This paper describes the difficult machinability of nickel titanium alloy (NiTi alloy) and its mechanism. As a result of examining the difficult cutting machinability via a turning experiment, NiTi alloy cutting showed larger cutting force, higher cutting temperature, and severe tool wear with plastic deformation of the tool compared to Ti-6Al-4V. In addition, the discharged chips were tangled with the jaw chuck and the cutting tool. As a result of investigating the cause of these difficult machining properties by orthogonal cutting, it was found that the progression of severe flank wear is affected by the elastic recovery due to the super elasticity of the material. The verification of the results according to the shear plane theory suggest that the large deformation resistance of the material is the cause of the increase in cutting temperature. Furthermore, because the cutting temperature exceeds the shape memory transformation temperature, the generated chips are shape memory processed. It was also found that because the generated chips are super elastic, chips are not easily broken and they are lengthened, and are easily entangled with a cutting tool and a jaw chuck.

Objective: Practical applications of nerve decompression using neurosurgical robots remain unexplored. Our ongoing research and development initiatives, utilizing industrial robots, aim to establish a secure and efficient neurosurgical robotic system. The principal objective of this study was to automate bone grinding, which is a pivotal component of neurosurgical procedures.Methods: To achieve this goal, we integrated an endoscope system into a manipulator and conducted precision bone machining using a neurosurgical drill, recording the grinding resistance values across 3 axes. Our study encompassed 2 core tasks: linear grinding, such as laminectomy, and cylindrical grinding, such as foraminotomy, with each task yielding unique measurement data.Results: In linear grinding, we observed a proportional increase in grinding resistance values in the machining direction with acceleration. This observation suggests that 3-axis resistance measurements are a valuable tool for gauging and predicting deep cortical penetration. However, problems occurred in cylindrical grinding, and a significant error of 10% was detected. The analysis revealed that multiple factors, including the tool tip efficiency, machining speed, teaching methods, and deflection in the robot arm and jig joints, contributed to this error.Conclusion: We successfully measured the resistance exerted on the tool tip during bone machining with a robotic arm across 3 axes. The resistance ranged from 3 to 8 Nm, with the measurement conducted at a processing speed approximately twice that of manual surgery performed by a surgeon. During the simulation of foraminotomy under endoscopic grinding conditions, we encountered a -10% error margin.

Background and Objectives: Although there have been research on bone cutting, there have been few research on bone grinding. This study reports the measurement results of the experimental system that simulated partial laminectomy in microscopic spine surgery. The purpose of this study was to examine the fluid lubrication and cooling in bone grinding, histological characteristics of workpieces, and differences in grinding between manual and milling machines. Materials and Methods: Thiel-fixed human iliac bones were used as workpieces. A neurosurgical microdrill was used as a drill system. The workpieces were fixed to a 4-component piezo-electric dynamometer and fixtures, which was used to measure the triaxial power during bone grinding. Grinding tasks were performed by manual activity and a small milling machine with or without water. Results: In bone grinding with 4-mm diameter diamond burs and water, reduction in the number of sudden increases in grinding resistance and cooling effect of over 100 °C were confirmed. Conclusion: Manual grinding may enable the control of the grinding speed and cutting depth while giving top priority to uniform torque on the work piece applied by tools. Observing the drill tip using a triaxial dynamometer in the quantification of surgery may provide useful data for the development of safety mechanisms to prevent a sudden deviation of the drill tip.

Dry cutting makes tool's life short because of lack of cooling factor. Generally speaking, heat generation in cutting are deformation heat, fractional heat, and oxidation heat. So we tried the nitrogen cutting; that is the cutting process in nitrogen gas, to reduce the oxidation heat. In this study, relation between nitrogen concentration and tool life was examined. Consequently, it was found that the nitrogen cutting was effective.