Mechanics, Materials Science & Engineering, March 2016
ISSN 2412-5954
A Virtual Stage-Gate Approach to Developing Injection Moulds for PolymerBased Drug-Delivery Systems Juster H.1,a, Steinbichler G.1 1
Institute of Polymer Injection Moulding and Process Automation, Johannes Kepler University, Linz, Austria
a
herwig.juster@gmail.com DOI 10.13140/RG.2.1.3533.9923
Keywords: mold design, drug delivery systems, stage-gate process, filling simulation.
ABSTRACT. This paper presents a stage-gate procedure for designing a polymer injection mould for the production of tablet-shaped drug-delivery systems and virtual analysis of the effects of temperature, shear rate and pressure during the filling phase. The approach, its theoretical background, methods and stages are presented and discussed. The mould was designed using the commercial computer-aided design software ProEngineer. The filling phase was analyzed by means of the commercial finite-volume analysis software package Sigmasoft, Version 5.0.1. The results show that our stagegate approach can be used to investigate moulds in terms of processing conditions in the virtual domain, which enables more accurate mould design for pharmaceutical drug-delivery systems.
Introduction. Pharmaceutical drugs with poor solubility in water have been a centre of academic and industrial attention over recent decades. Research in this area has shown that solubility can be improved by using hydrophilic polymers as carrier matrices for Active Pharmaceutical Ingredients (APIs) to form a solid dispersion system [1]. Such systems can be created using the Hot Melt Extrusion (HME) technique [2]. The standard tableting process requires two steps: first granulation and then tablet pressing. In the case of HME, this means that pelletizing (forming 2 mm pellets) is followed by grinding to powder and, subsequently, tablets can be pressed [3]. A one-stop procedure that increases the solubility of poorly soluble drugs may be possible using the polymer injection moulding technique. Clearly, a key element in polymer injection moulding is the mould, whose configuration and design elements must be optimized for a specific production process. There is an increasing demand in industry for accurate moulds and their production process in the virtual domain. At the same time, the polymer injection mould is poised to enter new fields, such as the pharmaceutical industry. Basic design strategies that allow simple modification and adaption to given design and process criteria are therefore paramount. In general, the product development process for polymer parts can be divided, according to the VDIguideline 2222, into three phases: designing, outlining and finishing phase [4]. The presented stagegate procedure allows to precise the outlining phase in a virtual domain and helping to reach the finishing phase faster. Designing a mould for a standard thermoplastic part requires some important factors to be taken into consideration, including mould size, overall number of cavities, cavity layouts, runner and gating systems, shrinkage and the ejection system [4]. In the design process of an injection mould for drug delivery systems, some additional factors must be taken into account, namely temperature gradients, mechanical stress as a result of shear rates and residence times of the melt. These parameters influence the miscibility of the drug in the molten carrier phase [5].
MMSE Journal. Open Access www.mmse.xyz
135