Konfeksiyon işletmelerinde üretim planlaması ve optimizasyon çalışmaları
Production planning and optimization studies on ready made clothes running
Yazar: ÜLKÜ ALPTEKİN
Danışman: PROF. DR. MUSTAFA KÖSEOĞLU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü
Derece: Yüksek Lisans, 1994
Konu: Tekstil ve Tekstil Mühendisliği = Textile and Textile Engineering
Dizin: Optimizasyon = Optimization ; Tekstil işletmeleri = Textile enterprises ; Üretim planlaması = Production planning

Özet:
Üretim planlaması ve optimizasyon çalışmaları üretim yapan bütün işletmelerde işletmelerin hedefleri ve işletim politikaları çerçevesinde, üretim kaynaklarının en uygun ölçüde tahsisi ve maksimum kar elde etmeyi amaçlar. Sağlıklı bir üretim planı, ürünleri uygun sürede kapasitenin en iyi kullanım şartlarında ve mimimum maliyette vermeli ve bir çok bütçe işlemlerine temel oluşturmalıdır. Bunların dışında insangücü ihtiyacım ve fazla mesaide dahil olmak üzere çalışma saatlerini de saptamalıdır. Bir konfeksiyon işletmesinde üretim planlaması ve üretimin optimizasyonu konusunda hazırlanmış çalışmanın ilk bölümünde, genel olarak üretim kavramı ve endüstrideki üretim çeşitleri üzerinde durulmuştur. İkinci bölümde, üretim yönetiminin önemli konularından biri olan üretim planlaması ve üretim planının hazırlanabilmesi için yapılması gerekli ön çalışmalar hakkında bilgi verilmiş, ana üretim planının yanında detaylı planlama ve üretim planlamanın ayrılmaz bir parçası olan üretim kontrolü anlatılmıştır. Üçüncü bölümde, bir optimizasyon tekniği olan doğrusal programlama tekniği ve doğrusal programlama probleminin çözüm yollarından grafik ve simpleks metod üzerinde durulmuştur. Dördüncü bölümde ise üretim planlamada kullanılan şebeke analizi tekniklerinden PERT (Proje Geliştirme ve Revizyon Tekniği) metodu ve bu metodun üretim planlamadaki yeri ve önemi anlatılmıştır. Son bölümde de bir konfeksiyon işletmesinde doğrusal programlama ve PERT metoduna dayalı optimizasyon çalışması yeralmaktadır. Seçilmiş iki ürünün imalat aşamalarının detaylı analizi sonucu elde edilen optimum değerlerle, işletme karını maksimum yapan üretim miktarları bulunmuştur. vıu

Abstract:
Production is defined by engineers as making some change on a fizical material to increase its value or converting raw material or semi manufactured material to manufactured material. In an economy, to make a different kind of benefits on the other hand, to make a product or utility hich have an advantages is called "production". Production is related with ensuring and associating of fizical unity rather than utility. For this reason, production is an operating of converting certain amount of inputs to outputs. Production planning basically is decided prosses to reply what kind of material when, how, where and who. Briefly, production planning is a operation that make desicions connected closely with all kind of running function like purchasing, marketing, control and financing. Details and level of production planning and control operations have some differences according to the types of production systems. These operations get simpler when amount of product increases and variation of product decreases. Briefly, production planning and control contains appreaciating, organizing and establishing of all kind of material to make a production. This means that production planning is a primary production operations to determine what kind of products will be produced, what kind of equipment will be need and to prepare a list to obtain right amount and times of product. Production planning and control system generally have 3 elements in spite of differences in different production system : 1 -Primary Production : It's impossible make reliable production planning without primary production. Primary production elements contain the subjects below. Consumer survey Product project and developing Policy of establishing investment CirAcr r\f\unr\c arf»n« Order of work areas 2-Planning : The planning has two subjects. Planning about sources : Materials, methods, machines and labour power planning Planning about works : Canalizing, estimating and programming IX3-Control : Elements of production control are described as distribution, following, control, examination and grading. The most important function of control is supply a feedback to described defect on planning and deviation from planning and have a improvement needed. For the future production planning, necessary amount of product is firstly decided. It's impossible to make a planning if the demand of product that will be produced is unknown. Estimating about future isn't necessary in the factory that makes order production. The methods used for estimating are : 1 -Demand estimate based on experiment and perception 2-Demand estimate based on economic sign 3-Demand estimate based on istatistical methodts Second primary production operations is capasity planning. Capasity is generally desribed as a production rate or production quantity in a certain period of time. In capasity estimating, defining the quantity and period of time have some difficulties. But in running which produce only one type of product don't have these difficulties. Capasity planning contains studies about adjustment for level of production operations which are needed to cover the total product demand. Capasity planning contains to planning studies related to each other. These are adjustment planning to define average production level and situations which force to deviate from that average. There are two main types of capasity adjustment strategy. First, changing the times or increasing the capasity by extra work or have them made by an other running. Second, the reason of capasity adjustment are decreases by stocking or by eliminating. Third element of primary production is work analizies. Work analizies have two operations grup which one of them is, surveying some possibility of making work basically (method study) and the other is related with the quantity of sources to achieve production, (work measurement) Method study is researching all operations sistematically to make them easier, at little expense and in a shorter period of time. At method study, firstly, a work that need labour power and takes a lot of time is chosen. Information about this work is gathered sistematically by means of diagrams. Details of work are investigated by the examination technique and defect are determined. New methods are developed after element of work are investigated seperately and a way of developing are determined and than it puts in to practice. Defects on practice are set right on last. Work measurement is a method to use for describing the period of times needed for a certain kind of work at a certain working rate by a qualified worker.Recently, time standarts are needed for managing running operations effectively. It's not possible to be beneficial that studies not based on time standarts about preparation of production planning and programming, estimates, control of cost, determination of worker's pay and encouragement rate, calculation of product costs that weren't produced before and activate of control. At time study, first, a work to measure is chosen and then a worker has knowledge and ability required and work station are chosen. Information about worker and work are gathered and work is separated to its element for easily observation and analysing effectively. Since only one observation is not possible to show real data, after adequate amount of observations are completed, estimates can be described. Most important part of time study is grading the worker's rate and tempo. For this reason different kind of grading methods are improved. Most commanly used methods is performance grading that grade worker's rate or tempo in accordance with usual tempo by kind of percentage. After that certain amount of tolerans are determined for the reason of delay can't be estimate previosly and the factor of weariness. At last, the formula determined time standarts ; t- " j.* u *... ", tempo.,, total tolerance. Tune standarts = observation time * £- * (1 + ) 100 100 Result of primary production studies are used for preparing main production planning. Production control is a part of production planning operations and it's target is planning and control the material flow inside or outside of running and optimum profit. In this study, linear programming and PERT methods are concern as optimization methods to use for production planning. Linear programming is most succesfixll method to use for mathematical approach. It's goal is improving some aproach to determine optimal allocation for alternative production sources of running. In linear programming problem, the function to minimize or maksimize is called "objective function", and sources capasity of running used depend on management policy is called "restrictive condition". If there aren't any restrictive condition, the value of objective function will be unlimited. Grafik and simpleks methods are used to solve the linear programming methods. If the linear programming problem has two variable, grafik method obtains basic solution. However, for existence a lot of variable, the simplex method based on "Extrem point theorem" is used. This theorem, shows that the solution of linear programming problem is one of the extrem point of solution area. At first, in the simplex algoritm inequalities are converted to equalities by means of slack and surplus »variation. Linear programming problem in the equation form, if there are m equalities, n variable and n is greater than m, n-m variable at least eqals "0" on extrem point. The solution that n-m equals "0" and solving remain m variables on m equation system is called "basic feasible solution". Briefly ; 1-At the condition of m equality and n variation, basic feasible solution is found if n-m variable at least eqals "0". 2-Objective function get optimal on the one of the basic feasible solutions. The logic and calculations of the simplex algorithm can be simplified even further by the use of the simplex tableau format for organizing the data. Second method for optimization is PERT.(Project Evaluation And Review Teqhnique) PERT method is improved to succed complex work programs formed by events and operations related each other. First action is get understanding the technical properties of plans. All event required to production are described for project success and then priority of events is determined. Information about events and operations can be shown in network so studies will be easier. Estimated times based the network on certain period of times are found by "Beta distrubution". Optimistic times (a) : Estimated times at most convenient condition. Pessimistic times (b) : Estimated times at most inconvenient condition. Most possible times (m) : Estimated times at normal condition. Time expected (ET)=(a+4m+b)/6 Variance (VT)=(b-a)2/36 The earliest start time (TE) of an activity is the sum of all the activities on the longest path to that activity. It is the earliest time an activity can begin. The latest start time (TL) for an activity is the latest time can be started without delaying completion of the project. The slack time (TS) of an activity is equal to the latest start time minus the earliest start time. The probability of the project completed times can be described from statistic as the central limit theorem. This theorem shows the distrubition of a sum of random variables follows a normal distrubition. This enables us to use the table of areas under the normal curve to calculate the probability of the project being completed. Project finishing times obtained by PERT needs planning the work programming over again. In this condition, various kind of methods can be used depend on running policy. At last part of study, optimization based on linear programming and PERT is applied on two products, short and dressing gown. Operations applied these two xiiproduct on production are listed and 15 measurements are made for every operations. Tempo values are determined in accordance with ability of worker and avarege personel tolerance is accepted %20 and then standart times are obtained. PERT networks for both of them are drawn to show production flowing. The earliest start times, latest start times and slack times are calculated and all of them are shown on the networks. From these networks we can see the critical path and total project times for two products. After that machines and workers requirements are shown in these networks. At first, only one machine or worker that can make a certain work is accepted and then total requirement of machines and workers are listed. For the reduce of standart times and machine requirements on critical path, some operations on critical path are loaded to other paths so that the total project times is shortened and slack times are reduced by the use of sources on other paths as a sources of critical paths. Optimum machine requirements networks are shown the conculution of this optimizing studies and when the optimum and total requirements of machine are comparisoned, reduction of requirements are obviously realized. All production times are separated four groups as cutting, sewing, quality control and last operations and standart times are calculated in accordance with optimum values obtained from network and they are used for daily capasities and production speeds of departmants. These details are improved to supply harmonious flowing of production and then they used for data at linear programming. At the end, the amount of product makes profits maximum with various production restrictions is obtained for two kind of product and in a certain period of time by grafic methods of linear programming techniques. Consequently, some alternative approach about production planning and optimization are improved by this study. Production planning and optimization are most important brach of production management at all kind of industry and they must be resarched carefully by engineers. xm