c quality managment in the pim process

8/2/2019 C Quality Managment in the PIM Process

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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

[email protected]

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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



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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nriCohrt Static Mixer

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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nriCohrt Decorative chromium coated

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



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


Content

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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



Content

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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


Cost of QM & QC


Cost of QM & QC


Cost of QM & QC


Cost of QM & QC


Cost of QM & QC


Cost of QM & QC


Cost of QM & QC


Cost of QM & QC


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


Mixing andHomogenization


Documentation related to Feedstock Preparation

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Granulation Working Instructions

FeedstockCharacterization

PropertiesProduction Data



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1. Introduction

2. What is possible



Content

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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

c quality managment in the pim process

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