Process Planning of the Automatic Polishing of the Curved Surface Using a Five-axis Machining Tool

Curved surface parts are widely used in aerospace industry, automotive industry and other fields due to their excellent features in aerodynamics, fluid dynamics and thermodynamics. Compared with the modeling technology of the curved surface, the development of the processing technology of the curved surface is slightly behind. In order to improve the processing quality and efficiency of the curved surface, this paper independently developed a five-axis CNC polishing machine tool, and studied the pre-processing and the post-processing when machining the curved surface. Taking a metal shell of the mobile phone as an example, three different paths are planned for the flat surface and the curved surface respectively, and a method for generating the tool path is proposed. The kinematics model of the five-axis CNC machine tool is established, which is used to obtain the calculation formula of the movement amount of each axis when polishing in the flat surface and the curved surface of the metal shell. The polishing effects of the different paths about the surface quality and the polishing efficiency of the metal shell are studied through the polishing experiments, and the polishing path with the best surface quality and the highest polishing efficiency is found.

Fretting and corrosion of metal liners from modular dual mobility constructs

Aims Dual mobility implants in total hip arthroplasty are designed to increase the functional head size, thus decreasing the potential for dislocation. Modular dual mobility (MDM) implants incorporate a metal liner (e.g. cobalt-chromium alloy) in a metal shell (e.g. titanium alloy), raising concern for mechanically assisted crevice corrosion at the modular liner-shell connection. We sought to examine fretting and corrosion on MDM liners, to analyze the corrosion products, and to examine histologically the periprosthetic tissues. Methods A total of 60 retrieved liners were subjectively scored for fretting and corrosion. The corrosion products from the three most severely corroded implants were removed from the implant surface, imaged using scanning electron microscopy, and analyzed using Fourier-transform infrared spectroscopy. Results Fretting was present on 88% (53/60) of the retrieved liners, and corrosion was present on 97% (58/60). Fretting was most often found on the lip of the taper at the transition between the lip and the dome regions. Macrophages and particles reflecting an innate inflammatory reaction to corrosion debris were noted in six of the 48 cases for which periprosthetic tissues were examined, and all were associated with retrieved components that had high corrosion scores. Conclusion Our results show that corrosion occurs at the interface between MDM liners and shells and that it can be associated with reactions in the local tissues, suggesting continued concern that this problem may become clinically important with longer-term use of these implants. Cite this article: Bone Joint J 2021;103-B(7):1238–1246.

Dimensional accuracy in quick plastic forming of aluminum alloy using demolding mechanism

This study focuses on quick plastic forming (QPF), product dimensional tolerances, and removal methods. The traditional curled metal shell mold in QFP, has limitations such as long process time and unstable quality. Therefore, this investigation designed a demolding mechanism, in order to improve the process efficiency and dimensional accuracy of QPF, in the manufacture of metal casings. The research results show that the proposed mechanism can significantly decrease the process time, because it replaces most of the operations of specimens movement after forming completely. The shorter process time reduce the die temperature loss during operation, thus also improving the efficiency by eliminating the need to wait for the die to return to its operation temperature. In terms of dimensional tolerance, the tolerance grade of QPF process was determined using the standard deviation, and found to be between IT10 and IT14. This range covers the scope of CNC cutting and stamping processing, indicating that the process has commercial value in the production of metal casings, because the current mainstream manufacturing process of metal casings comprises casting, stamping and CNC machining.

Biosense Webster’s QDOT Micro™ radiofrequency ablation catheter

The QDOT Micro™ catheter (Biosense Webster, Inc., CA, USA) is a new radiofrequency ablation catheter based on the SmartTouch SF™ (Biosense Webster, Inc.). It combines diffuse external irrigation with six thermocouples located within the outer metal shell and three additional microelectrodes in a 3.5 mm-tip contact force radiofrequency catheter. This article focuses on the different characteristics of the catheter, which incorporates the ability of high power delivery, irrigation flow control based on temperature sensing through the six thermocouples and the generation of microelectrograms. An outline of its performance in preclinical and clinical setting is presented, showing promising results, especially concerning procedural efficiency and short-term safety. Additional studies need to confirm long-term effectiveness, and durability studies should evaluate whether superiority on a lesion quality level can be achieved.

Finite Element Analysis and Experimental Study of Metal Shell of GIL

Mathematical modeling, finite element numerical simulation and experimental measurement of the stress-deformation distribution of the gas-insulated metal-enclosed transmission line shell were carried out. Also, Stress linearization analysis was used to analyze the maximum stress. The results show that the stress is linearly dependent on water pressure and the shell occurs elastic deformation without plastic deformation. The simulated maximum stress of 76.2MPa is fairly in good agreement with the measured one (69.9MPa). The stress linearization analysis results show that the shell well satisfies the environmental safety requirements. The experimental results are consistent with the finite element results.