Free state modifier, Constrained state Note

[sheevaraam]

Hi All,

I have this plastic part that is warped in free state. But it works well in the assembly which is all I want. What is the best way to call out a note in the drawing saying that the part is to be measured with the datums constrained. I looked up some notes and one says

"NOTES (UNLESS OTHERWISE SPECIFIED)
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
2. ALL TOLERANCES APPLY WHEN PART IS CONSTRAINED TO DATUM A."

Is this correct?

1. My question is is it sufficient to say that part to be constrained at Datum A. Or should I say Part to be constrained at Datum A, B and C (So that it represents the assembled state)?
2. Another question, I have another plastic part, that mates with two parts. So I have Datums A,B and C for the features that mate with part1, and D, E and F for where it mates with the part2. How Do I correctly call out the constrained state note for this situation. The two mates are independent and don't affect each others function. There is some flexing in the part, but when assembled it fits fine.


Thanks everyone in advance for replying.

 

[weavedreamer]

Tolerances apply when part is constrained with load of X.X N·m ±X.X N·m ­load applied in direction X at location(s) indicated Y while supported on Datum A.

This would usually be applied at the detail level, as the assembly would generally illustrate the part with its respective fasteners and their appropriate torque or loading values.

 

[KENAT]

Look at section 6.8 of ASME Y14.5M-1994, especially figure 6-54. My understanding is that you must restrain the features by simulating the restraining forces.

So as well as constraining to A, you have to say how to constrain to A. I'm not sure I can say about B & C without knowing it's function etc.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[SeasonLee]

1. You may think about your restraining requirement is based on functional condition or assembly condition.
2. Normally, when defining restraint conditions, following requirements need to be considered :
* Direction of restraining force
* Location of restraining forces
* Number of places the retraining force is to be applied.
* Amount of restraining force
* Sequence of applying the restraining force
3. The above five considerations will determine which datum need to be restrained, on most cases primary datum is sufficient.
4. The general restraint note should looks like weavedreamer noted.

SeasonLee