The importance of cutting forces in machining has been emphasized for monitoring and optimizing cutting conditions, leading to various method to detecting cutting forces researched. Cutting forces can be directly measured using dynamometer or indirectly estimated using AE sensors and accelerometers, etc. However, these external sensors demand high costs and have accuracy limitations due to environment issues. To compensate for these drawbacks, utilizing internal signals of machine tool has been developed. Among these, using internal electrical signals of machine tool is representative. In commercial machine tools, cutting forces are often estimated through current measurements. However, due to the characteristics of the spindle motor, electrical properties such as slip, power factor, and efficiency vary with the load, resulting in relatively lower accuracy. This study introduces current-based method considering characteristics of motor and power-based method for estimating cutting forces and compare accuracy of those methods with the measurements from dynamometer respectively.

The purpose of this study was to design a sledge frame for para ice hockey in which an athlete sits and plays on a sledge. A sledge comprises a bucket, a blade carrier, and a frame. A sledge frame is usually fabricated by welding a number of pipes, and thus its structural safety is degenerated at the welded joints. In this study, the sledge frame was redesigned using the principle of DfAM (Design for Additive Manufacturing), to reduce the frame weight as well as to have sufficient structural safety. As an application of DfAM, the part consolidation was performed for six joints from which the number of welding spots was reduced to 56% (From 16 to 9). Among the resulting four consolidated joints, topology optimization was performed for three joints to reduce their weight while maintaining higher structural stiffness and safety. As a result, the structural stiffness and safety of the joints improved remarkably, and the resulting frame weight was reduced by 20% (From 1.66 to 1.34 kg). This weight reduction with structural enhancement is expected to improve athletes’ performance and safety in para ice hockey games.