Process optimisation | software
Right-first-time is the goal in any plastic product development project. SigmaSoft’s Virtual Molding software aims to enable the full moulding process
to be optimised before any metal is cut
The virtual approach to moulding optimisation
Even today, it is still quite common to find moulding facilities where most production set ups are determined by trial and error. In the absence of any better informa- tion, the process window is established based on previous experience and, once an acceptable quality part is achieved, the mould put into production. However, this process window is often far from optimised and the cycle time often much longer than it could be. Traditional product development follows a sequential
process: the part is designed, then the cavity designed, the mould is built, the process defined, and finally the mould goes into production. If a mistake or incorrect assumption is made at any stage in this process, it only becomes evident once the mould is mounted on the ma- chine. By that stage the production pressure is on and there is little opportunity – for reasons of cost or time – to change anything. Virtual Molding software takes a different approach. Designed to work as a ‘virtual injection moulding machine’ it is intended to reproduce the outcome of a given mould and process configuration. Allowing a mould to be ‘built’ and ‘run’ in a virtual computer environment means potential problems can be identi- fied within hours and alternative production or design concepts can be evaluated inexpensively.
www.injectionworld.com
The following example explains how the Virtual Molding approach can be used to support the complete design process of a new mould. First, an injection moulding simulation is used to
determine the basic flow behavior of the melt, to identify the best position for the injection point, to evaluate the pressure drop in each cavity, and to get an early understanding of how the part will solidify. For this first evaluation of the solidification process a perfectly tempered mold is assumed (meaning a mould with a homogeneous temperature). This allows the theoretical cycle time to be established and the regions of late solidification to be identified. In this case, the mould temperature is set at 20°C. Once this initial information about part behaviour is
gathered, a mould is designed within the Virtual Molding software and used to perform a moulding analysis. The mould is run virtually using all its components and the same process conditions that would be experienced in reality. For this example, a four-cavity hot runner mould was modelled with tempering channels assumed to be at 20°C. The simulation allows the temperature distribution
in the cavities to be calculated (Figure 1). At the beginning of the start-up phase, the mould temperature is indeed homogeneous and very near to the theoretic
January/February 2015 | INJECTION WORLD 61
Main image: US company
Kalypso used Virtual Molding techniques to optimise this dimensionally- challenging
motor mount in 30% glass reinforced PA6,6
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