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Quality Management and Quality Controlin the
Powder Injection Moulding Process
Dr.-Ing. Henri CohrtMarschallstrasse 2aD-35444 Biebertale
rialEngineering
nriCohrt
Germany
Tel.: +49 151 2290 1386Fax: +49 6409 804970
Henri.Cohrt@powdercon.de
powderconMa
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The powder injection moulding process is widely used to produce highprecision structural parts of very high complexity in shape. The variety ofmaterials ranges from ceramics and hard metals to stainless steels andlow alloyed steels. As a near net shape process the entire process is verycomplex and needs the full attention of all the people incorporated. Theearly design activities are influencing the quality of the final product as
well as the tool design and fabrication, the selection of raw material andbinder system, and all single production steps and the secondaryoperations. For that, a well designed quality management and controlsystem is necessary to control the powder injection moulding process inall the details. Such a system should incorporate a carefully organized
Abstract
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systemat c a ure o e an ect na ys s . e com nat on oa high performance process monitoring system with the extensiveapplication of statistical procedures creates the basis for a StatisticalProcess Control (SPC) system that meets all the requirements to producemulti-functional structural parts of high complexity in shape and of highperformance materials. The paper will discuss such a quality
management and control system in detail.
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1. Introduction
2. What is possible
3. Principle problems
4. How to realize improvements with respect to technicalcharacteristics and economy?
Content
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5. Design of a Quality Management system6. Closing remarks
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Metal / Powder Injection Molding is
the combination of design features of plastic injection molded parts with
the properties of high performance metals, hard metals or ceramics
in a (near)-net-shape process
Characteristics of the Process
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Source: Schunk Sintermetalltechnik GmbH
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1. Introduction
2. What is possible
3. Principle problems
4. How to realize improvements with respect to technicalcharacteristics and economy?
Content
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5. Design of a Quality Management system6. Closing remarks
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Clamping device for a breakingsystem ( 3 MIM parts)
Functions
Guiding
Adjusting
Functional IntegrationSource: Schunk Sintermetalltechnik GmbH
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amp ng
Connecting
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Connector
Reduction of process steps
Production of a forged anddrilled bronze head
Production of a steel tube
Production of a spike
Reduction of production stepsSource: Schunk Sintermetalltechnik GmbH
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Elimination of a bracingoperation
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Elimination of electro-erosion
Simplification of ProductionSource: Schunk Sintermetalltechnik GmbH
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Combination of complex shape
Realization of new Design FeaturesSource: Schunk Sintermetalltechnik GmbH
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an g s reng s ee
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Production quantity of 1,5 Mil.ears er ear
Large Scale ProductionSource: Schunk Sintermetalltechnik GmbH
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protection cap for a carlooking system
Wide Range of Secondary Operations AvailableSource: Schunk Sintermetalltechnik GmbH
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Lever for a sun roof
Substitute for PrecisionCasting
Substitution of Existing Processes for Economic ReasonsSource: Schunk Sintermetalltechnik GmbH
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Carbonyl IronPowder
Micro-Structure Engineering Development of Pure Iron Carbon Steel
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25 m
10 m
Pure Iron Carbon Steel with 0,6 % C
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12,5 m10 m
Carbonyl IronPowder
Chromium CarbidePowder
Micro-Structure Engineering Development of 100 Cr 6 Bearing Steel
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2,5 m
100 Cr 6 Bearing SteelAs Sintered
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Inert Gas AtomizedStellite 6 Powder
7,5 m
Micro-Structure Engineering Development of Stellite 6 Wear Resistant Steel
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Stellite 6 wear resistant steel
5 m
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Hardened
Stress[MPa
]
Effect of Heat Treatment on Fe 2.5%Ni 0,6%C Steel
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Total Stain [%]
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Forging,
Die CastingPM (Die Pressing)
Metal / PowderInjection Molding
(MIM / PIM)
Medium
High
xityofGeometry
Competition of Processes
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Machining
Precision Casting
Low Medium High
Low
Complexity of Geometry
Compl
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1. Introduction
2. What is possible
3. Principle problems
4. How to realize improvements with respect to technicalcharacteristics and economy?
Content
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5. Design of a Quality Management system
6. Closing remarks
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MetalHard Metal- PowderCeramic-
Organic Binder
Mixing
Homogenizing andGranulating
Shaping using
Injection Molding
Removal of Binder
~ 40 vol-%
~ 60 vol-%
Process Schematic
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Sintering
SecondaryOperations
Complex Structural PartsReady to Use
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Typical Defects
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Shell-like arranged porosity due to sheer-induced separationprocesses in the feedstock during mold filling
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As molded(green condition)
De-bound
Typical Defects
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Shrinkage hole due to sheer-induced separation processes inthe feedstock during mold filling
(Visualization by means of micro-focus X-raying)
rown con on
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Material Specification: AISI 316L
cElongation
[%]
Round Robin Tests (Working Group MIM, Germany 1997)
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Code of Supplier
Pla
sti
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1. Introduction
2. What is possible
3. Principle Defects
4. How to realize improvements with respect to technicalcharacteristics and economy?
Content
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5. Design of a Quality Management system
6. Closing remarks
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Visualization of Process Optimization by means ofStatistical Process Control Procedures
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1action
ntering
2 ressure
tering1
3 ressure
tering2
a
action
BeltFurness
ba
ction
BeltFurness
c
action
BeltFurness
5PartialPressure
Furness
6lPressure
Furness
ension9,9
40
,06mm
Comparison of Different De-binding and Sintering Conditions
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T
est
Co2-
Extr
VacuumSi
T
est
N2-Partial
Vacuum
Si
T
est
N2Par
tial
Vacuum
Si
T
est
Co2-
Ext
HighTemper
atur
T
est
Co2-
Ext
HighTemper
atur
T
est
Co2-
Ext
HighTemperatur
Test
Co2
Extraction
,N
2-
WalkingBea
Test
Air,
N2-P
artia
WalkingBea
Specimen No.
D
im
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1. Introduction
2. What is possible
3. Principle Defects
4. How to realize improvements with respect to technicalcharacteristics and economy?
Content
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5. Design of a Quality Management system
6. Closing remarks
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Quality Control Quality Management
Quality control means: To find errors.
Quality management means: To avoid errors!
What is the Focus of Quality Management?
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From the economic point of view
avoiding errors has the priority
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Cost
Cost
Cost
Cost
Cost
Cost
Cost
Cost
Cost
Cost
ProcessDesign,
MaterialandEq
uipmentSelection
P
roductionProcess
FinalInspections
ShipmenttotheCustomer
AssemblyandInstallation
rrantyTime
andAfter
Cost of Quality Control and Lack of Quality
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Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Cost of QM & QC
Progress of the Process
Row
W
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DefectQuote
ProjectDefinition
Design &Development
ProductionPlanning
QualityControl
Product inOperation
Defect Generation
and Setting of itsPre-Conditions
Defect Detection
Schedule of Defect Generation and Defect DetectionSource: Deutsche Gesellschaft fr Qualitt
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Course of
Life CycleGeneration of
75 % of Defects
Detection of
80 % of Defects
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You need a strategy for your system!
Organization + Documentation
Manufacturing + Control Resources
Personnel + Training
How to realize a Quality Management System
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A Quality Management system should be regardedas a tool for a
never ending improvement
of the
Metal / Powder Injection Molding Process
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Strategy
GuidanceAnalysisCustomer
Satisfaction
The Nature of a Quality Management System
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Control
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Definition of Quality
Description of the Productand the Process
Process AnalysisFMEA, 6 Sigma
Prototype Production
Quality ManagementHandbook
Process Instructions
Working Instructions
Inspection of the QualityManagement Systemby means of
Development of a Quality Management System for the MIM/PIM Process
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Process Description Internal Audits
External AccreditedCertification Authoritye.g. in accordance toEN ISO 9001 - 2000
Customers
Start Production
Results fromQualityControl
Activities
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Potential consequence Potential DefectPotential Cause
of the DefectPreventive
Action
TestingProcedures
In-correctdimension
Wrong feedstockcomposition
Defectivescale
Preventivecalibration
Densitymeasurement offeedstock
In-correctdimension
Wrong sintering Furnacesetting
Training ofoperator
Comparison offurnace settingwith processdocumentation
Checklist(working
7 4 3 84
FMEA-Form according to Deutsche Gesellschaft fr Qualitt
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Risk Priority NumberRPZ = B x A x E
instruction)
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nriCohrt A - Probability of occurrence of a defect
1 unlikely, 2 to 3 very low 4 to 6 low
B Impact, that means the effect on the customer
1 hardly observable 2 to 3 inconsiderable or less disturbance 4 to 6 low disturbance 7 to 8 high impact, e.g. stop of production 9 to 10 very high impact, e.g. risk for human beings
Weighting Factors
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7 to 8 medium
9 to 10 high
E Probability of detection before shipment to the customer
1 high 2 to 5 medium
6 to 8 low 9 very low 10 unlikely
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MediumPriority
Highpriority
Lowpriority
Very highpriority
The Risk Priority Number is calculated by multiplying the Weighting Factors
RPZ = B x A x E
From the RPZ the priorities of actions are given by the following schema:
The interpretation of the Risk Priority Number
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125 500
Risk Priority Number
1 1000
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Maesuremen
t
20
30
40
50
60
Upper Control Limit (Mean plus 2)
Mean
Upper Specification (Mean plus 3)
Internal Spezification
External Specification(tolerance band according to technical drawing)
Design of a Quality Control Card
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Sample No.
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115
0
10
Lower Specification (Mean minus 3)
Lower Control Limit (Mean minus 2)
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Improvement of Process Capability by means of Statistical Process Control(SPC)
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Archer 1
Archer 2
Archer 3
Archer 3
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Dust Humidity
Problems
Human Beings
Education
Private
Job-Related
Material
MechanicalProperties
DimensionsScattering
Surface
Quality-Affecting Influences
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Environment
Machine
Cleaning
Tooling
MaintenanceMethods
Process
Organization
Workflow
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Short Term Evaluation ofMachine / Process Capability
Approval for Serial Production
Long Term Validation of
Machine / Process Capability
Focus on
Human Beings Machine Material Methods Environment
To beSubjected to a
Process of PermanentImprovement
Development
an
d
TestPro
duction
lProduction
Process Evaluation and Validation
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Process oriented,but, min. 50 measurements
Result: Cm and Cmk
Process Capability
Adequate long period of time under normal conditions of serial production
to secure that all quality affecting circumstances can become effective.Recommendation: min 125 single parts in 3 to 5 control samplesbetter is 20 Production days
Result: Cp and Cpk
S
eri
Working Instructions Handling
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Pure Powder
Pre-Alloyed PowderPowder Composition
Binder or
Components ofBinder
Recycled
Feedstock(Gating Material)
Metering Out
PropertiesProduction Data
Handling Storing Conditions
Working Instructions
Mixing andHomogenization
Working Instructions
Documentation related to Feedstock Preparation
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Granulation Working Instructions
FeedstockCharacterization
PropertiesProduction Data
Working Instructions
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1. Introduction
2. What is possible
3. Principle Defects
4. How to realize improvements with respect to technicalcharacteristics and economy?
Content
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5. Design of a Quality Management system
6. Closing remarks
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The Basics of the MIM / PIM process are well understood There are many different process routes available with respect to raw material selection binder selection and binder composition feedstock production de-binding processes
sintering processes In the mean time a lot of measurement technologies have been developed to control
the raw materials and feedstock characteristics in principle
also the basics of the two-phase-flow-mechanics are available
Closing Remarks
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e e ec ron ca y con ro e n ec on mo ng mac nes a ow g y sop s ca e con ro othe molding process
there are also highly sophisticated furnace systems available to control the de-binding andsintering processes
But nevertheless, very small scattering in the very complex system of a huge number ofindependent parameters have in special situations dramatic effects on the result ofthe entire MIM / PIM process and are causing big problems with respect to the quality of the
product.
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the MIM / PIM process as an entire process is still very young and has its secretes
the interdependences between the single, at the first glance independent processparameter are not very clear and cannot be descript precisely enough to makeMIM / PIM a fully automated process.
MIM / PIM still needs highly experienced operators to make the process successful.
A well designed Statistical Process Control system combined with an excellentQuality Management system is necessary to produce
Consequences
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mu - unc ona , comp ex s ape s ruc ura par s o g per ormance ma er a s
in high quantities in an economic wayutilizing the
Metal / Powder Injection Molding Process
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CO2 De-binding
Final de-binding and sintering in one Furnace
1.175
Pre-de-binding in air Final de-binding and sintering in one Furnace
1.250 ocessNum
ber
Economic Comparison of Different Processes - ideal Conditions and comparableCapacities (especially quality issues are not regarded)
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Pre-de-binding in air Final de-binding on N2 Sintering in Vacuum
1.550
Process Time [h]
P