Holistic Reliability
Achieving World Class Reliability with a Holistic Model
Holistic ‘is a belief that the parts of something are intimately interconnected and explicable only by reference to the whole’
This is particularly true with Reliability as simply carrying out an Accelerated Life Test or HALT test, etc will never achieve the ultimate objective you seek, we must go much deeper into understanding the whole suite of tests and proactive assessments required to PREVENT defects ever occurring.
Why do we need this model?
Due to low field failure rate targets and limited sample sizes, reliable statistical testing is often not feasible. Simulation models rarely align with actual field failure data, and accelerated stress testing doesn’t consistently reveal real defects. Therefore, an alternative method is needed to significantly improve reliability predictions.
When and who can use the model
Applying the Holistic model early in the design cycle allows for continuous measurement and a dynamic score throughout development, including into pilot or initial mass production. Project Managers can track group performance (Design Product Eng, Test Eng, Quality, NPI, Process Eng, etc.) using factor scores, quickly identifying which teams need attention to improve outcomes early in the process. The final score before full-scale production provides a clear assessment of how the product is likely to perform in manufacturing and real-world use.
Holistic Model Background
Product reliability depends on a range of interconnected factors, and the key is integrating these elements to impact the entire product. Reliability Solutions is now well-prepared to introduce a holistic model that directly relates to both product reliability and quality. This is an exciting time as we start to apply the solution model which companies have been waiting on for many years, though they never actually realised it, up until now that is !!
Implementing the Holistic Model
How would your company develop their unique holistic model to drive World Class Reliability?
Step 1 - Identify the key factors that ensure customer satisfaction in your product, such as longevity, functionality, appearance, durability, feel, or ease of use.
Step 2 – Outline Methods for developers and manufacturers to achieve their goals:
Maintain consistent manufacturing standards with tight tolerances.
Enable high-volume production to increase yield and reduce rework.
Improve process controls to minimize early-life defects.
Set field reliability targets 50% lower than previous products to cut failure costs and boost customer satisfaction.
Step 3 - Identifying tools that facilitate the achievement of objectives within short development cycles:
Implementing an enhanced and engaging DFMEA process to actively involve engineering teams.
Applying DFM and DFx principles to strengthen design for manufacturing, testing, and serviceability.
Utilizing an expedited and efficient form of Accelerated Reliability Testing at key component, sub-assembly, and full assembly stages, addressing all sources of defects.
Adopting a robust Design Quality testing approach that combines functional and stress testing to maximize defect detection rates.
Employing a comprehensive manufacturing readiness review methodology, ensuring a pragmatic and objective internal assessment process.
Conducting thorough, manufacturing-focused process reviews with GAP Analysis, as opposed to traditional ISO Quality audits, to add meaningful value both internally and throughout the supply chain.
Conducting thorough, manufacturing-focused process reviews with GAP Analysis, as opposed to traditional ISO Quality audits, to add meaningful value both internally and throughout the supply chain.
Developing rigorous Process Control Plans based on detailed process mapping.
Step 4 - Develop a comprehensive plan for the product and implement an organised methodology to apply selected tools effectively. Utilise a scoring system that directly reflects the contribution of each tool toward achieving World Class Quality and Reliability objectives.
Conduct a Design for Assembly review using a thorough approach informed by lessons learned and product analysis. This will significantly impact low-cost, high-volume products that demand error-free and efficient assembly.
Employ rigorous Design Quality testing and Design Maturity measurement processes to markedly improve the reliability of complex products with diverse operational capabilities.
Perform production readiness reviews for products with intricate manufacturing processes, ensuring process control to Six Sigma standards.
Establish detailed Accelerated Stress Test plans at component, sub-assembly, and full assembly levels, recognising the need for distinct stress tests to optimise defect detection capability at each stage.
Apply robust Supply Chain selection and management models to maximise supplier quality and performance.
Step 5 - Determine suitable metrics for each factor.
Use percentage of design maturity to assess Design Quality.
Evaluate Design for Assembly (DFM, DFx) with a rating score based on percentages.
Judge Early Life Reliability Testing by counting the number of defects.
Measure Accelerated Life Testing using predicted Mean Time To Failure (MTTF).
Establish and relate initial Mass Production yield targets to their corresponding scores.
Assign a percentage-based score to Production Readiness levels.
Compare Manufacturing Yield levels against set targets and score appropriately.
And so on.
Step 6 - How do we integrate everything into a matrix that yields an Output Metric?
Use a coordinated NPI matrix covering all elements affecting product failure and expected reliability.
Assign targets and scoring systems to each element, converting data into NPI scores.
Simulate past products using the new NPI Metric table; compare output scores to actual customer failure and reliability rates for data fitting and to determine the ‘correlation factor’.
After estimating the correlation factor, apply it to make comprehensive predictions using the information in the NPI matrix and make a HOLISTIC PREDICTION OF RELIABILITY
An example of a typical model is shown below ;
| NPI Metric Item | Measurement | Scoring Guide | Score | |
|---|---|---|---|---|
| 1 | Design for Manufacture / DFX | % DFX score | <70% (0), 70-80% (0.5), 80-85% (0.75), >85% (1) | 0.75 |
| 2 | DFMEA - Reliability defect focussed | Weighted RPN Average | <60 (1), 60-70 (0.5), 70-85 (0.25), >85 (1) | 0.5 |
| 3 | Design Quality Maturity from Design Quality Assurance (DQA) Testing | % Design Maturity | <70% (0), 70-80% (0.5), 80-85% (0.75), >85% (1) | 0.5 |
| 4 | Product Manufacture Process Readiness score | % score (ticksheet) | <80% (0), 80-85% (0.5), 85-90% (0.75), >90% (1) | 1 |
| 5 | Critical Sub-Assembly Early Life Rel Test | Score based on no. % def found | 0 fails (1), <5% fail (0.75), 5-10% (0.5), >10% (0) | 0.75 |
| 6 | Full Product Accelerated Life Testing (ALT) | Score based on no. % def found | 1 fails (1), <5% fail (0.75), 5-10% (0.5), >10% (0) | 1 |
| 7 | Full Product Operational Limit Test (Temp, RH, Voltage, pwr cyc) | Score based on no. def found | Meets spec conditions (50%), +20% margin outwith (75%), +30% Margin (100%) | 0.75 |
| 8 | Manufacturing Process Yield Measurement | % Rolled Yield | <70% (0), 70-80% (0.25), 80-90% (0.5), 90-95% (0.75), >95% (1) | 0.75 |
| 9 | Critical Component / Sub-Assembly Supplier Assessment Scores | % scoring | <70% (0), 70-75% (0.5), 75-85% (0.75), >85% (1) | 0.5 |
| 10 | Critical Component / Sub-Assembly Supplier Process Rolled Yield data | % Rolled Yield | <70% (0), 70-80% (0.25), 80-90% (0.5), 90-95% (0.75), >95% (1) | 0.5 |
| 11 | Full Product Assembly PFMEA | Weighted RPN Average | <60 (1), 60-70 (0.5), 70-85 (0.25), >85 (1) | 0.25 |
| AVG | 66% | |||
| Prediction | 3.5% | |||
Based on the correlation factor from simulations of previous products, the NPI score enables holistic prediction. In this case, a simple power-based equation fits the data best, yielding a prediction, such as 3.5% in the example above.
Where Next??
Where Next?
To find out more about this approach simply contact Martin Shaw on Reliabilitysolutions@yahoo.co.uk or Linkedin