;
- max. size of rectangle would be 2.70 x 3.70;
Since they result in different extreme sizes of the outline, they cannot be considered equal.
RE: profile and MMC
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: profile and MMC
A star for your valuable profile MMB post.
SeasonLee