Theoretical and Practical Aspects of Operational Planning for Industrial Enterprises

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1 INTERNATIONAL JOURNAL OF ECONOMICS AND STATISTICS Volue 2, 2014 Theoretical and Practical Aspects of Operational Planning for Industrial Enterprises Valery V. Leventsov, Igor V. Ilin Abstract The article considers the issues related to the use of atheatical tools in the for of ethods and odels in drawing up production schedules for production floors at industrial enterprises, which, to a large extent, depend on optial eployent of the resources available. The odels that have been suggested take into account various technical, technological, econoic and business features of production. This odel is distinctive due to its ulticriteriality. At the sae tie, in order to siplify the process of production schedules elaborating, the paper proposes a statistical odel that enables to facilitate operational plans and to consider, without loss of quality, the entire variety of business and econoic production paraeters. Keywords Operational planning, atheatical and statistical odels, profitability of production, production plan, econoic and atheatical odel, production scheduling. I. INTRODUCTION HE ost iportant factors of successful industrial T production are odern anageent technologies. These are business and technological processes, standards of project anageent, docuent circulation, organizational, functional, and organizational structures, service-oriented architecture, architecture of inforation systes and technology architecture. One of the is operational planning as a function of production anageent. The baseent of enterprise architecture is business and technology processes. Operational planning occupies one of the central places in the anageent of the business and technological processes. Operational planning is a detailed developent of plans of the copany and its subsidiaries. It cobines: 1. Operational scheduling, including details of the current plan of the enterprise and bringing jobs to each departent, division, section, brigade working. Plans and schedules in this case are for a onth, decade, day shift, and soeties every hour; 2. Operational scheduling, which provides: a. A continuous control over the production process and operational troubleshooting and failures at each workplace; Valery V. Leventsov is with the St. Petersburg State Polytechnic University, St. Petersburg, Russia (e-ail: vleventsov@spbstu.ru). Igor V. Ilin is with the St. Petersburg State Polytechnic University, St. Petersburg, Russia (phone: , e-ail: ilyin@fe.spbstu.ru) b. The organization of delivery for jobs of raw aterials, blanks and tools; export of finished products, waste production; functional testing of equipent; supply of energy, fuel, copressed air; organization of quality control. There are the following types of operational planning: 1. Interplant operational planning provides coordinated activities and the necessary production proportions between the shops of the enterprise in accordance with the sequence of processes and taking into account the functions of the ain and auxiliary, side and service shops; 2. Intrashop operational planning perfors work on the distribution of sites and jobs. The ain task of distribution is ensuring full and clear assignents of the production progra and saving sooth operation of the enterprise, its shops, sites, teas of workers. This article focuses on the following three tasks: definition of the objects sizes of labor parties launched into production; assignent of jobs to work centers (jobs); definition of the launch party objects for processing. The ost iportant tool for effective planning includes drafting calendar schedules (construction schedules calendar) of the plants (sites) where it is necessary to solve the probles entioned in the sae coplex. Drafting calendar schedules in the industry has its own characteristics: this process is tie consuing, that is, too large nuber of orders with coplex technological processes should be linked in tie and space; lack of autoation of the process of drawing up calendar schedules; if any part of the schedule as a result of violations in the production is not et, the rest of it can lose all eaning, which leads to tie consuing corrections of the plan or its coplete revision. Efficiency of an industrial enterprise depends directly on its production and econoic anageent syste and, to a large extent, on its in-house operational planning. Copetitiveness of an enterprise is strongly dependent on how flexibly production planning reacts to a change in arket conditions. In the current arket conditions, the following factors considerably increase the role and significance of in-house operational planning for any iportant anageent activities: focus of production on deand [1]; quick reaction to change in deand through odifying the line of goods and production output volue; possible deviation of the actual production process fro operational schedules. These factors are especially difficult to consider in recurring production. ISSN:

2 INTERNATIONAL JOURNAL OF ECONOMICS AND STATISTICS Volue 2, 2014 Today we have accuulated a wide range of econoic and atheatical odels and ethods of operational planning in recurring production, but this probleatic field still needs to be studied. In the id 1950s systeatic and very profound research was initiated in order to build and analyze atheatic scheduling odels, to elaborate and use routine decisionaking ethods. First exaples of successful research that was carried out at that tie and is worth entioning include network scheduling ethods. Soe interesting results were obtained in the field of queuing systes [2, 14]. At this very tie the ter scheduling theory appeared [5, 14]. Today, since industrial production in Russia is experiencing revival, there is growing interest towards scheduling probles. However, as any authors say [3, 7, 8, 14, 16, 18, 20], new real objectives in the scheduling theory have appeared and caused certain difficulties. So it is reasonable to expect a rise in relevancy of operational planning ethods. The analysis of papers dedicated to the scheduling theory lets us conclude as follows. First, all papers can be divided into four groups: individual proble stating and solving in the scheduling theory; proble solving ethods; applied proble solving in the conventional sector; new areas to apply the scheduling theory. It has to be entioned that publications, as a rule, address individual cases aong general ones. We can ake a note of the following probles: Johnson [4], Akers, Friedan, Lenstra & Reeg, Lenstra & Rinnooy Kan. In their turn, individual probles are arked off general ones in the entioned class. For exaple, Bellan-Johnson probles for two achine tools, the sae for three achine tools; two service proble; single route Johnson s proble; conveyer type probles. Thus, the literature sees into a wide range of individual probles of the scheduling theory and calendar planning quite in detail. However, the aforeentioned publications do not have general solutions to probles of the scheduling theory; tough probles of the scheduling theory are approached separately and indeterinate probles are entioned. The nuber of odels and degree of their siilarity and versatility are gradually growing and grasping a larger scope of possible applications scheduling of production, transport, ilitary operations, teaching, IT processes, etc. As these odels are getting ore and ore sophisticated the sae is happening to routine decision-aking ethods that use these odels. The following ay be said about the existing problesolving ethods. The scheduling theory objective is a specific optiization proble and practically all optiization ethods known today are used to solve it. The scheduling theory objectives coe down to the proble of atheatic prograing: linear, non-linear [18], dynaic, integralvalued, and discrete ones [19]. Network setting of a proble [2, 14], the gae theory ethod [6] are widely used. Asyptotic ethods and ethods of ulti-extree problesolving [3, 15] are studied. The cobining ethod, the graph theory ethod [2, 8], in particular, the ixed graph ethod [8]. Methods of ulti-criterion proble-solving are presented, ethods of stability analysis of proble-solving in the scheduling theory [17] are considered. A great nuber of research papers are dedicated to approxiation ethods: the Monte Carlo ethod [13], bottleneck ethod, etc. In connection with the above features, the planning for any doestic enterprises operating unsustainably. This situation is not satisfactory. Therefore, in our opinion, the developent of new planning ethods based on odels that are adequate to the real conditions of production is relevant and tiely. The failure of the first attepts to autoate the scheduling caused by reducing the to the decision of individual disparate tasks. The present stage is characterized by a systeatic approach and a coprehensive solution of scheduling probles. This eans entering scheduling syste as a subsyste in a single integrated autoated enterprise anageent syste, which iplies a close functional relationship with the other subsystes in the first place, with the subsystes of accounting and operational control over the course of production. Analysis of practical application of the scheduling theory ethods proves their high efficiency. The siplest and ost coonly used operational planning ethod is a graphic ethod. Charts and graphs are easy to read and allow anagers to analyze production capacity utilization and iprove operational plans following their gut feeling and coon sense. The Gantt chart of production capacity utilization has several ajor liits of use. One of the is that it does not take into account the variety of production situations, such as breakdowns or huan errors, which deand to do the sae job again. The chart has to be regularly updated when new works appear or tie assessents are revised. The drawback of siple graphic ethods is that dependences between operations are not clearly seen. It is especially noticeable when the process is coplicated, sub-divided and includes a lot of operations. This drawback of graphic ethods excludes network analysis. The coplex of works to be planned is reflected as a network odel. It gives ore opportunities to calculate tie characteristics and siulate situations. At the sae tie the network odeling of a work coplex does not allow us to see the workplace capacity charts. Different techniques, which we use today, treat the proble of optial values calculation of the given nors in a different way. In the context of scheduling proble-solving on big aounts of inforation, the 2nd, 6th and 8th techniques can be of the biggest practical interest. If these techniques, which contain different logical rules and priority functions, are used, scheduling probles can be siplified and actually solved. Thus, the aforeentioned allows us to conclude that the proble of the scheduling theory and calendar planning with the use of new ethods is an iportant and relevant scientific proble. ISSN:

3 INTERNATIONAL JOURNAL OF ECONOMICS AND STATISTICS Volue 2, 2014 II. PROBLEM FORMULATION Today s approaches to operational scheduling of workplaces as an optiality criterion, as a rule, use various tie characteristics that do not always properly reflect the dynaics of econoic paraeters of production. The ain scheduling probles are presented in Table 1. Table I. Approaches to selection of the best scheduling variants Year Authors Criterion , J. Muth, J. Thopson, P. Winters. Conway P.V., Maxwell, V.L., Miller, L.V. Sokolitsyn, S.A. Kuzin, B.I. Tyutyukin V.K Tsarev V.V. Cost iniization (stocks, equipent adjustent, supply lags) Miniization of the beginning oents su of final operations for all works V.A. Petrov s ethod is used as a basis: iniization of the production cycle length with the use of scheduling guidelines (priority sequence depends on whether production tie of separate ite batches increases or decreases). Miniization of the total production cycle length with the use of priority laws and preference functions Miniization of the total production cycle length through finding successive locally optial plans Miniization of planned eployent variances fro actual eployent of workers. Miniization of production in progress The ain drawback of ost scheduling odels that are recoended is the use of a single criterion approach to a given proble. However, the scheduling proble is, in its own sense, a ulti-purpose task: on the one hand, it is necessary to coplete the production progra to a full extent. On the other hand, it has to be done with axial efficiency of production. Thus, in scheduling, costs related to allocation and copletion of orders can change and the profit share that the workshop obtains can vary due to different scopes of work or as a result of dynaics in the used tie resources. Therefore, when choosing an index of production in progress as an optiality criterion for operational scheduling of workplaces, working assets of an enterprise are consciously and evidently understated, because scheduled work results in longer production cycle which is a ajor factor affecting the size of production in progress. According to the research of authors, when a workshop operates in accordance with the elaborated schedule, the size of production in progress is ties bigger in coparison to the value that is used to calculate rated working assets. If this condition is not considered, the value of rated working assets will be understated and, as a result, the production progra of an enterprise ay fail. Moreover, results of the research have shown that the production plan cannot always be fully copleted in the current planning horizon if the forer one has been elaborated based on the coon odel with restrictions of resource facilities. Hence, the equipent gets less used in coparison to the norative level and there is a drop in stock at the supply warehouse with siultaneous increase in the stock at the finished products warehouse due to the line of goods ade to cooperation. In recurring production it is econoically iportant to anufacture the order in bigger batches. If the batch size of parts put into production grows, less tie is needed to readjust the equipent, the fund of fieldwork per shift increases, labor productivity and quality of produced goods iprove. Furtherore, less aounts of aterials are consued and less working tie is spent to anufacture additional saples that are used for custoization technological purposes, for exaple, quality control of blanking operations. Econoic perforance of a copany also iproves because of steadier output and ore regular work of production divisions. Regular operation of workshops and sections is reached through ore accurate planning of deand for production capacities and a ore balanced utilization of separate groups of equipent and workplaces during a planning horizon. Utilization is usually balanced through changing calendar dates of goods production and transferring production of separate lines of goods between divisions. With less overtie work and lost hours due to organizational reasons, cost of anufactured goods goes down and their quality iproves. Thus, operational planning of production in the existing arket conditions is a useful tool to iprove efficiency of inhouse planning as a whole. Enhanced operational planning helps to obtain a positive financial result fro copany s activities, brings additional profits and iproves profitability. So, it is reasonable to develop such an optiization odel that would be based on ipleenting a ulti-purpose approach and consider the essential features of schedules. More appropriate optiality criteria of the scheduling proble, in our opinion, include axiization of production profitability and copliance with the scope and line of good of the production plan by eans of internal resources of a workshop. One of possible types of econoic and atheatical scheduling odels for achine shops can be an optiization odel that uses a ulti-criterion approach and is one of the structural eleents in the operational production anageent schee. III. PROBLEM SOLVING Let there be a achine shop (with subject or technological specialization) that has a certain nuber of achines, including doubling achines. Technological operations for production of batches of parts on the corresponding achines ISSN:

4 INTERNATIONAL JOURNAL OF ECONOMICS AND STATISTICS Volue 2, 2014 within a given tie period have to be organized in such a way that parts are produced and delivered within certain deadlines. Technological routes for parts to pass achines are different. Each separate batch of parts is characterized with preparation tie standard whereas each part is defined by the content and sequence of technological operations and standards of floorto-floor tie. Operation of workplaces of the achine shop has to be scheduled in such a way that a nuber of ajor requireents are et and certain objectives are reached, being represented as optiality criteria. Most iportant requireents to be considered in the optiization odel are the following: each achine can do no ore than one part-operation; before parts have been processed in the previous operation of the technological process, beginning of their processing in the following operation cannot be planned; the sae process operation to anufacture a part can be planned for any doubling achine that is off-duty; process of part-operation anufacturing on a achine cannot be interrupted; workplaces are loaded within the liits of the norative tie reserve. In the scheduling proble, beginning and end tie of technological process operations is unknown for certain achines and different batches of tie. The analyzed literary sources have brought us to a conclusion that various criteria and algoriths are used in operational scheduling of achine sections workplaces whereas ulti-criterion approach is ainly used in scheduling tasks. The econoic and atheatical scheduling odel of workplaces operation for subject and technological sections of achine shops that is proposed here includes two optiality criteria: percent copletion of the production plan by eans of the internal resources of a workshop and production profitability. The scheduling proble can be presented in the following way [10, 11]. It is necessary to choose such a variant of the standard-plan (schedule) of workplaces operation of a achine shop that P( µ ) ax, µ M ; (1) R µ ax, µ M ; (2) ( ) R( ) и ( ) < µ R ; (3) 0 < P µ ; (4) M = µ : µ K ; (5) { } ( π ) q 1 K =!, (6) where µ nuber of the schedule variant of workplaces operation of the workshop for iteration of calendar scheduling; µ nuber of the best schedule variant for workplaces operation for iteration of its developent; M anifold of principally possible variants of schedules for workplaces operation; K total nuber of principally possible variants of schedules for workplaces operation; π total nuber of batches of parts (orders) that represent the line of goods in the production plan of the workshop; q nuber of pieces of production equipent in the workshop; R production profitability if the workshop operates by µ variant of schedules that reflects efficiency of workshop s contribution into the net profit value of the copany in relation to the share of the copany capital (fixed and working one) allocated to the workshop for operational anageent, %; R и production profitability ediated by the line of goods and scope of the production plan set for the workshop, established prices and structure of production prie costs, aount of fixed production assets of the workshop and working assets that depend on the accepted batching of products, %; P percent copletion of the production plan by eans of the workshop s internal resources if it operates in accordance with µ variant of the schedule. Objective function (1) reflects the condition for search of such a variant of the schedule that would result in the biggest percentage of the workshop production plan ipleented with the use of internal resources of the workshop. Objective function (2) contributes to finding such a variant of the schedule that would provide axial production profitability. Restriction (3) allows considering only those variants of the schedule that would ake it possible to get a positive production profitability value and would not exceed the value that the workshop could get if it operated in ideal conditions. Restriction (4) reflects the need for coplete or partial ipleentation of the workshop production plan by eans of internal resources of the workshop. Forulae 5 and 6 reflect the anifold and nuber of possible variants of the schedule at the set qualities of batches of parts (orders) π and nuber of pieces of technological equipent q. Practical experience shows that it takes a lot of tie to elaborate one variant of the schedule if no coputer is used. Thus, to develop one variant of the part-operation schedule for a large achine-tool section, which produces 120 or ore types of parts per year, about 20 an-onths are needed [20]. Such a big tie consuption and need for schedules to operate efficiently justify application of odern personal coputers to elaborate schedules for sections and workshops, which considerably diinish labor intensity of scheduling. Thus, it takes 1-4 hours for a coputer to elaborate one variant of a part-operation schedule, depending on the diension of the proble and coplexity of the calculation syste, which are conditioned by the optiization odel applied and atheatic ethod of its ipleentation [20]. The two-criterion odel elaborated for scheduling of a ISSN:

5 INTERNATIONAL JOURNAL OF ECONOMICS AND STATISTICS Volue 2, 2014 achine shop calls for lots of input business, econoic and technological paraeters to be ipleented, which are not always available to the full extent for an operating enterprise [11, 21]. This drawback can be eliinated with a ore copact econoic and statistical scheduling odel for a achine shop. It just needs few technological and organizational paraeters, such as operational technological routes, nors of floor-to-floor tie by operations, structure of the technological equipent park, line of goods and scope of the production plan, tie reserves, workplace capacity with one type of technological operation (work) within one onth and soe others [8, 10]. Study of cause and effect relations between indices of profitability, recurring production level, equipent utilization and others has allowed finding the factors with the biggest ipact on production profitability variation. This statistical study of econoic processes at an enterprise has revealed connection between the phenoena that are reviewed, its qualitative assessent and analytical expression. In our opinion, change of the effective condition or criterion index of the econoic and atheatical odel production profitability is conditioned by change of such factors as coefficient of workplace capacity with one type of work within one onth, an average size of a labor subject batch, capacity efficient of technological equipent or standard calculated floor-to-floor tie. As a result, the only econoic paraeter of the odel is production profitability in the for of functional dependence on the coefficient of workplace capacity with one technological operation (work) within one onth. Expressions of the econoic and statistical odel (7), (9), (10), (11) do not require clarifying since they have not been reviewed in the econoic and atheatical odel. The expression of the econoic and statistical odel (8) is analogous to the expression of the econoic and atheatical odel (2), the only difference being the fact that the production profitability value, which is obtained in a statistical way and which represents a functional dependence, is used in its restrictions. IV. CONCLUSION At the heart of all the ethods for calendar scheduling jobs enterprise traffic regulations are ade. The ost coon are: the size of the shipents of parts and assebly units; duration of the production cycle of anufacturing batches, parts and assebly units; craft backlogs (cyclic, technology, assets, insurance). They deterine the econoically justified in ordering blanks, assebly units in tie and space to process transactions processing and assebly. Existing at the tie of different ethods in different ways solve the proble of finding the optial values of these regulations. Fro the point of view of solving operational scheduling on large aounts of inforation, the greatest practical interest are Gantt charts, based on the construction of which is necessary siulations and rules of precedence. Using these techniques, containing a variety of logical rules and priority function, we can siplify and solve the real probles of drawing calendar schedules. The essence of one of the algoriths for constructing the tietable that ay be proposed, consists of three stages and is as follows. At the first stage the sequence of any given order (anufacturing batches of objects). It is provided only when the control is localized to the horizon of five to seven days. Blocking of the first stage is carried out when the calendar Tietable jobs echanical areas of the shop is for the control horizon equal to one onth. In the second phase, the consolidation of the positions of the noenclature of industrial application running in production in this horizon control for specific jobs. In the third stage the production of a calendar schedule batches of objects in which the selected control horizon is reached iniu value cycle tie under the following restrictions: Prevention of anufacturing at one workplace in the sae tie interval of two different lot nubers of subjects; Preventing the shift to the left, followed by the start of the operation to coplete a batch of ites copared with the end of the previous operation. At the end of the third stage is a viable option tietable of the echanical workshop. Theoretical and ethodological basis of the research relies on papers of Russian and foreign scientists on atheatic and instruent econoic ethods of scheduling for achine shops of echanical engineering enterprises. Probles have been solved through principles of coprehensive approach, theory of sets, econoic and atheatical odeling, including siulation odeling, statistical and logical analysis. Thus, the research results have allowed the author to propose a new two-criterion approach to finding an acceptable scheduling option for workplaces of achine sections that would consider both deand for goods of the enterprise and production profitability. This approach has been used to develop an optiization two-criterion econoic and echanical odel and one-criterion econoic and statistical odel of operational scheduling for achine shop sections. The optiization odel that has been developed is based on ipleentation of ultipurpose approach and considers the essential feature of operational scheduling for workplaces. The odel uses two optiality criteria: axiization of production profitability and ipleentation of the production plan by eans of the internal resources of a workshop. REFERENCES [1] G. Vagner, Fundaentals of Operation Research. Moscow: Mir, 1972, Vol.3, pp [2] V.N. Goncharov, Operational Production Control. (Experience of syste developent and enhanceent). 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