1. Research Update 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 Ukmig meeting November 5 th 2003

2. Contents Introduction Equipment Process Interrogation Investigation Comments Introduction Equipment Process Interrogation Investigation Comments

3. Battenfeld Microsystem 50

4. Conventional 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

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

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

7. Process Interrogation How? Process characteristic? Peak injection pressure? How? Process characteristic? Peak injection pressure?

8. Process Interrogation How? Process characteristic? Peak cavity pressure? How? Process characteristic? Peak cavity pressure?

9. Process Interrogation How? Process characteristic? Pressure/time integral? How? Process characteristic? Pressure/time integral?

10. Process Interrogation How? Process characteristic? Pressure/time integral? How? Process characteristic? Pressure/time integral?

11. Typical Micromoulding Process Data Mean = 99.56 S.D. = 6.88 Mean = 22.50 S.D. = 3.55

12. Experimental 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

13. Experimental - 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

14. Process Conditions Screw Speed30rpm Back Pressure150Bar Shot Size220mm3 Injection Speed500mm/s Melt Temperature200C Mould Temperature20C50C80C

15. Process Data

16. Injection Pressure Curves

17. Cavity Pressure Curves

18. Product Mass – Hapex, step plaque 0.12% variation

19. Comments Methods of cavity pressure assessment Direct measurement Transducer installed flush with cavity wall Impractical in small cavities, frozen layer errors Indirect measurement Piezo force tranducer mounted behind ejector pin Errors due to friction, bending of pin, frozen layer Ultrasound? Methods of cavity pressure assessment Direct measurement Transducer installed flush with cavity wall Impractical in small cavities, frozen layer errors Indirect measurement Piezo force tranducer mounted behind ejector pin Errors due to friction, bending of pin, frozen layer Ultrasound?

20. Future Work Extended run of top-hat mouldings Repeatability assessment Mould temperature/morphology variations Ultrasound sensor studies Feb 2004 Extended run of top-hat mouldings Repeatability assessment Mould temperature/morphology variations Ultrasound sensor studies Feb 2004