Hidetake Tanaka

Machinability Evaluation of Inclined Planetary Motion Milling System for Difficult-to-Cut Materials

CFRP and Titanium alloy, which are known as difficult-to-cut materials have been widely used as structural material in aviation industries. The orbital drilling is one of an effective drilling technique for the industries. However this technique has some disadvantages such as increase of cutting force due to cutting with tool center point, inertial vibration generated by revolution and high installation cost. In order to improve the disadvantages, we have invented a new drilling technique which is called inclined planetary motion milling. The inclined planetary motion milling and the planetary mechanism drilling has two axes of cutting tool rotation axis and revolution axis. Cutting tool rotation axis of the orbital drilling is moved parallel to the revolution axis in eccentric. On the other hand, in the case of the inclined planetary motion milling, eccentric of the cutting tool rotation axis is realized by inclination of a few degrees from the revolution axis. Therefore, the movement of eccentric mechanism can be reduced by comparison with the orbital drilling because inclined angle is smaller than eccentricity of the cutting tool tip. As a result, eccentric mechanism can be downsized and inertial vibration is reduced. In the study, a geometrical cutting model of inclined planetary motion milling was set up. The theoretical surface roughness of the inside of drilled holes by use of two types cutting tool geometry were calculated based on the model. And cutting experiments using the new prototype for CFRP were carried out in order to evaluate the effect on machinability with change of cutting point atmosphere. In addition, optimal cutting condition was derived according to cutting experiments for titanium alloys utilizing the orthogonal array.

Development of a CAM System with Linear Servo Motor for Automation of Metal Hammering

The study deals with an automation of the metal hammering process by use of a linear motor on the basis of CAD data. Metal hammering is one of a traditional handcrafts and only skilled technician can form objective shape from a blank sheet metal without die/mold. It shall be regarded as a type of rapid manufacturing process that is it can be applied to make small amount of sheet metal part. However, to master metal hammering is difficult because of its intricate forming procedure. In this study, a linear servo hammering system, which developed in-house, is adopted as a good mimic of human hammering operation. We have already proposed a calculation method of form difference between workpiece and its CAD data quantitatively in order to assess how workpiece formed accurately and to identify primary factors for the formability. Previous version of our own developed hammering system could form workpiece without considering temporary shape of workpiece with feed-forward control. The operator had to try several times to obtain optimal hammering condition for different shapes of CAD data. It is one of the major differences in comparison with the skilled human operators do. In the study, the authors improved the hammering system to measure shape of workpiece in hammering process. This modification made hammering process to be able to feedback temporary condition to form more accurately. From the experimental result, robustness of the system performance for input shape, compared with that previous system requires several experiments to determine hammering parameter has been demonstrated.