Kazuaki Iwata

Chip Formation Mechanism in Single Crystal Cutting of β-Brass

Summary The subject of this study is to analyse chip formation mechanism of single crystals. The mechanism during diamond cutting of 3-brass is investigated in association with the crystallographic orientation of the cutting geometry system. The main experimental technique used is the direct scanning electron microscope observation of in-situ chip formation. It is found that the pattern of chip formation of the single crystal is largely affected ty the cutting direction with respect to the crystallographic orientation. Continuous chip due to lamellar slip structure formation in the shear zone is mostly observed. However, the pattern changes to the discontinuous type caused by micro-cracking for the particular orientation. The shear angle changes from about 15 decrees up to 60 degrees, depending on the variation of the crystallographic orientation. The shear angle measured is compared with the value predicted from the crystal plasticity analysis. The effect of the orientation on the cutting force characteristics and the surface integrity are also discussed.

Optimization of Cutting Conditions for Multi-Pass Operations Considering Probabilistic Nature in Machining Processes

This paper deals with the problem of optimizing the number of passes required together with the cutting speed, the feed, and the depth of cut at each pass for a given total depth of cut to be removed from a workpiece, considering both the probabilistic nature of the objective function and the constraints in the machining processes. Applying the concept of dynamic programming and stochastic programming, the problem is formulated in an analytically tractable form and a new algorithm is developed for determining the optimum value of the cutting speed, feed, depth of cut, and number of passes, simultaneously. For illustration, a typical example is solved to obtain the cost-minimizing cutting conditions in a turning operation, and the effect on the optimum cutting conditions of the various factors such as total depth of cut, uncertainty of the tool life, and constraints are discussed.

Solution of Large-Scale Scheduling Problems for Job-Shop Type Machining Systems with Alternative Machine Tools

Summary This paper deals with a large-scale scheduling problem for a Job-shop type machining system taking into account alternative Machine tools for each machining process of parts. The problem is treated by using a network graph and an algorithmic procedure is proposed, applying dispatching rules. Two new dispatching rules, i.e., EFT and EFTA rules, are proposed by taking account of the alternative Machine tools, setup times and lapphasing. Numerical examples with various scales are provided to demonstrate the validity of the proposed rules, comparing the resulting schedules with those base on the conventional dispatching rules. It is found that EFTA rule is useful to solve the large-scale scheduling problems. The makespan of the schedule is decreased and the efficiency of machine tools in increased by taking into account the alternative machine tools for the processes of the parts.

Production Scheduling of Flexible Manufacturing Systems

Summary This paper deals with the production scheduling of a flexible manufacturing system which consists of machine tools, buffer storages, and material and cutting tool transportation systems. The parts are produced randomly, and alternative machine tools for each processing stage of parts are permitted. Each machine tool has a buffer of specified capacity and some particular cutting tools for common use are automatically delivered by a cutting tool transportation system. The problem is to determine the schedules of machining and transporting parts, and of transporting cutting tools simultaneously so as to minimize the makespan of production. A heuristic procedure is presented to obtain better schedules by using the decision rules. A new decision rule, named ESTA (Earliest Starting Time with Alternatives considered), is proposed to achieve a high utilization of the machine tools and the transportation systems. An experimental comparison is performed to investigate the effectiveness of the proposed decision rules through a case study.

Fundamental analysis of the mechanism of built-up edge formation based on direct scanning electron microscope observation

Abstract Direct scanning electron microscope (SEM) observation of the dynamic behaviour of the built-up edge (BUE) and local strain analysis around the BUE were carried out to investigate fundamentally the mechanism of BUE formation for low carbon steel. There are two types of crack which play significant roles in the mechanism of BUE formation: one forms below the flank face of the tool and the other forms subsequently ahead of the rake face of the tool. The former starts at the machined surface, a few tens of micrometres from the cutting edge of the tool, and grows in the primary shear zone accompanied by severe strain concentration. The latter occurs along the secondary shear zone and is caused by extensive shearing a certain distance away from the cutting edge of the tool. The morphology of the BUE is determined by the formation of both cracks, its growth depending on the strain concentration and the growth of the cracks.

Basic Study of High Speed Micro Deep Drilling

Summary Experimental studies on high speed micro drilling down to 0.1 mm in diameter have been carried out. Two types of drilling machines were manufactured for this purpose, in one of which the workpiece was fixed vertically to the table, and in the other relative rotary motions were applied in horizontal direction to both tool and workpiece. The spindles are supported by hydrostatic air bearings and driven by air turbines. The maximum rotational speeds of the spindles are 180000 rpm for the tool side and 50000 rpm for the workpiece side. The feed motion is controlled by a microprocessor via a stepping motor. The paper describes the outlines of structures and accuracies of the drilling machines used. The torque and the thrust were measured employing a quartz-type piezo-electric load washer when drilling free machining stainless steels and brass with twist drills made of carbide K10 and high speed steel. The tool wear was measured and optimum cutting conditions were obtained for a given range of rotational speed and feed rate. The drilled holes were observed employing optical microscope and SEM. The influence of cutting fluid and the method of application on the cutting forces were examined. Recommended cutting conditions within the range tested are also given.

Representation of Know-How and Its Application of Machining Reference Surface in Computer Aided Process Planning

Summary This paper proposes a process planning system based on the know-how of experienced process planners. In order to realize this, the following four subjects were studied in detail, (1) the role of know-how in the process planning of machining, (2) systematic representation of know-how by applying knowledge engineering, (3) design of a know-how acquisition system, and (4) application of a know-how base for determining machining reference surface. From the systematic analysis of know-how collected, a combined technique of the Frame and the Production Rule was found to be useful in representing the know-how. The newly developed know-how acquisition system was clarified to be effective to build the know-how base based on the proposed know-how representation. A prototype process planning system using know-how was developed and applied for determining machining reference surface. The effectiveness of this process planning system was shown in the results of case studies which were similar to the ones determined by experienced process planners.

Simulation for Design and Operation of Manufacturing Systems

Summary The purpose of this paper is to develop a general purpose discrete-event type simulator. This simulator can be used as a useful tool when newly designing an effective and economic manufacturing system as well as effectively operating the installed manufacturing system through the evaluation of the performance of hardware and/or software systems prior to their implementation. The manufacturing system is modeled as a combination of the following modules so as to be able to simulate different configurations; various types of work stations (machining, assembly, inspection, loading/unloading), cart and/or conveyor type transportation system, material handling system (shuttles, robots), storage system (warehouse, buffers), other auxiliaries (cutting tools, jigs, fixtures, pallets), and operators as well as production information processing system including the software. In addition, graphic animation capability is incorporated in the simulator which allows the user to visually monitor the dynamic behavior of the system and also displays the intermediate and final simulation results on a graphic CRT terminal in the form of a table and chart.

A Knowledge-Based Production Control System to Accommodate Unscheduled Disruptions in the Manufacturing Process

Summary This paper deals with a knowledge-based production control system to accommodate unscheduled disruptions, such as the breakdown of machines, high-priority jobs, and power failures. In particular, we mainly discuss the representation and utilization of experiential knowledge concerning the counterplans against unscheduled disruptions in the manufacturing process. A hierarchical method was proposed to represent a set of rules concerning the counterplans. A knowledge based system was implemented based on the representation method. It has been shown through case studies that the system is effective in selecting suitable counterplans against unscheduled disruptions.

A Computer Aided Conceptual Design System of Machine

Abstract The characteristics of conceptual design are first analyzed, and then, the basic functions required for computer aided conceptual design systems are discussed. To represent design objects at the conceptual design stage, a machine representation based on the state-effect formalism is introduced. The conceptual design and the concept of the functional structure of a machine are explained. Based on the concepts introduced, an experimental system for conceptual design is developed, with which design requirements can be organized into a functional structure. The description forms, the basic architecture, the functions of the system are explained.