Conceptual Design of Integrated Production Center

CONCEPTUAL DESIGN OF INTEGRATED PRODUCTION CENTER F. Honda* and H. Takeyama** -Mechanical Engineering Laboratory, 4·12·1, Igusa, Suginami·ku, Tokyo,Japan --Tokyo University of Agriculture and Technology, 2·24·16, Nakamachi, Koganei·shi, Tokyo, Japan

production of products of appropriate shape, but it is not the final solution. There must be a more suited pattern of machine tool for each production mode which is the function of lot size, shape of product, size or weight of product, required accuracy of product, etc. In order to rationalize batch and piecewise production which plays an extremely important role in the national output, the greatest effort has been devoted to investigation of a normative pattern of machine tool as an element of production system and a normative pattern of the system itself. An ideal mode of production for batch and piecewise production will give a revolutionary impact even to mass production which leads to drastic reduction of lead time and higher flexibility. Then the following equation will hold as the ideal state:

ABSTRACT Based upon three years' survey study on modelling of unmanned machinery factory, the conceptual design of a multi-purpose automated Integrated Production Center for batch or piecewise production, which is the core subsystem of the factory, was performed in 1976. The input of the Production Center is standardized material and the output is complete machine units or machinery of average quality up to 700 mm in size. It is aimed at a normative Production Center for the future to perform the throughout activities from material to products such as blank fabrication, machining, heat treatment, inspection, assembly, etc. The Production Center is featured by modular design of construction, convertibility of modular working units and process merger in view of function, time and space.

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It has been analysed from various angles whether such an overall Production Center can be implemented by a single machine like an existing machining center, a transfer machine, or a mixed one. Apart from the aforementioned hardware, the basic idea of the Production Center is to eliminate the human participation in the production activities of the real time area to attain higher programmability, flexibility and reliability for batch and piecewise production.

Piecewise

Production~

Mass Production

On the basis of such the philosophy, the National Big Project has started from 1977 as a seven year program to create a normative model of Integrated Production Center covering blank fabrication, machining and assembly which will be adaptable to batch and piecewise production. The total budget is approximately 15,000,000,000 yen for seven years. Prior to this program survey and design study was conducted for four years (1973~1976), and for the early three years the conceptual design of an unmanned machinery factory was completed and for the last year, 1976, the subsystem of the factory, so-called Integrated Production Center, was intensively designed so that the National Big Project can be smoothly started. Although it has not reached a conclusive conceptual design, it has yielded a valuable guideline for the Big Project.

INTRODUCTION Every effort in research and development had been directed to automation in Japan. However, due to the inevitable constraints such as limited natural resources and energy and lowering rate of economic growth, the policy of industrial investment, research and development have been modified in order to adapt the foregoing constraints. Neverthless, automation is still justified in order to reduce manufacturing cost and to establish a tough structure of enterprise against serious economic recession and steep rise of labour cost. Increased energy consumption accompanied with automation is to be solved by centralizing or integrating manufacturing activities.

Products to be manufactured. Fundamental machinery units such as speed-changing gear box, pump, compressor, engine, control valve, etc. up to 700 mm in size.

EXisting machining centers which originated from the system concept have been very much appreciated in industry especially for batch

T~pe of production. Order making by pieceWlse and batch production of which lot size ranges 1 to 30.

DESIGN SPECIFICATION OF INTEGRATED PRODUCTION CENTER

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F. Hond a and H. Takey ama

Type of process. Blank fabrication, machining, assembly and service activities involved. Inputs from outside. Tools, jigs and fixtures, standard parts such as bolts and nuts, springs, O-rings, washers, keys, etc., smaller parts than 100 mm, and standard sheet, bar and block material. Machining and assembling accuracy. Rougher than I. T. 7 except for mating parts of I. T. 6 ....... 7.

Clarification of human functions. Planning, altering and modifying of engineering and management programs, developing and introducing of new technologies, integrating of knowhow, trouble shooting, etc. Extent of automation. All activities except for human functions described above and all activities in the real time area are to be fully automated. Flexibility. To aim at an Integrated Production Center for dealing with approximately 70 % of ordinary machinery smaller than 700 mm in the market, the rest (approximately 30 %) counting for special processings inherent in individual products, processings of extremely high accuracy, smaller parts than 100 mm, etc . as described before. Promotion of process merger. To combine, delete or centralize processes and operations in view of function, space and time. Date of development and commercialization. To be developed in the earlier part of 1980's and commercially utilized in the middle part of 1980's. SIGNIFICANCE OF PROCESS MERGER Process merger is one of the most important target of the project. Conventionally the activities of blank fabrication, machining and assembly have independently functioned in a production system. Since products are to be manufactured in a closed system, the Integrated Production Center, process merger in view of function, space and time, as shown in Fig. 1, seems to be advantageous in production cost, production control and required parts accuracy. Furthermore, this concept has a possibility to lead to a new image of "Production tool". Process merger is defined as collective execution of plural processes or operations in time and / or space domains. Here the space domain denotes the coordinates of both workpiece and machine. Following after each workpiece a standard process sequence can be described by a block diagram shown in Fig. 2 takin~the time axis from left to right. Here LJ denotes a principal process activity such as blank fabrication, machining, assembly and material treatment, and () denotes an

auxiliary activity such as work transfer, inspection, etc. Starting from the standard sequence in Fig. 2, conceivable types of process merger will be classified into A, B, C and D as shown in Fig. 3 by deleting or combining principal and auxiliary processes. The benefits of process merger consist of primary and secondary ones. The primary benefit is direct reduction of processing time or deletion of processes themselves, and the latter the macroscopic effect such as reduction of inventory cost and easiness of production control resulted from less causes of disturbances or unba1ances in production. Fig. 4 shows the comparison between conventional and process-merged process p1annings when manufacturing a speed changing gear box of two parallel shafts. The simulation for several products has revealed that the gross production time can be reduced averagely down to one third by process merger. This has been verified by an existing example, B. T. M. (Boring, Turning and Milling) COMPLEX developed by a bulldozer manufacturer, although the process is confined to only machining. With horizontal movement of the ram (X), cross movement of the rotary table (Y), vertical movement of the ram (Z) and indexing movement of the rotary table (C), turning, milling, boring, drilling and tapping can be performed in one chucking of workpiece, and five surfaces of a cubic workpiece can be machined. The statistics indicates that the average proportion of net machining time to non-machining time for ordinary machinery parts in small lot production is down 30 % very often, but with the aforementioned machine it reaches up 70 % approximately. Fig. 5 shows the comparison of production cost with such the integrated machine and conventional machines. The concept of process merger must affect the machine tool design, and the ultimate machine will be a working center in which blank fabrication, machining and assembly can be performed at one station. To what extent mechanical and functional integration is justifiable depends upon the following questions: (1) How far is the mechanical and functional integration allowed economically? (2) To what extent can high working load and high working accuracy coexist? (3) To what extent can high temperature or severe environment and high working accuracy coexist? (4) What is the dimensional range of workpiece to be covered? (5) To what extent can the modular units and structures of machine be commonly utilized? Unfortunately there have been no reliable data to answer the above questions. Concerning (2) and (3) a trial plot is shown in Fig . 6, in which the motor power is directly related to the working load and indirectly to the heat generated. Summarizing experiences and rough data obtained so far, the structure of a possible Production Center

Con ceptual design of inte grated production ce nte r

will consists of at least the following capsules and subsystems: Blank fabrication capsule. The capsule is one machine in which limited plastic forming such as free forging, building-block die forging, roll bending, helical roll forming, spinning, etc. and some kinds of machining can be performed . Machining and assembling capsule. The capsule is to be implemented into one machine so that cutting, grinding, assembling, welding and local heat treatment can be performed randomly by automatically changing tools and units. Deburring and cleaning capsule. System of material transfer between capsules and subsystems. Control system. SOFTWARE For higher flexibility and programmability the quantity and type of products, and even the mode of production must be able to be changed primarily by software with a flexible hardware construction. On the other hand the burden of software becomes heavier in accordance with (Freedom of hardware) X (Automation level of software) . Considering the limitation of software cost and human functions aforementioned there must be an optimal software size for a specific production system. Concept of Software Design There are two phases of software in a production system; one is the software for production planning and control and the other the technological one. The former is to be designed as the image of real hardware and factory system, whereas the latter can be developed as a general purpose program, and also existing general purpose programs can be built-in for the respective technological activities in a specific production system. Since a closed Production Center to cover blank fabrication to assembly is to be newly designed, and furthermore process merger is to be realized, the most consistent and compatible program covering all activities involved is desirable. But this is a gigantic task. Now let us explain the design concept of technological software for the Integrated Production Center. Process Planning Based upon the input data of product design written in a specific language, the product will be disintegrated into constituting parts, and finally the process sequence will be generated. COI-B"

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Since there has not been an automatic process planning system to cover blank fabrication, machining and assembly and to meet process merger of them, a completely new system has to be developed. Operation Planning Each process such as blank fabrication, machining and assembly is disintegrated into required operations to arrange the operation sequence . Control of Tool Path and Working Conditions In the software for the Integrated Production Center even the geometrical description of workpiece is not easy because it will change from time to time, for instance, when a subassembled workpiece is to be machined. Therefore, even the software for machining should be reformed on the basis of a new concept . Especially no general purpose software for assembly has been developed yet. Conceivable ways of control for assembly are numerical control, sensory control and play-back control. The most promising one will be numerical control assisted by sensory feedback. Because the operations performed in the Integrated Production Center are extremely complex, it is difficult to identify the status of workpiece in process by means of the data generated by a conventional N/C software, this being especially the case with when processing subassembled workpieces. This will necessitates a data base which holds the data concerning work geometry, function, accuracy and relative coordinates of parts being built up into a product. Based upon such the special data base the process and operation sequences can be planned, and the consistent working programs can be generated by means of the respective softwares such as APT or the like . On the other hand, in the real time operations of assembly and inspection, especially, the programs of machine control should be modified by the feedback signals from the sensors. EXAMPLE OF DESIGN Several machine tool builders and users participated in the preliminary project and each independently worked out the conceptual design of the Integrated Production Center assuming the most adequate products individually, although unfortunately blank fabrication was not included. One example is the TRIANGLE Production Center as shown in Fig. 7, in which machining, assembly and inspection for blocky workpieces can be performed by automatically changing tools and working units of modular structure. Another example is the SUPER BOX Production Center capable of machining, assembly and inspection of blocky workpieces .

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F. Honda and H. Takey ama

REFERENCE

This is characterized by higher rigidity for the machine weight because of box structure as shown in Fig. 8. The CIRCULAR Production Center including blank fabrication proposed by the author is shown in Fig. 9.

Report on Mode1ing of Unmanned Machinery Factory, Sponsored by the Ministry of International Trade and Industry, Association of Mechanical Technology, March, 1977.

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Fig. 4 Example of process merger (Speed changing gear box)

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Fig. 7 TRIANGLE Production Center for cubic workpieces

Fig. 8 SUPER BOX Production Center for cubic workpieces

Conceptual design of integrated production center

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ABM: Area of Blank Fabrication and Machining AMS: Area of Machining and Subassembly AFA: Area of Final Assembly AT: Assembling Table SBFU: Storage of Blank Fabrication Units SMU: Storage of Machining Units SP: Storage of Parts SPA: Storage of Pallets SSW: Storage of Subassembled 40rks SPP: Storage of Purchased Parts SAU: Storage of Assembling Units

Fig. 9 CIRCULAR Production Center

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