【正文】 Do231。. Dr. B252。lent Sezen 1 Fundamentals of the Theory of Constraints Do231。. Dr. B252。lent Sezen Do231。. Dr. B252。lent Sezen 2 Introduction In recent years a rather unique and interesting approach to visualizing and managing an operation has emerged. Originally developed by Eliyahu M. Goldratt in his book The Goal, this Theory of Constraints has allowed many people to successfully rethink their approaches to improving and managing their production processes. Do231。. Dr. B252。lent Sezen 3 Introduction Opinions about the Theory of Constraints differ. Some think that the Theory of Constraints (TOC) is a good way to improve process capability while using other control systems such as JlT or MRP, while others believe that TOC is a standalone approach pletely unique and separate from other techniques. In this context, it is suggested that TOC can provide approaches to design, manage, schedule, and improve virtually any production system. Do231。. Dr. B252。lent Sezen 4 Introduction… Still others believe it can be either just a process improvement approach or a plete system approach, depending on the extent of the implementation taken. It may not, in the opinion of this third group, be the most appropriate approach for certain business environments, while it may prove highly effective for other business environments. Do231。. Dr. B252。lent Sezen 5 Fundamental Principles of the Theory Of Constraints The fundamental concept behind the TOC is that every operation producing a product or service is primarily a series of linked processes. Each process has a specific capacity to produce the given defined output for the operation, and that in virtually every case there is one process that limits or constrains the throughput from the entire operation. Do231。. Dr. B252。lent Sezen 6 The Linked Process Pipe Analogy Do231。. Dr. B252。lent Sezen 7 Fundamental Principles of the Theory Of Constraints… The analogy often used is that production flowing through operational processes is like liquid flowing through a pipeline. Each process has a certain defined capacity, illustrated in the analogy by the diameter of the associated pipe. In the diagram shown, process E has the largest capacity to process production, while operation C has the least amount of capacity. Do231。. Dr. B252。lent Sezen 8 Fundamental Principles of the Theory Of Constraints… Since operation C is the constraint on the entire process, it will limit the amount of output from the process, regardless of the capacity of the remaining processes. Improving any of the other operations (increasing the size of the pipe in that section) will not improve the total amount of liquid ing out of the system of pipes. Do231。. Dr. B252。lent Sezen 9 Fundamental Principles of the Theory Of Constraints… A constraint, in its most general form, is anything that limits the firm from meeting its goal. For most firms, that goal is to make money, which manifests itself by increasing throughputas measured by sales, not just production. Do231。. Dr. B252。lent Sezen 10 Fundamental Principles of the Theory Of Constraints… As a numerical example, consider the operation producing product A in Figure. Do231。. Dr. B252。lent Sezen 11 Fundamental Principles of the Theory Of Constraints… It should be clear from this simple example that the total operation is constrained by process 3 at 4 per hour. No matter how much efficiency you have in the other processes and how many process improvements are made in processes 1,2, and 4, you will never be able to exceed the overall operational output of 4 per hour unless you address the constraints of process 3. Do231。. Dr. B252。lent Sezen 12 Fundamental Principles of the Theory Of Constraints… Increased efficiency and utilization in processes 1 and 2 will, in fact, only increase inventorynot sales. That issue is one of the key points of TOCthe major measure for any operation should be on the throughput of the anization, or, in other words, the contribution to sales. Any other measures of process efficiency, utilization, or other monly used operational measures have little relevance to the overall effectiveness of the entire system. Do231。. Dr. B252。lent Sezen 13 Fundamental Principles of the Theory Of Constraints… This approach has implications far beyond how the process is viewed. Even accounting systems are impacted. For example, many accounting systems allocate overhead costs to products based on direct labor hours of production. Such systems may give the impression that producing more product will help to pay for the overhead costs. Unfortunately, if the extra product produced is not linked to actual sales, the result is only more costly inventory and an overall negative impact on the business. Do231。. Dr. B252。lent Sezen 14 Fundamental Principles of the Theory Of Constraints… TOC principles make the point that only sales should be counted as operational throughput. Another accounting implication is the labor cost itself. Most traditional accounting systems view direct Iabor as a variable cost. TOC principles, on the other hand, contend that in the short run all operational costs except direct material are largely fixed and should, therefore, be lumped together into an overall operational expense. Do231。. Dr. B252。lent Sezen 15 Fundamental Principles of the Theory Of Constraints… One of the key points made by this example is that products do not really have a profitpanies do. This point helps to view the operation more as a system rather than as a set of largely independent functions. Such a view is a critical part of managing by TOC principles. Do231。. Dr. B252。lent Sezen 16 Understanding and Managing The Con