Checkweigher Calibration Stability
A comprehensive case study demonstrating how FMEA analysis, regression modeling, and GR&R testing identified span adjustment calibration as a critical control point, enabling standardized procedures that transformed post-sanitation weight variation into stable, compliant, and predictable manufacturing performance.
Project Overview
Statistical Control Ensures Food Safety Compliance
The Challenge
Food manufacturer experiencing recurring product weight variation (500g target ±0.5g spec) after sanitation cycles. High post-sanitation drift creating regulatory compliance risk (78% compliance vs 95%+ requirement). Checkweigher inconsistency suspected but root cause unclear. Standard equipment checks passed, yet process remained incapable (Cpk=0.29).
The Methodology
FMEA identified span adjustment as critical failure mode (RPN=504, severity 9 regulatory impact). Regression analysis proved span accuracy explains 88.7% of weight variation (R²=0.887)—primary KPIV. GR&R study (11% total variation) confirmed system capability; variation source is process input (span calibration), not measurement equipment defect.
The Implementation
Deployed three complementary controls: (1) Standardized Span-Adjust SOP (-75% calibration drift), (2) Visual process controls addressing human error (-60%), (3) Operator skill training ensuring consistency (+55%). No equipment replacement—focused controls of the critical process variable addressed root cause completely.
The Results
Weight variation reduced from 2.3g to 0.93g standard deviation (-60%), process capability transformed from incapable (Cpk=0.29) to highly capable (Cpk=1.79, +517%), regulatory compliance achieved 99.7% (+21.7 percentage points), zero giveaway reduction, customer satisfaction +62%. Replicable across 2 additional product lines (700-1000g packages) with annual savings of 18,000 units reduced giveaway.
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Checkweigher Calibration Stability Case Study
Learning Outcomes
Key Takeaways for Process Improvement Practitioners
FMEA Guides Statistical Investigation
FMEA identified span adjustment (RPN=504, severity 9) as highest-risk failure mode. Statistical investigation then validated FMEA insight, proving span accuracy explains 88.7% of variation. FMEA prioritization + statistical verification = confidence in solution targeting.
Regression Quantifies KPIV Impact
R²=0.887 (88.7% variance explained) proves span accuracy is dominant lever for weight control. Poor span adjustment adds 1.7g standard deviation. Regression-driven insight justified focused control development rather than broad process overhaul.
GR&R Study Redirects Investigation
11% GR&R (well below 30% threshold) proved weighing system is capable. Variation source is PROCESS input (span calibration), not equipment defect. Prevented costly equipment replacement; investment in process control was correct strategy.
Food Safety Compliance Driven by Statistics
Regulatory compliance improved from 78% to 99.7% (+21.7 percentage points) through data-driven span adjustment control. Statistical rigor ensures food safety > regulatory protection > customer trust. Framework applicable to any food manufacturing process.
Process Control Beats Equipment Replacement
Standard equipment checks passed, yet Cpk=0.29 (incapable). Investment in SOP, visual controls, and operator training achieved Cpk=1.79—better solution at fraction of equipment replacement cost. Statistical evidence guided cost-effective strategy.
Scalability Across Product Weight Ranges
Proven span adjustment framework applies to 2 additional product lines (700-1000g packages). Standardized control methodology scales across weight ranges without redesign. Enterprise-wide implementation: 18,000 units/year reduced giveaway. Framework validated for replication.
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