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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
10
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00
Time (s)
Inje
cti
on
/Ca
vit
y P
res
su
re (
Mp
a)/
D
isp
lac
em
en
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
0
10
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00
Time (s)
Inje
cti
on
/Ca
vit
y P
res
su
re (
Mp
a)/
D
isp
lac
em
en
t (m
m)
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
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00
Time (s)
Inje
cti
on
/Ca
vit
y P
res
su
re (
Mp
a)/
D
isp
lac
em
en
t (m
m)
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
20
30
40
50
60
70
80
90
100
0.00 0.50 1.00 1.50 2.00
Time (s)
Inje
cti
on
/Ca
vit
y P
res
su
re (
Mp
a)/
D
isp
lac
em
en
t (m
m)
Injection Pressure
Cavity Pressure
Typical Micromoulding Process DataTypical Micromoulding Process Data
0
20
40
60
80
100
120
140
160
0 20 40 60 80 100 120
Cycle No
Pre
ssu
re M
pa
Peak Injection Pressure
Peak Cavity Pressure
0
20
40
60
80
100
120
140
160
0 20 40 60 80 100 120
Cycle No
Pre
ssu
re M
pa
Peak Injection Pressure
Peak Cavity Pressure
Mean = 99.56S.D. = 6.88
Mean = 22.50S.D. = 3.55
0
20
40
60
80
100
120
0 20 40 60 80 100Cycle No
Pre
ssu
re M
pa
Injection Pressure
Cavity Pressure
0
20
40
60
80
100
120
0 20 40 60 80 100Cycle No
Pre
ssu
re M
pa
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
0
1
2
3
4
5
6
7
8
9
0 1 2 3 4
Mod
ulu
s (
GP
a)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Hard
nes
s (G
Pa)
Fixed
Moving
Fixed
Moving
Position
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