 Q-QUIZ NOVEMBER 2017 Do you know how to calculate process capabilities?

Hardly any manufacturing company can do without process capability indices (Cp and Cpk). Even though you normally use software solutions to calculate them, you can estimate them easily based on graphics.

Determine both process capability indices in the following three graphics. Use the following information to figure it out in your head.

Cp = tolerance width divided by natural process variation
Cpk = critical distance divided by half the natural process variation

1. Calculate Cp and Cpk.

• Cp = -0.17 / Cpk = 0.8
• Cp = 1.33 / Cpk = 1.0
• Cp = 2.0 / Cpk = 1.0

2. Determine process capability indices Cp and Cpk.

• Cp = 1.0 / Cpk = 1.0
• Cp = 1.0 / Cpk = 1.33
• Cp = 2.0 / Cpk = 2.0

3. Calculate the capability indices in this case.

• Cp = 0.8 / Cpk = -0.17
• Cp = 1.0 / Cpk = 0.8
• Cp = 1.33 / Cpk = 1.33

Our Q-QUIZ is published once a month. You can find the answer to all questions of the current quiz in the PDF file below.
This quiz was originally published in the August issue 2015 of the German magazine QZ Qualität und Zuverlässigkeit (http://www.qz-online.de/service/preisraetsel).