The purpose of this paper is to investigate the polyamide 12 (PA12) powder properties deterioration in the laser sintering (LS) process and propose a methodology for more…
The purpose of this paper is to investigate the polyamide 12 (PA12) powder properties deterioration in the laser sintering (LS) process and propose a methodology for more efficient powder recycling. The main goals are: to recommend a level of input PA2200 powder properties which could guarantee acceptable part quality in the LS process; and selection of the refresh rate in order to minimise the consumption of fresh material.
The paper analyses the LS processing conditions and current recycling practices in relation to the deterioration or ageing of the PA12‐based powders. Samples of new and recycled grades of PA2200 powder were artificially aged in a temperature‐controlled oven and then tested using melt flow rate (MFR) indexer. Also, un‐sintered powder samples collected from different locations within various builds, and different LS machines (EOSINT P700 and Sinterstation® 2500 HiQ) were tested.
The powder exposed at higher temperature and longer time experiences a much higher deterioration rate. The temperature and the time at which the un‐sintered material was exposed are the most influential parameters for the powder aging. It was confirmed that the MFR index is a very sensitive indicator of the changes in the powder properties and provides a relatively fast and inexpensive method of measuring the rate of the powder degradation because of the LS process. The powder located in the periphery and the top of a build has a higher MFR and therefore is less deteriorated. In contrast, powder located in the centre, or in the bottom of a long build has much lower MFR and therefore is less usable.
Based on the findings, a methodology for powder recycling is proposed. It allows a better control of the input material properties, a consistent quality of the fabricated parts, and more efficient use of the LS material.
The paper provides some useful information for the properties deterioration of PA12‐based powders (PA2200) in relation to the temperature and time at which the material is exposed in the LS.
The purpose of this paper is to discuss the opportunities and challenges of mass customisation (MC), together with the possibilities for enablement using the technologies…
The purpose of this paper is to discuss the opportunities and challenges of mass customisation (MC), together with the possibilities for enablement using the technologies of rapid manufacturing (RM).
A thorough evaluation of numerous approaches to RM of customised products is presented, with particular focus on relative advantages and limitations of each technology. To demonstrate the applicability of specific techniques, case studies from both consumer and medical applications are reported based on original research.
The paper highlights not only the opportunities for RM technologies, but also the limitations of specific processes. This approach provides guidance for practitioners in the selection of appropriate technologies for MC enablement.
The focus of this practitioner review is limited to proprietary RM materials and systems which are already commercially available, with relatively little attention given the technologies presently in development.
Whilst RM and MC have already received much attention in the literature, comparatively little consideration has been given to the unification of both concepts. This paper has particular emphasis on this unification with respect to the selection of appropriate technologies, and presents an appraisal of existing applications making use of RM. Through this approach, practitioners gain information in the selection of appropriate technologies for MC.
The main objective of this paper is to analyse all stages of the CastForm™ polystyrene (CF) pattern fabrication process, identify the reasons leading to inferior quality…
The main objective of this paper is to analyse all stages of the CastForm™ polystyrene (CF) pattern fabrication process, identify the reasons leading to inferior quality, and outline techniques for its improvement and reduction of failures.
This paper describes rapid manufacturing of patterns for shell or flask investment casting using the laser sintering (LS) technique with CF material. The process involves data preparation, LS fabrication of a “green” part, cleaning, and wax infiltration. All process stages are equally important for successful project completion in terms of pattern quality and delivery time. A failure at any stage requires a part or pattern to be produced again, which would incur additional time and cost.
The conducted experiments show how the CF material strength varies at different process stages and temperatures. Cleaning and wax infiltration are considered the main reasons for part distortion and breakage.
The paper proposes a new approach for wax infiltration. Deformation and breaking of unsupported features could be reduced or eliminated by introducing a supporting structure under these features.