Multi-Perspective Eco-Efficiency Assessment to Foster Sustainability in Plastic Parts Production: An Integrated Tool for Industrial Use

Introduction

Plastic is one of the most common and versatile materials used worldwide, being used to produce a wide variety of products (Ribeiro et al., 2013; Ribeiro et al., 2014) and bringing extensive economic benefits due to their combination of low cost, durability and light weight, among other important characteristics (Ellen MacArthur Foundation, 2016). Most of these plastic products are manufactured through the use of moulds in the injection moulding process, which is a significant cost driver in the plastic industry and simultaneously regulates the injection moulding process efficiency (Ribeiro et al., 2009). Any change in the mould design can affect significantly the injection moulding efficiency and effectiveness, the investment and the production costs and also the resources consumed, emissions, i.e. the environmental impact.

In the injection moulding industry there is an increasing competiveness, even in countries with low production costs. As such, new and innovative technologies and adaptable business models are likely to be developed in order to increase value and decrease cost, without compromising on process efficiency and without increasing environmental impacts (Folgado et al, 2010; Pecas et al, 2009; Ribeiro et al., 2016)]. To accomplish that in the mould’s use phase (injection moulding), it is crucial to improve the plastic part’s material requirements and the consumed energy because these are considered as the most relevant factors for the economic and environmental performance in this process. The performance in those two aspects, depends on the mould design (which determines the cycle time and the amount of material wasted in the process) and also depends on the injection machine type and power (Thiriez & Gutowski, 2006; Ribeiro et al, 2012, Ribeiro et al., 2013). In the realm of the injection mould industry, moulds with better performance in their use phase require more complex and high embedded engineering, as well as more effort in the manufacturing phase of the mould. As such, this may lead to higher production costs as well as higher energy and material consumption in manufacturing – yet, by assuming that a single mould can produce up to a few million parts, the significance of the economic and environmental impacts of the manufacturing phase in the plastic part overall performance may be considered as residual (Noble et al., 2014; Esteves et al., 2014). As such, a life cycle perspective should be adopted when selecting the most adequate mould design, considering the environmental and cost impacts of mould manufacturing, use and end-of-life phases. So, the evaluation of all life cycle phases is necessary to allow an informed and sustainability conscious decision making process.