Theory of Constraints (TOC)是由Eliyahu.M.Goldratt在1984年写的书The Goal中提出来的。它的基本假设组织从产量、运营成本、库存三个维度来被衡量和控制的。理论在优化生产技术(Optimized Production Technology,OPT)基础上发展起来的管理哲理,提出了在制造业经营生产活动中定义和消除制约因素的一些规范化方法,以支持连续改进(Continuous Improvement)。同时TOC也是对MRPII和JIT在观念和方法上的发展。一切妨碍企业实现整体目标的因素都是约束。
The underlying premise of Theory of Constraints is that organizations can be measured and controlled by variations on three measures: throughput, operating expense, and inventory. Throughput is money (or goal units) generated through sales. Inventory is money the system invests in order to sell its goods and services. Operating expense is all the money the system spends in order to turn inventory[库存] into throughput[产出].
1.The goal (i.e., to make money) may be achieve in short-term but it can be counter-productive in long-term. A simple example is: generate money by selling plant or equipment. But, this would be detrimental in long run. Therefore, the emphasis should be on the goal of “making money now as well as in the future”. //兼顾短期的和长期的利益
2. To achieve The Goal, i.e., the make more and more money, one must try to:
(a) increase throughput //增加产量
(b) minimize operating expenses //削减运营成本
(c) minimize inventory //最小化库存
2.关键步骤
1.Identify the constraint (the resource or policy that prevents the organization from obtaining more of the goal) //识别约束(阻止组织获得目标的资源和政策)
2.Decide how to exploit the constraint (make sure the constraint's time is not wasted doing things that it should not do) //如何使用约束(确定约束时间消耗在不该消耗时间的地方)
3.Subordinate all other processes to above decision (align the whole system or organization to support the decision made above) //在高层决策下细分所有流程(对整个支持高层决策的系统和组织进行排序)
4.Elevate the constraint (if required or possible, permanently increase capacity of the constraint; "buy more") //更新升级约束(如果可能,不断增加约束能力)
5.If, as a result of these steps, the constraint has moved, return to Step 1. Don't let inertia become the constraint.//经过这几步骤,约束消减,继续这个步骤循环。
定义与处理约束下的思维过程(Thinking Processes),包括三个部分:
因果关系法(Effect Cause Effect Method),找出“要改变什么(what to change?)”设定一些尽可能少的假设,通过分析和考验,逐一排斥,找出造成约束的根本原因(root cause),从而找出解决要害问题的有效方法。
驱散迷雾法(Evaporation Cloud Method),处理“改变的方向(what to change to?)”问题,发展了JIT对消除无效劳动和浪费的“刨根问底(fine WHYS)”思想,并提出了一些指导性的规则。
当做完CRT、EC、FRT的一系列工作以后,就要找一些与改进后果相关程度最大的人来参与,以保证改进的成功实施。思维流程法是一项需要高度开放、广泛参与的活动。如果不和这些利益相关者进行全面和充分的沟通的话,就很难消除这部分员工的抵制改革的情绪。思维流程法认为,正是这些受改进影响最大的人,才对那些意料之外的负面效应(即“负效应枝条”)了解得最清楚。所以,思维流程法要求主动寻求这些人的参与,并与他们一道找出避免这些“负效应枝条”长出的办法,以避免实施的失败。此过程可以形象地描述为“剪去负效应枝条”(Trimming the Negative Branches)。
Critical Chain Project Management (CCPM) is utilized in this area. CCPM is based on the idea that all projects look like A-plants: all activities converge to a final deliverable. As such, to protect the project, there must be internal buffers to protect synchronization points and a final project buffer to protect the overall project. //CCPM基于类似A类企业(所有活动最后聚集到一起为可交付对象),内部缓冲保护并行的活动,项目缓冲则保护整个项目。