Introduction to Micromoulding Dr Ben Whiteside IRC in Polymer Engineering, Dept. Mechanical & Medical Engineering, University of Bradford, Bradford UK.

Introduction to MicromouldingIntroduction to Micromoulding

Dr Ben WhitesideDr Ben Whiteside

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 WhitesideDr Ben Whiteside

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

• Micro/nanotechnology• Micromoulding

• Challenges• Process Technology• Mould Manufacture• Product Assessment

• Micro/nanotechnology• Micromoulding

• Challenges• Process Technology• Mould Manufacture• Product Assessment

Capsule EndoscopyCapsule Endoscopy

Capsule contains: Camera Transmitter Optics Battery

Capsule contains: Camera Transmitter Optics Battery

Capsule EndoscopyCapsule Endoscopy

Full colour images for diagnosis of bowel problemsFull colour images for diagnosis of bowel problems

Digital Micro mirror Device (DMD)Digital Micro mirror Device (DMD)Texas Instruments

16 m x 16 m pixel geometry

Micro-assembly: Laser-fibre alignment- packaging?

Micro-assembly: Laser-fibre alignment- packaging?

Lab-on-a-Chip devicesLab-on-a-Chip devices

Circuits similar to conventional silicon circuits but using fluids rather than electricityCircuits similar to conventional silicon circuits but using fluids rather than electricity

Allows rapid chemical and biological screening of samples

Each chamber in the illustation contains 1/1 000 000 000th of a litre!

Allows rapid chemical and biological screening of samples

Each chamber in the illustation contains 1/1 000 000 000th of a litre!

Current Manufacturing TechniquesCurrent Manufacturing Techniques

Silicon wafer techniques requiring:Clean-room fabricationExpensive Illumination Processes

Silicon wafer techniques requiring:Clean-room fabricationExpensive Illumination Processes

Micro-Injection MouldingMicro-Injection Moulding

• Can the injection moulding process be adapted to offer a cheap, high output process for the production of micro-scale components?

• Can the injection moulding process be adapted to offer a cheap, high output process for the production of micro-scale components?

ChallengesChallenges

• Controlling the moulding machine• Melting the polymer• Measuring the required amount of material• Injecting the material rapidly

• Making the moulds• Contain very fine details• Need to be durable

• Checking/Packaging the product• Quality control• Handling very small products

• Controlling the moulding machine• Melting the polymer• Measuring the required amount of material• Injecting the material rapidly

• Making the moulds• Contain very fine details• Need to be durable

• Checking/Packaging the product• Quality control• Handling very small products

Standard IM – material wasteStandard IM – material waste

Conventional MouldingConventional Moulding

4-cav. Mould4-cav. Mould

• Part weight:Part weight: 4 mg4 mg• Sprue weight:Sprue weight: 2530 mg2530 mg• Shot weight:Shot weight: 2546 mg2546 mg• Material efficiency:Material efficiency: 0,16 %0,16 %• Cycle time:Cycle time: 17 sec.17 sec.

courtesy: Battenfeldcourtesy: Battenfeld

Standard IM – Material DegradationStandard IM – Material Degradation

• Screw/barrel typically contains 500g polymer• Assuming a 0.5g product running every 20

seconds – material would be at melt temperature for 5½ hours

• Material can degrade

• Screw/barrel typically contains 500g polymer• Assuming a 0.5g product running every 20

seconds – material would be at melt temperature for 5½ hours

• Material can degrade

Picture of injection barrel here

• Purpose built micro injection process

• Servo-electric injection

• Optimum screw size – 14mm

• Automatic parts handling

• Clean room filtration

• Modular

• Purpose built micro injection process

• Servo-electric injection

• Optimum screw size – 14mm

• Automatic parts handling

• Clean room filtration

• Modular

Battenfeld Microsystem 50Battenfeld Microsystem 50

Battenfeld Microsystem 50Battenfeld Microsystem 50

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

POM Micro-gearPOM Micro-gear

Weight 2,2 mgWeight 2,2 mg courtesy: Battenfeldcourtesy: Battenfeld

Polycarbonate hearing aid sensor housing

Polycarbonate hearing aid sensor housing

Micromoulding – the truth?Micromoulding – the truth?

Making the mouldsMaking the moulds

• Moulds need to have:• Very accurate dimensions• Good surface finish• Good durability

• Moulds need to have:• Very accurate dimensions• Good surface finish• Good durability

Making the moulds - MicromillingMaking the moulds - Micromilling

Cutters as small as 0.1mm rotating at speeds up to 120 000 rpm

All held in special housing to minimise vibration and changes in temperature

Cutters as small as 0.1mm rotating at speeds up to 120 000 rpm

All held in special housing to minimise vibration and changes in temperature

Making the moulds – Micro Electro Discharge Machining

Making the moulds – Micro Electro Discharge Machining

The electrode and woprkpiece are connected to a DC power supply and are brought close together, but never touch

Sparks jump across the small gap which heats up the workpiece metal to about 1200ºC, causing it to evaporate

The electrode and woprkpiece are connected to a DC power supply and are brought close together, but never touch

Sparks jump across the small gap which heats up the workpiece metal to about 1200ºC, causing it to evaporate

Making the moulds – Laser MachiningMaking the moulds – Laser Machining

High frequency pulsed lasers focussed on the steel causing it to evaporate.

The laser is aimed using a computer to cut out a cavity in the steel

Problems can occur when the steel ‘spatters’ or is recast in the local area

High frequency pulsed lasers focussed on the steel causing it to evaporate.

The laser is aimed using a computer to cut out a cavity in the steel

Problems can occur when the steel ‘spatters’ or is recast in the local area

Making the moulds – Micro-StereolithoraphyMaking the moulds – Micro-Stereolithoraphy

Object is built up of slices created by illuminating the top surface of a bath of special polymer with a laser

When a slice is complete, the stage holding the part drops down a fraction of a millimeter so the next slice can be made

Object is built up of slices created by illuminating the top surface of a bath of special polymer with a laser

When a slice is complete, the stage holding the part drops down a fraction of a millimeter so the next slice can be made

T-Shaped cavity made for us by Rutherford Appleton Labs

Electroplating required to create mould

Cylinders will form holes for pins to eject the moulded part

T-Shaped cavity made for us by Rutherford Appleton Labs

Electroplating required to create mould

Cylinders will form holes for pins to eject the moulded part

Making the moulds – Micro-StereolithoraphyMaking the moulds – Micro-Stereolithoraphy

Making the moulds – LIGA ProcessMaking the moulds – LIGA Process

• Able to form a number of cavities simultaneously

• Excellent surface finish

• Only 2.5D structures

• Requires expensive hardware

• Able to form a number of cavities simultaneously

• Excellent surface finish

• Only 2.5D structures

• Requires expensive hardware

Product AssessmentProduct Assessment

• How is quality control implemented for such small components?• Optical systems

• How do we find out how rigid and hard the product is?• Need to use Atomic Force Microscopy techniques

• How is quality control implemented for such small components?• Optical systems

• How do we find out how rigid and hard the product is?• Need to use Atomic Force Microscopy techniques

Machine Vision SystemsMachine Vision Systems

CCDCameraCCDCamera

RobotRobot

ProductProduct

• Fully Automatic – no user intervention required

• Able to measure dimensions/areas/geometric features

• Can be performed during the process

• Fully Automatic – no user intervention required

• Able to measure dimensions/areas/geometric features

• Can be performed during the process

Machine Vision SystemsMachine Vision Systems

Smallest product moulded at the UniversityLargest diameter 1mmMass 0.34mg

Smallest product moulded at the UniversityLargest diameter 1mmMass 0.34mg

Atomic force microscopyAtomic force microscopy

Can be used to study very small areas of a component to measure:-

Surface finish

Internal structure

Mechanical properties – hardness etc

Can be used to study very small areas of a component to measure:-

Surface finish

Internal structure

Mechanical properties – hardness etc

Surface detailsSurface details

‘Ridges’ caused by the tools used to make the cavity‘Ridges’ caused by the tools used to make the cavity

Structures inside the productStructures inside the product

Rose patterns tell us about the structure of the polymer and how strong we can expect the product to beIndent shape also indicates how hard the product is

Rose patterns tell us about the structure of the polymer and how strong we can expect the product to beIndent shape also indicates how hard the product is

Indent

ConclusionsConclusions

• Standard injection moulding machines are not well suited for producing microscale components

• Micromoulding offers a cheap and productive means for the manufacture of small components

• A number of techniques are being explored to find the best method for cavity production

• Testing of the moulded parts is currently only possible using expensive, high-tech apparatus.

• Standard injection moulding machines are not well suited for producing microscale components

• Micromoulding offers a cheap and productive means for the manufacture of small components

• A number of techniques are being explored to find the best method for cavity production

• Testing of the moulded parts is currently only possible using expensive, high-tech apparatus.