SPC Port Check

[Paul Sarrach]

Its been awhile for me. What's the best way to make a check for SPC Ports? I don't remember how to offset my Plane the -31mm from the top of the bushing.

Thanks

[Scott Appleyard]

We always measure SPC ports in this manner:

1) Measure the SPC bushing using an auto-circle with sample hits.
2) Update the Theo nominal and vector values to the measured values. (We do this because PC-DMIS will project along Theo values when you add a thickness.)
3) Create a CAST point from the circle.
4) Make a copy of the circle and convert it to a surface point.
5) Project the point using thickness the 31mm or whatever distance is needed.
6) In the edit window, remove the thickness, but make sure you don't update the tagets and actuals. Copy the target values back to the nominals so they match the projected nominal values.
7) F9 on the updated surface point and hit Find Nominals. This will find the true contact point on the surface from the CAD file.
8) Create a 3D distance from the point on CAD to the CAST point.

There are other ways of doing the same thing, but this is the method we use.

HTH!!!

[R. Farr]

This is how we do ours with fixture IGES.

1. Measure the top of the bushing as a cylinder (sample w/ 2 rows).
2. Create an alignment. Level and origin to the cylinder.
3. Create an offset point 31 mm (point of contact).
4. Recall the fixture/part coordinates in-between the offset point and the output.
5. Refresh the output of the offset point so the nominal updates.

If you want to check the point of contact, you can always re-type the offset point's nominal into a surface/vector point and find noms.

[Paul Sarrach]

Thanks

[Mr.Natural]

OK here goes, I know how to do it, but trying to explain it is another story.
Example below, Hope this helps.


1 ~ Pgm the bushing Manually Measure the bushing as a cylinder, the face of the bushing W 3 hits, for a plane & 2 rows, 4 hits in the bushing, then let it measure it in DCC mode
2 ~ Create an argument to move the centerline/centerpoint of the bushing you just measured 31mm from the cylinder centerline along the "IJK vectors of the cylinder.
3 ~ create a generic point with the SC point nominal XYZ & the vectors used in the argument you created, as shown below.
4 ~ Dimension the generic point for location.



CYL_3 =AUTO/CYLINDER,SHOWALLPARAMS = YES,SHOWHITS = NO
THEO/955.05,-52.87,1350.35,0.0008777,0.0010103,0.9999991,10
ACTL/955.07,-52.87,1350.34,0.0001675,0.0003626,0.9999999,9.53
TARG/955.05,-52.87,1350.35,0.0008777,0.0010103,0.9999991
THEO_THICKNESS = 0,RECT,IN,CIRCULAR,LEAST_SQR,ONERROR = NO,$
AUTO MOVE = BOTH,DISTANCE = 10,RMEAS = None,None,None,$
READ POS = NO,FIND HOLE = NO,REMEASURE = NO,USE THEO = YES,$
NUMHITS = 4,NUMROWS = 2,INIT = 3,PERM = 3,SPACER = 2,PITCH = 0,$
START ANG = 0,END ANG = 360,DEPTH = 5,$
ANGLE VEC = 0,1,0
ASSIGN/V1 = DELTA(CYL_3.XYZ,CYL_3.IJK,-31)
SC3Z =GENERIC/POINT,DEPENDENT,RECT,$
NOM/XYZ,955,-53,1319.35,$
MEAS/XYZ,V1.X,V1.Y,V1.Z,$
NOM/IJK,0,0,1,$
MEAS/IJK,0,0,1
DIM D1= LOCATION OF POINT SC3Z UNITS=MM ,$
GRAPH=OFF TEXT=OFF MULT=1.00 OUTPUT=BOTH
AX MEAS NOMINAL +TOL -TOL DEV OUTTOL
X 955.06 955.00 0.20 0.20 0.06 0.00 -----#---
Y -52.88 -53.00 0.20 0.20 0.12 0.00 -------#-
Z 1319.34 1319.35 0.20 0.20 -0.01 0.00 ----#----
END OF DIMENSION D1

[Scott Appleyard]

Mr. Natural,
I have to disagree with your procedure. The offsetting of the point using the argument will always be the perfect distance indicated from the bushing face. This would only work if you had the exact XYZ location of the SPC point and then dimension the point by changing the nominals. Even if you did have the location, most companies allow for variance in the non-check directions. I don't believe your method will check the actual distance from the bushing face to the actual point of contact on the part.

[Mr.Natural]

Mr. Natural,
I have to disagree with your procedure. The offsetting of the point using the argument will always be the perfect distance indicated from the bushing face. This would only work if you had the exact XYZ location of the SPC point and then dimension the point by changing the nominals. Even if you did have the location, most companies allow for variance in the non-check directions. I don't believe your method will check the actual distance from the bushing face to the actual point of contact on the part.

Scott,
We do have the exact XYZ location so this works out fine, sometimes you have to add metal thickness to the move distance. Sometimes if metal thickness is involved & they move the point square to grid -vs- normal to surface we need to do a little more figuring to get the exact location of the point. We used +/- 1.0mm in non check directions & +/- .20mm for check directions, but now all axis are +/- .20mm. I realize that there are probally 3 or 4 ways to get the dimension that we are looking for, this is just the way we do it & it has worked fine. I am open to learning anything i can to make myself more efficient with this ever changing software.

[Bill **********]

This works when you have CAD and don't know the nominal location of the SPC point.

1) 3 point plane on the bushing head.
2) Gage pin in the bushing 3 hits three rows for a manual cylinder. Rerun the cylinder in DCC.
3) Level to the cylinder, origin to the cylinder
4) Auto Features Vector point - X0 Y0 check the box beside Z and hit find.
5) Create but don't measure this point.
6) Switch back to your original alignment and dimension the point just found.
7) Use the ACTUALS from the dimension as your nominal for a vector point and do a find. Once the vector point nominals match the ones you dimensioned, change from a vector point to a cylinder with height of 40 and a depth of 35. Control your measurement angles and approach vector so that you can get 90 to -90 around a gage pin and measure this cylinder.
8) create a generic plane with the theoretical X Y Z and I J K of the DCC cylinder from 7 above.
9) Intersect the bushing head plane with the cylinder
10) Intersect the generic plane and the cylinder
11) Dimension the circle created at the generic plane for SPC location
12) Create an alignment leveled to the cylinder and origined to the circle in 10 above. Dimension the circle created at the top of the bushing head in Z with a nominal of 31.
13) Don't forget to go back and delete all the crap you used to find the surface point/cylinder from your program.

This is long and drawn out, but if you don't know the location of the SPC point to begin with this will tell you where it really is.

Bill

[R. Farr]

Mr. Natural,

Our two methods came up with the same actual when I tried yours. Sometimes we don't have the point of contact, but if we create our generic point before we measure the cylinder the actual should be the nominal.

Thanks