Alignments/TP

[AuRules]

99.9% of our blueprints uses +/- tolerance to control feature locations. Now after running these part for 40 years, the engineers wants to convert to GD&T (70+ prints) which I have used on MM4 quite a bit, not much on PCDMIS. So I need a little help in understanding the TP callout icon. I have three datum I use to create an alignment that will check every feature on the part back to. So do I even need to use the Matrials Condition callout, trying to understand that is a little bit hard. Does any one have any litature or help on this. I'm using V3.7MR3. Also it says in the materials block use datums, do we have to assign a datum name to certain feature.???????

Thanks..

[Matthew D. Hoedeman]

99.9% of our blueprints uses +/- tolerance to control feature locations. Now after running these part for 40 years, the engineers wants to convert to GD&T (70+ prints) which I have used on MM4 quite a bit, not much on PCDMIS. So I need a little help in understanding the TP callout icon. I have three datum I use to create an alignment that will check every feature on the part back to. So do I even need to use the Matrials Condition callout, trying to understand that is a little bit hard. Does any one have any litature or help on this. I'm using V3.7MR3. Also it says in the materials block use datums, do we have to assign a datum name to certain feature.???????

Thanks..

TP or not TP, that is the question....

IF you are aligned to ABC and your TP callout is to ABC, you don't need to do a THING! Simply dimension the TP of the hole, with or without MMC (part of the TP). IF your FCF calls the TP out to ABC and includes the MMC for A, B, or C, you won'y like what Pcdmis does (TTRUST ME!). IF you do NOT need any of the MMC bonus from the datums to be in tolerance, IGNORE IT, you will have MUCH MORE peace of mind. Each version of Pcdmis does MMC on datums differently (if they do it at all, some do NOT!). V4+ will let you pick which way, all others do NOT and they all do it differently.

ONE THING! When doing TP dimensions, ONE option is "DEV PERP TO CENTER LINE", I would suggest you use that, other wise, ANY surface deviation from surface sample hits WILL show up and be part of the TP deviation.

[winston]

Material Condition on a hole for example will give you a chance for bonus tolerance. it is dependant on the hole size, the closer the is to the biggest allowable size (LMC Least Material Condition) the more bonus tolerance you can get. if the hole is at the smallest allowable size (MMC Maximum Material Condition) then you get zero bonus.

in laymans terms - a bigger hole will give the mating part a better chance at fitting when assembled.

this is just a small tidbit of GD&T i think you are kind of asking for a GD&T course, you may want to purchase the ASME Y14.5M-1994 Dimensioning and Tolerancing manual.

[winston]

heres a diagram

[winston]

it is, but the condition of the hole being the biggest size is called Least Material Condition because there is less material there. if it were a stud then the biggest size would be Max Material Condition.

but ya you have to have the little M with the circle around it to get bonus and the main reason an engineer should use that M is because it has a mating part that could benefit by a larger hole.

edit: err... i think someone deleted a post that this ^ response was directed at.

[AuRules]

TP or not TP, that is the question....

IF you are aligned to ABC and your TP callout is to ABC, you don't need to do a THING! Simply dimension the TP of the hole, with or without MMC (part of the TP). IF your FCF calls the TP out to ABC and includes the MMC for A, B, or C, you won'y like what Pcdmis does (TTRUST ME!). IF you do NOT need any of the MMC bonus from the datums to be in tolerance, IGNORE IT, you will have MUCH MORE peace of mind. Each version of Pcdmis does MMC on datums differently (if they do it at all, some do NOT!). V4+ will let you pick which way, all others do NOT and they all do it differently.

ONE THING! When doing TP dimensions, ONE option is "DEV PERP TO CENTER LINE", I would suggest you use that, other wise, ANY surface deviation from surface sample hits WILL show up and be part of the TP deviation.

I have the MMC/LMC thing down pat. I was asking about applying it in the TP icon. Which MATT as the "UG" answered it again. The only MMC I see on any of these print is the 2 locating dowel holes with are .5002 +/- .0003. and the rest of the holes use threaded center finders.

Thanks......again all for your input.

[winston]

sorry i misread your post as that you needed help understanding GD&T.

as far as using the CMM to calculate bonus, i use gage pins and calculate it manually and only if its needed to bring the hole loc in tol. if you dont need bonus to bring it into tolerance i wouldnt even worry about it unless some bean counter tells you so. gage pins are the way to go for checking hole sizes which is why pcd4.0+ su>< since its such a pita to edit reports. thats just me thou.... im not a UG only 22 posts so im not uber like matt.

[AuRules]

sorry i misread your post as that you needed help understanding GD&T.

Your quite welcome....

Knowing it and applying it or 2 different monsters.

[Adam Olson]

Winston, I deleted my post. After looking at your chart it made sense. So trying to save face I deleted it. Thank you.

[winston]

Winston, I deleted my post. After looking at your chart it made sense. So trying to save face I deleted it. Thank you.

heh no worries, i tried posting that as a pdf but it was over the limit so i had to screenshot it, paste it in to paint, save it as a jpeg, open it with this crappy Microsoft Picture Manager, crop it then up load it and i tried to quote your post but there are two quote buttons on these forums for some reason and i picked the wrong one i guess.