Sigma, σ, is the Greek character we use to represent standard deviation. 6 σ represents the spread of data about the mean. For data with a normal distribution 6 σ includes 99.7% of the data.
The 6 σ design approach incorporates knowledge of the variation that will occur within the design such that the design has is unlikely to fail. Continue reading
If you buy more than one of an item used in your product, you will have to deal with variability. In general, the variability from part to part is minimal and expected. Occasionally, the variability is large and causes reliability problems.
According to O’Connor and Kleyner, “The main cause of production-induced unreliability, as well as rework and scrap, is the variability inherent in production processes.” O’Connor, Patrick D. T. and Andre Kleyner. 2012. Practical Reliability Engineering. Chicester: John Wiley and Sons. Web. Continue reading
Let’s say you run across a lightweight, inexpensive, easy-to-manufacture metal that you are considering for a new bike frame. Beyond the functional considerations of strength, size, and finish options what else do you consider?
Is it durable? If it fails, how does it fail (e.g., a shattering of a bicycle frame would not be good). You may also consider how the bicycle will be used and stored. What stress will the frame experience over its lifetime? Continue reading
A project-specific reliability plan is a guide or roadmap for intended action. It is also a collection of specific tasks and milestones, enhanced with rationale to allow the entire team to fully understand its role in accomplishing the reliability objectives.
The plan is a way to achieve the desired business objectives. This means that the product must be reliable enough to meet customer expectations, minimize warranty expenses, and garner market acceptance. The plan is just a plan. It is the accomplishment of the tasks, the decision that improve the design, the signals monitored that stabilize the supply chain and assembly process that all make the difference. Continue reading
Do you have derating & safety margin manual in your organization? Is it used regularly? If not, your organization’s products are likely not as reliable as they should be. You are shipping products that are not as robust nor as reliable as your customers deserve.
Derating and safety factors provide a means to select components or create design features that have sufficient margin to accommodate variation in use and strength over time. So why are these tools routinely ignored or given only fleeting attention? Continue reading