David Aitchison

A Review of State-of-the-Art Large Sized Foam Cutting Rapid Prototyping and Manufacturing Technologies.

Purpose – Current additive rapid prototyping (RP) technologies fail to efficiently produce objects greater than 0.5 m3 due to restrictions in build size, build time and cost. A need exists to develop RP and manufacturing technologies capable of producing large objects in a rapid manner directly from computer‐aided design data. Foam cutting RP is a relatively new technology capable of producing large complex objects using inexpensive materials. The purpose of this paper is to describe nine such technologies that have been developed or are currently being developed at institutions around the world. The relative merits of each system are discussed. Recommendations are given with the aim of enhancing the performance of existing and future foam cutting RP systems.Design/methodology/approach – The review is based on an extensive literature review covering academic publications, company documents and web site information.Findings – The paper provides insights into the different machine configurations and cutting...

Rapid manufacturing facilitation through optimal machining prediction of polystyrene foam

The findings reported in this paper provide a model for consistently achieving optimal cutting conditions when shaping foam plastic, such as polystyrene, with an electrically heated wire-based cutting tool. General relationships between wire temperature, power input, feed-rate, kerf width and work piece material composition were developed and an optimal machining algorithm was proposed and tested. The findings provide a significant advancement toward a fully automated machining facility and the associated development of a novel, large scale rapid manufacturing (RM) system.

Modelling and system identification of a stiff stay wire fence machine

Abstract The present paper investigates a severe gear backlash problem encountered in a stiff stay machine that is capable of producing a 26-line fence up to 2.6 m in height at a speed of 80 stays/min. Related problems in the literature typically concentrate on the effect of gear backlash on the ability to control a shaft. However, in this case, very good control of the reference speed of the shaft was maintained in spite of the gear backlash. The problem was that the commanded torques were excessively large and threatened to damage the gearbox. This problem motivated a complete analysis of the systems dynamics including the development of a model to better understand the response and allow the identification of external loads on the system. It was found that the method of sensing the shaft position (resolvers) was a major factor as well as the upgrading of the motor, which was over-responding to disturbances in the shaft. The model was validated using several torque limiting experiments and gave accurate prediction of the machines major dynamics. The simulation tool developed provides the basis to predict the effect of different loads, wire types, and/or motors on the machine for future designs, minimizing the amount of experimentation on the machine.

Force feedback temperature control for hot-tool plastic foam cutting:

Abstract This paper presents the ideation of a force feedback temperature control system for advanced hot-tool plastic foam cutting systems. With respect to other controllers, the force feedback temperature control strategy is simple to apply given that it modulates the electrical power input independent of the predetermined tool path and feed rate. The control strategy is implemented by making a series of one-dimensional cuts with a hot wire. The electrical power input to the hot wire is modulated to provide constant tool temperature. Since the cutting force and kerf width are both dependent on the tool temperature, maintaining a constant tool temperature results in consistent cut surface characteristics. The force feedback temperature control theory and its practical implementation in one dimension are presented as well as an accurate description of the cutting process. Experimental results are presented to validate both theoretical assumptions and practical benefits. A number of barriers to implementation for three-dimensional sculpting are discussed with possible solutions. The experimental results validate the predictions that force feedback temperature control is an effective control method for hot-tool plastic foam cutting.

Wire Fencing (Part 1): Determinants of Wire Quality

Knotted wire fences are fabricated on specialised machines. The input material is typically galvanised steel wire. However, the quality of the input wire used by the Fence Producer is beyond control of the Machine Manufacturer. The problem is that wire strand breakages have been reported during fabrication and subsequent field erection. This is an issue for the Fence Producer because of the lost productivity, and the potential for reputation (brand) damage for both the Manufacturer and Producer. While existing standards do exist for wire, even wire that meets these standards is known to fail during fence fabrication. Thus there is a need to better understand how the quality of wire affects the manufacturabil- ity of fences, and to identify, or if necessary create, a test for wire quality that is able to be conducted by Fence Producers. In this research, samples were obtained from known good and failed fences and wire coils, and subjected to a variety of physical and metallurgical tests. These were then statistically examined and compared to the known fate of the fence, to determine the sensitivity of the test. Four potential tests were evaluated: Tensile strength (UTS), ductility, 3-point bend- ing, microstructural, impact energy, plus a fifth novel new test called linear torsional ductility (LTD). From these tests, it was evident that the linear torsional ductility test was the most sensitive and reliable indicator for wire quality. This paper is part of a collection, with companion papers examining material properties of wire, microstructure, impact energy for wire, knot performance, and the testing of whole fences.

Data Management in Small and Medium-Sized Enterprises Using Metadata Acquired by ‘Spyware’

Abstract Data generated during a product development process are increasingly created and communicated using a digital format. Management of these data can be a key enabler of the design process; strategic, tactical, and operational management of the data can lead to shorter product development timeframes and hence competitive advantage in the marketplace. While larger companies have both the infrastructure and resources to implement sophisticated software to manage the myriad of data created, small and medium-sized enterprises (SMEs), owing to their inherent characteristics, lag in the adoption of data management tools. This paper describes research using so-called ‘Spyware’ software and reports how this software is used in a novel methodology to develop information management functions for SMEs.

A passively adaptive screwdriver: A novel concept for controlling off-diagonal stiffness:

Abstract A concept for an automated screw driving mechanism is presented. The proposed mechanism has a self-adjusting axial stiffness that depends on the torsional resistance against screwing. It delivers a greater axial thrust when the torsional resistance is greater, for example, towards the final stage of a screwing operation.

Integrated rapid-response mould development in virtual enterprise

Abstract Integrated product development methodology has been applied in the fast response mould development in virtual enterprise environment. Based on a neutral common product model, conventional plastic part design, mould design, process planning, and production scheduling are placed into an integrated context As for the special mould development process, the concept of set space is employed for the knowledge share throughout virtual moulding enterprise.

Integrated product development in virtual one-of-a-kind production

Abstract Integrated product development methodology and information support depend on the business structure of a manufacturing company. In virtual one-of-a-kind of production environment, it composes three main elements: information integration, customer involved strategy, and incremental product design and process planning. The approach places conventional product design, process planning, and production plan into an integrated context. Focus is placed on reuse of history data with integrated data structures. A STEP based product model supporting incremental product design and process planning scheme is presented. QFD is employed to organise object class and coordinates activities throughout a virtual enterprise. From a case study, some further research directions are discussed.