Need help with a position callout of a plane

[pcdmisstudent]

Hey all
Ill upload a snapshot for your convience.

I have this true position callout of a angled plane to A and B.
Basically what I did was measuring A (plane), and B(Midplane) and then measured the feature (angled plane), then I reported the position using Xact. I also tried aligning to the datums and just callout the angle/position, but it doesnt give me any good results.

When I measured it using Xact, the theoretical values becomes very weird, nominal X value 6.975, Y 5.321 etc...
can anyone guide me through how i can report this callout? both so i get the true position tolerance 0.04 and the boxed dimensions?

[pcdmisstudent]

And also bonus points if you can help me understand the purpose of this dimensioning, (especially the 8mm and 12.5mm dimension). Why not just do angularity and maybe dimension a lenght to the point where the angled plane pierces the flat planes

[Schlag]

This could have been dimensioned allot of different ways. Position is about the last callout they should have used..

[JEFMAN]

And also bonus points if you can help me understand the purpose of this dimensioning, (especially the 8mm and 12.5mm dimension). Why not just do angularity and maybe dimension a lenght to the point where the angled plane pierces the flat planes

Dimensionning like this would give different results fro a part to another, the tolerances are very large.
You can construct a generic plane with boxed dimensions, then measure the distances of hits to this plane, it will show you the right result.

[pcdmisstudent]

Thanks, yeah I had an idea i had to experiment with generic elements, but i havent been working with them a lot.
So basicailly i just align on A & B, then construct generic plane at Y12.5 (dependent), and then another plane at X8 (also dependent). and dimension the lenght to it from the datums?

edit: just tried this method (as i explained), and when i dimensioned the generic planes to the datums the measured are the same as nominal (8 and 12.5)

[JEFMAN]

I would (assuming Z + to the top and X+ to the right on your picture)

ASSIGN/V1=COS(DEG2RAD(20))
ASSIGN/V2=SIN(DEG2RAD(20))
F1 =GENERIC/PLANE,DEPENDENT,CARTESIAN,$
NOM/XYZ,<8,0,12.5>,$
MEAS/XYZ,<8,0,12.5>,$
NOM/IJK,<V1,0,V2>,$
MEAS/IJK,<V1,0,V2>

You can write a Y value instead of 0, but not in the vector !

[pcdmisstudent]

Thanks, I just tried this without any success
Ill post the code if that clarifies it

A12 =ALIGNMENT/START,RECALL:A11,LIST=YES
ALIGNMENT/LEVEL,YMINUS,PLAN_YMIN
ALIGNMENT/ROTATE,XPLUS,TO,PLAN_SYM,ABOUT,YMINUS
ALIGNMENT/TRANS,YAXIS,PLAN_YMIN
ALIGNMENT/TRANS,XAXIS,PLAN_SYM
ALIGNMENT/TRANS,ZAXIS,D_10
ALIGNMENT/END

ASSIGN/V1=COS(DEG2RAD(20))
ASSIGN/V2=SIN(DEG2RAD(20))

F1 =GENERIC/PLANE,DEPENDENT,CARTESIAN,$
NOM/XYZ,<8,0,12.5>,$
MEAS/XYZ,<8,0,12.5>,$
NOM/IJK,<V1,0,V2>,$
MEAS/IJK,<V1,0.0000079,V2>

DIM DIM2= LOCATION OF PLANE F1 UNITS=MM ,$
GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=BOTH HALF ANGLE=NO
AX NOMINAL MEAS +TOL -TOL DEV OUTTOL
X 8.000 8.000 0.050 -0.050 0.000 0.000 ----#----
Y 0.000 0.000 0.050 -0.050 0.000 0.000 ----#----
Z 12.500 12.500 0.050 -0.050 0.000 0.000 ----#----
END OF DIMENSION DIM2

F2 =GENERIC/PLANE,DEPENDENT,CARTESIAN,$
NOM/XYZ,<8,12.5,0>,$
MEAS/XYZ,<8,12.5,0>,$
NOM/IJK,<V1,V2,0.5773503>,$
MEAS/IJK,<V1,0.0000085,V2>

DIM DIM3= LOCATION OF PLANE F2 UNITS=MM ,$
GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=BOTH HALF ANGLE=NO
AX NOMINAL MEAS +TOL -TOL DEV OUTTOL
X 8.000 8.000 0.050 -0.050 0.000 0.000 ----#----
Y 12.500 12.500 0.050 -0.050 0.000 0.000 ----#----
Z 0.000 0.000 0.050 -0.050 0.000 0.000 ----#----
END OF DIMENSION DIM3

Also as you see the vector that was "0" changed to .00008 for some reason when measuring it

[JEFMAN]

The code that I posted was "assuming the top is Z", and it's Y...

ASSIGN/V1=COS(DEG2RAD(20))
ASSIGN/V2=SIN(DEG2RAD(20))
ASSIGN/ZERO=0

F2 =GENERIC/PLANE,DEPENDENT,CARTESIAN,$
NOM/XYZ,<8,12.5,ZERO>,$
MEAS/XYZ,<8,12.5,ZERO>,$
NOM/IJK,<V1,V2,ZERO>,$
MEAS/IJK,<V1,V2,ZERO>

Then, you measure the plane, and dimension the 3D distance to F2, by selecting MAXMIN in the dimension.

[pcdmisstudent]

doh!!
Thanks, now it worked perfectly!
love u jeff

[KIRBSTER269]

This should be profile callout back to A and B, this way it would control the angularity, location, form of the plane. If you chose angularity of the plane, that doesn't control the location of that plane, it could be 42 inches away from where your picture shows and as long as the angle is 70° that plane can be anywhere, so that doesn't help you. Position doesn't help either, because that would just take the average of the plane in the X and Y and Z location. that would not show you if the 70° is good or not. Profile would create an envelope of a particular location at the right angle and that plane would have to fit in that envelope. taking care of all the basics and correctly giving all the information about that plane you seek Schlag is correct on this.

[pcdmisstudent]

Nice explanation!
Thank you

[KIRBSTER269]

no problem

[NinjaBadger]

Whilst I agree Profile would have been what I'd prefer to see, Position achieves the same thing from a GD&T perspective.

We're talking ISO here (which I assume the drawing is, as ASME can't have position for a plane).

Position or profile would give the same tolerance zone, and all the feature must be contained within the tolerance zone. The issue would be for Position PC-Dmis would only look at the centroid of the feature where as profile would look at the hits.

[pcdmisstudent]

The issue would be for Position PC-Dmis would only look at the centroid of the feature where as profile would look at the hits.

Is this why the nominals in the Xact window are not relating to the nominals in the drawing (70degrees, 8 & 12.5mm) ?

Since I followed Jeffs solution, i made two linear dimensions for L12.5 & L8 and then two angular dimensions for 70 degrees around A, and 70 degrees around B, all with tolerances of +/- 0.02mm. But with Position, some of these dimensions could deviate up to 0.04.