To Örebro University

Herein, the quality and accuracy to manufacture delicate parts from NiTi powder using electron beam powder bed fusion (EB-PBF) technology is investigated. Therefore, benchmarks with thin cylinders and thin walls are designed and fabricated using two distinct scan strategies of EB-PBF manufacturing (i.e., continuous melting and spot melting) with different process parameter sets. After these optimizations, four different lattice structures (i.e., octahedron, cell gyroid, sheet gyroid, and channel) are manufactured and characterized. It is shown both continuous melting and spot melting modes are able to manufacture lattices with relative densities over 97%. And as-built lattice structures exhibit an excellent pseudoelasticity up to 8% depending on the design of the structure, e.g., the channel structure shows more deformation recoverability than the cell gyroid. This is attributed to the integrity of geometry as well as compressive mode of the mechanical loading. Of course, the compressive strength and ultimate compressive strength also increase with the increasing volume fraction. Moreover, the spot melting can be used as an engineering tool to customize a delicate beam-shaped structure with a superior pseudoelasticity.

This study explores the precision of electron beam powder bed fusion (EB-PBF) for NiTi parts using continuous and spot melting scan strategies for the density and mechanical properties.image (c) 2024 WILEY-VCH GmbH

Wire drawing is one of the oldest and most common cold metal forming processes. Wire is drawn through a single die or a set of conical dies to make it longer and stronger. In the drawing die there are three geometrical parameters that affect the drawing force: die diameter, die angle and bearing length. The force required to pull the wire through the drawing die has been investigated numerous times over the years and new drawing force equations have been developed. However, some of today's most widely used equations do not include the influence of the bearing length. In this paper the most common methods to calculate the drawing force are evaluated by means of wire drawing experiments and finite element studies. From the results, a novel equation for calculating the drawing force is proposed. The proposed equation is dependent on the bearing length and was compared with experiments and validated using finite element simulations with promising results.

Wire made from metal is a fundamental component found in almost every complex product, ranging from a simple pen to a spacecraft. It is used to manufacture nails, screws, springs, rivets, cables, welding electrodes, and numerous other items that surround us daily.

In an era characterized by increased environmental concerns and the pressing need for the industry to become more sustainable, process monitoring has emerged as a key instrument for strengthening the sustainability improvements of diverse industries and operations. Many industries have transitioned into the realm of Industry 4.0, entering an era of digital transformation and datadriven decision-making. However, the production of steel wire has fallen behind. The wire drawing process has been performed in a similar manner for the last century and the production machines generally lack advanced monitoring systems. To catch up, there is a great need to digitize the wire drawing process and that is the focus of this thesis, Monitoring of the wire drawing process.

In this thesis several different methods to monitor the wire drawing process are developed and evaluated, resulting in a process monitoring system for the wire drawing process.

Components made from wire can be found all around us, cables, screws, nails and many other things that are vital for our modern society are made from cold drawn wire. The wire is produced by pulling hot rolled wire through a single or a series of tools called drawing dies. In this process the cross section of the wire is reduced and the mechanical properties of the material is enhanced. Even though it is classified as a cold working process, there are rather high temperatures in the dies during the process due to extreme tribological conditions resulting in high frictional forces between the wire and the die. Previous studies have shown that the temperature of the drawing tool has an impact on the performance of the process and on the wear rate of the tool. Hence, cooling of the drawing dies is of high importance for the wire drawing process. In this paper, case studies where different approaches have been utilized to improve the cooling capacity of the drawing die in industrial wire drawing processes are presented.

In-situ evaluation (monitoring) of the wire drawing process is often performed manually in today’s industry which is a difficult task for the operator, requiring both time and experience. Previous research at Örebro university has been performed to identify and evaluate automated in-situ monitoring methods for the wire drawing process. From this research, several methods that can be applied for monitoring purposes have been identified. However, the advantage of using multiple sensors has not yet been investigated. How data from different monitoring sensor signals correlates with each other and if they can be combined to obtain a better understanding of the wire drawing process will be investigated and discussed in this work. Four different sensor signals; vibration, wire temperature, brightness of the wire surface and drawing force, will be compared and evaluated in wire drawing experiments where the process conditions are controlled. The results show that all the evaluated sensors indicate similar to deviations in the lubrication process, however, some problems could only be detected by some sensors. Using multiple sensors can have advantages in both detection and misrepresentation of problems and might be used to classify specific types of problems in the process.

Recent process developments in Fused Filament Fabrication (FFF), such as the possibilities to use high end polymers (for example PEEK) or to manufacture metal parts and parts reinforced with continuous fibers, have increased industrial interest. Previously, this additive manufacturing (AM) technology was mostly popular among hobbyists thanks to its low investment cost. With the increased industrial interest comes higher demands on product strength and production efficiency.

The FFF process has many parameters that should be optimized to meet these tougher requirements. One of these parameters is the size of the nozzle through which the filament is extruded. Today a fairly wide range of sizes are available on the market, but most standard-sized printers come equipped with a 0.4 mm nozzle.

In this study, a wide range of nozzles of different sizes have been manufactured to investigate how the nozzle size affects both the printing process and the mechanical properties of the printed parts. Tensile bars have been manufactured in polylactic acid (PLA) using 7 different nozzle sizes. The samples were investigatedby means of computer tomography (CT) and optical microscopy and subjected totensile testing.

Wire is all around us and it forms joints in our structures, stabilizes our tires andtransports electricity. In almost every complex product there are components made fromwire. In wire drawing hot rolled material is drawn through a single or a series of tools calleddrawing dies, reducing the cross-section and enhancing the mechanical properties of thematerial. The tribological conditions in wire drawing are quite extreme and the high frictionbetween the wire and the die which leads to plenty of heat going into the die, resulting in hightool temperatures. Previous studies have shown that by reducing the tool temperature it ispossible to increase the productivity without risking an increased tool wear, this makes thecooling of the tool of high importance for the wire drawing process.Triply periodic minimal surfaces (TPMS) which have lately been enabled to be manufacturedby the use of additive manufacturing (AM) have shown great potential to be used for coolingapplications with demand on high efficiency. In this study a tool holder for wire drawing wasdesigned utilizing TPMS and was manufactured using laser powder bed fusion (LPBF). Thecooling efficiency of the manufactured tool holder was evaluated and compared to a con-ventional tool holder in an industrial wire drawing process. The study shows promisingresults on improving the cooling efficiency in the process by using the TPMS AM toolholder.

Components made from wire can be found in almost all complex products. In the wire drawing process, hot rolled wire is drawn through a single or a series of tools, which reduces the cross section of the wire and enhances the mechanical properties of the material. The tribological conditions in the process are extreme and the high frictional forces between the wire and the die results in high tool temperatures. Previous studies have shown that by reducing the temperature of the drawing tool it is possible to decrease the tool wear rate. Hence, cooling of the tool is of high importance in the wire drawing process.

In this study, the possibilities to decrease the tool temperature by introducing conformal cooling in the drawing tool was investigated. Drawing tools made of cemented carbide like material were designed to utilize conformal cooling and manufactured by additive manufacturing. Results on cooling efficiency in an industrial-like wire drawing process are presented and discussed.

Wire drawing is one of the oldest and most used metal forming processes. In a conventional wire drawing process, the cross-section of the wire is reduced to the final dimension by drawing the wire through a series of drawing dies made of cemented carbide or polycrystalline diamond. Despite the use of different types of lubricants wear of the dies, frequently resulting in time-consuming die changes, is a problem which limits the possibility to increase the productivity of the process. Also, the requirements for a high wire surface quality have become very high during the last years, especially for products such as spring steel wires. In the present work, the gradual surface degradation and wear of uncoated and PVD-coated (AlCrN+DLC) cemented carbide drawing dies have been investigated when drawing low alloyed carbon steel wire. The results show that the initial wear of uncoated cemented carbide is due to preferential removal of the binder metal in combination with plastic deformation and cracking of individual carbide grains resulting in a topographic surface. The increased surface topography tends to increase the tribological interaction with the mating steel wire surface increasing the tendency for cracking and fragmentation of the carbide phase and a more pronounced wear rate (steady state wear conditions). PVD coated cemented carbide dies exhibit an increased wear resistance compared to uncoated cemented carbide die by significantly reducing the wear initiation of the cemented carbide and extending the transition from the mild wear regime (low wear rate) to the severe wear regime (high wear rate). The prevailing wear mechanisms are illustrated and characterized using optical surface profilometry, high resolution scanning electron microscopy and energy dispersive X-ray spectroscopy.

Wire drawing is a manufacturing process in which metal rods or wires are drawn through a single or a series of dies, reducing the wire cross-section and enhancing the mechanical properties of the wire. The tribological conditions in wire drawing are quite extreme and high friction between the wire and the die results in an increased die temperature. Previous studies have shown that by reducing the die temperature the lifetime of the die increases and thus efficient cooling of the die is of high importance.

Additive manufacturing enables fabrication of tools with advanced conformal cooling channels with high cooling efficiency. This technique may, therefore, be of high importance in the design of the cooling system of drawing dies. In the present study, the effect of conformal cooling design of die holder on the die temperature, and thus die performance, was investigated. A die holder was manufactured by means of laser powder bed fusion (LPBF) in an EOS M290 machine using atomized corrosion resistant steel (Corrax). The cooling efficiency of the manufactured tool holder was evaluated in an industrial wire drawing process and further analysed using FEM modelling. This study shows promising results on improved cooling efficiency for die holder designed and manufactured by additive manufacturing.