【正文】 ted from) variations in product mix. Do231。. Dr. B252。lent Sezen 64 Buffer… As an example, suppose variations in processing and the probability of some disruptions in operations upstream from the constraint could mean that material could be held up“ for as much as 4 hours. The implication, then, would be that based on the processing schedule at the constraint the material for constraint processing would be released into the first operation 4 hours earlier than the normal. Do231。. Dr. B252。lent Sezen 65 Scheduling and the Theory of Constraints… Rope The analogy is that the rope pulls production to the constraint for necessary processing. While this may imply a Kanbantype pull system, it can be done by a wellcoordinated release of material into the system at the right time. As can be seen, even the scheduling system has its primary focus on effective management of the anization39。s constraint to throughput and sales. Do231。. Dr. B252。lent Sezen 66 Multipletime Buffers Time buffers are used to make sure the constraint is not starved, but other time buffers are also necessary. An example may help to illustrate: Suppose you have a product made from three ponents. Component 1 is processed from raw material and then assembled with ponent 2 after it is processed from raw material. Do231。. Dr. B252。lent Sezen 67 Multipletime Buffers… Do231。. Dr. B252。lent Sezen 68 Multipletime Buffers… The subassembly is then assembled with ponent 3 after it is processed from raw material. The final product is then shipped to the customer. The constraint in the system is located in the middle of the processing for ponent 1. Do231。. Dr. B252。lent Sezen 69 Multipletime Buffers… Once ponent 1 has been processed on the constraint, its value to the system has risen significantly because constraint time has been invested. Nothing should, therefore, impede the progress of ponent 1. The problem could arise, however, that ponent 1 will arrive at the Assembly 1 area before ponent 2 because of some problem with ponent 2. Do231。. Dr. B252。lent Sezen 70 Multipletime Buffers… Since we would never want constraintinvested material to wait for nonconstrained material, we should stage a time buffer of material for ponent 2 before the Assembly 1 area. This is done by releasing it earlierthe amount earlier depending on the time buffer based on the time estimate needed to overe any unanticipated shock in the system. In this case the time buffer is called an assembly time buffer, as opposed to the time buffer before the constraint, which is usually called a constraint time buffer. Do231。. Dr. B252。lent Sezen 71 Multipletime Buffers… The same argument applies to the Assembly 2 area. The subassembly from ponents 1 and 2 have constraint time invested, so we would not want them waiting for ponent 3. This calls for another assembly time buffer to be generated at the Assembly 2 area. Unfortunately, the need for buffers has not been fulfilled. Do231。. Dr. B252。lent Sezen 72 Multipletime Buffers… It is possible that the final product with its constraintinvested material could be held up at shipping, since the processes that take place between assembly and shipping have not been part of the protection. This implies an additional time buffer before the shipping area, referred to as a shipping time buffer. Do231。. Dr. B252。lent Sezen 73 Multipletime Buffers… Do231。. Dr. B252。lent Sezen 74 Control Points and Batches All this discussion regarding buffers and scheduling may start one to think that the scheduling using TOC approaches are more difficult and plex than standard approaches. That does not need to be the case. Do231。. Dr. B252。lent Sezen 75 Control Points and Batches… Based on the flow of material and the type of operation, there are specifically defined types of control points that may be important for TOC scheduling, measurement and control. A control point is a point in the process where measures are taken and decisions made based on those measures. Typical control points for TOC include: Do231。. Dr. B252。lent Sezen 76 Control Points and Batches… The constraint this is clearly the most critical control point, and needs to be scheduled carefully based on sales. The first operation (or the gateway) it is quite important to release the right material at the right time into the system so it will reach the constraint. This is, in effect, the rope of the drumbufferrope system. Diverging points these points are where a mon part can be processed into one of several different options. They must be managed to ensure that material, especially constraint material, is used in the correct manner for the correct assembly. Do231。. Dr. B252。lent Sezen 77 Control Points and Batches… Converging points these are really assembly operations where material from nonconstraint operations is bined with constraint material to produce an assembly or subassembly. – it is important to manage these points to make sure constraint material is not held up from being processed. The buffers these indude constraint buffers, assembly buffers, and shipping buffers as described earlier. Do231。. Dr. B252。lent Sezen 78 Control Points and Batches… TOC also recognizes there can be fundamental differences between process batches (the amount of material produced at an operation for a given setup) and transfer batches (the amount of material moved from one operation to the next operation). In general, process batches should be fairly large for constraint operations in order to minimize the time lost for setups. Do231。. Dr. B252。lent Sezen 79 Control Points and Batches… Process batches for nonconstraints are l