huangyhg

surface profile at mmc?
i have a project involving two irregular shapes which must fit inside each other without interference. i'm trying to figure out if i have the gdt notation correct. the attached picture should explain itself. anyone care to offer a suggestion?
thanks!
first post, i goofed the attachment. i hope this works...
1.when profile control is specified without datum references, it will control the form only. for your irregular complex feature surface application, i will recommend to specify with datum references since it will control the size, location, orientation and form.
2.profile tolerance may be combined with positional tolerancing where it is necessary to control the boundary of the feature, asme y14.5m standard fig 6-19 is an excellent example on your application.
3.you need to add an "all around" symbol on bend of the leader line to specify the profile tolerance zone covers all surfaces around the outline of the feature.
4.material modifier mmc is not allowed here, but it is allowed on datum.
5.to avoid the interference, i will recommend:
*to choose unilateral inside tolerance for male part.
*to choose unilateral outside tolerance for female part.
seasonlee

season lee:
you mentioned that mmc is not allowed here but is allowed on a datum?? what standard are you using? if one is using the 2009 standard, mmc is allowed on the datum if it is a feature of size or surface. using the 94 standard, mmc is only allowed on a datum that is feature of size but not on a surface.
dave d.
the gd&t as shown on your drawing is illegal. as seasonlee said and dingy confirmed, you can use an mmc modifier on the datum that the profile is called out to as long as the datum is a feature of size. using an mmc modifer in the tolerance portion of the fcf is never allowed.
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i agree with seasonlee's suggestions of adding an all around symbol and deleting the mmc modifier. i'm not a fan of the "boundary position" method though, so i wouldn't recommend that.
regarding the need for datum features, it depends on how the two parts go together. if the two irregular surfaces just need to mate with one another without any other features being aligned in any particular way, then datum references are not needed. this seems unlikely though.
i would guess that the two parts would need to mate together with full contact between the "bottom" face of the upper (female) part and the "top" face of the lower (male) part. in this case, the mating face on each part should be labeled as a datum feature and referenced in the profile callout for that part.
it is also possible that certain "sides" of the two parts are used to align the parts to each other. if this is the case, the aligning sides need to be labeled as datum features and referenced in the profile fcf's.
evan janeshewski
axymetrix quality engineering inc.
thanks all for your comments. i just purchased geometrics iii and will use that in addition to the above comments to take another crack at this. i'll post it up when i think i've got it to see if you agree. thanks again.
tandqbpoii,
definitely with the 1994 standard, you can use a broken line on one side of the profile to show which way it can vary. this allows you to draw and specify at mmc or lmc. i do not see why the 2009 standard would change this.
figure 6-18 in asme y14.5m-1994.
jhg
as i understand it, the 2009 standard allows the use of "u" in a circle, used the same as in y14.41. this eliminates the necessity of graphically showing which direction to apply the tolerance.
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after reading your comments and going through asme y14.5-1994 i think what i have attached is correct. the standard seems to say it would be incorrect to use mmc here unless its attached to a position control. thanks for your comments.
goofed the attachment again. see if this works.

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