Purpose – A recent study confirmed that the particle size distribution of a metallic powder material has a major influence on the density of a part produced by selective laser melting (SLM). Although it is possible to get high density values with different powder types, the processing parameters have to be adjusted accordingly, affecting the process productivity. However, the particle size distribution does not only affect the density but also the surface quality and the mechanical properties of the parts. The purpose of this paper is to investigate the effect of three different powder granulations on the resulting part density, surface quality and mechanical properties of the materials produced.Design/methodology/approach – The scan surface quality and mechanical properties of three different particle size distributions and two layer thicknesses of 30 and 45 μm were compared. The scan velocities for the different powder types have been adjusted in order to guarantee a part density≥99.5 per cent.Findings ...

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Influence of the particle size distribution on surface quality and mechanical properties in AM steel parts

The paper reports an experimental study of die-casting dies with conformal cooling fabricated by direct-metal additive techniques. The main objective is to compare the benefits and limitations of the application to what has been widely discussed in literature in the context of plastics injection molding. Selective laser melting was used to fabricate an impression block with conformal cooling channels designed according to part geometry with the aid of process simulation. The tool was used in the manufacture of sample batches of zinc alloy castings after being fitted on an existing die in place of a machined impression block with conventional straight-line cooling channels. Different combinations of process parameters were tested to exploit the improved performance of the cooling system. Test results show that conformal cooling improves the surface finish of castings due to a reduced need of spray cooling, which is allowed by a higher and more uniform cooling rate. Secondary benefits include reduction of cycle time and shrinkage porosity.

/pdf/slm-tooling-for-die-casting-with-conformal-cooling-channels-1ypsb20gyg.pdf

SLM tooling for die casting with conformal cooling channels

This paper presents an automatic method for designing conformal cooling circuits, which is an essential component that directly affects the quality and timing for products fabricated by rapid tooling. To reduce the time of cooling and to control the uniformity of temperature and volumetric shrinkage, industry expects to have cooling channels that are conformal to the shape of the products. We achieve the goal of automatically designing such conformal cooling circuits in a twofold manner. First, the relationship between the conformal cooling and the geometry shape of cooling circuit is formulated. Based on that, we investigate a geometric modeling algorithm to design a cooling circuit approaching conformal cooling. Simulations have been made to verify the advantage of the cooling circuit generated by our algorithm.

Automatic design of conformal cooling circuits for rapid tooling

Recently, researchers related to the development of eco-friendly molding and forming tools have refocused on the laser assisted metal rapid tooling process to cope the global warming and the resource depletions. The advantageous inherent features of the laser assisted metal rapid tooling process, include an additive proves, switchable supply material and material deposition along an arbitrary trajectory, provide the tool designer and manufacturer with a chance to overcome the limitations of the conventional molding and forming tools from viewpoints of the energy consumption, the environmental impact and the material usage. This paper presents recent researches related to the application of laser assisted metal rapid tooling process to manufacture molding and forming tools. In addition, key technologies of important applications are discussed. Finally, the future issues of the laser assisted metal rapid tooling process related to the development of eco-friendly molding and forming tools are described.

Applications of laser assisted metal rapid tooling process to manufacture of molding & forming tools — state of the art

In this paper, cooling performance of conformal cooling channel in plastic injection molding (PIM) is numerically and experimentally examined. To examine the cooling performance, cycle time and warpage are considered. Melt temperature, injection time, packing pressure, packing time, cooling time, and cooling temperature are taken as the design variables. A multi-objective optimization of the process parameters is then performed. First, the process parameters of conformal cooling channel are optimized. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using a radial basis function network is used to identify a pareto-frontier. It is found from the numerical result that the cooling performance of conformal cooling channel is much improved, compared to the conventional cooling channel. Based on the numerical result, the conformal cooling channel is developed by using additive manufacturing technology. The experiment is then carried out to examine the validity of the conformal cooling channel. Through numerical and experimental result, it is confirmed that the conformal cooling channel is effective to the short cycle time and the warpage reduction.

M. Camilotto

Papers

Design and optimisation of conformal cooling channels in injection moulding tools