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Temperature and
Dimensional
Measurements
Jim Salsbury, Ph.D., Corporate Metrology
Mitutoyo America Corporation
www.mitutoyo.com/on-demand
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“Technical Presentations”
2
© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Mitutoyo America Calibration Lab
20±0.1°C, 3500 sq. ft.
0.03°C/hour, 0.03°C/meter
Environmental specifications based on accuracy requirements
Temperature Impacts all Measurements
• Listen and understand. Temperature is out
there. It can’t be bargained with. It can’t be
reasoned with. It doesn’t feel pit, or remorse,
or fear. And it absolutely will not stop, ever,
until all your measurements are screwed up.
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© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Example: Long Gage Block Calibration
0.03°C/meter
Master and test block
soak overnight
Match materials
Heat shields to block
operator heat
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Example: Step Gage Calibration on CMM
20±0.1°C
0.03°C/hour
Separate room
to reduce traffic
Automated to
remove operator
body heat
CMM controller
in adjacent room
Temperature compensation
© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Example: High Accuracy CMM Calibration
20±0.1°C
Use gage blocks of
low thermal
expansion material
(about 500X less
than steel)
Example: Ultra Accuracy Length Calibration
NIST Moore CMM in 20 ± 0.01°C room
Separate control room
No people in room for many
hours prior to measurements
“Whoever has the best thermometer wins” - Dr. Doiron, NIST
© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Justify Expense for Temperature Control
• CMM specifications in
accordance to ISO 10360-2.
• Calibrate with Checkmasters.
• E0 test run in 7 positions. In
each position, 5 lengths and
3 repeats, for a total of 105
measurements.
• We need Checkmasters
calibrated with adequate
uncertainty.
All manufacturers specify CMM accuracy
following the ISO 10360 standards
© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
E0,MPE = 1.9 + 3L/1000 m, with L in mm
E0,MPE = 75 + 3L inches, with L in inches
Measured Length L (mm)
3.1
2.4
1.6
0.8
E0,MPE
Eo,MPE
(m)
At 40” (1000 mm), E0,MPE   0.0002” (5 m)
(0.0001”) 0
-0.8
-1.6
-2.4
-3.1
0
8
16
24
32
40
48
56
64
Measured Length L (inches)
Legex CMM – Length Calibration
1
Sandia
Oak Ridge
Uncertainty
comparison
0.9
0.8
MAC
MJ
0.7
0.6
0.5
0.4
0.3
NIST
0.2
0.1
0
0
250
500
750
1000
To ensure quality in CMM
calibration, Mitutoyo America
developed methods that are the
most accurate of any commercial
laboratory in the U.S.
© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Fight Temperature to the Level You Need
•
•
•
•
•
•
•
•
•
•
Temperature stability (vs 68°F).
Match materials between gage and part.
Allow proper thermal soak-out time.
Reduce handling and operator influences.
Reduce traffic and large doors.
Reduce heat sources (lights/people/equipment).
Eliminate direct blowing of air.
Monitor the environment (with alarms).
Keep the lights on all the time.
Temperature compensation.
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Understanding Temperature Issues
• Thermal expansion:
L = (L)()(T-20)
where  is the coefficient of
thermal expansion, or CTE,
of the material.
• 20” gage block at 21°C.
L = (20)(10.8)(21-20)
L  0.0002 inches
• 20” gage block, Grade 00,
tolerance is 10x smaller.
Long gage block
calibration
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© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Coefficient of Thermal Expansion (CTE)
CTE (10-6/°C)
20
• 10.5 ± 1.5 x 10-6/°C:
- Aluminum
15
10
5
0
- Steel
- Ceramic (ZrO2)
- Glass scales
- Tungsten Carbide
–
–
–
–
–
–
–
Most steels
Steel gage blocks
Ceramic gage blocks
Calipers
Carbon fiber calipers
Micrometers
Micrometers standards
Use of similar CTE
reduces thermal errors
- Zero CERA
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Matching Materials (similar CTE) is Good
• Similar CTE materials
at same temperature
(even not 68°F) will
reduce thermal errors
Calibrate in lab and use on shop
floor relies on similar materials
between micrometer and standard
© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Thermal Error – Aluminum Part, Steel Micrometer
0.0016
0.0012
Thermal Error (inches)
78°F
To reduced this error:
(1) Manually compensate
(2) Adjust zero point
0.0014
76°F
0.0010
74°F
0.0008
0.0006
72°F
0.0004
70°F
0.0002
0.0000
0
2
4
6
8
10
12
14
16
18
20
22
24
Measured Length (inches)
High Accuracy Height Gage: Mitutoyo LH-600
Calibration at 20°C
Used at 23°C
Use built-in temp comp
High accuracy equipment often requires temperature compensation
to fully utilize the accuracy for which you paid
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© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Steel Part on LH-600 without Temp Comp
0.00040
78°F
0.00035
76°F
Thermal Error (inches)
0.00030
0.00025
74°F
0.00020
72°F
0.00015
0.00010
70°F
0.00005
LH-600 Spec
0.00000
0
2
4
6
8
10
12
14
16
Measured Length (inches)
18
20
22
24
LH-600 Temperature Compensation
• LH-600 temperature
compensation is
built-in and is easy to
use.
• Historical good
practice of “thermal
equilibrium” needs to
be updated for
modern equipment.
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© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Aluminum Part on LH-600 without Temp Comp
0.00100
73°F
0.00090
0.00080
Thermal Error (inches)
72°F
0.00070
0.00060
71°F
0.00050
0.00040
70°F
0.00030
0.00020
69°F
0.00010
LH‐600 Spec
0.00000
0
2
4
6
8
10
12
14
16
Measured Length (inches)
18
20
22
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Built-In Real-Time Temperature Compensation
• Temp comp is standard
on many CMMs today.
• CMM accuracy relies on
use of temp comp.
• If not used properly, you
may create a false
temperature differential
that results in big errors.
Workpiece temperature sensor
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© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Steel part on temp comp CMM when NOT
correctly using the temperature compensation
0.0016
78°F
Thermal Error (inches)
0.0014
0.0012
76°F
0.0010
74°F
0.0008
0.0006
72°F
0.0004
70°F
0.0002
CMM spec
0.0000
0
2
4
6
8
10
12
14
16
Measured Length (inches)
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20
22
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CMM Accuracy across Temperature Range
• CMMs are generally
specified to be accurate
across a range of
temperatures.
• Example for Mitutoyo
Crysta-Apex S:
– 16–26°C (60.8–78.8°F)
• Specification assumes
proper use of temperature
Workpiece temperature sensors
compensation.
in use during calibration
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© 2018 Mitutoyo America Corporation
www.mitutoyo.com/education
Temp Comp on CMMs Made Easy
• Part temperature can be
estimated by keeping
workpiece temperature
sensors attached to
nearby fixturing.
• Must still use correct
CTE of measured part.
• Also helps eliminate
wear and tear on the
temperature sensor.
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Thank You
For a copy of this presentation, visit
www.mitutoyo.com/on-demand
© 2018 Mitutoyo America Corporation