iigdt - measurement uncertainty
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
International Institute of GD&TInternational Institute of GD&T
2 Loring Road, Hopkins, MN 553052 Loring Road, Hopkins, MN 55305
www.iigdt.comwww.iigdt.com
GD&T & Measurement Uncertainty
International Institute of GD&TInternational Institute of GD&T
IIGDT
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
Global Simplification of GD&T
Profile of a
Surface
Profile of a
Line
3D Surface
Control
2D Surface
Control
Axis Control
Position
Flatness
Angularity
Perpendicularity
Parallelism
Angularity
Perpendicularity
Parallelism
Straightness
Straightness
Circularity
Cylindricity
Circular Runout
Total Runout
Symmetry
SymmetryConcentricity
Concentricity
IIGDT IIGDT
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
Measurement
Eyeball: L=Lest 1 inch
Tape: L=Lest 1/16 inch
Micrometer: L=Lest 0.001inch
Gage block comparator: L=Lest 1 microinch
Uncertainty
Cost of metrology
Profit
Target U
Dollars
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
Coordinate Measuring Machines
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
Correlating Physical Measurements to Functional Parameters
-Input for FEA Models and Experimental Validation
3D Characterization of Tooling & Product Components
-Standardized Software for Programming Efficiency & Analysis)
-Extraction of Surface Roughness, Waviness, Form
Maintaining Commodity Plans with Key Measurement Suppliers
CMMs, Vision Systems, Laser Sensors
Fly Height
Uc
Pitch Torque
2
++
2Roll
Torque
2TotalGramVar
2Slider's
ABSVar+
+P-SA P-StiffxGram Var(2)
POffsetxR-SA R-Stiffx +
Gram Var(2)
R Offsetx
P-LPtCust. SBO+R-LPt
CustSBO+
GramVar(1)
Cust.ZHV
SpringRate x +( ( () ) ) ) )( (
DriveDyn
Functional
Etched Tower Formed DimplePhysical-Suspension
Physical-
Tooling
U1=Mat'l Thickness at bend area
U2=Width at bend area
U3=Length at bend area
U1=Datums
U2=Clamp Force
U3=Clamp Reference Location
U4=B.P. position at assembly
U5=B.P. edge break
U6=B.P. Flatness
U7=B.P. Squareness
U1=Tongue Flantess
U2=Loadbeam Profile
U3=Welding
U4=Heat Treat
U5=Dimple Location
U6=Dimple Height
U1=Flexure Mat'l Thickness
U2=Arm Length
U3=Arm WidthU1=Loadbeam profile under load
U2=Diameter
U3=Position of Tower
U4=Datums
U1=Loadbeam profile under load
U2=Apex Location
U3=Apex Shape
U1 + U2 + U32 22
U1 + U2 + ... + U72 22
U1 + U2 + ... + U62 22
U1 + U2 + U32 22
U1 + U2 + ... + U42 22
U1 + U2 + U32 22
U1=Datums
U2=Dimple Punch Location
U3=Dimple Punch Shape
U1 + U2 + U32 22
FHSTG
2FHSRT
2FHPT
2
12 Contact
CMMs170 Non-Contact
Coordinate Meas. Systems
15+ Other Meas. Systems
(Orbotech, Cognex VM)Micro-Scale CMM
(Contact)
Micro-Scale CMM
(Non-Contact)
Open-Loop Scanning
Geometric Error Analysis
Thermal Modeling
Surface Analysis
3D Analysis
Non-Contact CMMs
Other Meas. Systems
3D Measurement
Worcester Polytechnic Institute
Center for Holographic Studies and Laser micro-mechaTronics
LOAD BEAM DYNAMICSLOAD BEAM DYNAMICSOEH AND FEM RESULTS OEH AND FEM RESULTS -- MODE 2 AT 2,582 Hz MODE 2 AT 2,582 Hz
Contact
CMMs
Physical to Functional Characteristic Hierarchy
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
ASME B89 Committee on Metrology
Comprised of 7 Divisions:
B89.1 Length
B89.2 Angles
B89.3 Geometry
B89.4 Coordinate Measuring Technology
B89.5 General Principles and Definitions
B89.6 Environment
B89.7 Measurement Uncertainty
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
B89.7 Measurement Uncertainty
Motivations
Need for a uniform approach (GUM) to the treatment of
uncertainty in ASME B89 document
Need for simplified guidance documents as GUM moves into
industrial arena
General dissatisfaction with quality of existing written
standards produced by ISO
Design
MeasurementMfg
GD&T
&
Uncertainty
ASME Y14.5M1994 GUMASME Y14.5.1M1994
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
ASME B89.7 Committee
Measurement Uncertainty
B89.7.1 - Guidelines for B89 Docs
B89.7.2 - Inspection Planning
B89.7.3 - Decision Rules
B89.7.4 - General Principles
B89.7.5 - Communications
B89.7.6 - Uncertainty Considerations in Tolerancing
B89.7.7 - Advanced Uncertainty Concepts
B89.7.8 - Traceability
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
expansion
bending
temperature
systematic effects
r
r
random effects
probingprocess
long term stabilitykinematic anddynamic effects
x
x
measurement task
& strategy
basic axis geometry
x
z
y
= +=
=
+
=N
i
ji
j
N
ij i
N
i
i
i
c xxux
f
x
fxu
x
fu
1 1
1
1
2
2
2 ),(2)(
Variances Covariances
software forevaluation ofmeasurement
[ ] = 2(),( xxaaxJ iObjective Function:
)(),,()( xxaaxxdxdd iiii ===Distance Equation:
Uncertainty
Management
Physical-to-
Functional
Hierarchies
Dimensional
Management
Design of
Experiments
Reliability
Analysis
Regression
AnalysisHistograms
Fishbone
Diagrams
Repeatability
Gage R&R
ANOVA
Control
Charts
Cp, Cpk
Scientific Approach
Current Approach
HTI Chassis Arm Model
Phase 3 HTI_p3.vsl, May 16, 2000
Session: 20000517-141912
sae14_r 5000 samples
-> Slider/Bond Pad SAE Assembly Method [A|F|0.12] deg
Nominal : 0.645211
Mean : 0.634629
Standard Deviation : 1.660454
Lower Spec Limit : N/A
Upper Spec Limit : 0.050000
Cp : N/A
Cpk : -0.126553
Distribution : Tested Normal
Sample Est Sample Est*
% < Low Limit N/A N/A Low -5.426040 -4.346695
% > High Limit 63.780000 63.761454 High 6.822226 5.615953
% Out of Spec 63.780000 63.761454 Range 12.248265 9.962649
95% C.I. for % Out of Spec : 62.447744 to 65.112256 * Est Range : 99.7300%
F
R
E
Q
0
100
200
300
400
500
600
700
-5.500000 2.500000
USL
-3S +3S
Nominal at Median : 0.645211 HLM Study
HLM Variance : 3.748766
Tolerance Effect
weld_base_p3_FEAT_44_GTP 39.90%-> Comp: weld_base_p3 Feat: weld_base_p3_FEAT_44-> (BONUS 0.00) CompPos(DIA) 0.1270(M)[A|B|C]
load_beam_st_FEAT_1_GTL 15.55%-> Comp: load_beam_st Feat: load_beam_st_FEAT_1-> Position(DIA) 0.0800[A|P]
slider_FEAT_2_GTS 15.55%-> Comp: slider Feat: slider_FEAT_2-> Size +- 0.0400
flex_cu_up___hti_p3_GM4 8.27%-> flex_cu_up___hti_p3 assembleop float
load_beam_st_FEAT_4_GTL 3.89%-> Comp: load_beam_st Feat: load_beam_st_FEAT_4-> Position(DIA) 0.0200(S)[A|B|C]
slider_pos_err 3.89%-> Slider Position Error zone 0.020
weld_base_p3_FEAT_12_GTL 3.82%-> Comp: weld_base_p3 Feat: weld_base_p3_FEAT_12-> (BONUS 0.00) Position(DIA) 0.0076(M)[A|D]
load_beam_st_FEAT_26_GTL 2.78%-> Comp: load_beam_st Feat: load_beam_st_FEAT_26-> Position(DIA) 0.0500[A|B|C]
weld_base_p3_FEAT_7_GTL 2.75%-> Comp: weld_base_p3 Feat: weld_base_p3_FEAT_7-> (BONUS 0.00) Position(DIA) 0.0076(M)[A|D]
96.41%
1 additional contributor(s)
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
expansion
bending
temperature
systematic effects
r
r
random effects
probingprocess
long term stabilitykinematic anddynamic effects
x
x
measurement task
& strategy
basic axis geometry
x
z
y
= +=
=
+
=N
i
ji
j
N
ij i
N
i
i
i
c xxux
f
x
fxu
x
fu
1 1
1
1
2
2
2 ),(2)(
Variances Covariances
software forevaluation ofmeasurement
[ ] = 2(),( xxaaxJ iObjective Function:
)(),,()( xxaaxxdxdd iiii ===Distance Equation:
Analytic Solutions
Graphic courtesy of Dr. Trapet - PTB
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
U95 Estimates Distribution of Multiple
Measurement Systems Over a Period of Time
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
1. Environment
2. Reference Element for Measurement Equipment
3. Measurement Equipment
4. Measurement Setup
5. Software & Calculations
6. Metrologist / Operator
7. Measurement Object
8. Definition of the Characteristic
9. Measuring Procedure
10.Physical Constants & Conversion Factors
Sources of Error / Contributors toMeasurement Uncertainty
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
1. Environment for the measurement
Temperature: absolute temperature, time variance, spatial variance
Vibration/noise
Humidity
Contamination
Illumination
Ambient pressure
Air composition
Air flow
Gravity
Transients in the power supply
Pressured air (e.g. air bearings)
Heat radiation
Sources of Error
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
2. Reference element of measurement equipment
Uncertainty of the calibration
Stability
Scale mark quality
Temperature expansion coefficient
Physical principle: line scale, optical digital scale, magnetic digital
scale, spindle, rack & pinion, interferometer
Sources of Error
+
+
+
+
+
+
++
+
+
+
++
+
+
+
+
+
+
+
+
+
+
++
+
+
+
++
+
+
+
++
True Center of
Sphere
Incorrect
Center of
Sphere
+++++
+
+
+ +
+
++
+
+
+
+
x+
True Center of
Sphere
Incorrect
Center of
Sphere
+++++
+
+
+ +
+
++
+
+
+
+
x
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
3. Measurement equipment
Interpretation system
Magnification-electrical or mechanical - error wavelength!!
Zero-point stability
Force stability/absolute force
Hysteresis
Guides/slide-ways
Temperature expansion
Parallaxes
Time since last calibration
Responds characteristic
Interpolation system - error wavelength
Interpolation resolution
Sources of Error
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
4. Measurement setup (excl. the placement and clamping
of the workpiece)
Cosine errors
Abbe principle
Temperature sensitivity
Stiffness/rigidity
Tip radius
Form deviation of tip
Stiffness of the probe system
Optical aperture
Interaction between workpiece and setup
Warming up
Sources of Error
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
5. Software and calculations
Rounding/Quantification
Algorithms
Implementation of algorithms
Number of significant digits in the computation
Sampling
Filtering
Correction of algorithm/Certification of algorithm
Interpolation extrapolation
Sources of Error
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
6. Metrologist operator
Education
Experience
Training
Physical disadvantages/ability
Knowledge
Honest
Sources of Error
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
7. Measurement Workpiece or Measuring Instrument
Surface Roughness, Waviness, & Form
Temperature expansion coefficient
Weight
Size
Shape
Magnetism
Cleanliness
Internal stress
Creep characteristics
Sources of Error
0
0.5
1
1.5
2
2.5
3
3.5
0
0.5
1
1.5
2
2.5
3
3.5
-10
0
10
X axis (mm)
Original Surface
Y axis (mm)
Z
a
x
i
s
(
u
m
)
0
0.5
1
1.5
2
2.5
3
0
1
2
3
-10
0
10
X axis (mm)
Roughness
Y axis (mm)
Z
a
x
i
s
(
u
m
)
0
0.5
1
1.5
2
2.5
3
0
0.5
1
1.5
2
2.5
3
-5
0
5
X axis (mm)
Waviness
Y axis (mm)
Z
a
x
i
s
(
u
m
)
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
8. Definition of the Characteristic
Toleranced feature
Reference system
Degree of freedom
Distance
Angle
Sources of Error
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
9. Measuring procedure
Number of measurements
Order of measurements
Duration of measurements
Choice of principle of measurement
Reference standard
Alignment
Clamping
Fixturing
Number of points
Probing principle
Drift check
Sources of Error
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
10. Physical constants and conversion factors
Lacking knowledge of the correct physical values of e.g. material
properties (workpiece, measuring instrument, ambient air, etc.)
Sources of Error.
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IIGDT GD&T: Advanced Applications & Analysis June 25, 2006
Business Drivers to Support a Decision to
Invest into Aggressive GD&T Training
1. Increased Business due to Increased Capability
2. Increased Profit with Reduced or Eliminated Returns
3. Increased Recognition as a Leading Edge Supplier/Customer
4. Increased Customer Satisfaction Based on Improved Conditions
5. Increased Yield / Reduced Inspection (reduced scrap and rework)
6. Unambiguous and Understood Engineering Requirements
7. Better ability to predict and control processes