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8/12/2019 Profile of Surface in a nutshell
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Regarding to the drawing.(For the GD&T Profile of surface)
For more understanding please see the presentation.
1. The indicated symbol is not clear.
2. The intent of GD&T symbols are not yet completely to control the surface properties.
3. The proper feature what we have to use to control GD&T Profile of Surface
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That mean : Control only the indicated surface
All around symbol
That mean : Control all around surface
ASME Y14.5-2009 Page 159
1.The indicated symbol is not clear.
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2. The intent of the datum reference also no clear.
They have only one datum , The meaning is shown as below.
The indicated surface must lie between two parallel two boundaries 0.001 apart perpendicular to datum
plane G and equally disposed about the true profile.
ASME Y14.5-2009 Page 162
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The indicated surface must lie between two parallel two boundaries 0.001 apart perpendicular to datum
plane G and equally disposed about the true profile.
ASME Y14.5-2009 Page 162
Tol. 0.001
nominal
Size deviation Form deviation Orientation deviation
actual
Three deviation was
controlled from theGD&T symbols
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Size,Form,Orientation deviation have been control by the Profile of Surface tolerance 0.001
Tol. 0.001
Size deviation Form deviation Orientation deviation
But for Location deviation have not been control
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Location deviation have not been control
That’s mean if the actual surface was located at the wrong position.(out of tolerance)
But the measurement results may be acceptable.
Even though the actual profile was located very far from the datum (DRF)
The nominal profile will move following to the actual profile position and do the best fit
Actual
0.001 G
DRF (Datum G , H , I)
The deviation are calculated between the nominal profile and the actual profile.
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5.220
H
1.0969
I
0.004 G H I
0.001 G
For example. In this case if they want to control all the complete of dimensioning.
Especially for the case of the Location control
The upper segment of the feature control frame locates the feature to specified datums.
The lower segment of the feature control frame specified the size,form,shape and orientation to specified datums.
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5.220
H
1.0969
I
0.004 G H I
0.001 G
That’s mean the datum reference frame(DRF) must be established.
Primary datum : G , Secondary datum : H , Tertiary datum : I
The profile nominal will
be made by getting the
value of the basic
dimension which is
reference from the origin
of DRF
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Size,Form,Orientation deviation have been control by the Profile of Surface tolerance 0.001
Tol. 0.001
Size deviation Form deviation Orientation deviation
Location deviation have been control by the Profile of Surface tolerance 0.004
0.004 G H I
0.001 G
Tol. 0.004
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Location deviation have been control by the Profile of Surface tolerance 0.004
That’s mean even if the actual surface was located at the wrong position.(out of tolerance)
The Judgment will be very clear.
Actual
But the nominal still located at the position where is reference from the datum (DRF)
Tol. 0.004
The deviation are calculated between the nominal profile and the actual profile.
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3. The proper feature what we have to use to control GD&T Profile of Surface
In term of the the symbol “profile of surface” . We have to measuring by 3D feature.
That’s mean : It would be better to use freeform of surface.
