1. What is Process Capability (Cp)?

Process Capability (Cp) is a statistical measure that compares the spread of a process to the width of specification limits. It indicates how well a process can meet specification requirements when the process is centered.

2. How Does the Calculator Work?

The calculator uses the process capability formula:

Where:

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

Explanation: The formula calculates the ratio of the specification range to the process variation (6σ). Higher Cp values indicate better process capability.

3. Importance of Cp Calculation

Details: Cp is crucial for quality control and process improvement. It helps manufacturers determine if their processes are capable of producing within specification limits and identifies areas for improvement.

4. Using the Calculator

Tips: Enter the upper and lower specification limits, and the process standard deviation. All values must be valid (standard deviation > 0, USL > LSL).

5. Frequently Asked Questions (FAQ)

Q1: What is a good Cp value?
A: Generally, Cp ≥ 1.33 indicates a capable process. Cp = 1.0 means the process just meets specifications, while Cp < 1.0 indicates the process is not capable.

Q2: What's the difference between Cp and Cpk?
A: Cp measures potential capability assuming the process is centered, while Cpk measures actual capability accounting for process centering.

Q3: When should I use Cp?
A: Use Cp when you want to assess the inherent capability of a process without considering its centering relative to the target.

Q4: What are the limitations of Cp?
A: Cp assumes the process is normally distributed and centered between the specification limits. It doesn't account for process shifts from the target.

Q5: How often should Cp be calculated?
A: Cp should be monitored regularly as part of ongoing quality control, especially after process changes or improvements.