Six Sigma and Beyond: Design for Six Sigma, Volume VI

KEY DEFINITIONS IN R&M

The following terms are commonly encountered in R&M:

Accelerated life testing

Verification of machine and equipment design relationship much sooner than if operated typically. Intended especially for new technology, design changes, and ongoing development.

Derating

The practice of limiting stresses that may be applied to a component to levels below the specified maxima in order to enhance reliability. Derating values of electrical stress are expressed as ratios of applied stress to rated maximum stress. The applied stress is taken as the maximum likely to be applied during worst-case operating conditions. Thermal derating is expressed as a temperature value.

Design of experiments (DOE)

A technique that focuses on identifying factors that affect the level or magnitude of a product/process response, examining the response surface, and forming the mathematical prediction model.

Design review

A review providing in-depth detail relative to the evolving design supported by drawings, process flow descriptions, engineering analyses, reliability design features, and maintainability design considerations.

Dry run

The rehearsal or cycling of machinery, normally with the intent of not processing the work piece, to verify function, clearances, and construction stability.

Durability

Ability to perform intended function over a specified period under normal use with specified maintenance, without significant deterioration.

Equipment

The portion of process machinery that is not specific to a component or sub assembly.

Failure

An event when machinery/equipment is not available to produce parts under specified conditions when scheduled or is not capable of producing parts or performing scheduled operations to specifications. For every failure, an action is required.

Failure mode and effects analysis (FMEA)

A technique to identify each potential failure mode and its effect on machinery performance.

Failure reporting, analysis, and corrective action system (fracas)

An orderly system of recording and transmitting failure data from the supplier's plant to the end users fits into a unitary database. The database allows identification of pattern failures and rapid resolution of problems through rigorous failure analysis.

Fault tree analysis (FTA)

A top down approach to failure analysis starting with an undesirable event and determining all the ways it can happen.

Feasibility

A determination that a process, design, procedure, or plan can be successfully accomplished in the required time frame.

Finite element analysis (FEA)

A computational structure analysis technique that quantifies a structure's response to applied loading conditions.

Total productive maintenance (TPM)

Natural cross-functional groups working together in an optimal balance to improve the overall effectiveness of their equipment and processes within their work areas. TPM implementation vigorously benchmarks, measures, and corrects all losses resulting from inefficiencies .

Life cycle

The sequence through which machinery and equipment pass from conception through decommission.

Life cycle costs (LCC)

The sum of all cost factors incurred during the expected life of machinery.

Machine condition signature analysis (MCSA)

An application that applies mechanical signature ( vibration ) analysis techniques to characterize machinery and equipment on a systems level to significantly improve reliability and maintainability.

Machinery

Tooling and equipment combined. A generic term for all hardware (including necessary operational software) that performs a manufacturing process.

Maintainability

A characteristic of design, installation, and operation, usually expressed as the probability that a machine can be retained in, or restored to, specified operable condition within a specified interval of time when maintenance is performed in accordance with prescribed procedures.

Mean time between failures (MTBF)

The average time between failure occurrences. The sum of the operating time of a machine divided by the total number of failures. Predominantly used for repairable equipment.

Mean time to failure (MTTF)

The average time to failure for a specific equipment design. Used predominantly for non-repairable equipment.

Mean time to repair (MTTR)

The average time to restore machinery or equipment to specified conditions.

Overall equipment effectiveness (OEE)

Percentage of the time the machinery is available (Availability) — how fast the machinery is running relative to its design cycle (Performance efficiency) — percentage of the resulting product within quality specifications (Yield).

Perishable tooling

Tooling which is consumed over time during a manufacturing operation.

Plant floor information system (PFIS)

An information gathering system used on the plant floor to gather data relating to plant operations including maintenance activities.

Predictive maintenance (PdM)

A portion of scheduled maintenance dedicated to inspection for the purpose of detecting incipient failures.

Preventative maintenance (PM)

A portion of scheduled maintenance dedicated to taking planned actions for the purpose of reducing the frequency or severity of future failures, including lubrication, filter changes, and part replacement dictated by analytical techniques and predictive maintenance procedures.

Probability ratio sequential testing (PRST)

A reliability qualification test to demonstrate if the machinery/equipment satisfies a specified MTBF requirement and is not lower than an acceptable MTBF (MIL-STD-781).

Process

Any operation or sequence of operations that contributes to the transformation of raw material into a finished part or assembly.

Product

In relation to tooling and equipment suppliers, the term "product" refers to the end item produced (e.g., machine, tool, die, etc.).

Production

In relation to tooling and equipment suppliers, the term "production" refers to the process required to produce the product.

R&M plan

A reliability and maintainability (R&M) plan shall establish a clear implementation strategy for design assurance techniques, reliability testing and assessment, and R&M continuous improvement activities during the machinery/equipment life cycle.

R&M targets

The range of values that MTBF and MTTR are expected to fall between plus an improvement factor that leads to MTBF and MTTR requirements.

Reliability

The probability that machinery and equipment can perform continuously, without failure, for a specified interval of time when operating under stated conditions.

Reliability growth

Machine reliability improvement as a result of identifying and eliminating machinery or equipment failure causes during machine testing and operations.

Root cause analysis (RCA)

A logical, systematic approach to identifying the basic reasons (causes, mechanisms, etc.) for a problem, failure, non-conformance, process error, etc. The result of root cause analysis should always be the identification of the basic mechanism by which the problem occurs and a recommendation for corrective action.

Simultaneous engineering (SE)

Product engineering that optimizes the final product by the proper integration of requirements, including product function, manufacturing and assembly processing, service engineering, and disposal.

Things gone right/things gone wrong (TGR/TGW)

An evolving program-level compilation of lessons learned that capture successful and unsuccessful manufacturing engineering activity and equipment/performance for feedback to an organization and its suppliers for continuous improvement.

Tooling

The portion of the process machinery that is specific to a component of sub assembly.