Can I Add MMB to Datum A to get Datum shift to Facilitate Bigger Diameter during Assembly

[2020Learner]

Hello Team,

I have a question on the attached picture. CAn I make Datum "A"(Dai. 40) as MMB to get DAtum Shift to facilitate Assembly of bigger Diameter (Dia.90) with counterpart during Assembly?. This is Sheet Metal part.

 

[ewh]

You may get a better response here -> forum1103

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[2020Learner]

Thank you

 

[drawoh]

2020Learner,

Is this one or two sheet metal parts? Do they assemble?

--
JHG

 

[2020Learner]

Hello drawoh,

this is only one 1.5 mm thickness single sheet halfshell(Front view & left side view). there is one more halfshell which fits from right side to a depth of 6mm

regards,
2020Learner

 

[drawoh]

2020Learner,

Your piece is not what I would call sheet metal. You are fabricating from sheet metal, but the fabrication process is deep drawing, a progressive die, or some guy with a hammer and forge.

I think your datum[ ]A feature is a spherical radius, not a flat one. It is not a feature of size. MMB is meaningless unless it is being measured from some other datum features.

Your part is sort of like a casting in that it is wildly non-orthogonal. Your best bet would be to define datum targets somewhere. Datum targets will give you a practical fixture from which to inspect your part. MMB may not be a useful concept here. It sounds like you have a maximum allowable spherical radius.

--
JHG

 

[2020Learner]

drawoh (Mechanical,

Thank you for your reply and Sorry I am replying late. I somewhat agree with you but here is my explaination.
Yes you are right, this shape is achieved by stamping process of 1.5 thickness sheet metal part. Datum A is half circled profile of Diameter 40mm.
For Datum A,I have applied profile tolerance of 1 acting on ID of dia40 so we will get two Size right?, i means there are two sizes, One is Dia41 and Dia 39. So when i use Expanding Mandril at Datum A(RMB) & Datum B(RMB), After Stamping, part will be rigid in gauge(deviated part) or during Assembly right?

Hence i want to apply MMB for Datum A & Datum B (Gauge will be fixed at MMB) hence there will some gap between Gauge and the part (if part departs from MMB). This gap (shift at Datum A & Datum B) will facilitate to pass inspection or to assemble with counterpart of similar contour.

Thanks,
2020Learner

 

[3DDave]

MMB only helps if the mating part is to have clearance up to the amount of the deviation from the minimum contour - in other words, if it's OK that the mating part has a sloppy fit.

 

[2020Learner]

Thank you 3DDave.

Initially I thought this will work for DAtum Shift according to the datums mentioned. This is fabricated part, Now datum targets were provided for this part.

Thank you all for your replies.