Geometric Dimensioning and Tolerancing

Unit 4 – Position Verification

EML 2023Computer Aided Design

Coordinate Measuring Machine (CMM)

• Typical ‘bridge’ CMM is composed of 3 axes.

• A touch probe indicates contact with a body.

• Typical precision measured in microns or micrometers (10-6 m)

EML 2023Computer Aided Design

EML 2023Computer Aided Design

CMM

EML 2023Computer Aided Design

EML 2023Computer Aided Design

EML 2023Computer Aided Design

Position Tolerance Verification

• This unit covers some simple verification techniques for position tolerancing.

2.500

1.500

Position TolerancingVerification

2.503 Actual

.003

.004

X² + Y² = Z² - Pythagorean Theorem

X² + Y² = Z

X² + Y² = Diameter Tol Zone2

Actual Manufactured Part

Let us check this part to see if the hole location is within tolerance.

2.500.750.758

1.500

CBA.010

.750±.005

A

B

C

1.504Actual

.005

2X .005 = Ø.010 Tol Zone

Size of hole is producedat .750 (MMC).

M

3.6

4.7/4.8

2.500

1.500

Position TolerancingVerification

2.503 Actual

.003

.004

Actual Manufactured Part

2.500.750.758

1.500

CBA.010

.750±.005

A

B

C

1.504Actual

.005

2X .005 = Ø.010 Tol Zone

M

Since the hole is produced at MMC (.750), it is allowed .010 position tolerance. The actual calculated position of the hole falls within the .010 zone.

3.6

3.62.500

1.500

Position TolerancingVerification

2.506 Actual

.006

.005

Actual Manufactured Part

2.500.750.758

1.500

CBA.010

.750±.005

A

B

C

1.505Actual

Size of hole is producedat .755.

M

Let us try another example, this time the hole is produced at .755.Is the location good or bad?

Let us check this part to see if the hole location is within tolerance.

4.7/4.8

2.500

1.500

Position TolerancingVerification

2.506 Actual

.006

.005

2.500.750.758

1.500

CBA.010

.750±.005

A

B

C

1.505Actual

.00782X .0078 = Ø.0156 Tol Zone

M

If the hole is produced at .755, it is allowed a position tolerance of .015. The calculations show the hole is produced within a .0156 zone, so the hole location is out by .0006.

The above part may be repaired by opening the size of the hole by .0006.

3.6

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

4.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371

MMC =Smallest Hole

MMC = Smallest Hole

4.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376

Actual Size of Hole

Actual Size of Hole

4.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010

.005 Position

Plus

.005 Departure from MMC

.010

Position + Departure from MMC = .010

4.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010

X Deviation

-.004

4.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002

Y Deviation

Y Deviation

4.5

4.7

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002

From Chart

.0089

4.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002

From Chart

.0089 X

4.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002 .0089 X

.3714.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002 .0089 X

.371 .3794.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002 .0089 X

.371 .379 .0134.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002 .0089 X

.371 .379 .013 +.0044.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002 .0089 X

.371 .379 .013 +.004 +.0054.5

4.7

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002 .0089 X

.371 .379 .013 +.004 +.005 .01284.5

Class Exercise

Position Verification

At MMC- Inch

As drawn

Produced part

.371 .376 .010 -.004 +.002 .0089 X

.371 .379 .013 +.004 +.005 .0128 X4.5

POSITION

Hole Verification at MMC

4.3

Workshop Exercise

4.6 - Inch

4.14

Workshop Exercise

4.6 - Inch

4.14