Reliability Improvement - Technique

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Reliability improvement techniques

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Product Reliability

Quality improvement has two faces - internal and external. Internal quality improvements deals with reduction of scrap, rework, inspection costs etc. External quality improvement means enhancing the performance that the customers experience throughout the product’s life span.

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Product Reliability

The major gains of external quality come from reduced field repairs, recalls, warranty, product redesign etc. Another benefit is the increase in future sales not only for the product in hand, but for the additional product the company manufactures. For example the improvement in the reliability of motorbikes can also favorably impact the company’s sale of cars .

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Reliability - top priority

Reliability has been defined as quality over time. It is the ability of the product to satisfactorily perform its designated function over its customer intended life time.

Examples of unreliable products will include inability of a product to function upon delivery , failure of a switching devise to perform when called upon, premature changes in appearance, breakdowns etc.

Reliability improvement is the top priority for all customers.

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Techniques of improving product Reliability

An effective reliability improvement program involves more than statistics. Reliability is the key element to quality improvement, it is often the part of quality that affects the customers the most. To achieve reliability improvement it is essential that management insists on comprehensive reliability improvement program at the product design stage itself.

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1. Reliability should be proactive

As per Henry Ford if you need an equipment to improve the product reliability but don’t buy it, you pay for it even though you don’t have it. The most important goal of product life data analysis is proactive reliability improvement preferably before the product release and at the DESIGN stage itself.

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2. Conducting Failure analysis

To improve reliability one must understand why the failure occurred. Once the process has been established and the machinery has been acquired and set up, it is extremely important to determine the failure modes and effects they have on the customer.

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Conducting Failure Analysis...

A comprehensive and carefully designed product failure database is fundamental to trouble-free products.

This database is the vital source of information to product developers about failures in similar previous designs. But, many other groups in your company also have needs for the data, often with slightly different requirements. These groups include: field service, customer service, warranty, accounting, procurement and inventory control, suppliers, and manufacturing.

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For the design engineers, the data base should include for each failure:

Part that failed Failure mode Root cause of failure Period in the life of the product of the failure (infant,

useful, end) Severity to customer Statistical summaries of the data above

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Engineers need to know in what period of life the part failed. Failures during the infant period may indicate a manufacturing defect rather than a reliability issue. Random failures during the useful life usually have other root causes, often correctable by better design. Failures at end of life may indicate wear and merit attention if they occur before the planned lifetime has passed. So, the failure database must collect and maintain data to indicate when the failure occurred.

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Specialists often perform Failure Analysis because the field service people have a mission to satisfy the customer, not to analyze why the failure occurred. Failure Analysis strives to get to the root cause of the failure. Failure Analysis Reports should be well designed and integrated with the failure database. Design engineers should have a close working relationship with technicians performing failure analysis.

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Knowledge about field failures is more valuable than knowledge from lab tests. Why?

The field failures occurred under true conditions in the hands of the customers.

The number of products being "tested" by customers is very large, giving more statistically valid results.

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3. Accelerated Testing.

Obtaining relevant reliability data early in the product design process is a critical element of proactive reliability improvement. Such accelerated testing may require increasing the use rate of a product.

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4. HALT

Highly accelerated life testing (HALT) is becoming popular among reliability and design engineers for faster elimination of key failure modes before product release.

The objective of HALT application is to rapidly identify failures, which may require long time to discover under normal use conditions.

Such testing is typically done on a few prototype units that are subjected to combinations of stresses at much higher levels than encountered in a normal operation.

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5. Robust design experiments

Robust design experiments have great potential for leading to improvements in products and process design, and thus, reliability. The key idea behind robust design methods proposed by Taguchi is to choose design conditions that make the product robust to environmental factors. Car crash tests are examples of testing robust designs in real conditions.

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6. Six Sigma

Six sigma is a product reliability improvement approach that seeks to find and eliminate causes of mistakes or defects in business processes by focusing

on outputs that are of critical importance to customers. It is also known as DMAIC ( Define, Measure,

Analyze, Improve & Control ) strategy

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Six Sigma

The ability to produce products with only 3.4 defects per million is described as Six sigma. Six sigma is action oriented and focuses on processes used to serve customers and defect

reduction.

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Aspects of Six Sigma

Human elements

• Bottom line

• Manufacturing leadership

• Sense of urgency

• Customer focus

• Project teams

• Culture Change

Process elements

• Process improvement

• Analysis of variation

• Disciplined approach

• Quantitative measures

• Statistical methods

• Process management

A Six sigma approach integrates the human and process elements of improvement to produce breakthrough results

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b. Clear focus on the bottom line

Six sigma places a clear focus on getting the bottom line results along with the time frame . No six sigma project is approved till the bottom line or the success factors are clearly spelt out. Each project must be completed within a given time frame which is usually 3-6 months

FICCI CEProduct reliability measures

• Mean time to failure

• Failure rate

• Probability of failure occurrence during given time interval

• Probability of failure non-occurrence during given time interval

• Mean life time

• Mean time to first generate overhaul

• Mean time to repair

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7. Product Design - Checklist

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Product Design Controls

Product design controls can be categorized in 3 parts I. Means of knowing the product II.Means of testing designs III.Means of regulating designs

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I. Means of knowing the product

Do the designers know the variety of application of the product.

Do they have complete information on the operating environments.

Do they have access to the user to discuss applications.

Do they know the potential field misuses of the product.

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Means of knowing the product...

Do they have clear understanding of product requirement on :- Performance Life Warranty period Reliability Maintainability Accessibility Safety Operating costs

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Have the non quantitative features of the product been defined in some manner?

Do the designers know the level of product sophistication suitable for the user involved?

Are adequate design guidelines, standards, handbooks and catalogues available?

Do the designers understand the interaction of their part of design with remainder of the design?

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Do the designers understand the consequences of a failure or other inadequacies of their designs on:-

1. The functioning of the total system

2. Warranty costs and

3. User costs ?

Do they know the relative importance of various components & characteristics within components?

Do the designers know what are the manufacturing capabilities relative to the design of tolerances?

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Do the designers derive tolerances based on customer/functional needs or just use standard tolerances?

Do the designers know the shop and field costs incurred because of incomplete design specifications or designs required in change?

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II. Means of testing designs

Do the designers have the means of testing their design with regard to the following :-

a. Performance & reliability tests

b. Tests for unknown design interaction or effects

c. Pilot run

Is their an independent review of design?

Have the detailed drawings been checked?

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Means of testing designs...

Do the designers record analysis for the design?

Do the designers receive adequate feedback from development tests, manufacturing tests, acceptance tests and user experience?

Are the results quantified where possible including frequency of problems and costs to the manufacturer and user?

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Means of testing designs...

Does failure information contain sufficient technical details on causes?

Are the designers aware of material substitutions or process changes?

Do the designers receive notice when their designs specifications are not followed in practice?

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III. Means of regulating Design

Have the designers been provided with the means of regulating the design process?

Are they provided with information on new alternative materials or design approaches?

Have they been given performance information on previous designs?

Are the results of research efforts on new products transmitted to the designers?

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Means of regulating Design...

Are the approvals required from the designers to use products from the new suppliers?

Do the designers participate in defining the criteria for shipment of the product?

Can the designers propose changes involving trade-offs between functional performance, reliability and maintainability?

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Are designers told of changes to their designs before they are released?

Have causes of design failures been determined by thorough analysis?

Do designers have the authority to follow their designs through the prototype stage and make design changes where needed?

Can the designers initiate design changes?

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Are field reports reviewed with designers before making decisions on design changes?

Do designers understand the procedures and chain of command for changing a design?

Reliability Improvement - Technique

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