Impact of rapid manufacturing on design for manufacture for injection moulding

Rapid manufacturing (RM) employs similar technologies and processes to rapid prototyping (RP), hence resulting in a tool-less manufacturing process. This is achieved by assuming that RP machines have been converted to proper manufacturing machines. The current approaches to the design process, product development cycle and manufacturing considerations at the design stage within a concurrent engineering environment are closely examined. An attempt is then made to investigate the effect of the RM processes on the design process and product development cycle. This is further expanded to consider the impact of RM on rules and guidelines that have been established for design for manufacturing (DFM). This paper is limited to a comparison of RM with regards to injection moulding as RM is most likely to compete with this process in the first instance. This is the first research work to investigate the impact of RM on the design process

The pivotal role of rapid manufacturing in the production of cost effective customised products

The concept of Rapid Manufacturing (RM) is emerging from the so-called Rapid Prototyping technologies where additive rather than subtractive techniques will be used to make parts or even completed assemblies. As no tooling is required, one of the main benefits of RM will be the ability to make cost-effective custom products that could all be entirely individualised to a particular consumer or user. Thus, Rapid Manufacturing is the enabling technology for true, cost effective custom manufacturing and has the potential to revolutionise the design and manufacturing worlds. This paper will introduce results from a current research project that is being undertaken at Loughborough University looking into the effects that will occur to the logistics and supply chain infrastructure with the advent of RM

Cost estimation for rapid manufacturing — simultaneous production of mixed components using laser sintering

Rapid manufacturing (RM) is a production method able to build components by adding material layer by layer, and it thus allows the elimination of tooling from the production chain. For this reason, RM enables a cost-efficient production of low-volume components favouring the customization strategy. Previous work has been developed on costing methodologies applicable to RM, but it was limited to the scenario of the production of copies of the same part. In reality, RM enables the production of different components simultaneously, and thus a smart mix of components in the same machine can achieve an enhanced cost reduction. This paper details this concept by proposing mathematical models for the assignment of the full production cost into each single product and by validating through a case study. This paper extends previous work on RM costing by adding the scenario of simultaneous production of different parts

Efficient three dimensional modelling of additive manufactured textiles

Purpose – To investigate, develop and validate a three dimensional modelling strategy for the efficient generation of conformal textile data suitable for Additive Manufacture. Design/methodology/approach – A series of Additive Manufactured textiles samples were modelled using currently available Computer Aided Design software to understand the limitations associated with the generation of conformal data. Results of the initial three dimensional modelling processes informed the exploration and development of a new dedicated efficient modelling strategy that was tested to understand its capabilities. Findings – The research demonstrates the dramatically improved capabilities of the developed three dimensional modelling strategy, over existing approaches by accurately mapping complex geometries described as STL data to a mapping mesh without distortion and correctly matching the orientation and surface normal. Originality/value – To date the generation of data for AM textiles has been seen as a manual and time-consuming process. The research presents a new dedicated methodology for the efficient generation of complex and conformal Additive Manufactured textile data that will underpin further research in this area

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

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

Low cost optical fibre based Fabry Pérot strain sensor production

The production of Fabry-Pérot based optical fibre sensors has long been an iterative and labour intensive process. This paper demonstrates the production of Fabry-Pérot based optical fibre strain sensors using chemical etching techniques. Utilising hydrofluoric acid (HF) and singlemode optical fibres, a preferential etching mechanism was observed around the core portion of the fibres. These etched fibre ends were then spliced together successfully to form enclosed Fabry-Pérot cavities between 18 and 60 μm in length. These sensors have then been deployed for strain monitoring and have been subjected to strains of up to 1400 με on tensile test specimens. Etched Fabry-Pérot cavity lengths were monitored using a white light interferometry (WLI) system based on a CCD spectrometer and an 850 nm super luminescent diode (SLD). A linear and repeatable response to these strain tests has been shown with negligible sensitivity to temperature

An empirical laser sintering time estimator for Duraform PA

This paper presents work on the development of a build time estimator for Rapid Manufacturing (RM). A time estimator is required in order to develop a comprehensive costing tool for RM. An empirical method has been used to estimate build times utilising both simulated and actual builds for a Laser Sintering (LS) machine. The estimator presented here is based upon object geometry and therefore the fundamental data driving the model is obtainable from current three dimensional Computer Aided Design (3D-CAD) models. The aim of the paper is to define a model describing the build times for a laser sintering machine either for single or multiple objects

Investigation of the effect of relative humidity on polymers by depth sensing indentation

Stereolithography (SL) resins absorb varying amounts of moisture dependent on the relative humidities, which can significantly affect the mechanical properties. In this work, the influence of relative humidity (RH) on the mechanical behaviour of an SL resin is investigated using depth sensing indentation (DSI). The samples were conditioned by two methods. In the first method, samples were pre-conditioned at 33.5, 53.8, 75.3 and 84.5% RH using saturated salt solutions. These preconditioned samples were tested at 33.5% RH, using a humidity control unit (HCU) to control RH in the DSI system. In the second method, samples were conditioned and tested at 33.5, 53.8, 75.3 and 84.5% RH by regulating humidity in the DSI system using the HCU. Temperature was kept constant at 22.5 C for the conditioning and DSI testing. It was seen that hardness and modulus decreased with increasing RH and conditioning time but recovered significantly when tested after drying. This study demonstrates that RH needs to be taken into account during the DSI testing of polymers

Implications on design of rapid manufacturing

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 designer's method of working will change with the introduction of rapid manufacturing and also there will be changes to the overall design process

Modelling the effect of moisture on the depth sensing indentation response of a stereolithography polymer

Stereolithography (SL) resins are highly hygroscopic and their mechanical properties are significantly affected by the level of moisture in the environment. In addition, the load response of these materials is highly time dependent, hence, an appropriate rate dependent constitutive model is required to characterise their mechanical behaviour. In this work, the time dependent mechanical behaviour of an SL resin is investigated under varying humidity conditions using depth sensing indentation (DSI) tests. In the experimental study, a DSI system fitted with a humidity control unit was used to explore the influence of moisture on the mechanical properties of a SL resin. Samples were tested with 33.5%, 53.8%, 75.3%, 84.5% relative humidity (RH) inside the chamber while the temperature was kept constant at 22.5 C. It was seen that hardness and modulus decreased with increasing absorbed moisture in the resin. Material parameters obtained through bulk tests were used to develop a coupled stress-diffusion finite element model incorporating rate dependent material behaviour. It is proposed that this model can be used in predicting the effect of the environment on the performance of SL manufactured components