1. What Is The Cpk Formula?

The Cpk (Process Capability Index) formula measures how well a process meets specification limits. It considers both the centering of the process and its spread relative to the specification limits.

2. How Does The Calculator Work?

The calculator uses the Cpk formula:

Where:

• \( USL \) — Upper Specification Limit
• \( LSL \) — Lower Specification Limit
• \( \mu \) — Process Mean
• \( \sigma \) — Process Standard Deviation

Explanation: The formula calculates how many standard deviations the process mean is from each specification limit and takes the minimum value.

3. Importance Of Cpk Calculation

Details: Cpk is crucial for quality control and process improvement. It helps determine if a process is capable of producing within specification limits and identifies opportunities for improvement.

4. Using The Calculator

Tips: Enter all values in consistent units. Standard deviation must be greater than zero. The calculator will compute Cpk based on the input values.

5. Frequently Asked Questions (FAQ)

Q1: What is a good Cpk value?
A: Generally, a Cpk value of 1.33 or higher is considered acceptable, with values of 1.67 or higher indicating excellent process capability.

Q2: How is Cpk different from Cp?
A: Cp measures process potential without considering centering, while Cpk considers both spread and centering of the process.

Q3: Can Cpk be negative?
A: Yes, Cpk can be negative when the process mean is outside the specification limits.

Q4: What if my process has only one specification limit?
A: For one-sided specifications, use the appropriate part of the formula (either the USL or LSL calculation).

Q5: How often should Cpk be calculated?
A: Cpk should be monitored regularly as part of ongoing process control, with frequency depending on process stability and criticality.