Datum callout question 2

[SeasonLee]

I have some questions about this print, and I tried to make some changes as shown below. The reasons for making these changes are:

• The common datum(A-B) is constructed after the individual feature is designated as the datum feature.
• The existing DRF refers to the datum feature itself, normally we will consider it as a coaxial part, but here is a multiple skewed cylinder.

Do you agree with the changes on the datum callout? Please correct me if I am wrong here.
Thanks for your help.

Season

 

[3DDave]

The one without FCFs on the datum features do not control the datum features relative to each other. They could be individually angled at 45º and the part could still be accepted.

 

[pmarc]

SeasonLee,
If you don't like the A(M)-B(M) option in the position FCFs for datum features A and B, you can specify position FCFs without datums and with SIM REQT note associated with them.

But, as was already said, you need to have a position tolerance (or other tolerance that will is able to control mutual location of the datum features) to have the relationship between the features fully defined.

 

[Burunduk]

SeasonLee,
If you don't like the A(M)-B(M) option in the position FCFs for datum features A and B, you can specify position FCFs without datums and with SIM REQT note associated with them.

But, as was already said, you need to have a position tolerance (or other tolerance that will is able to control mutual location of the datum features) to have the relationship between the features fully defined.

Or as shown in these examples...


The first one is the same as using a Continuous Feature modifier for the 35+/-0.1 diameter.

 

[CheckerHater]

I have strong suspicion that simulated datum feature will rather look like this:

 

[SeasonLee]

Thanks again on all comments.

If you don't like the A(M)-B(M) option in the position FCFs for datum features A and B, you can specify position FCFs without datums and with SIM REQT note associated with them.

Is this your idea? hope I am right.

Season

 

[pmarc]

SeasonLee,

Yes.

Of course, depending on the function, you may still add MMB modifiers after both datum feature letters in the position FCF for the large cylinder.

The other option suggested by Burunduk may work as well, but only if the datum cylinders can be defined with the same size callout.

 

[greenimi]

pmarc,
Is it true that figure 10-58 in Burunduk's laytest replay will have an interpretation problem IF the callout is RFS?
Otherwise stated 2x size xxx.xxx ; position Ø0.15 RFS -datum feature A is ambiguos? Or is okay to be used?

 

[mfgenggear]

pmarc,
Is it true that figure 10-58 in Burunduk's laytest replay will have an interpretation problem IF the callout is RFS?
Otherwise stated 2x size xxx.xxx ; position Ø0.15 RFS -datum feature A is ambiguos? Or is okay to be used?

why?
it would require a more precise machine.
there has been times I had true poison of .0005 at rfs. but the cost increase

 

[greenimi]

It's a pattern at RFS so I am asking how that works?

 

[mfgenggear]

True position. 6 mm (.026)
It doesn't get any bonus
But that is liberal

 

[Burunduk]

greenimi,
RFS would be interpretable.
In terms of the requirement it's two dia. 0.15 mm coaxial cylindrical tol. zones in which the two unrelated actual mating envelope axes must fit. In terms of the measurement It's two measured zones fitted over the two unrelated measured mating envelope axes.