1. What is Cpk?

The Cpk (Process Capability Index) measures how close a process is running to its specification limits, relative to the natural variability of the process. It indicates how well a process meets specifications.

2. How Does the Calculator Work?

The calculator uses the Cpk formula:

Where:

• \( d \) — Distance to nearest specification limit
• \( s \) — Standard deviation of the process

Explanation: The formula calculates how many standard deviations fit between the process mean and the nearest specification limit.

3. Importance of Cpk Calculation

Details: Cpk is crucial for quality control, helping determine if a process can produce output within specification limits. Higher Cpk values indicate better process capability.

4. Using the Calculator

Tips: Enter the distance to the nearest specification limit and the standard deviation of your process. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a good Cpk value?
A: Generally, Cpk ≥ 1.33 is considered capable, while Cpk ≥ 1.67 is excellent. Cpk < 1 indicates the process doesn't meet specifications.

Q2: How is Cpk different from Cp?
A: Cp measures potential capability assuming the process is centered, while Cpk considers both centering and variation.

Q3: When should I use Cpk?
A: Use Cpk when you need to evaluate how well your process meets specifications, especially in manufacturing and quality control.

Q4: What are limitations of Cpk?
A: Cpk assumes normal distribution and stable process. It doesn't work well for non-normal distributions or unstable processes.

Q5: How can I improve my Cpk?
A: You can improve Cpk by centering your process between specification limits or reducing process variation.