Control Charts SPC Types of Control Charts SPC
- Slides: 12
Control Charts - SPC Types of Control Charts: SPC – Statistical Process Control 1) X – Chart & R Chart Quantitative Data – Control Mean and Variation for a Process 2) P – Chart Qualitative Data – Control Percent Defective 3) C – Chart Blemish Rate – Control the Number of Non-Fatal Flaws per Item
3 – Sigma Control Limits . 9973 obs µ - 3σ µ + 3σ LCL = µ - 3σ UCL = µ + 3σ Six – Sigma – Design the Process so Product can vary by 6 Sigma Product Meets Specifications µ - 6σ . 99998 obs µ + 6σ
X – Chart and R – Chart Take m Samples of Size n Each.
Ex 18. 1: m = 20 n=6 X = 5. 00217 R =. 136 Control Chart: Bearing Diameter 5. 10963 5. 05590 Mean 5. 00217 Bearing Diameter UCL = 5. 0679 4. 94844 Average = 5. 0022 4. 89471 1 2 3 4 5 Sigma level: 3 6 7 8 9 10 11 12 13 14 15 16 17 18 19 LCL = 4. 9364 20
Control Chart: Bearing Diameter. 4. 3 Bearing Diameter Range. 2 UCL =. 2725 . 1 0. 0 Average =. 1360 1 2 3 4 5 6 7 9 11 13 15 17 19 8 10 12 14 16 18 20 Sigma level: 3 LCL =. 0000
Remove Data Sets: 3, 5, 11, 16, 19 X = 4. 997 R =. 12
P – Chart X j = Number of Defects in j th Sample out of n pj = X j / n Ex 18. 3: m = 20 n = 50 Sample Proportion ∑X j = 53
C – Chart c j - # Flaws in the j th Sample Poisson Distribution – Std Dev = Square Root of the Mean Ex 18. 4: m = 25 ∑c j = 50
Interpreting Control Charts: Points above UCL and/or below LCL UCL Centerline LCL
Interpreting Control Charts: 8 Consecutive Points on One Side of the Centerline UCL Centerline LCL
Interpreting Control Charts: 7 Consecutive Increasing Points UCL Centerline LCL
2 out of 3 Consecutive Points in Outer 1/3 UCL Centerline LCL 4 out of 5 Consecutive Points in Outer 2/3 UCL Centerline LCL
