Richard J.M. Hague

Implications on design of rapid manufacturing

Abstract During the last few decades, designers have been educated to develop designs with restricted geometry so that parts can be made easily. The revolutionary aspect of rapid manufacturing will be that geometry will no longer be a limiting factor. The introduction of rapid manufacturing will have a number of effects on design. It will be possible to have re-entrant shapes without complicating manufacturing, no draft angles, variable wall thickness, no split lines and fewer parts, leading to easier assembly and lower stock. The individual designers method of working will change with the introduction of rapid manufacturing and also there will be changes to the overall design process.

Cost estimation for rapid manufacturing - laser sintering production for low to medium volumes

Abstract Rapid manufacturing (RM) is a modern production method based on layer by layer manufacturing directly from a three-dimensional computer-aided design model. The lack of tooling makes RM economically suitable for low and medium production volumes. A comparison with traditional manufacturing processes is important; in particular, cost comparison. Cost is usually the key point for decision making, with break-even points for different manufacturing technologies being the dominant information for decision makers. Cost models used for traditional production methodologies focus on material and labour costs, while modern automated manufacturing processes need cost models that are able to consider the high impact of investments and overheads. Previous work on laser sintering costing was developed in 2003. This current work presents advances and discussions on the limits of the previous work through direct comparison. A new cost model for laser sintering is then proposed. The model leads to graph profiles that are typical for layer-manufacturing processes. The evolution of cost models and the indirect cost significance in modern costing representation is shown finally.

Material and design considerations for rapid manufacturing

An investigation into how the advent of Rapid Manufacturing will influence an individual designers approach to product design and materials selection is detailed. The assumption is made that Rapid Prototyping machines have evolved into viable manufacturing systems and all associated problems with accuracy, surface finish and repeatability have been resolved. Without the restriction of removing a product from a tool, designers will be free to design any complexity of geometry that they either desire or require. This tool-less approach to manufacturing will have profound implications on the way designers are accustomed to working and will eliminate most Design for Manufacture considerations. Design investigations are presented to highlight the potential importance and scope of Rapid Manufacturing. With advances in a new range of materials, some Rapid Manufacturing is happening today—albeit with existing Rapid Prototyping equipment. However, to enable designers to use existing Rapid Prototyping equipment for manufacturing purposes, there is a need for comprehensive information relating to the mechanical properties of the available materials. This is required to enable ‘Design for Rapid Manufacture’. The most comprehensive analysis to date of three new materials aimed for end-use part manufacture at differing ages, humidities and temperatures is presented.

Rapid manufacturing facilitated customization

The current paper presents a novel method for the production of body-fitting customized seat profiles utilizing the following digital methods: three-dimensional laser scanning, reverse engineering and rapid manufacturing (RM). Seat profiles were manufactured in order to influence the comfort characteristics of an existing ejector seat manufactured by Martin Baker Aircraft Ltd. The seat, known as the Navy Aircrew Common Ejection Seat (NACES), was originally designed with a generic profile. This paper shows the replacement of this profile with shapes captured from fast jet pilots. Pressure mapping of occupied seats, has shown that the pressure distribution under the buttocks can be influenced using body-fitting design and thus comfort is directly affected. The paper discusses the relevance of RM with respect to mass customization and personalization and, in addition, recognizes RM as a next generation manufacturing system (NGMS) capable of satisfying increasingly diverse products and lower volume production. A generic customization process is reviewed to identify areas of technical difficulty and key issues in the cost-effective customization of products.

A Study on the Laser Spatter and the Oxidation Reactions During Selective Laser Melting of 316L Stainless Steel, Al-Si10-Mg, and Ti-6Al-4V

Abstract The creation of an object by selective laser melting (SLM) occurs by melting contiguous areas of a powder bed according to a corresponding digital model. It is therefore clear that the success of this metal Additive Manufacturing (AM) technology relies on the comprehension of the events that take place during the melting and solidification of the powder bed. This study was designed to understand the generation of the laser spatter that is commonly observed during SLM and the potential effects that the spatter has on the processing of 316L stainless steel, Al-Si10-Mg, and Ti-6Al-4V. With the exception of Ti-6Al-4V, the characterization of the laser spatter revealed the presence of surface oxides enriched in the most volatile alloying elements of the materials. The study will discuss the implication of this finding on the material quality of the built parts.

Rapid manufacturing: impact on supply chain methodologies and practice

This paper demonstrates the use of Rapid Manufacturing (RM) as the enabling technology for flexible manufacturing in a number of industrial sectors. This paper discusses the evolution of Rapid Prototyping (RP) to RM and the current issues that require further research for the successful integration of this technology within manufacturing companies. The use of RM will have particular impact on supply chain management paradigms such as lean and agile and has particular strategic fit with mass customisation. The effect of RM will have on these paradigms is discussed and confirmed with example cases from automotive production, motor sport and medical devices industries. In conclusion, RM has already been shown in the three cases to offer benefits, particularly where fast reconfiguration of the manufacturing process is required and with the production of customised components.

Investigating mechanical anisotropy and end-of-vector effect in laser-sintered nylon parts

Abstract A study investigating the effects of part-build orientation in the laser sintering process is presented. The investigation uses tensile, flexural, and compression testing methods to assess the changes in the mechanical properties of laser-sintered nylon-12 parts. The test parts were built in the x, y, and z orientations with the x axis parallel to the direction of the laser scanning, the y axis perpendicular to the direction laser of scanning, and the z axis in the direction of powder layers. The results from the tests show that the build orientation of the parts has an effect on the mechanical properties produced. The tensile tests show a maximum difference of 16 per cent and 11.2 per cent in strength and modulus respectively for parts built in the x, y, and z axes. The flexural tests show a 9.4 per cent and 7 per cent maximum difference in strength and modulus respectively for the parts produced in the x, y, and z axes. For the compressive tests, there is a 3.4 per cent and 13.4 per cent maximum difference in strength and modulus respectively for the parts produced in the x, y, and z axes. A statistical analysis of the results obtained highlights the presence of anisotropy in tensile and compression parts owing to their build orientation in the laser sintering machine. The test parts built in the x axis orientation showed the highest strength and modulus values while the parts built in the z axis orientation showed poor strength and modulus values. However, this is not the case for the flexural test parts, which show the highest strength and modulus values are from those built in the y axis orientation. Analysis has shown that this is due to the end-of-vector effect, which is most prominent in the y axis orientation. This effect should always be considered during laser sintering, when mechanical integrity is vital.

Sustainability of additive manufacturing: measuring the energy consumption of the laser sintering process

The term additive manufacturing (AM) describes a collection of production techniques enabling the layer-by-layer manufacture of components using digital data and raw material as inputs. The AM technology variant most frequently used in the production of end use parts is laser sintering (LS). It has been suggested that efficient usage of the energy inputs is one of the advantages of the technology. This paper presents a comparative assessment of the electricity consumptions of two major polymeric LS platforms: the Sinterstation HiQ + HS from 3D Systems and the EOSINT P 390 from EOS GmbH. The energy inputs to a build consisting of two prosthetic parts were recorded during power-monitoring experiments conducted on both platforms. This paper injects clarity into the ongoing research on the AM energy consumption by applying a novel classification system; it is argued that the AM energy usage can be divided into the job-dependent, time-dependent, geometry-dependent, and Z-height-dependent energy consumption values. The recorded mean real power consumption conforms to the values that have been reported for similar platforms. The measured energy consumption rates are higher than reported elsewhere. It is also shown that the purely time-dependent energy consumption is the main energy drain. Furthermore, the presentation of results in the context of previous literature highlights the caveats attached to summary metrics of the AM input usage.

Transparency Built‐in

The supply chains found in modern manufacturing are often complex and long. The resulting opacity poses a significant barrier to the measurement and minimization of energy consumption and therefore to the implementation of sustainable manufacturing. The current article investigates whether the adoption of additive manufacturing (AM) technology can be used to reach transparency in terms of energy and financial inputs to manufacturing operations. AM refers to the use of a group of electricity‐driven technologies capable of combining materials to manufacture geometrically complex products in a single digitally controlled process step, entirely without molds, dies, or other tooling. The single‐step nature affords full measurability with respect to process energy inputs and production costs. However, the parallel character of AM (allowing the contemporaneous production of multiple parts) poses previously unconsidered problems in the estimation of manufacturing resource consumption. This research discusses the implementation of a tool for the estimation of process energy flows and costs occurring in the AM technology variant direct metal laser sintering. It is demonstrated that accurate predictions can be made for the production of a basket of sample parts. Further, it is shown that, unlike conventional processes, the quantity and variety of parts demanded and the resulting ability to fully utilize the available machine capacity have an impact on process efficiency. It is also demonstrated that cost minimization in additive manufacturing may lead to the minimization of process energy consumption, thereby motivating sustainability improvements.

Design opportunities with rapid manufacturing

The advent of rapid manufacturing (RM) will have profound implications on all aspects of product development and manufacture. Within the design discipline, three areas are of importance, namely, design freedom, material properties and changes to the design process. These issues are currently under investigation as part of an EPSRC funded research project and this paper will outline the effects of RM on the design process with the introduction of RM and give the progress of the project to date.