Masatoshi Hirao

NC program evaluator for higher machining productivity

The productivity of machining centers is influenced directly by the quality of NC programs. Conventionally it was effective to calculate machining time based on the values commanded in the NC program. However, as cutting speed/feedrate and machining accuracy increase, more factors have to be considered in the estimation of productivity. In this research, such factors have been found. These are the feed acceleration and average per-block feed distance, besides command feedrate. Furthermore, an effective feedrate factor and a kinematic factor are suggested to express the relations among the above three factors. With the kinematic factor improvements on productivity can be made by changing appropriate parameters in the light of specific conditions. Based on the above analysis, an NC program evaluator was developed to investigate the productivity. With the evaluator, the machining time can be accurately calculated even in high-speed and high-precision machining which is impossible by a conventional CAM tool or an NC controller. Applying the evaluator, three actual NC programs used in high-speed and high-precision cutting were analyzed and the results show that increasing the acceleration and per-block feed distance rather than command feedrate is effective to productivity in high-speed and high-precision cutting.

Simple Testing Method for Spindle Rotating Accuracy of Machining Tool

This paper deals with a new method for spindle rotating accuracy of machine tools. Most method to determine spindle rotating accuracy requires conventionally special measuring equipments which have some weak points like sensitivity. reliability caused by a non touch sensor to measure directory spindle rotating accuracy. But ‘in the new method, spindle rotating accuracy is determined based on a work piece accuracy machined. A popular circularity measuring instrument and surface finish measuring equipment having a higli sensitivity and reliability are applied for the method. The measured data are analyzed and the error motion is composed by a personal computer. Six NC lathes are tested and the error of circularity of machined products are fully agreed with that of analysis. The analysis and circularity of machined test piece revealed that the error of angular motion of spindle rotation is not negligible small but it becomes stable after 10 rotations.

AUTOMATION OF CHAMFERING BY AN INDUSTRIAL ROBOT (DEVELOPMENT OF POSITIONING SYSTEM TO COPE WITH DIMENSIONAL ERROR)

ABSTRACT The study deals with an automation of chamfering by an industrial robot. The study focused on the automation of chamfering without influence of dimensional error piece by piece. In general, products made by casting have dimensional error. A cast impeller, used in water pump, is treated in the study as an example of the casting product. The impeller is usually chamfered with handwork since it has individual dimensional errors. In the system, a diamond file driven by air reciprocating actuator is used as a chamfering tool and image processing is used to compensate the dimensional error of the workpiece. The robot hand carries a workpiece instead of a chamfering tool both for machining and for material handling. From the experimental result, the system is found to have an ability to chamfer a workpiece has the dimensional error automatically.

Improved machinability of nitriding steel (SACM 645)

Abstract Nitriding steel (SACM 645) is a base material which has a high resistivity of wear and high fatigue strength. However the machinability is very low, because the hardness of this steel is relatively high. To improve the machinability of SACM 645, molybdenum and vanadium are added during making this steel. Two kinds of improved machinability steel (Mo 1.3, 2.1%, V 0.48%) and standard steel are made and cutting mechanism is investigated. In chip formation, easy treatment chips are produced in cutting of two kinds of improved steels. But in cutting of standard steel, that length of chip is a little bit long continued type and not easy treatment. In cutting temperature, average temperature of standard steel is about 200C° lower than that of two improved steels. This is an opposite result of tool life experiment. In tool life, improved steels have a long tool life as compared with standard steel in conventional cutting velocity (150–200 m/min). However in high cutting velocity (more than 260 m/min), tool life of three kind of steel is almost the same. The addition of alloying element (Molybdenum and Vanadium) and the resulting different microstructures are responsible for AMV1 and AMV2 having a higher degree of machinability than standard SACM645 nitriding steel.