Lmc

[simcityguy]

I need a good explanation of why I can use bonus on a LMC true position. The customer is telling me I cant do that. Im not sure how to put in words how the cmm does it. Help please

[bw_bob]

I need a good explanation of why I can use bonus on a LMC true position. The customer is telling me I cant do that. Im not sure how to put in words how the cmm does it. Help please

LMC is just the opposite of MMC. The smaller the ID the more bonus you get & at MMC the larger an ID gets the more bonus.Also look here.

http://www.tec-ease.com/tips/december-02.htm

[craiger_ny]

If LMC is in the FCF you most certainly can use it. If it is not in the FCF then you will most definately lose an argument that you can because it is not implied, never was as far as I know.

Is this another one of those cases of the supplier educating the customer on his own drawings? Again...........

[simcityguy]

Yes I think thats what its turning into. There telling me that if the core is on the larger side I get none.

[craiger_ny]

Is LMC in the feature conrol frame? Is the feature within the size and orientation specification? If so you can apply LMC as long as you are appling it only to the features that the modifier is attached to. If it is in the feature control frame where your target zone size is specified it is applied to the feature. If it is also on a datum it can be applied to the datum that LMC is attached to. As long as all of your feature's (including datums) size and orientation are good you can aply it. Unless there is something I am missing.

[simcityguy]

This is how both TP's look on the print.

[BillP]

I was under the impression the larger hole got or the smaller a shaft got
was least material condition ???????

[bw_bob]

I was under the impression the larger hole got or the smaller a shaft got
was least material condition ???????

MMC = the larger the ID gets the more bonus you get.
LMC = the smaller the id gets the more bonus you get.

[bw_bob]

This is how both TP's look on the print.

As long as the diameters are in tolerance & not at the max or min range depending if ID or OD then you get bonus tolerance for L in FCF.

[craiger_ny]

The largest hole is LMC as it gets smaller additional positional tolerance can be applied. The smallest shaft is LMC as it gets larger additional positional tolerance can be applied. By the looks of that callout you can apply additional positional tolerance to the feature as it departs LMC. Is there something in particular to your method that they question or just the fact that you are doing it?

[simcityguy]

Just the fact that Im doing it, They said if the core is on the larger side even if it is in dim, I dont get LMC I had one part that the TP check .510 and it showed good with LMC and they say I cant do that. Goofy People.lol

[BillP]

bw_bob
I went to the url in you'r post and checked term, did I mis-read it ???

http://www.tec-ease.com/gdt-terms.htm

[bw_bob]

bw_bob
I went to the url in you'r post and checked term, did I mis-read it ???

http://www.tec-ease.com/gdt-terms.htm

No you read it correctly. What that means pertaining to LMC
The ID...If the hole is at its largest then you get zero bonus, but when it starts getting smaller you start getting extra bonus

The OD... The shaft at its smallest gets zero tolerance, but when it starts getting larger the bonus kicks in.

[bob mappes]

per ASME y14.5-1994

2.8.4 Effect of LMC
Where a positional tolerance is applied on an LMC basis, the allowed tolerance is dependent on the actual mating size of the considered feature. The tolerance is limited to the specified value if the feature is produced at its LMC limit of size. Where the actual mating size of the feature has departed from LMC, an increase in the tolerance is allowed equal to the amount of such departure. The total permissible variation in position is maximum when the feature is at MMC, Likewise, referencing a datum feature on an LMC basis means the datum is the axis or center plane of the feature at the LMC limit. Where the actual mating size of the datum feature has departed from LMC, a deviation is allowed between its axis or center plane and the axis or center plane of the datum.

hope this helps ya

[tking]

Typical use of MMC is the larger the hole (within tolerance) the more tolerance you get.

Typical use of LMC is the smaller the shaft (OD), again within tolerance, the more tolerance you get.

My take on it,

TK