1. What is Cpk for One-Sided Specification?

The Cpk (Process Capability Index) for one-sided specification measures how well a process meets a single specification limit (in this case, lower specification limit for steel). It indicates the process capability relative to the lower specification boundary.

2. How Does the Calculator Work?

The calculator uses the one-sided Cpk formula:

Where:

• \( mean \) — The average value of the process measurements
• \( LSL \) — The lower specification limit
• \( sigma \) — The standard deviation of the process

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

3. Importance of Cpk Calculation

Details: Cpk is crucial in quality control for steel manufacturing, helping to ensure products meet minimum strength or composition requirements. Higher Cpk values indicate better process capability.

4. Using the Calculator

Tips: Enter the process mean, lower specification limit, and standard deviation. All values must use consistent units. Standard deviation must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is a good Cpk value for steel production?
A: Generally, Cpk ≥ 1.33 is acceptable, with ≥ 1.67 preferred for critical applications.

Q2: How is this different from two-sided Cpk?
A: One-sided Cpk evaluates capability against a single limit, while two-sided considers both upper and lower limits.

Q3: When should one-sided Cpk be used?
A: When only one specification limit is relevant (e.g., minimum yield strength in steel).

Q4: What if my Cpk is negative?
A: A negative Cpk indicates the process mean is below the LSL, meaning non-conforming product.

Q5: How many samples are needed for reliable Cpk?
A: Typically ≥ 30 measurements for stable estimates, though more may be needed for highly variable processes.