Measurement System Analysis (MSA)
Discussions at CSIR
S.A.
28-07-2005
Measurement System
Sources of Variations
Manufacturing
Process
Machine
Tooling
Process
design
Input Material
Parameter
variation
Method
variation
Processing
material
Product
Design
(Tolerancing)
Environment
Measurement
Fundamental Properties of a GOOD
measurement system
• ADEQUATE SENSITIVITY – 10 TO 1 RULE –
Instrument ACCURACY (and therefore Least Count)
should divide the tolerance ( or process variation) into 10
parts or more – practical minimum point for gauge
selection
• Measurement system ought to be in statistical control –
presence of only common causes of variation and not the
special causes
• Variation of measurement system must be small compared
to specification limits or process variation (6-sigma) –
more PRECISION
Inaccurate and imprecise
+
Accurate and imprecise
+
Precise but inaccurate
+
Accurate and precise
+
U : UNCERTAINITY
RU =
0.0001
U=
0.0001
NATIONAL
STANDARD
RU =
0.001
U=
0.001005
RANDOM UNCERTAINITY –
FOUND THRU
CALIBRATION
LABORATORY
STANDARD
SYSTEM UNCERTAINITY – OF
MASTER
TOTAL UNCERTAINITY –
SQRT( RU*RU + SU*SU)
RU = 0.01
RU = 0.05
U=
0.01005
WORK
U=
0.05099
GAUGE FOR
INSPECTION /
TESTING
STANDARD
Process Capability
Lower Spec. Limit
Upper Spec. Limit
6
Tolerance = T
Process Capability = T / 6  > 1.33
Means, 6  < (0.75*T)
Impact of Uncertainty
ERROR identified through
Calibration Process
Lower Spec. Limit
Upper Spec. Limit
Uncertainty
6  Process
Tolerance = T
Questions
•
Can an ISO/TS 16949: 2002 certification program ensure systems
and processes which deliver products which conform to a
technical specification?
•
Yes, TS SCOPE, point # 1.1, states…
•
This international standard specifies requirements for a quality
management system to demonstrate ability to CONSISTENTLY
provide PRODUCT that meets product, customer and regulatory
requirements
•
Requirements specified in standard are complementary to product
requirements
•
Emphasis on PROCESS DESIGN to deliver conformance to
product specifications CONSISTENTLY …. Focus on REDUCTION
IN VARIATION by asking ongoing capability evaluation…including
measurement systems’ variation, which an process engineer must
evaluate during development
•
Product and process approval is a requirement throughout
SUPPLY CHAIN, which includes elements such as FMEAs, Control
Plans, SPC & MSA
Questions
•
Are customer specific MSA requirements addressed in ISO/TS
16949: 2002 audits?
•
Yes, the scope of certification includes ISO/TS-16949 +
CUSTOMER SPECIFIC REQUIREMENTS
•
ISO/TS 16949:2002,
•
POINT # 0.5 : Goals of this Technical Specification, Para #2
•
This Technical Specification, coupled with applicable customer
specific requirements, defines the fundamental quality
management system requirements for those subscribing to this
documents.
•
Most of the subscribing customers (OEMs asking vendors to get
registered to TS 16949) ask usage of AIAG MSA MANUAL
Questions
•
To what degree are customer specific MSA requirements
addressed in ISO/TS 16949: 2002 audits?
•
Audits wrt TS-16949 are planned considering business processes
identified by organization to meet the product and customers
needs and expectations, calibration and MSA is one of such
processes
•
ISO/TS-16949:2002 (Point # 7.6.1: Measurement System Analysis)
•
Statistical Studies SHALL BE conducted to analyze the variation
present in the results of EACH TYPE of measuring and test
equipment system.
•
The requirement shall apply to measurement systems
REFERENCED IN THE CONTROL PLAN
•
The analysis methods and acceptance criteria used SHALL
confirm to those in CUSTOMER REFERENCE MANUALS on
measurement systems analysis
Questions
•
Would ISO/TS 16949:2002 auditors benefit from additional training
in Measurement System Analysis?
•
Certainly Yes. Rather it’s a REQUIREMENT. Otherwise how could
they assess suitability and impact of MESUREMENT SYSTEM
ERRORs on products’ quality?
•
Auditor Qualification requires….
•
6 years prior experience in AUTOMOTIVE, out of which 4 years in
Quality
•
Qualification Course contents and examination includes CORE
TOOLS – APQP, PPAP, FMEA, SPC, MSA, etc
•
Ford & GM specific requirements demand even the internal
auditors shall be trained and evaluated wrt knowledge on core
tools including MSA.
• Who conducts the MSA? (supplier/OEM?)
• The user of measurement system shall conduct the MSA
• Are FOP, (first of production), tests conducted?
• Review is Must, if necessary do it!
• Who is responsible for conducting these tests, OEMs or suppliers?
•Of course the manufacturer (supplier)
• Who is responsible for evaluating that the measurement system is capable of
performing the required measurements with the desired level of accuracy?
•Of course the manufacturer (supplier)
• Do these tests form part of the control plan?
•Yes, they have to be!
• Is the understanding that an MSA addresses the measurement accuracy of a
measurement system or merely its repeatability/reproducibility?
•It addresses both – location (accuracy) and variation (precision)
Application of appropriate method
TYPE OF
GAUGE
BIAS /
UNCERTANITY
LINEARITY


CMM
0-1500mm


SLIP GAUGES

VERNIER
0-150mm
PLUG GAUGE
FOR BORE OF
20.025/20.00
0

STABILITY
GRR

SKILL IN
HOLDING THE
JAWS PARALLALY


SKILL OF
RINGING

SKILL ON
BORDERLINE
CASES