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Title: Micro injection moulding : tooling and process factors
Author: Griffiths, Christian Andrew
ISNI:       0000 0004 2751 786X
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2008
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The development of new micro devices is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. Micro injection moulding is one of the key technologies for micro-manufacture and is considered as a cost effective replication method for mass production. The capabilities of this replication technology have to be studied systematically in order to determine the process constraints. The present work concerns the tooling and process factors that influence micro injection moulding. The requirements of this manufacturing process are identified, and a review of the current state of the art in the field, Chapter 2, is used to assess the potential of this technology. To analyse further the manufacturing capabilities of this technology against the requirements, an investigation of the pre-filling, filling and part removal stages of the process cycle is conducted. In particular, in Chapter 3 the pre-filling capabilities of multi cavity micro tools with the use of a runner system is explored. The filling performance of spiral-like micro cavities was studied as a function of runner size in combination with selected process factors. Then, in Chapter 4 the filling of micro mould cavities with controlled tool surface finishes is investigated. Factors affecting the flow behaviour are discussed and a special attention is paid to the interaction between the melt flow and the tool surface roughness. Using the same part design as that of the tool surface finish investigation, in Chapter 5 a Finite Element Analysis (FEA) is used to verify the effects of process parameters, particularly the factors affecting shear rate, pressure and temperature. The results of this investigation were then compared with those reported in the experimental study. Finally, in Chapter 6 the application of micro mould surface treatments is analysed. The effects of different surface treatments on the de-moulding of parts with micro features are investigated to identify the best processing conditions in regards to de-moulding behaviour. To validate the process effects for these three process stages micro injection moulding experimental set-ups were specially designed and implemented. These experiments apply various part designs, tool-making techniques, process factors, part inspection and condition monitoring techniques, and FEA. To further understand the importance of process characteristics at the micro scale, an in depth analysis of the experimental results for each of the selected investigations was carried out. Finally, in Chapter 7 the results from each of the investigations are summarised, and the main research findings identified, in particular the influence of runner size on the process performance, tool surface finish effects on the filling process, the accuracy and sensitivity of the proposed FEA model, and the effects of tool surface treatment on part de-moulding.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available