第三章_工艺流程分析.ppt

1、第二篇 运作系统的设计,第三章 工艺流程分析 工艺流程的基本概念 工艺流程的类型 工艺流程的绩效衡量指标 工艺流程的分析 工艺流程的改进,How Important is It?,Case,McDonald VS Chinese Food Las Vegas Slot Machine: Mechanical VS Electronic,工艺流程的定义及描述,工艺流程（Process） 是指能够把一定投入变换成一定产出的一系列任务（即工序），这些任务由物流和信息流有机地连接在一起 流程图（Flowchart）是分析流程的一个理想的工具,Flowchart Symbols,Tasks or ope

2、rations,Examples: Giving an admission ticket to a customer, installing a engine in a car, etc.,Decision Points,Examples: How much change should be given to a customer, which wrench should be used, etc.,Flowchart Symbols (Continued),Storage areas or queues,Examples: Sheds, lines of people waiting for

3、 a service, etc.,Flows of materials or customers,Examples: Customers moving to the a seat, mechanic getting a tool, etc.,Example: Flowchart of Student Going to School,Yes,No,Stay at home,Go to school today?,Walk to class,Drive to school,多步工艺（Multistage Process）,阻塞Blocking occurs when the activities

4、in a stage must stop because there is no place to deposit the item just completed. 挨饿Starving occurs when the activities in a stage must stop because there is no work. 瓶颈Bottleneck is a resource that limits the capacity or maximum output of the process.,具有缓冲的多步工艺（Multistage Process with Buffer）,Buff

5、er allows stages to operate independently.,工艺流程的构成要素,投入 为了生产产品或提供服务所需的人力、物料、设备、能源等资源要素 产出 具有一定使用价值的产品或服务 衡量产出的价值需同时从其价格、质量及时间性等几个方面去考虑 任务 把投入的资源要素向产出方向转换的行为或活动，又可称为工序 一项任务的完成要使用一定的人力和设备，要充分考虑自动化技术的应用 物流和信息流 所有任务的完成和物料的移动都离不开信息 物流和信息流可同步发生，也可以不同步发生 库存 处于停滞或储藏状态的物料（或产品），既不是在被执行任务，又不是在被运送，不增加任何价值，应当越少越

6、好,工艺流程中的一些基本概念（1）,工艺（ Process ）是指能够把一定投入变换成一定产出的一系列任务（即工序），这些任务由物流和信息流有机地连接在一起。 周期（ Cycle Time ）是指连续完成相同的两个产品之间的间隔时间，即完成一个产品所需的平均时间，通常只是用于定义一个流程中某一具体工序或环节的单位产出时间。 生产能力(Capacity)是指一个设施的最大产出率，设施可以是一个工序、一台设备，可以是由若干工序或若干设备组成的一个流程，也可以是整个企业组织。一个流程或工序的能力正好是其周期的倒数。 生产能力利用率（Utilization）是指相对于生产能力所实际获得的产出。 瓶颈（

7、Bottleneck）是指一个流程中周期最长的工序或环节，它限制了流程的能力或最大产出。 空闲时间（Idle Time）是指工作时间内没有执行有效工作任务的那段时间，可以指设备或人的时间。 流程的平衡（Flow Balance）是指使流程中各个工序都与瓶颈同步，缓解瓶颈，减少空闲时间。,工艺流程中的一些基本概念（2）,总生产时间（Throughput Time）是指要加工的产品从以原材料的状态进入一个工艺流程直至变换成产成品为止所需的全部时间，不仅包括在各个工序的加工时间，而且也包括排队、等待、储藏和搬运时间。 生产批量（Lot Size）是指在特定时间段内加工某种零件或产品的数量，有时批量可

8、由管理者自行确定或根据订单来决定，有时批量受一定的物理限制。 调整时间（Setup Time）是指工艺流程中的设备从一种产品的生产更换到另一种产品的生产时所花费的准备时间。,工艺流程的类型,按企业组织生产的特点划分： 备货型生产 订货型生产 按订单装配 按工艺的特点划分： Conversion转化工艺 Fabrication制造工艺 Assembly 装配工艺 Testing测试工艺 按工艺流程结构划分 线型 间歇型 项目型,工艺流程结构,定义：如何组织物流或信息流来生产产品或提供服务的 类型 线型流程：采用线型运作顺序来组织产品或服务的生产，即按照预定的顺序从一个运作中心或工位到下一个运作中

9、心或工位，个个工作任务之间紧密关联，并且任务大小应力求平衡以避免出现上一个任务耽搁下一个任务的情况，采用产品对象专业化的运作组织形式（即不同的设备、员工技能是按照产品的生产顺序进行组织的） 连续生产方式：通常应用于高度一致或标准化的产品或服务中，机器提供着连续性操作 装配线生产方式：又称大量生产方式或重复性制造，其生产的产品允许一定的变化，但这些产品非常相似又不完全相同 间歇型流程：生产按批量间歇式进行，是用于产品非标准化或产量小的情况，采用工艺对象专业化的运作组织形式（即把功能相近的设备和技能相同的工人组织成若干工作中心），产品或工作只是流入那些需要进入的工作重心，而跳过其他工作中心 批量生

10、产方式：应用于企业需要生产中等规模的相似产品，批量产出可以是标准化的，也可以是订货型的 工艺专业化生产：又称加工车间，应用于比批量生产更具有多样性工作要求的加工，它适应顾客的特殊要求进行生产，工作通常随着顾客的需求而变动 项目型流程：是用于生产独一无二的产品，从本质上讲，一个项目不存在产品流，只有生产运作的顺序。,工艺对象专业化与产品对象专业化的比较,不同工艺流程结构的比较,There are five basic process flow structure: Job shop (工艺专业化生产，多品种小批量生产) Batch shop （批量生产，多品种标准化产品的相对小批量生产， 产品的

11、定期批量生产降低了设备调整时间的影响） Assembly Line （装配线生产，制造零散部件，可控速率装配） Continuous Flow （连续流程，连续的工序生产，自动） Project （项目，少品种小批量）,企业组织生产的特点,Make-to-order(MTO) Only activated in response to an actual order. Both work-in-process and finished goods inventory kept to a minimum. Make-to-stock(MTS) Process activated to meet

12、expected or forecast demand. Customer orders are served from target stocking level. Hybrid (Assemble-to-order,ATO) Combines the features of both MTO and MTS. Typically a generic product is made and stocked at some point in the process.These generic units are customized in a final process to meet act

13、ual orders.,工艺流程绩效指标,操作时间Operation time = 安装时间（调整或准备时间）Setup time + 运行时间Run time 总生产时间Throughput time = Average time for a unit to move through the system 工艺周转率Velocity（Throughput ratio） = 总生产时间Throughput time 附加值时间 Value-added time,工艺流程绩效指标(Continued),周期Cycle time = Average time betweencompletion o

14、f units 产出率Throughput rate = 1 . Cycle time 效率Efficiency = Actual output Standard Output,工艺流程绩效指标(Continued),生产率Productivity = Output Input 利用率Utilization = Time Activated Time Available Littles Law: 在制品库存Wok-in-process= 总生产时间 Throughput time产出率Throughput rate,为什么要进行工艺流程分析,工艺流程的绩效影响着运作的成本、质量、交货和灵活性，

15、了解、分析工艺流程对于确保企业竞争力是非常关键的； 合理、高效的工艺流程将有助于改善物流、客户流和信息流 一个设计好的新流程是需要不断改进的 不可能有一步到位的完美设计，总有可能寻求更好、更经济的方法 企业内外部环境在不断变化，流程也需要不断地加以改进，以适应新的要求 工艺流程分析的目的 了解流程并进行管理 解决已出现的问题 改进现有流程,Mix,Proof,Bake,Mix,Proof,Bake,Pack,Raw Material,Work in Process,Finish Goods,This is called a process flow diagram. Elements: inp

16、uts, outputs, flow units, activities, buffers, precedence.,Example: The bakery operates two parallel baking lines, each with a mixer, a proofer, and an oven. A single packaging line is shared by the two bread-making lines.,Batch Size, Processing Time,Mixing, proofing and baking are performed in batc

17、hes of 100 loaves. (Here the Batch size equals 100). Packaging is done one loaf at a time. (The batch size equals 1.) OperationProcessing Time mix45 minutes per batch of 100 loaves proof45 minutes per batch of 100 loaves bake60 minutes per batch of 100 loaves pack27 seconds per batch of 1 loaf (27 s

18、econds per loaf means 45 minutes per 100 loaves),Resource and Capacity,Mix,Proof,Bake,Mix,Proof,Bake,Pack,Raw Material,Work in Process,Finish Goods,100 loaves/ hour,100 loaves/ hour,100 loaves/hour,Mixer:133 loaves/hour Proofer:133 loaves/hour Oven:100 loaves/hour,Packaging machine: 133 loaves/hour,

19、Bottleneck and Capacity,Which operation is the bottleneck of each bread-making line? Which operation is the bottleneck of the whole process? What is the maximum output of the process per hour? This is the maximum flow rate possible.,Cycle Time,Recall: Flow Rate is also called Throughput Rate Cycle T

20、ime = 1/(Flow rate) = The average time between completion of successive units What is the difference between flow time and cycle time? Flow time （ i.e. Throughput time ）refers to how long a unit spends in the process. Cycle time refers to how often units “drop off” at the end of the process.,Resourc

21、e Utilization,Suppose the process is run at maximum capacity. While the packaging machine needs 3/4 hour for every 100 loaves, the packaging operator spends only 40 minutes on each 100 loaves. Find the utilization of the following resources:,Packaging machine Packaging operator,Mixers Ovens,Process

22、Flow (Throughput) Time,How long does it takes to actually make and pack a batch of 100 loaves, assuming there is no waiting? (3/4) + (3/4) + 1 + (3/4) = 3.25 hours. The actual flow time may be longer due to in-process waiting or transport time. Flow time depends on the way a process is managed.,More

23、 on Flow Time ,Bread making,Pack,Raw Material,Work in Process,Finish Goods,100 loaves/hour,133 loaves/hour,Flow time = the sum of all the activity times,More on Flow time ,Bread making,Pack,Raw Material,Work in Process,Finish Goods,100 loaves/hour,133 loaves/hour,Bread making,Packaging is operated f

24、or three shifts (8 hours per shift) and bread making for two shifts.,Inventory and Capacity,If it takes 1 hour to cool the bread before it can be packaged, and there is ample storage space in the cooling area, what is the overall output capacity of the process? What if the cooling time is 2 hours? Q

25、uestions: How does cooling affect the process flow time? What if the cooling area is limited?,Capacity Improvement,The bakery is considering replacing some of its existing equipment with more advanced and faster equipment. The choice is between purchasing: two ovens, each capable of baking a batch o

26、f 100 loaves in 3/4 hour, or a new packaging line capable of packaging 100 loaves in 1/2 hour. Which option would allow a greater increase in the bakerys overall output capacity?,Mix,Proof,Bake,Mix,Proof,Bake,Pack,Raw Material,Work in Process,Finish Goods,100 loaves/ hour,100 loaves/ hour,100 loaves

27、/ hour,Two new ovens, each capable of baking 100 loaves in 3/4 hour.,First Option,Overall capacity = ?,Mix,Proof,Bake,Mix,Proof,Bake,Pack,Raw Material,Work in Process,Finish Goods,100 loaves/ hour,100 loaves/ hour,100 loaves/ hour,A new packaging line capable of packaging 100 loaves in 1/2 hour.,Ove

28、rall capacity = ?,Second Option,Changeover or Setup,Assume there is no change in equipment. The bakery is considering producing wheat bread in addition to white bread. The bakery would dedicate one bread-making line to white and the other to wheat. The packaging line would switch between packaging w

29、hite and wheat bread every 100 loaves. Changing the bags requires a setup time of 1/4 hour. What is the overall output capacity of the process?,Mix,Proof,Bake,Mix,Proof,Bake,Pack,Raw Material,Work in Process,Finish Goods,100 loaves/?,100 loaves/ hour,100 loaves/hour,Wheat,White,Changeover Time and C

30、apacity,Reducing the Flow (Throughput) Time,Perform activities in parallel Change the sequence of activities Reduce interruptions Identify and make max use of bottlenecks Plan and coordinate process activities better,Bottleneck Management,Bottleneck dictates the performance of a process Avoid idling of the bottleneck Subordinate non-bottleneck operations to support the bottleneck Add capacity to the bottleneck by adding more resources, effective scheduling and shifting work to non-bottlenecks Improvement at the current bottleneck might lead to a ne