Process Analysis 流程分析. Fang Aihua Wuhan University Process Analysis Process Analysis...

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


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


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.


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.


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.


Example: Flowchart of Student Going to School

Yes

No

Goof off

Go to school today?

Walk to class

Drive to school


Multistage Process多阶段的流程

Stage 1 Stage 2 Stage 3


Multistage Process with Buffer具有库存的多阶段流程

Stage 1 Stage 2

Buffer

缓冲器

BlockingStarving

Bottleneck


• 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

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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


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.

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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）


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）


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


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


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


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）


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


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


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

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