DESIGN AND IMPLEMENTATION OF THE FORGED PIECES PRODUCTION PLANNING AND CONTROL CONCEPT BASED ON PRODUCTION PATHS

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1 DESIGN AND IMPLEMENTATION OF THE FORGED PIECES PRODUCTION PLANNING AND CONTROL CONCEPT BASED ON PRODUCTION PATHS Radim LENORT a, Roman KLEPEK b a VŠB Technical University of Ostrava, 17. listopadu 15, Ostrava - Poruba, Czech Republic, radim.lenort@vsb.cz b LOGICONSULT v.o.s., Zátiší 779, Bohumín-Skřečoň, Czech Republic, roman.klepek@dynfut.cz Abstract The article presents a new concept to be used for planning and control of complex metallurgical secondary manufacturing processes and the follow-up engineering production, based on a production paths principle. A production path is a time or space-reserved production capacity, intended for the realization of product segment with the same degree of production repetition. This principle enables complex production to be divided into fast and slow production paths. The greater part of the assortment is processed using fast production path that can be controlled on the basis of the concept of large-batch and mass production, which enables to take advantage of its benefits. The remaining part of the assortment is controlled according to the small-batch and unit production principles. The implementation of the production paths concept and its benefits are documented on the forged pieces manufacturing process. Keywords: Production planning and control, production path, forging process 1. INTRODUCTION Production planning and control is a complex process, which requires enterprise to work out dynamic production plan and adjusts manufacturing processes rapidly [1]. Production planning and control ensures production systems fulfil individual customer orders while meeting specifications, remaining within budget, and delivering on time [2]. The planning and control of metallurgical secondary manufacturing is made considerably more difficult due to: Limited repeatability of the structure and volume of the individual products in the requirements for a given planning period. Variable technological procedures and production methods, variable number and order of operations performed at individual workplaces. Material backflows that make the products pass through selected workplaces even several times. Different product processing times at individual workplaces (the mutual deviations are substantial, ranging from minutes to hours). Occurrence of floating bottlenecks caused by high dependency of the equipment performance on the type of processed product (floating bottleneck changes its position in the production process, depending on the processed assortment [3]). Large reverse material flows, especially waste material flows [4]. The objective of this article is to present a new concept for planning and control of complex metallurgical secondary manufacturing and the follow-up engineering production, which allows increasing the smoothness, uniformity and permeability of material flow. The article is divided into four sections introduction, the characteristics of the new production planning and control concept, case study of the concept applications in production of forged pieces and the conclusion.

2 2. NEW CONCEPT OF PRODUCTION PLANNING AND CONTROL The concept of planning and control of complex metallurgical secondary manufacturing and the follow-up engineering production is based on the principle of "production paths". A production path is a time or spacereserved production capacity, intended for the realization of a product segment with the same degree of repetition of production. Spatially specified capacity can be defined as a set of production resources, which are designed exclusively to manufacture a single product segment. On the other hand, capacity defined in terms of time means that the processing of a selected segment is taking place while utilizing the production resources only for a limited period of time. It means these resources are used for various production paths. In terms of repetition of production, the product portfolio can be divided into two boundary categories [5]: 1. Small-batch and unit production produces goods in batches of one or a few products designed to customer specification. 2. Large-batch and mass production a large volume of standardized products is produced. The production paths are created and controlled in order to divide the material flow at least into two groups: 1. "Fast production path" a capacity reserved for processing a segment of products with a mass or largebatch character of production. 2. "Slow production path" a capacity designated for production of small-batch and unit products. The production paths defined spatially and in terms of time are shown schematically in Figure 1. The fast production path is displayed in gray colour, the slow one in white. Sources 1, 3, 4, 5, 6, 8 and 9 have spatially defined paths, while sources 2 and 7 have their path defined only in terms of time. Fig. 1 Schematic illustration of production divided into fast and slow paths The concept is based on two fundamental assumptions. Firstly, the production is characterized by a variability of material flows (production can run alternatively, using different manufacturing sources). Secondly, it can be found sufficiently large production volume for the fast production path. Suitably selected criteria are used to identify it, while respecting the production technology in particular. Fast production path is the source of continuous material flow with a balanced load of selected production facilities and workplaces (elimination of floating bottlenecks), with minimum adjustment and conversion times, and work in progress volume, while maximizing the capacity utilization and product passage through the process. Significant simplification of the process of planning and control in this part of production and the possibility of applying the well-known Production Planning and Control (PPC) concepts and systems represent other positive effects, leading to further improvement of the production performance parameters. Classification of the PPC concepts and systems suitable for application on fast production path is described by Lenort [6]. Although the slow production path requires responding to the complexity of the material flows, the dynamic transfer of bottlenecks and the control of buffers prior to these restrictions, but on a significantly smaller scale (attention is limited only to selected facilities or workplaces from the entire production process).

3 As a result of the changing structure of production in the individual planning periods, it is necessary to identify the production path assortment and balance of production capacity load for each of these periods again. The application of the production paths in processes, where it is allowed by the variability in the space arrangement of equipment and workplaces, diversity and length of life cycles of manufactured products (especially engineering production), can be supplemented by a putting together equipment dedicated to the individual production paths or by arranging workplaces into complex groups (production nests or cells). However, this can usually be done only in spatially defined production paths. For time-defined paths, it is possible only in case of significantly prevailing production of selected segment of products. The time definition of the production paths is mainly associated with metallurgical secondary manufacturing (where the variability of the space arrangement of the process is limited) or processes with a limited number of production resources. If a logistics chain consisting of different production technologies is planned and controlled the production path principle is applied to each of them. In this case, however, there is a situation where a different group of production assortment, suitable for fast production path, is identified in each link of the chain. This contradiction must be solved systemically for the chain as a whole (the global optimum must have priority before the different sub-optima of the individual links). 3. CASE STUDY The application of the proposed concept has been verified in specific metallurgical secondary manufacturing processes and in the follow-up engineering production. The following section will present the application in the process of production of forged pieces. The researched process consists of several production stages (operations), through which the input materials (steel blooms) are transformed into heat-treated forged pieces of required shape and quality. Material flow diagram with basic production equipment is illustrated in Figure 2. The input material divided in length is heated in continuous furnace, to be forged to the required shape using a forging press at the next stage. Heat treatment of forged pieces is carried out in two continuous furnaces, their straightening in one straightening press. This is followed by cooling in the cooling bed or bath hardening. Blasted forged pieces prepared for machining are the output of this process. Passage of forged pieces through the process and their order in each device is given by the technological prescripts. Fig. 2 Material flow diagram of the forging process Figure 2 clearly shows the two places in the material flow, where introduction of the production path concept can be considered. Variable material flow is possible in heat treatment furnaces as well as in case of hardening baths and cooling bed. However, the later of them is clearly defined by the technological prescripts, which leaves only the heat treatment furnaces as a suitable base for application of the production path concept. These furnaces can achieve a high degree of repetition of production (large-batch and mass production) by cumulating production orders (forged pieces) with the same heat treatment technique, otherwise, it is

4 necessary to perform a large number of time-consuming furnace conversions. Each heat treatment technique involves many different time-temperature regimes, dedicated for different kinds of forged pieces (especially shapes and dimensions). It is also necessary to carry out a conversion of furnaces between them, but this one is less time consuming. The analysis of the assortment composition of production orders has revealed that forged pieces requiring normalization prevail (about 80% of all processed forged pieces). This leaves sufficient potential to create spatially defined production paths: Fast production path capacity of furnace 1 was reserved for fast production path. The largest production orders with the requirement of normalization were selected to maximize the repeatability of production. This way are completely eliminated the most time-consuming conversions of furnaces between the heat treatment techniques. Furnace 1 operates in a large-batch production mode with shorter furnace conversions between the individual production orders (time-temperature regimes). Slow production path the remaining production orders are allocated to furnace 2. They are accumulated here according to the heat treatment techniques in such a way to minimize the number of conversions and to respect the technological prescripts. The implementation of the production paths created this way is strongly influenced by the following production equipment, which is the straightening press. The researched process is designed in such a way that it does not allow any interruption of material flow between the furnaces and the press (creation of buffer). That is why it is necessary to straighten the heat-treated forged pieces immediately when they come out of both furnaces. In case production orders of different shapes and dimensions were processed in each of the furnaces simultaneously, it would be necessary to straighten the forged pieces alternately (always one forged piece from furnace 1 and another one from furnace 2, etc.). This would call for readjustment of the press after each forged piece, resulting in furnace downtime caused by waiting for the completion of the press adjustment, which is in contradiction with the principle of production paths (see Figure 3 A). That is why the furnaces can simultaneously process only production orders of the same shape and dimensions (see Figure 3 B) or they can process production orders of different shape and dimensions with such a time shift, to avoid alternate straightening of forged pieces from both production orders (see Figure 3 C). A comparison of both options makes it clear that it is more convenient to process production orders of the same shape and dimensions. Using the presented potential can help to divide the production orders from fast production path in half, with each half being processed in one of the furnaces. However, this is convenient only for large production orders. In case of small production orders, there is a significant increase in conversions of furnaces, resulting in deceleration of the fast spatially defined production path (furnace 1). That is the way how the time-defined production paths are created in furnace 2: Fast production path processes halved production orders requiring normalization. These orders are processed simultaneously in both furnaces. Slow production path handles small production orders requiring normalization, which exceed the capacity of furnace 1 and the production orders require other heat treatment techniques. In this case, the production orders are processed in furnaces with a time shift minimizing the number of adjustments of the straightening press. With the given assortment composition of the researched production process, the time-defined fast production path of furnace 2 has available production volume ranging from 7 to 9 days of the calendar month.

5 Fig. 3 Time diagram of forged pieces heat treatment and straightening: A overlap processing of production orders of various shape and dimensions, B overlap processing of production orders of the same shape and dimensions, C processing of orders of various shape and dimensions with a time shift 4. CONCLUSION The verification of the new production planning and control concept taking place in an environment of complex forging processes has proven its viability and has shown its potential benefits and limitations. Creating a production path in the researched process has led to an increased utilization of the available capacities by an average amount of 25% (depending particularly on the product mix in the given planning period). However, their efficient creation and implementation must be supported by routine and standardized

6 procedures and systems. A detailed heuristic algorithm for planning and scheduling of forged pieces heat treatment has been designed in compliance with the defined production paths, in order to serve this purpose [7]. At the same time, the concept has been successfully applied in the follow-up engineering production (forged pieces machining). The future research will be oriented on design of: Cost model Activity Based Costing is suitable for metallurgical and heavy machining industry [8]. Complex decision support system a hybrid approach is appropriate for planning and control of complex metallurgical production and logistics processes [9]. ACKNOWLEDGEMENTS The work was supported by the specific university research of Ministry of Education, Youth and Sports of the Czech Republic No. SP2012/42. LITERATURE [1] CHEN, Z., LIU, S., WANG, X. Application of Context-Aware Computing in Manufacturing Execution System. In 2008 IEEE International Conference on Automation and Logistics, Qingdao, China, 2008, pp [2] TSENG, M. M., RADKE, A. M. Production Planning and Control for Mass Customization A Review of Enabling Technologies. In FOGLIATTO, F. S., DA SILVEIRA, G. J. C. (Eds.) Mass Customization: Engineering and Managing Global Operations, Springer Series in Advanced Manufacturing, 2011, Part III, pp [3] LENORT, R., SAMOLEJOVÁ, A. Analysis and Identification of Floating Capacity Bottlenecks in Metallurgical Production. Metalurgija, January-March 2007, Vol. 46, No. 1, pp [4] MICHLOWICZ, E., ZWOLIŃSKA, B. Reverse Logistics Systems in a Steel Mill a Full Production Cycle. In Conference Proceedings of 19th International Metallurgical and Materials Conference METAL Ostrava: TANGER, 2010, pp [5] DAFT, R. L., MARCIC, D. Understanding Management. Mason: Cengage Learning, [6] LENORT, R. Production Logistics Concepts and Systems: Potential for Use in Metallurgical and Waste Processing Companies. Krakow: AGH University of Science and Technology Press, [7] LENORT, R., KLEPEK, R., SAMOLEJOVÁ, A. Heuristic Algorithm for Planning and Scheduling of Forged Pieces Heat Treatment. Metalurgija, April-June 2012, Vol. 51, No. 2, pp [8] SANIUK, A., SANIUK, S., WITKOWSKI, K. Using Activity Based Costing in the Metalworking Processes. In Conference Proceedings of 19th International Metallurgical and Materials Conference METAL Ostrava: TANGER, 2010, pp [9] SAMOLEJOVÁ, A., FELIKS, J., LENORT, R., BESTA, P. A Hybrid Decision Support System for Iron Ore Supply. Metalurgija, January-March 2012, Vol. 51, No. 1, pp