Investigation into Layered Manufacturing Technologies for Industrial Applications
Additive processes, which generate parts in a layered way, have more than 20 years of history can be defined as layered manufacturing. Layered manufacturing is gaining ground for rapid prototypes (RP), rapid tools (RT) and rapid manufacturing (RM) for production of functional parts. The paper describes which mechanism of layered manufacturing and definition and classification of rapid prototypes can be applied to complex geometries for long-term consistency. The paper demonstrates the application examples of layered manufacturing fulfilling the required physical, mechanical and geometrical properties. The most notable advantage is the integration of production planning and testing within the product development period.
Incremental metal-powder solidification by localized microwave-heating and its potential for additive manufacturing
Abstract This paper presents a concept of solidifying small quantities of metal powders in an additive manner, using localized microwave heating (LMH). The experimental results show solidification of metal powders in forms of spheres and rods (of ∼2 mm diameter) and extension of these rods by adding batches of powder and consolidating them locally as building blocks by LMH. A theoretical model applied for the LMH interaction with metal powders attributes a magnetic heating effect also to powders made of non-magnetic metals, due to eddy currents. The experimental observations and numerical results also suggest that micro-plasma discharges between the powder particles initiate their heating process. The additive LMH approach presented here is intended to extend microwave sintering capabilities, mainly known in volumetric molds, also to applications in the framework of rapid prototyping, additive manufacturing, and 3D-printing. The potentials and limitations of the powder solidification by LMH are discussed in this view.
Prevention of Barite Sag in Oil-Based Drilling Fluids Using a Mixture of Barite and Ilmenite as Weighting Material
Drilling high-pressure high-temperature (HPHT) wells requires a special fluid formulation that is capable of controlling the high pressure and is stable under the high downhole temperature. Barite-weighted fluids are common for such purpose because of the good properties of barite, its low cost, and its availability. However, solids settlement is a major problem encountered with this type of fluids, especially at elevated downhole temperatures. This phenomenon is known as barite sag, and it is encountered in vertical and directional wells under static or dynamic conditions leading to serious well control issues. This study aims to evaluate the use of barite-ilmenite mixture as a weighting agent to prevent solids sag in oil-based muds at elevated temperatures. Sag test was conducted under static conditions (vertical and inclined) at 350 °F and under dynamic conditions at 120 °F to determine the optimum ilmenite concentration. Afterward, a complete evaluation of the drilling fluid was performed by monitoring density, electrical stability, rheological and viscoelastic properties, and filtration performance to study the impact of adding ilmenite on drilling fluid performance. The results of this study showed that adding ilmenite reduces sag tendency, and only 40 wt.% ilmenite (from the total weighting material) was adequate to eliminate barite sag under both static and dynamic conditions with a sag factor of around 0.51. Adding ilmenite enhanced the rheological and viscoelastic properties and the suspension of solid particles in the drilling fluid, which confirmed sag test results. Adding ilmenite slightly increased the density of the drilling fluid, with a slight decrease in the electrical stability within the acceptable range of field applications. Moreover, a minor improvement in the filtration performance of the drilling fluid and filter cake sealing properties was observed with the combined weighting agent. The findings of this study provide a practical solution to the barite sag issue in oil-based fluids using a combination of barite and ilmenite powder as a weighting agent to drill HPHT oil and gas wells safely and efficiently with such type of fluids.