Micromoulding: process repeatability + product quality issues In Process Measurement Meeting 3 rd September 2003 Dr Ben Whiteside, Dr Mike Martyn, Prof.

Micromoulding: process repeatability + product quality issues

In Process Measurement Meeting3rd September 2003

Micromoulding: process repeatability + product quality issues

In Process Measurement Meeting3rd September 2003

Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates,

IRC in Polymer Engineering, IRC in Polymer Engineering,

Dept. Mechanical & Medical Engineering, Dept. Mechanical & Medical Engineering,

University of Bradford, Bradford UKUniversity of Bradford, Bradford UK

Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates,

IRC in Polymer Engineering, IRC in Polymer Engineering,

Dept. Mechanical & Medical Engineering, Dept. Mechanical & Medical Engineering,

University of Bradford, Bradford UKUniversity of Bradford, Bradford UK

ContentsContents

• Introduction• Equipment• Process Interrogation Investigation• Micromoulding Product Property

Assessment• Final Comments

• Introduction• Equipment• Process Interrogation Investigation• Micromoulding Product Property

Assessment• Final Comments

Part weight 0,0008 gPart weight 0,0008 g courtesy: Battenfeldcourtesy: Battenfeld

IntroductionIntroduction

Battenfeld Microsystem50Battenfeld Microsystem50

•Specifically designed for moulding of products <1g

• Accurate shot dosing and high injection speed with little material wastage

• Incorporation of clean room conditions and sealing/ packaging systems

•Specifically designed for moulding of products <1g

• Accurate shot dosing and high injection speed with little material wastage

• Incorporation of clean room conditions and sealing/ packaging systems

Battenfeld Microsystem 50Battenfeld Microsystem 50

Conventional vs. MicromouldingConventional vs. Micromoulding

Conventional

• Injection control switch-over to avoid pressure ‘spike’

• Feed system vol << part volume

• Heat to be removed from product using cooling system – cycle times ~tens of seconds

Conventional

• Injection control switch-over to avoid pressure ‘spike’

• Feed system vol << part volume

• Heat to be removed from product using cooling system – cycle times ~tens of seconds

Micromoulding

• High speed injection without switchover and corresponding pressure ‘spike’ – material compression

• Feed system volume > part volume

• Very rapid freezing of material allows very low cycle times BUT smaller processing window

Micromoulding

• High speed injection without switchover and corresponding pressure ‘spike’ – material compression

• Feed system volume > part volume

• Very rapid freezing of material allows very low cycle times BUT smaller processing window

Dynisco PCI 4011 Piezo load transducer

Dynisco PCI 4011 Piezo load transducer

Dynisco PCI 4006 piezo load transducer

Dynisco PCI 4006 piezo load transducer

The Data Acquisition SetupThe Data Acquisition Setup

Temposonics R series displacement transducer

Temposonics R series displacement transducer

J-type thermocouplesJ-type thermocouples

Process InterrogationProcess Interrogation

• What can we measure to give an accurate representation of process/product quality?

• What can we measure to give an accurate representation of process/product quality?

Process InterrogationProcess Interrogation

• How?• Process characteristic?

• Peak injection pressure?

• How?• Process characteristic?

• Peak injection pressure?

Nylon6 NC in stepped plaque mould

0

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0.00 0.50 1.00 1.50 2.00

Time (s)

Inje

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/Ca

vit

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a)/

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isp

lac

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t (m

m)

Injection Pressure

Cavity Pressure

Process InterrogationProcess Interrogation

• How?• Process characteristic?

• Peak cavity pressure?

• How?• Process characteristic?

• Peak cavity pressure?

Nylon6 NC in stepped plaque mould

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isp

lac

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t (m

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Injection Pressure

Cavity Pressure

Process InterrogationProcess Interrogation• How?

• Process characteristic?• Pressure/time integral?

• How?• Process characteristic?

• Pressure/time integral?

Nylon6 NC in stepped plaque mould

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Injection Pressure

Cavity Pressure

Process InterrogationProcess Interrogation• How?

• Process characteristic?• Pressure/time integral?

• How?• Process characteristic?

• Pressure/time integral?

Nylon6 NC in stepped plaque mould

0

10

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0.00 0.50 1.00 1.50 2.00

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Injection Pressure

Cavity Pressure

Typical Micromoulding Process DataTypical Micromoulding Process Data

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160

0 20 40 60 80 100 120

Cycle No

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ssu

re M

pa

Peak Injection Pressure

Peak Cavity Pressure

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Cycle No

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Peak Injection Pressure

Peak Cavity Pressure

Mean = 99.56S.D. = 6.88

Mean = 22.50S.D. = 3.55

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0 20 40 60 80 100Cycle No

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ssu

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Injection Pressure

Cavity Pressure

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0 20 40 60 80 100Cycle No

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ssu

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Injection Pressure

Cavity Pressure

Typical Process DataTypical Process Data

Mean = 78.9S.D. = 4.42

Mean = 26.83S.D. = 4.86

Nylon6 NC – Step Plaque MouldNylon6 NC – Step Plaque Mould

ExperimentalExperimental

• Test response of process data to change in process conditions

• Use three different mould temperature settings during a production run

• Test response of process data to change in process conditions

• Use three different mould temperature settings during a production run

Experimental - step plaque mouldingExperimental - step plaque moulding

Material: HAPEX (40% sintered hydroxyapatite HDPE matrix)

Produced by IRC in Biomaterial Science

Queen Mary and Westfield College, London

Material: HAPEX (40% sintered hydroxyapatite HDPE matrix)

Produced by IRC in Biomaterial Science

Queen Mary and Westfield College, London

Process ConditionsProcess Conditions

Screw Speed 30rpm 30rpm 30rpm

Back Pressure 150Bar 150Bar 150Bar

Shot Size 220mm3 220mm3 220mm3

Injection Speed 500mm/s 500mm/s 500mm/s

Melt Temperature 200C 200C 200C

Mould Temperature 20C 50C 80C

Process DataProcess Data

Injection Pressure CurvesInjection Pressure Curves

Cavity Pressure CurvesCavity Pressure Curves

Product Mass – Hapex, step plaqueProduct Mass – Hapex, step plaque

0.12% variation0.12% variation

ObservationsObservations

• Process measurements required in the cavity itself for accurate process monitoring

• Challenges• Size!• Techniques

• Solutions• Indirect measurements

• Ejector pins• Ultrasound

• Process measurements required in the cavity itself for accurate process monitoring

• Challenges• Size!• Techniques

• Solutions• Indirect measurements

• Ejector pins• Ultrasound

Product Property AssessmentProduct Property Assessment

Product Property AssessmentProduct Property Assessment

Conventional

• Part mass• Balance

• Dimension testing• Custom Rig• Scanner

• Mechanical testing• Instron

Conventional

• Part mass• Balance

• Dimension testing• Custom Rig• Scanner

• Mechanical testing• Instron

Micromoulding

• Part Mass• ?

• Dimension testing• Machine Vision• Atomic Force Microscopy

• Mechanical Testing• Nano-Indenting

Micromoulding

• Part Mass• ?

• Dimension testing• Machine Vision• Atomic Force Microscopy

• Mechanical Testing• Nano-Indenting

Machine Vision SystemsMachine Vision Systems

• Allow in-process quality control• Fully automated – removes the need for visual

inspection• Ideal for micro-scale products

• Allow in-process quality control• Fully automated – removes the need for visual

inspection• Ideal for micro-scale products

Machine VisionMachine Vision

• Allows detection of flawed products during the process and suitable action can be taken

• Allows detection of flawed products during the process and suitable action can be taken

Atomic Force MicroscopyAtomic Force Microscopy

AFM – surface feature measurementAFM – surface feature measurement

AFM scan size 75 µm x 75 µm

Pitch of scroll marks ~ 6µm

AFM scan size 75 µm x 75 µm

Pitch of scroll marks ~ 6µm

Cavity Product

Surface feature replication -downstreamSurface feature replication -downstream

AFM scan size 75 µm x 75 µm

Pitch of scroll marks ~ 6µm

AFM scan size 75 µm x 75 µm

Pitch of scroll marks ~ 6µm

Cavity Product

AFM - Morphology MeasurementAFM - Morphology Measurement

• Component sectioned using glass-knife microtomy

• Surface is etched using potassium permanganate solution to produce representative surface

• Surface imaged using AFM

• Component sectioned using glass-knife microtomy

• Surface is etched using potassium permanganate solution to produce representative surface

• Surface imaged using AFM

Surface following microtomy Surface following etching

Morphology Measurements – Spherulite size

Morphology Measurements – Spherulite size

Morphology - experimentalMorphology - experimental

Line of indents 25µm separationLine of indents 25µm separation

800 µm

Material: BP Rigidex 5050 HDPE

Melt temp: 190C

Mould temp 50C

Injection speed 500mm/s

Material: BP Rigidex 5050 HDPE

Melt temp: 190C

Mould temp 50C

Injection speed 500mm/s

250µm

Morphology MeasurementsMorphology Measurements

Morphology MeasurementsMorphology Measurements

Nano-IndentingNano-Indenting

Properties of POMC109 1.00 mm test bar

A B C

A B

CGate end

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ResultsResults

CommentsComments

• AFM and nano-indenting very powerful techniques • + Allow direct evaluation of influence process conditions

on product properties• - Time consuming• - Sample preparation issues

• Machine Vision Systems• + Well suited for micromoulding assessment• + Performed during processing• - Cannot determine morphology/mechanical properties

• AFM and nano-indenting very powerful techniques • + Allow direct evaluation of influence process conditions

on product properties• - Time consuming• - Sample preparation issues

• Machine Vision Systems• + Well suited for micromoulding assessment• + Performed during processing• - Cannot determine morphology/mechanical properties

Future experimentsFuture experiments

• Longer runs with smaller (top hat) cavity• Individual sample collection• Assessment

• Longer runs with smaller (top hat) cavity• Individual sample collection• Assessment

FinFin