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Process Analysis
流程分析
Fang Aihua Wuhan University
Process Analysis
• Process Analysis 流程分析
• Process Flowcharting 流程图的绘制方法
• Types of Processes 流程类型
• Process Performance Metrics 流程绩效评价
Fang Aihua Wuhan University
Process Analysis Terms基本术语
• Process: Is any part of an organization that takes inputs and transforms them into outputs.
• Cycle Time: Is the average successive time between completions of successive units.
• Utilization: Is the ratio of the time that a resource is actually activated relative to the time that it is available for use.
•流程 / 步骤
•节拍 / 周期
•时间利用率
Other Process Terminology
• Bottleneck– Occurs when the limited
capacity of a process causes work to pile up or become unevenly distributed in the flow of a process
– If an employee works too slow in a multi-stage process, work will begin to pile up in front of that employee. In this case, the employee represents the limited capacity causing the bottleneck.
• Pacing– Refers to the fixed timing of
the movement of items through the process
• 瓶颈
• 节拍 (?) / 定时
Fang Aihua Wuhan University
Process Flowcharting流程图的绘制方法
• Process flowcharting is the use of a diagram to present the major elements of a process. – The basic elements can include
• tasks or operations, • flows of materials or customers, • decision points, • and storage areas or queues.
• It is an ideal methodology by which to begin analyzing a process.
Fang Aihua Wuhan University
Flowchart Symbols 流程图符号
Tasks or operations
任务或操作
Examples: Giving an admission ticket to a customer, installing a engine in a car, etc.
Decision Points
决策点
Examples: How much change should be given to a customer, which wrench should be used, etc.
Fang Aihua Wuhan University
Flowchart Symbols (Continued)
Storage areas or queues
库存或排队
Examples: Sheds, lines of people waiting for a service, etc.
Flows of materials or customers
物流或顾客流动
Examples: Customers moving to the a seat, mechanic getting a tool, etc.
Fang Aihua Wuhan University
Example: Flowchart of Student Going to School
Yes
No
Goof off
Go to school today?
Walk to class
Drive to school
Fang Aihua Wuhan University
Multistage Process多阶段的流程
Stage 1 Stage 2 Stage 3
Fang Aihua Wuhan University
Multistage Process with Buffer具有库存的多阶段流程
Stage 1 Stage 2
Buffer
缓冲器
BlockingStarving
Bottleneck
Fang Aihua Wuhan University
• A buffer refers to a storage area between stages where the output of a stage is placed prior to being used in a downstream
stage• Blocking
– Occurs when the activities in a stage must stop because there is no place to deposit the item just completed
– If there is no room for an employee to place a unit of work down, the employee will hold on to it and not able to continue working on the next unit
• Starving– Occurs when the activities in a stage must stop because there is no
work – If an employee is waiting at a work station and no work is coming to
the employee to process, the employee will remain idle until the next unit of work comes
11
Types of Processes流程类型
• Conversion
• Fabrication
• Assembly
• Testing
• 转化(如:冶炼)
• 制造(如:机械切削)
• 装配
• 测试
Fang Aihua Wuhan University
Types of Processes流程类型
• Make-to-order 为订单生产 (MTO)– Only activated in response to an actual order.
– Both work-in-process and finished goods inventory kept to a minimum.
• Make-to-stock 为库存生产 (MTS/MTI)– Process activated to meet expected or forecast demand.
– Customer orders are served from target stocking level.
• Hybrid processes 混合– combine the features of both MTO and MTS.
12
Process Flow Structures工艺流程结构
• A process flow structure refers to how a factory organizes material flow using one or more processes technologies.
• Robert Habert Hayes (贺氏) and Steven Wheetwright (威尔莱特) . Restoring out competitive edge:competing through manufacturing(New York: John Wiley & Sons. 1984). P209..
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Process Flow Structures Hayes & Wheelwright 贺氏 / 威尔莱特• Job shop
• Batch
• Assembly Line
• Continuous Flow
• 单件小批量生产 / 工艺专业化(宋国防译)
• 批量生产
• 装配线生产(大量)
• 连续流程生产(大量)
Fang Aihua Wuhan University
生产类型的划分(按生产的连续程度)
• 连续型:炼油厂 24 小时
• 重复型: 汽车流水线(零配件)
• 间断型:(零活混杂型 、 单项工程)
Fang Aihua Wuhan University
生产类型的划分 -I(按产品品种和数量的需求)
大 量 生 产
´ óÅ úÁ ¿É ú² ú Ö ÐÅ úÁ ¿É ú² ú Ð ¡Å úÁ ¿É ú² ú
批 量 生 产 单 件 生 产
É ú² úÀ àÐ Í
批量生产大量大批生产 单件小批量生产
Fang Aihua Wuhan University
生产类型的划分 -II(按产品品种和数量的需求)
大 量 生 产
´ óÅ úÁ ¿É ú² ú Ö ÐÅ úÁ ¿É ú² ú Ð ¡Å úÁ ¿É ú² ú
批 量 生 产 单 件 生 产
É ú² úÀ àÐ Í
订货间断生产系统大量连续生产 单项工程
Fang Aihua Wuhan University
Process Performance Metrics流程绩效评价 ( 基本时间)
• Operation time = Setup time + Run time运营时间 调整时间 作业时间
• Throughput time = Average time for a unit to 全过程生产周期 move through the system
• Cycle time = Average time between节拍 completion of units
Fang Aihua Wuhan University
Process Performance Metrics (Continued)
• Throughput rate = 1 .
Cycle time
– The output rate that the process is expected to produce during a period time
• Process Velocity = Throughput time
(throughput ratio) Value-added time
产出率(生产速度)
工艺周转率
(任建标译)
Fang Aihua Wuhan University
Process Performance Metrics (Continued)• Efficiency = Actual output
Standard Output
• Productivity = Output
Input
• Utilization = Time Activated
Time Available
生产力
生产效率
时间利用率
Fang Aihua Wuhan University
Cycle Time Example
• Suppose you had to produce 600 units in 80 hours to meet the demand requirements of a product. What is the cycle time to meet this demand requirement?
• Answer: There are 4,800 minutes (60 minutes/hour x 80 hours) in 80 hours. So the average time between completions would have to be: Cycle time = 4,800/600 units = 8 minutes.
Process Throughput Time Reduction降低生产周期的方法
• Perform activities in parallel. 平行作业
• Change the sequence of activities. 变换次序
• Reduce interruptions. 减少停顿
Fang Aihua Wuhan University
Little’s Law 利特法则• Throughput time=WIP/Throughput rate
• 总生产周期 = 在制品数量 / 生产速度
补充术语• LT (Lead time)
– MLT: manufacturing lead time
• WIP (work-in-process)
• Lot size / batch size
• 提前期
• 在制品
• 批量