Micromoulding: process repeatability + product quality issues In Process Measurement Meeting 3 rd September 2003 Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, IRC in Polymer Engineering, Dept. Mechanical & Medical Engineering, University of Bradford, Bradford UK Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, IRC in Polymer Engineering, Dept. Mechanical & Medical Engineering, University of Bradford, Bradford UK

Contents Process repeatability investigation Methods Results Micromoulding Product Property Assessment Methods Results Process repeatability investigation Methods Results Micromoulding Product Property Assessment Methods Results

Micromoulding benefits for medical applications Allows production of complex 3-dimensional products with dimensional tolerances <10um Highly repeatable process with little material wastage Incorporation of clean room conditions and sealing/ packaging systems Allows production of complex 3-dimensional products with dimensional tolerances <10um Highly repeatable process with little material wastage Incorporation of clean room conditions and sealing/ packaging systems

Battenfeld Microsystem 50

Dynisco PCI 4011 Piezo load transducer Dynisco PCI 4006 piezo load transducer The Data Acquisition Setup Temposonics R series displacement transducer J-type thermocouples

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

Process repeatability How? Process characteristic? Peak injection pressure? How? Process characteristic? Peak injection pressure?

Process repeatability How? Process characteristic? Peak cavity pressure? How? Process characteristic? Peak cavity pressure?

Process repeatability How? Process characteristic? Pressure/time integral? How? Process characteristic? Pressure/time integral?

Process repeatability How? Process characteristic? Pressure/time integral? How? Process characteristic? Pressure/time integral?

Typical Process Data Mean = S.D. = 6.88 Mean = S.D. = 3.55

Typical Process Data Mean = 78.9 S.D. = 4.42 Mean = S.D. = 4.86 Nylon6 NC – Step Plaque Mould

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 Data

Product Mass – Hapex, step plaque 0.12% variation

Comments Limited correlation between injection and cavity pressures Method? Alternatives? Limited correlation between injection and cavity pressures Method? Alternatives?

Micromoulding Product Property Assessment Methods Machine Vision Atomic Force Microscopy Nano-Indenting Methods Machine Vision Atomic Force Microscopy Nano-Indenting

Machine Vision

Atomic Force Microscopy

AFM – 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 -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 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 microtomySurface following etching

Morphology Measurements – Spherulite size

Nano-Indenting

Future experiments Longer runs with smaller (top hat) cavity Individual sample collection Assessment Mass? AFM techniques? Longer runs with smaller (top hat) cavity Individual sample collection Assessment Mass? AFM techniques?

Thank you