https://popups.uliege.be/esaform21/index.php?id=1222 Index terms fr 0 https://popups.uliege.be/esaform21/index.php?id=3749 In recent years, polymeric materials are being used at an increasing rate in the biomedical industry. In particular, Ultra-High-Molecular Weight Polyethylene (UHMWPE), a thermoplastic polymer characterized by high toughness, good chemical stability and self-lubricating properties, is an ideal candidate for the manufacture of bearing implants used in hip or knee replacements. Nevertheless, it is difficult to achieve a good level of surface finish when turning it, because of its high instability at increasing temperature. In the present study, cryogenic machining was applied instead of dry cutting to machine a biomedical grade UHMWPE at different cutting speeds. The surface finish was assessed in terms of surface roughness, crystallinity degree and hardness in correspondence of the surface. To correlate machinability results with the UHMWPE mechanical behaviour, uniaxial tensile tests were performed in a wide range of temperatures. The obtained results showed that the application of cryogenic machining was an efficient mean to increase the surface finish: in fact, smoother and harder surfaces were obtained regardless of the adopted cutting parameters. Mon, 29 Mar 2021 14:24:30 +0200 Mon, 12 Apr 2021 11:27:39 +0200 https://popups.uliege.be/esaform21/index.php?id=3749 https://popups.uliege.be/esaform21/index.php?id=3793 Plunge milling is a critical process step in mass manufacturing of rectangular shapes in electrical connector components. These shapes are manufactured by drilling a pilot hole and subsequent plunge milling with a radial offset (pitch) one or more times. The plunged cavity serves as guidance for the final broaching cut. In light of new legislative initiatives, the electronics industry is forced to use lead-free Cu-Zn-Alloys for mass manufacturing of these connectors. The plunging tool is deflected due to the higher cutting forces experienced in machining of lead-free CuZn-alloys in comparison to alloys with lead. This results in an offset of the milled cavity and negatively impacts tool guidance in the subsequent broaching process. Therefore, the geometric tolerances cannot be met. In this paper, the effect of tool geometry and cutting parameters on the workpiece geometry in plunge milling is investigated. The effect of the microstructure of the work-piece materials CuZn37, CuZn42 and CuZn21Si3P on the tool deflection and cutting force components is examined. The tools used vary regarding the design of the corner in terms of the corner chamfer and the inner shaft thickness. Friction between chips in the tools inner flutes and the cavity walls reduced workpiece accuracy. Improvements were achieved by reducing the width of the cutting corner chamfers, using large inner flutes and applying low cutting parameters. Mon, 29 Mar 2021 14:39:29 +0200 Thu, 08 Apr 2021 20:31:31 +0200 https://popups.uliege.be/esaform21/index.php?id=3793 https://popups.uliege.be/esaform21/index.php?id=4246 Sustainable machining involves the use of environmentally friendly cooling and lubrication fluids. A novel approach of lubricated liquid carbon dioxide (LCO2) can be used to replace conventional cutting fluids while promising benefits such as cleaner machining and higher productivity. In this study, milling of martensitic stainless steel was performed under different cooling and lubrication conditions (dry, flood, LCO2, LCO2 + MQL). Cutting tool (ball end mill, d = 8mm) was protected by a TiAlSiN PVD hard coating, while the same uncoated tool was used as a reference. Tool life time measurements were taken under different cooling and lubrication conditions at pre-determined time intervals, until the critical tool wear of 0.2 mm was reached on the flank face. At the same time, thermocouples were inserted into the workpiece to measure the temperature directly below the cutting zone. The influence of different cooling and lubrication conditions on surface roughness parameters was also investigated. From the experimental results, surprisingly, conventional flooding machining outperformed LCO2 and LCO2 + MQL assisted machining in terms of surface roughness. Moreover, the TiAlSiN coated tool exhibited roughly three times longer tool life time when compared to the uncoated tool at the same machining conditions. Whereas both, LCO2 and LCO2 + MQL cooling/lubricating strategies significantly reduce the temperature in the cutting zone, dry machining strategy provides the longest tool life time. Thu, 01 Apr 2021 17:15:38 +0200 Thu, 01 Apr 2021 17:15:43 +0200 https://popups.uliege.be/esaform21/index.php?id=4246 https://popups.uliege.be/esaform21/index.php?id=2424 The highly used Ti6Al4V alloy is a well know hard-to-machine material. The modelling of orthogonal cutting process of Ti6Al4V attract the interest of many researchers as it often generates serrated chips. The purpose of this paper is to show the significant influence of cutting speed on chip formation during orthogonal cutting of Ti6Al4V along with different material constitutive models. Finite element analyses for chip formation are conducted for different cutting speeds and are investigated with well-known Johnson-Cook constitutive model, a modified Johnson–Cook model known as Hyperbolic Tangent (TANH) model that emphasizes the strain softening behavior and modified Johnson-Cook constitutive model that consider temperature dependent strain hardening factor. A 2D Lagrangian finite element model is adopted for the simulation of the orthogonal cutting process and the results from the simulations such as calculated forces, chip morphologies are analyzed and are compared with the experimental results to highlight the differences. The results analysis shows that, the temperature in the secondary deformation zone is directly proportional to the cutting speed. Tue, 23 Mar 2021 18:41:10 +0100 Mon, 29 Mar 2021 09:19:29 +0200 https://popups.uliege.be/esaform21/index.php?id=2424 https://popups.uliege.be/esaform21/index.php?id=1903 Burnishing is a Severe Plastic Deformation process having the potential to replace expensive finishing post processes. It is considered a super finishing process due to its results in terms of drastic roughness reduction. Also, additional advantages include the surface integrity improvement functionalized to the specific application. Even though burnishing is widely applied for surface improvement of conventional materials, knowledge about its effect on additively manufactured metals is still limited. This paper aims to fill this gap presenting experiments on roller burnishing on additively manufactured stainless steel in order to improve its tribological performance. The experimental campaign was carried out to find suitable process parameters able to drastically improve the tribological behavior of the final product. In particular, the influence of the burnishing forces on the whole surface quality has been addressed. The overall results demonstrate that the selected burnishing configuration is able to successfully modify the surface characteristics of the steel, making it appropriate for critical applications. Furthermore, the experimental findings allow to conclude that burnishing process can replace a series of post processes needed after additive manufacturing, drastically reducing the time and costs associated to the manufacturing process and meeting Industry 4.0 requirements. Tue, 23 Mar 2021 10:33:26 +0100 Tue, 23 Mar 2021 12:12:26 +0100 https://popups.uliege.be/esaform21/index.php?id=1903