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Micro-Moulding of Polymers:Process and Product Assessments
Micro-Moulding of Polymers:Process and Product Assessments
Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates,
IRC in Polymer Engineering, University of Bradford, Bradford UK.IRC in Polymer Engineering, University of Bradford, Bradford UK.
P S Allan, G. Greenway and P Hornsby,
Wolfson Centre for Materials Processing, Brunel University, Uxbridge, UK
Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates,
IRC in Polymer Engineering, University of Bradford, Bradford UK.IRC in Polymer Engineering, University of Bradford, Bradford UK.
P S Allan, G. Greenway and P Hornsby,
Wolfson Centre for Materials Processing, Brunel University, Uxbridge, UK
ContentsContents
• Micromoulding • Process technology
• Results of studies at Bradford• Process dynamics• Process interaction• Product properties
• Micromoulding • Process technology
• Results of studies at Bradford• Process dynamics• Process interaction• Product properties
• Purpose built micro injection process
• Servo-electric injection
• Automatic parts handling
• Clean room filtration
• Modular
Battenfeld Microsystem 50Battenfeld Microsystem 50
Battenfeld Microsystem 50Battenfeld Microsystem 50
Metering PistonMetering Piston
HopperHopper
Shut off valveShut off valve
Extrusion screwExtrusion screw
Heated RegionsHeated Regions Injection pistonInjection piston
Operation CycleOperation Cycle
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
1 Process Measurement – Data Capture
1 Process Measurement – Data Capture
Injection Pressure
Cavity Pressure
Ram Displacement
Ram Velocity
3 Temperature Channels
Injection Pressure
Cavity Pressure
Ram Displacement
Ram Velocity
3 Temperature Channels
Max sampling rate ~ 30 000HzMax sampling rate ~ 30 000Hz
Mould temperature investigationMould temperature investigation
HypothesisHypothesis
• The high surface area to volume ratio of micro-moulded products allows rapid removal of heat from the product through the cavity wall
• Mould temperatures should be higher than those used in conventional IM to prevent premature solidification and part-filled products
• The high surface area to volume ratio of micro-moulded products allows rapid removal of heat from the product through the cavity wall
• Mould temperatures should be higher than those used in conventional IM to prevent premature solidification and part-filled products
Step plaque mouldingStep 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
Cavity Pressure – Hapex, step plaque
Cavity Pressure – Hapex, step plaque
80C
50C
20C
Product Mass – Hapex, step plaqueProduct Mass – Hapex, step plaque
0.12% variation0.12% variation
Mould temperature - conclusionsMould temperature - conclusions
• For products ~25mg recommended mould temperatures for standard injection moulding can be used with confidence for the Hapex material
• Further investigations to be performed at smaller length scales
• For products ~25mg recommended mould temperatures for standard injection moulding can be used with confidence for the Hapex material
• Further investigations to be performed at smaller length scales
High shear rate experimentsHigh shear rate experiments
Calculated wall shear ratesCalculated wall shear rates
0.1 x 0.1mm
0.2 x 0.2mm
0.5 x 0.5mm
1.0 x 1.0mm
In-process rheometryIn-process rheometry
• Measurements performed on a 30 tonne Cincinnatti Milacron servo-electric injection moulding machine with a custom rheometric nozzle
• Measurements performed on a 30 tonne Cincinnatti Milacron servo-electric injection moulding machine with a custom rheometric nozzle
Dynisco Pressure Transducer 435-30M
Dynisco Pressure Transducer 435-30M
Capillary dieinsertsCapillary dieinserts
0.5 x 8.0 mm0.5 x 0.25 mm
1.0 x 16 mm1.0 x 0.25 mm
ThermocoupleThermocouple
High-shear capillary rheometry test resultsHigh-shear capillary rheometry test results
Shear heating effectsShear heating effects
Source: Anthony Bur, Steven Roth, NISTSource: Anthony Bur, Steven Roth, NIST
‘Top Hat’ Cavity‘Top Hat’ Cavity
• Large diameter = 1.0mm• Small diameter = 0.5mm• Gate dimension 0.1 x 0.2mm• Material BP Rigidex 5050 HDPE
• Large diameter = 1.0mm• Small diameter = 0.5mm• Gate dimension 0.1 x 0.2mm• Material BP Rigidex 5050 HDPE
Molecular weight measurementMolecular weight measurement
• Sample material taken from runner system and cavity
• Gel Permeation Chromatography (GPC) analysis performed by Rapra Technology Ltd on each sample to determine molecular weight distribution
• Sample material taken from runner system and cavity
• Gel Permeation Chromatography (GPC) analysis performed by Rapra Technology Ltd on each sample to determine molecular weight distribution
Molecular weight distributionsMolecular weight distributions
Source: RAPRA UKSource: RAPRA UK
High shear investigation - conclusions
High shear investigation - conclusions
• The process contains shear rates orders of magnitude higher than those encountered in conventional IM
• Viscosity curves behave predictably in this region
• Shear heating will be a factor• Stable materials show no sign of
degradation• Temperature sensitive materials?
• The process contains shear rates orders of magnitude higher than those encountered in conventional IM
• Viscosity curves behave predictably in this region
• Shear heating will be a factor• Stable materials show no sign of
degradation• Temperature sensitive materials?
Surface feature replicationSurface feature replication
Surface feature replicationSurface feature replication
• Plaque cavity 25 x 2.5 x 0.25 mm• Fabricated using micro-milling technique
• Kern machine• 0.2mm cutter at 75 000 rpm.• Left in an unpolished state.
• Plaque cavity 25 x 2.5 x 0.25 mm• Fabricated using micro-milling technique
• Kern machine• 0.2mm cutter at 75 000 rpm.• Left in an unpolished state.
Surface feature replication - gateSurface feature replication - gate
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 - gateSurface feature replication - gate
AFM scan size 75 µm x 75 µm AFM scan size 75 µm x 75 µm
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
Surface feature replication - comments
Surface feature replication - comments
• Mould features of the order of a few µm are accurately replicated on the product assuming pressure is sufficient
• Further work to be performed to investigate the limit to which a feature is adequately moulded on a product
• Mould features of the order of a few µm are accurately replicated on the product assuming pressure is sufficient
• Further work to be performed to investigate the limit to which a feature is adequately moulded on a product
Morphology MeasurementMorphology Measurement
• Component sectioned using glass-knife microtomy
• Surface is etched using potassium permanganate solution to produce representative surface
• Surface imaged using microscopic technique (TEM, AFM etc)
• Component sectioned using glass-knife microtomy
• Surface is etched using potassium permanganate solution to produce representative surface
• Surface imaged using microscopic technique (TEM, AFM etc)
Surface following microtomy Surface following etching
Morphology Measurements - Structure Morphology Measurements - Structure
Nano-indentNano-indent
Crystal StructureCrystal Structure
Morphology Measurements – Spherulite size
Morphology Measurements – Spherulite size
Morphology VariationMorphology Variation
Line of indents 25µm separationLine of indents 25µm separation
800 µm
Morphology Measurements – Amorphous layer
Morphology Measurements – Amorphous layer
The Rondol Micro-Injection Compounder
The Rondol Micro-Injection Compounder
The Rondol Micro-Injection Compounder
The Rondol Micro-Injection Compounder
The Rondol Micro-Injection Compounder
The Rondol Micro-Injection Compounder
Prism twin-screw extruderPrism twin-screw extruder
The Rondol Micro-Injection Compounder
The Rondol Micro-Injection Compounder
Advantages:
• Minimise residence time of polymer in plasticising screw
• Exposure to single heating/cooling cycle
• Positive displacement allows use of low viscosity materials
Advantages:
• Minimise residence time of polymer in plasticising screw
• Exposure to single heating/cooling cycle
• Positive displacement allows use of low viscosity materials
OperationOperation
The Rondol Micro-Injection Compounder
The Rondol Micro-Injection Compounder
Initial testingInitial testing
• It works!• Able to process low molecular weight materials• It works!• Able to process low molecular weight materials
• Dosing control can fluctuate• Toggle clamp can result in flashing• Dosing control can fluctuate• Toggle clamp can result in flashing
ExperimentalExperimental
Battenfeld Microsystem50Stepped plaque cavity
60mg total shot massHDPE 5050Injection speed – 200, 400, 600 mm/sScrew speed 40revs/mMelt temp 200CMould temp 50C
Battenfeld Microsystem50Stepped plaque cavity
60mg total shot massHDPE 5050Injection speed – 200, 400, 600 mm/sScrew speed 40revs/mMelt temp 200CMould temp 50C
