Laser sintering of polyamides and other polymers

Objective This paper provides a brief review of relatively new additive manufacturing technologies for the fabrication of unusual and complex metal and alloy products by laser and electron beam melting. A number of process features and product microstructures are illustrated utilizing 3D optical and transmission electron microscope image compositions representing examples of 3D materials science. Methods Processing methods involving electron beam melting (EBM) and a process referred to as direct metal laser sintering (DMLS), often called selective laser melting (SLM) are described along with the use of light (optical) microscopy (OM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to elucidate microstructural phenomena. Results Examples of EBM and SLM studies are presented in 3D image compositions. These include EBM of Ti-6Al-4V, Cu, Co-base superalloy and Inconel 625; and SLM of 17-4 PH stainless steel, Inconel 718 and Inconel 625. Conclusions 3D image compositions constituting 3D materials science provide effective visualization for directional solidification-related phenomena associated with the EBM and SLM fabrication of a range of metals and alloys, especially microstructures and microstructural architectures.

https://cyberleninka.org/article/n/753005.pdf

Fabrication of Metal and Alloy Components by Additive Manufacturing: Examples of 3D Materials Science

Selective Laser Melting (SLM) is an additive manufacturing (AM) technique which has been heavily investigated for the processing of Ti-6Al-4V (Ti64) which is used in the biomedical, aerospace and other industries. To date the SLM processing of this material has been inhibited by the requirement of post processes due to three primary challenges of martensitic microstructures, undesired porosity and residual stresses which are present in the as-built state. This work identifies the state of the art in process optimisation which is being used to confront these challenges in the as-built state with a view to removing the reliance on post processing. Regarding process optimisation, maximising part density is the primary goal due to the negative influence of pores on fracture and fatigue properties. To accomplish this, a high energy input is required which results in high cooling rates during processing. It is these cooling rates which are instrumental in the microstructural evolution and residual stress production. Accordingly novel methods have been proposed which aim to maintain the necessary high level of energy input but control the cooling rates to tailor the microstructure and reduce residual stresses. Research gaps have been identified pertaining to all three of these challenges when considering mechanical properties of as-built components. Thus in its current state post processes remain critical, however promising techniques in early stage development provide encouragement going forward.

Optimisation of process parameters to address fundamental challenges during selective laser melting of Ti-6Al-4V: A review

Newer variants of milk powders and milk-based powders are being produced are looking for prospective end users Powders possess physical and functional properties that are of significance in its usage notably powder structure, particle size distribution, powder density, bulk density, particle density, occluded air, interstitial air, flowability, rehydration (wettability, sinkability, dispersibility, solubility), hygroscopicity, heat stability, emulsifying ability, water activity, stickiness, caking, and others Some of the functional properties of significance to milk powders and milk-based powders are discussed in this review Applications with regard to specific milk powders for reconstituted cheese making, coffee creamers, and those suited for milk chocolate and for the baking industry are described

Functionality of Milk Powders and Milk-Based Powders for End Use Applications-A Review

Characterization of flow properties of cohesive powders: A comparative study of traditional and new testing methods

The term powder flowability is used loosely and has generally been more closely associated to the test method used to measure it than the significance to the process. To the formulator, flowability is linked to the product. To the engineer, flowability relates to the process. Relating powder flowability results to actual behavior in the production process is the true reason flowability is measured. This article connects typical powder handling processes to flow property measurements of value to the formulator and the process engineer.

On powder flowability

The primary focus of this chapter is to provide guidance in designing bulk solids handlingequipment to provide consistent, reliable “flow.” The principles discussed in this chaptercan be applied to analyzing new or existing equipment designs, as well as comparingdifferent bulk solids using the various test methods discussed. The chapter will focus onthe equipment used from the final blend step to the press/encapsulation machine/etc. (i.e.,machine used to create the unit dose), though the technologies apply to almost any bulksolids handling process. The chapter is divided into six primary sections, including:1. Introduction: A review of introductory concepts, such a defining “flowability.”
2. Common Bulk Solids Handling Equipment: A description of the common handlingequipment and the equipment parameters that affect flowability.

Roger Barnum

Papers

On powder flowability

Flow: General Principles of Bulk Solids Handling

Addressing Powder Flow and Segregation Concerns during Scale-Up of Nutraceutical Solid Formulations