S. W. Lye

ECoDE – An Environmental Component Design Evaluation Tool

Abstract. Mass consumerism has brought about increasing consumption of non-renewable natural resources and manufactured goods, and is creating a waste disposal problem of unprecedented magnitude in the process. In the long run, sustainable manufacturing is only attainable given environmentally responsible product design. There are many tools for the analysis of the impact of manufactured products on the environment, but they do not offer a level of detail sufficient to identify environmentally offensive components in the product. This paper discusses a computer-based design evaluation tool, ECoDE, developed for assessing the environmental impact of components in a product. ECoDE makes use of the Analytical Hierarchy Process to compare each criterion, and rank them in an ascending order of relative significance. The types of materials used, their costs, manufacturing processes, reliability, and ease of access for disassembly are some of the key assessment criteria being considered. Finally, a multi-attribute (or criteria) rating technique is used to compute the scores against each of the criteria for both components and the overall product. The larger the score, the less severe the impact of the component or product on the environment. A discussion is then made on an evaluation test case conducted by ECoDE. Preliminary tests have found that ECoDE is able to calculate the least environmentally friendly component and highlight its likely causes.

Computer-assisted mould design for styrofoam products

Abstract Most electronic household appliances are packaged with protective buffers to minimise goods damage during transportation and handling. These protective buffers are commonly made from styrofoam, an expandable polystyrene material. The steam injection moulding process is a popular technique used to mass-produce these buffers. In this paper, the development of a PC-based computer-assisted tool for the mould design of these styrofoam buffers is discussed. The algorithmic routines used in the selection of the available machine type, the positioning of the injection guns, ejector pins and steam vents for the mould-making are also highlighted.

An investigation into the rapid prototyping of moulds for expanded polystyrene foam

Expanded polystyrene foam, a packaging material, is traditionally injection-moulded by classical moulding techniques. However, the design and fabrication of these moulds is both intricate and time-consuming. In todays manufacturing environment of short time-to-market, the luxury of producing a mould for, often, a first-off article for client approval, is virtually untenable. Rapid prototyping technologies appear to offer an alternative method of fabrication which promises to drastically reduce the time for mould fabrication. When rapid prototyping of the mould is combined with microwave curing of the polystyrene, as an alternative source of energy to traditional steam heating, the benefit of considerably short throughput times can be expected. This paper describes the computer-integrated design and fabrication of both the mould and foam product, and discusses the main issues associated with rapid prototyping the mould, viz. accuracy of the prototype mould and the suitability of acrylic resin used in stereolithography apparatus for fabricating the mould, as well as the parameters for moulding expanded polystyrene using microwave energy. Initial results suggest that both the stereolithography process, and the acrylic resin used to build the stereolithographic model, can be used for rapid prototyping expanded foam products and their associated mould.

Virtual design and testing of protective packaging buffers

Manufactured products are commonly encased in moulded protective packaging buffers to protect them from damage due to impact shock during handling and transportation. The materials used to fabricate these buffers are well-known and cost-effective but not friendly to the environment. New bio-degradable materials such as paper pulp and starch have emerged as formidable alternatives, but little is known about how to design buffers from them.This paper describes a novel intelligent methodology for the virtual modeling, testing and design of protective packaging buffers. The methodology employs the use of genetic algorithms, finite element model and design routines developed to determine the optimal buffer design. Based on an ANSYSTM finite element model of the buffer, simulated drop tests were performed. The magnitudes of the largest reaction forces for the simulated drop tests as encountered by the model are computed and translated into the highest G value that the buffer can sustain without damage to the product. From the results, a more superior set of buffer designs is then derived with each passing generation.Validation tests were conducted on six different buffer configurations designed to protect six common consumer electrical appliances. The simulated G values were found to differ by a maximum of 11.8% from empirical results. The industrial norm of 10% deviation between empirical and simulated values can easily be realized when further refinements are made to the basic finite element model of the buffer. The findings validate the new methodology in buffer design in particular for new packaging materials where there are only a limited number of explicit or heuristic design rules.

Design automation of two-stage collapsible core using design prototype

Internal features such as undercuts in plastic products obstruct the removal of the moulded product and so special moulding tools have to be custom-designed. Since there is a lack of design knowledge of such tools, heuristic knowledge has first to be formalised and then organised into a framework so that the design can be automated. This paper discusses how a functional reasoning approach for the design of a two-stage, lever-actuated collapsible core for the moulding of uPVC pipe fittings with internal undercuts was implemented as design prototypes that were subsequently computer automated. In functional reasoning, a design is represented in a hierarchy of functions and the behaviours that realise the functions. A structure contains specific variables such as the way in which the design should be assembled. Four different types of knowledge bind together function, behaviour and structure. These are relational, qualitative, computational and context knowledge. The design prototype for the collapsible core was implemented in UniGraphics II. The time required to design these moulding tools has been drastically reduced in the plastic injection moulding company with whom this research was jointly undertaken.

Redesigning protective packaging buffers from the failure modes derived from crack characteristics

Protective packaging buffers are commonly used for the purpose of containment, protection, communication, and marketing of consumer products. Because the use of protective packaging is expected to increase markedly in the years ahead, it is imperative that their designs be cost-effective. Much of the known design heuristics have been encapsulated in design methodologies and procedures, except for one aspect, that is, the failure modes of the buffers upon impact with the ground after being dropped from a height. All packaging designs are subjected to a series of confirmatory impact tests, before design deficiencies are rectified through iterative cycles of redesign and retest. Because of the heuristic nature of packaging design, many cycles of redesign are necessary before a satisfactory design solution is found. This article discusses how, from the nature and severity of the cracks, the probable causes of failure and corrective redesign measures may be estimated. Based on the value of the crack ratio (i.e., the ratio of the depth of the crack to the buffers bearing thickness), three distinct modes of failure can be identified: marginal, critical, and catastrophic. The variation of G-value with crack ratios was studied for varying drop heights. By comparing the measured G-value to the failure mode, the conditions contributing to the failure-viz. height of drop, direction of impact, the location of the centroid, the type of fit, and degree of contact between the buffer and the product-may be estimated. Redesign guidelines to avert catastrophic buffer failure are also discussed.

A Multimedia Guide to Protective Product Packaging

A multimedia courseware on protective product packaging has been developed using a commercial authoring tool, IconAuthor™. The courseware contains general information on packaging and packaging materials, the design of expandable polystyrene foam protective packaging buffers and the moulding process. The courseware, designed with the novice designer in mind, is characterized by easy navigation, and contains self-assessment quizzes at the end of each module that is a judicious mix of questions that test both recall as well as comprehension. The choice of authoring tool is also discussed. Interactive multimedia was chosen as the medium of delivery as it has many advantages such as the inclusion of video, sound, animation, which are not found in conventional instructional media.

Characterisation of Moulded Paper Pulp for Protective Packaging

Many different types of materials are being used for protective packaging of products, most notably the use of expandable polystyrene (EPS). The main drawback of using EPS is that of disposability, especially so since it is non-biodegradable. Because of this and the concern to use more environmental friendly materials, paper pulp packaging mouldings have been explored for greater usage especially for smaller and lighter products. Presently, the design of the paper pulp packaging cushion is being performed mainly through experience and it is not uncommon to find that many design iterations have to be carried out before the paper pulp packaging met customer’s requirements.

A tool condition monitoring system in a CIM workcell

Abstract This paper describes a CIM cell to cater for all the necessary steps involved in the manufacture of turned components. It allows a user to define the geometry of the component, prepare the process plan, generate part programmes and post-process the data for CNC machining. The highlight of this paper is the development of a module for on-line tool condition monitoring in turning. It enables the condition of the tool be monitored based on the cutting forces experienced by the insert during the turning operations. A simple tool wear estimation algorithm has been developed from the results of the experimental work for flank wear estimation. Tests conducted on the module showed that it has a force measurement error of 1%. This error for the wear estimation is translated to within 0.035 mm from the calculated flank wear value.