Bir kablo donanım üretim sisteminde tam zamanında üretim uygulaması

Abstract

Tam Zamanında Üretim Sistemi, Endüstri Mühendisliğinin kurucusu olarak kabul edilmiş Taylor'dan bu yana keşfedilmiş olan ve Hareket-Zaman Etüdleri, Hareketli Montaj Hatları gibi buluşların yanında yeralan en önemli olaylardan bir olarak, yönetim literatüründeki yerini almıştır. Tam Zamanında Üretimin en genel tanımı; üretim için gerekli olan malzemenin gerektiği anda ihtiyaç noktasında bulunmasını temin eden ve sıfır envanteri hedef alan bir "malzeme yönetim sistemi" olarak verilebilir. Bu sistem Japon Endüstrisinin 1960 lı yıllarda başlattığı Kalite Geliştirme çalışmalarıyla birlikte, ülkenin küçük coğrafi yapısı ve kıt kaynakların yarattığı zorlayıcı çevre koşullarıyla ortaya çıkmış, verimlilik arttırıcı, maliyet düşürücü sonuçlarıyla tüm dikkatleri üzerine çekmiş ve giderek yaygınlaşmıştır. Japonya'da bu yaklaşım ilk olarak Toyota fabrikasında Kanban adı verilen kartlar yardımıyla uygulanmaya başlanmıştır. Bu yüzden bir çok Batı ve Japon firmasında Tam Zamanında Üretim, Kanban Sistemi veya Toyota Üretim Sistemi olarak tanımlanmaktadır. Sistemlerin modellenerek, bileşenlerindeki çeşitli değişikliklerin sisteme olan etkisini değerlendirmek amacıyla kullanılması olarak tanımlanabilecek simülasyon ise, yönetim kademesine karar vermede yardımcı olan önemli araçlardan biridir. Tam Zamanında Üretim felsefesi doğrultusunda üretim sistemini yönlendirmek ve sistemi yönlendirmeden evvel sistem değişikliğini bilgisayar ortamında denemek, bu tez çalışmasının temelini oluşturmaktadır. Çalışmanın ilk bölümünde, genel olarak Tam Zamanında Üretim ile ilgili kavramlar kısaca tanıtıldıktan sonra Üretim Sistemlerinin açıklanması yapılmıştır. Geleneksel İmalat Sistemleri, Modern İmalat Sistemleri ve bunların temel alt sınıflarıyla özellikleri verilmiştir. İkinci bölümde ise Tam Zamanında Üretim konu edilmiştir. Tam Zamanında Üretim sisteminin temel karakteristikleri ve bu karakteristiklerin sağlanabilmesi için yapılması gereken işlemler belirlenmiştir. Üçüncü bölümde ise sırasıyla Simülasyon kavramından ve bir simülasyon dili olan Arena'dan bahsedilmiştir. Simülasyon yaklaşımı ve Arena programının özellikleri konu edilmiştir. Dördüncü bölümde ise, otomotiv sanayi için elektrik tesisatı imal eden bir firmada yapılan uygulamadan bahsedilmiş ve gerçekleştirilen uygulamada elde edilen sonuçlar verilerek yorumlar yapılmıştır.

Just In Time production system has became very important subject in Management, since Frederick Taylor who known as founder of Industrial Engineering and became very important finding such as Motion-Time Studies, Moving Assembly Lines, etc.. Just In Time generally can be identified as, It is a Material Management System, providing the required material on time at the requiring place and aiming zero inventory. Because of the geographic structure of the land and very hard environment conditions which were caused by insufficient resources, Just In Time has been identified in Japanese Industry with the same time Quality Improvement Studies, in 1960. Just In Time has been implemented in Toyota plants firstly with the Kanban cards, so it is known as either Kanban System or Toyota Production System in West Countries. In the first chapter of this study, production systems were considered. First of all identification of production was given as; production is making any changes which add value on the physical object or transform raw or semi material into product. In the last part of Chapter 1, production categories and their fundamental characteristics were given. In the second chapter of this study, Just In Time philosophy was considered. Characteristics and benefits of Just In Time were given with some examples from different applications and fundamental aspect of the Just In Time, Kanban, was also considered. Just In Time is an organisational philosophy which strives for excellence. The term JIT used interchangeably with "zero inventory" and "stockless production" but it represents a production strategy and not just an inventory control technique. It identifies a philosophical pursuit or set of goals that apply to any type of production organisation. Some Just In Time goals are listed below:. zero defects,. zero set-up time, IX . zero lot excesses,. zero handling,. zero surging,. zero breakdowns,. zero lead time, Just In Time encompasses the successful execution of all production activities required to produce a product from design engineering to delivery. It encourages solving entire spectrum of production problems, not covering them up excess inventory, safety stock or padded lead time. Among the targets for elimination are large lot sizes, quality rejects, machine breakdowns and excessive lead times. Just In Time production means making and buying just enough, no more or less, of the right items just in time, no sooner or later. It may be easier to explain Just In Time by what it is not. Its opposite, the more convential just in case approach, manages operations expecting something (not sure of what) to go wrong. It provides contingencies to cover all even qualities, and the contingency is usual excess inventory. Buffering the impact of uncertainty instead of eliminating it is misguided. It is more desirable to smooth the flow of product than to maintain inventory buffers. The goal of Just In Time, if achieved to perfection, is a balanced, continuous flow of the product through the organisation. Just In Time" attempts virtual elimination of all costs (waste) that do not add value to a product. Waste is identified as anything other than to the absolute minimum resources of materials, machines and personnel required to add value to the product. Machining, assembling, finishing and packaging add value to a product. Activities such as moving, storing, counting, sorting and scheduling add cost to product but not value. Inspection, backup sources, expediters, safety stocks and safety time add cost but not value. Cost without value is waste. The general idea is to eradicate all encumbrances to the smooth flow of product through the facility. Inventory is considered as undesirable cost, and by lowering its level, hidden quality and productivity impediments are revealed. By working to eliminate costs that do not add value, opportunities to synchronise and link operations become apparent. It must be emphasised that Just In Time is a long term approach that can not be installed quickly; it can take for years effective implementation. Inventory and lot sizes are reduced incrementally (month after month) The result is sustained productivity quality improvements with greater operational flexibility and delivery responsiveness. The essence of Just In Time is simplification and elimination through problem solving. Continuous improvement and attention to any barrier to product flow (smooth production) is the key. Just In Time does not use automation and robotics until all that can be done to rearrange, synchronise and balance operation is completed. Initial savings are in overhead reduction of indirect labour (stockroom personnel, material handlers, planners, controllers, inspectors, etc..) These functions do not add value to the product. Direct labour reductions occur subsequently when automation takes place. Just In Time makes automation easier and more effective, but automation is not the main thrust. Inventory hides or conceals many types of problems, such as; machine breakdowns, poor quality or high scrap, bad raw materials, worn tools, worker absences or tardiness, late delivery of parts, unavailable materials handling equipment, unavailable inspectors or set-up persons, Just In Time assumes the following goals desirable; Lot sizes should be as small as possible, Quality must be consistently high, People must perform reliably, Inventory is inherently wasteful and should be minimised. Machines must run reliably, Production plans should be level and stable, Space is a scarce resource, too valuable to be used for storage. In order to achieve the above goals, pressure is applied to; shorten set-up times, develop multifunctional employees, (no restrictive work rules) commit employees to total quality control, (zero defects) control quality at the source, assure machine reliability via preventive maintenance, group machines sequentially and dedicate them to part families, use reliable sole source suppliers, have suppliers deliver frequently in small lots. Just In Time attacks anything that slows or disrupts its planned activity but refuse to plan more activity than is necessary. Quality must be near perfect; materials must move, not sit; people and equipment must only be used to produce what is needed. Performance evaluations based on capacity utilisation become less appropriate. The issue is whether there is an immediate need for the part being produced, not whether the workers meet or exceed standards, nor whether the machines are fully utilised. Employees should make only what is needed, when it is needed. Just In Time attitudes are better suited for a "pull" execution system of shop floor control than a "push" execution system. A "push" system is where orders are launched and pushed through the system to meet some established due date. The order is moved to the next work center upon completion, with the expectation that the next work center needs it. If the rate of flow of materials from level to level of XI the product structure is controlled or determined by the lower levels, it is a push system. A "pull" system is where orders are placed at the end item level and work is pulled through the facility to satisfy the demand of the end item. The order is not moved to the subsequent work center until it is needed or demanded by it. If the rate of flow of materials from level to level of the product structure is controlled or determined by the higher level, it is a pull system. Uniform plant loading is accomplished by establishing a firm production plan in which output is fixed (usually for a month) The same mix of products are produced every day, even though the total quantities are small. Uniform plant loading attempts to produce at the rate they are demanded. There are costs and side effects from producing more than its demanded. If products are produced faster than the demand rate, then containers are needed to hold them, trucks are needed to move them, warehouse space are needed to store them, money is needed to finance the inventory, cycle counters are needed to count it, accounts are needed to keep track of it and schedulers are needed to indicate when to produce more. Minimised set-up times aim for single digit (less than ten minutes) set-up time on every machine. Small lots are not be run if set-ups take hours. Reduced set-up times increase equipment utilisation, which is equivalent to a capacity expansion. Kanban type production control systems are simple, self-regulatory and paperless systems for scheduling and shop floor control. (Kanban is a Japanese word meaning card.) Kanban is a "pull" type of order system where authority to produce or supply comes from the final assembly schedule (usually the master production schedule) In the thirth chapter of this study, simulation and one of the simulation language were subjected. First of all, what is the simulation, what is the reason for using it, evaluation of simulation, modelling period in simulation, some examples from applications and what is the position of simulation in manufacturing systems were considered. Nowadays we can say that management is very big problem because of the organisational and physical conditions. In another word, greater the system is greater the management problem in this system. Because of this, when the system gets greater, it starts to include much more elements which have very related relationship between them, than the inital status. All of these organisational and physical conditions and mixed relationship between elements brought us to think whole system; "system thinking". System thinking also brougt us another thing; Simulation: The proper way to design and analysis the systems. It can be said that very shortly for simulation, it is modelling of the system. With another identificaiton, simulation is the art and the science of modelling of the systems for realizing the system behaviour against some different conditions. Xll By the end of thirth chapter of the this study, a simulation language- ARENA- was considered. How a model of any system is simulated with Arena was explained. Workspace, bar and panel region with their sub-regions which are used for modelling any system were explained. In the fourth chapter of this study, a simulation model which was executed with the information that provided one of the autumotive wiring assemblies and harnesses producer, NURSAN ELEKTRİK DONANIM SANAYİ VE TİCARET A.S., was explained. With the simulation study, style of the assembly line were discussed: Assembly on the table, conveyor line and walking decoupler styles were considered. Eleven different scenario in the model were tried and according to the several criteria, the performance of the system were determined. These are the performance criteria for the system performance:. processing time before assembly,. assemble time and processing time after assembly,. interarrival time for harnesses,. average queue length,. utilization of workman,. meeting % of demand,