profile of a surface

[psalm2]

Can you pick up a bonus tol on profile of a surface when you have the MMC modifer on the -B- and -C- datums? If so how do I show that in my report. I am checking a part on a fixture using the MMC pins so my part is floating. When I use the RFS pins my Ppk study looks good on the form but with the MMC pins it doesent look as good, but if I pick up any extra bonus tol I think I would be in.

[Jan d.]

What version are you running?

[psalm2]

3.52

[Jan d.]

Sorry, I can't help on that one. I know that there are a few issues on V4.0.


Jan.

[craiger_ny]

You can code it in. Do a search for MMC I have posted an example. I code my bonus for everything including Profile.

Craig

EDIT: OK I just tried that and MMC yielded nothing try this

[psalm2]

I did a serch for MMC nothing came up

[craiger_ny]

Right that is why I put a link in my edit.

Craig

[c_bearden]

am I missing something here?????.........Since when do you get any kind of bonus tolerance when measuring a profile??????........Doberman

[Paul Sarrach]

am I missing something here?????.........Since when do you get any kind of bonus tolerance when measuring a profile??????........Doberman

Does this explain it better Doberman? Its the last line that really counts. Craiger you rock. Here is the last line.
What they often miss is the resulting shift that may occur between mating parts. Using profile of a surface in this manner provides the most tolerance while protecting an assembly's fit and shift.

I usally let you all answer these questions, Just trying to let you all remember I am not just the " Forum Hoe' I know a thing or two about a thing or too.

http://www.tec-ease.com/tips/february-99.htm

MMC and LMC
Another MMC Tip Position - Material Condition Modifiers
Profile - Boundaries

Protect Your Boundaries with Profile "Most holes will have both a size and position tolerance. This combination causes the hole to "act" larger and smaller than the actual size from a fit and shift stand point. The smallest the hole may act is called the inner boundary. The largest the hole may act is called the outer boundary. The inner boundary represents the closest the surface of the hole may ever get to the basic location relative to the referenced datums. This boundary often affects the fit of mating parts. The outer boundary represents the farthest the surface of the hole may ever get from the basic location relative to the referenced datums. This boundary often affects the shift or slop between mating parts. The dynamic tolerancing diagrams illustrated below show how the boundaries are affected when position and profile tolerances are applied to a hole. The solid area indicates all of the tolerance of both size and position (including bonus tolerance allowed by modifiers) allowed on the hole. The blue area in each example shows the allowable tolerance when position at RFS is used. The green areas show additional or bonus tolerance."
In this first example Regardless of Feature Size is implied. This is the most restrictive (expensive) control. Although the size may not be less than 9.8mm or greater than 10.2mm, the hole may act like 9.5mm to 10.5mm. Any holes made from 9.5mm to 9.8mm or from 10.2mm to 10.5mm should be rejected for size even though they may function.
By using the MMC modifier, a bonus is allowed that could permit the hole to be out of position by as much as 0.7mm. Although the inner boundary did not change, the outer boundary has grown to 10.9mm since a 10.2mm size hole may be out of position by as much as 0.7mm due to bonus tolerance. This could cause shift problems if this hole is being used to locate parts in an assembly.

http://www.tec-ease.com/tips/febuary-99-1.gif http://www.tec-ease.com/tips/febuary-99-2.gif

By using the LMC modifier, a bonus is allowed that could once again permit the hole to be out of position by as much as 0.7mm. This time the outer boundary did not change from the first RFS example, but, the inner boundary could be as small as 9.1mm since a 9.8mm size hole may be out of position by as much as 0.7mm due to bonus tolerance. This could cause fit problems in an assembly.

http://www.tec-ease.com/tips/febuary-99-3.gif

Although historically profile of a surface has not been widely used to locate holes, it is acceptable and offers many advantages. When the size and locating dimensions are basic, profile controls both size and position. The green areas represent the additional tolerance realized if profile rather than position at RFS is used. The closer to 9.5mm or 10.5mm production makes the hole, the better the position of the hole must be. Production is given the greatest position allowance of 0.5mm if they produce holes at 10mm. This gives production the most possible tolerance while protecting both the inner and outer boundaries. It also encourages production to keep their process centered at 10mm. Designers often use position at MMC for holes because it provides bonus tolerance while assuring fit between mating parts. What they often miss is the resulting shift that may occur between mating parts. Using profile of a surface in this manner provides the most tolerance while protecting an assembly's fit and shift.

http://www.tec-ease.com/tips/febuary-99-4.gif

[craiger_ny]

Maybe I'm missing something but the way I read his post was that he has an MMC material condition modifier on the datums and he'd like to report it.

[kbotta]

Thats kind of what I was thinking. He wanted to include datum displacement (or shift) in his reporting method....right!?
kb

[bw_bob]

I'm running 3.5 mr2........You will have to write some code to get your bonus. Create an array and assign the bonus to that. What i do sometimes is use TP which allows a bonus. Couple of ways to do it.

[c_bearden]

Paul, I have never seen a profile callout on a hole or shaft like your example shows.....Profiles are for Lines and surfaces........you cannot add MMC to a profile callout.......Again, Maybe I misread the original post and maybe I am not as experienced as you but in all my teachings and experience, you cannot add bonus tolerance to a profile of a line or surface........all your examples show holes.....I've never seen that

Doberman

[Paul Sarrach]

I am waiting on a answer from my GD&T guru, will touch back when I get my answers

[kbotta]

I believe you could use profile on a hole, or cylindrical feature's. I don't think the standard says you can't (I could be wrong). I'm not sure why you would want to though, and I have not sen it. Position for "holes", profile for surf's. I suppose that the design engineer would have to pay special attention between the mating parts, as the profile control would yield a different boundary than position, when position has MMC applied to size. (I think that is what Paul was getting at).

I do not believe however, that you can use a material condition modifyer on the size for the tolerance zone(profile example)[matter of fact,,,I am pretty darn certain I've had this disscussion with a member of the standard's committee], as the size will (should) be a basic.
You can however, use shift on the datum references.
0.02
Kev