文档介绍：SPC Part II:
Sampling Plans for X-chart
Learning Objectives
Revision of SPC Fundamentals/SPC原理校正
Misconceptions of SPC/SPC 误解
Process Control Model/制程控制模型
Two Basic Causes of Variability/2种基本变异原因
Review of X-R Chart and X-s Chart/均值极差及单值控制图回顾
Review of Attributes Control Charts属性控制图回顾
Designing the X-chart均值控制图的设计
Sampling Risks (a and b)抽样风险
ARL0 and ARL1
Determining Sampling Interval决定抽样时间间隔
Determining Sample Size决定样本大小
Misconceptions of SPC
Let’s check our understanding by looking at the mon control chart, X-,检阅我们对SPC的了解
LSL
USL
Putting USL & LSL on X-chart helps ensure that parts are meeting Cpk requirements.
Myth No. 1
It is alright to shrink USL & LSL down to, say, 70% or 80%, to establish UCL and LCL.
Myth No. 2
More myths and misconceptions on the X-
LSL
USL
Fortunately, parts still meet customer spec. although process is out of control
Myth No. 3
Process in control: therefore parts meet customer spec. as well as Cpk requirements
Myth No. 4
Misconceptions of SPC
LSL
USL
More myths and misconceptions of the X-
How did we establish the sampling plan?
- Gut feel?
- Passed-down figures?
- Statistical calculation?
- Technical judgement?
5 pcs/2 hr
Myth No. 6
Misconceptions of SPC
Myth No. 5
A2R
We know A2R = 3s. But which s? sx, sx, swithin, soverall??
Process Control Model for Quality Control
Raw Material, Components& Sub-Assemblies原材料,零件及半成品
Process
Product
Observation观察: Data Collection数据收集
Evaluation评估: Data Analysis数据分析
Diagnosis诊断: Fault Discovery错误发现
Decision决策: Formulate Action阐明行动
Implementation推行: Take Action采取行动
Uncontrollable Inputs不可控的输入
Controllable Inputs可控的输入
Statistical Process Control
The process control model shifts focus to the home front, . the manufacturing process, taking a preventive instead of reactive ,如,制造制程,是采取预防措施而非直接解决问题
It also has something which the old concept of product control lacked - statistics. This allows use of sample