Abstract
This paper reports an investigation of the effects of process parameters on the quality characteristics of polymeric parts produced by micro injection moulding (μIM) with two different materials. Four injection moulding process parameters (injection velocity, holding pressure, melt temperature and mould temperature) were investigated using Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS). Three key characteristics of the mouldings were evaluated with respect to process settings and the material employed: part mass, flow length and flash formation. The experimentation employs a test part with four micro fingers with different aspect ratios (from 21 up to 150) and was carried out according to the Design of Experiments (DOE) statistical technique. The results show that holding pressure and injection velocity are the most influential parameters on part mass with a direct effect for both materials. Both parameters have a similar effect on flow length for both PP and ABS at all aspect ratios and have higher effects as the feature thickness decreased below 300 μm. The study shows that for the investigated materials the injection speed and packing pressure were the most influential parameters for increasing the amount of flash formation, with relative effects consistent for both materials. Higher melt and mould temperatures settings were less influential parameters for increasing the flash amount when moulding with both materials. Of the two investigated materials, PP was the one exhibiting more flash formation as compared with ABS, when corresponding injection moulding parameters settings for both materials were considered.
Highlights
For the mass production of micro products, micro injection moulding represents one of the most important manufacturing processes because it matches the capabilities of a low-cost process and the requirements of micro products, such as dimensions in the sub-millimetre range and low tolerances
The design of experiment (DOE) approach was applied to assess the effects of four parameters, each varying between a maximum and minimum value
Optimal process conditions could lead to a relative standard deviation
Summary
For the mass production of micro products, micro injection moulding (μIM) represents one of the most important manufacturing processes because it matches the capabilities of a low-cost process and the requirements of micro products, such as dimensions in the sub-millimetre range and low tolerances (in the order of few micrometres down to the sub-micrometre range). Their direct effect on the melt flow property and flow status is proven in conventional injection moulding The importance of those factors has been assessed for different applications, including microfluidic systems [3,4], micro channel moulding optimization [5,6,7], replication of micro ribs and micro features [8,9,10,11,12,13,14,15,16,17,18,19,20] and the effects of the processing parameters on micro cantilever using micro fingers dimensions as output response [1,2,21,22].
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