Process Failure Mode and Effects Analysis (PFMEA) is often developed at the time when a new product or process is being introduced. This activity is very beneficial when ordering tooling and equipment as well as determining process controls. PFMEA is a collection of possible causes and mechanisms for failure modes, as determined by a team. It can also play an important role in day to day improvement and problem solving.
The relationship between Eight Disciplines of Problem Solving (8D) and Process FMEA (PFMEA) is very strong. When a problem is encountered, the 8D is often used to find a Root Cause and permanent solution. The PFMEA may provide many of the 8D inputs. Many organizations struggle with the relationship between 8D and PFMEA. Quality-One has developed a process which seamlessly integrates the 8D and PFMEA to ensure the tools are always used together.
The PFMEA and 8D share many similarities:
- 8D Symptoms are similar to PFMEA Effects
- 8D Problem Statements and Problem Descriptions are similar to PFMEA Failure Modes
- 8D Possible Causes and Root Causes are similar to PFMEA Causes
- 8D Escape Points are PFMEA Process Controls
The PFMEA is often placed on a shelf and forgotten about after initial development. When done properly by a Cross Functional Team (CFT), PFMEA can be used by Kaizen or Continuous Improvement teams.
PFMEA Development activities can be shortened significantly by reviewing all known data and preselecting areas which are new, changed, historical issues or impacted by the environment. The Quality-One PFMEA Legacy Matrix (shown below) allows known and brainstormed Failure Modes and Causes/Mechanisms to be captured in an easy to use spreadsheet. The Q-1 Legacy Matrix has been constructed from many years of experience in a variety of industries and is used to shorten the time required to develop a valuable and focused PFMEA. Elements on the Matrix include:
- Technology or Process Names (Verbs and Synonyms)
- Failure Modes (Historical and Perceived)
- Causes by Six Categories (Man – Human Factors, Method, Material, Machine, Measurement and Environment)
- Process Controls Detection
- Process Controls Prevention
- Historical Severity Rankings
- Historical Linkage between Failure Modes and Causes
- Linkage between Causes and Prevention approaches
A PFMEA is not always easy to develop. Thorough PFMEA Development is critical to receive value from the exercise, but should not translate into an excessive amount of time. The Quality-One Methodology and PFMEA Facilitation Techniques help to reduce the time needed to develop a thorough and beneficial PFMEA.
Collecting and using a database of legacy information for PFMEA Development ensures the same problem will never have to discussed and brainstormed more than once. Failure Modes and Causes can be quickly reviewed for their relevance for the specific PFMEA being developed. Process Controls are linked and easily developed into the Control Plan.
Operator Error is often used in PFMEA as a Cause of Failure. Although operators can make errors, Operator Error is not an acceptable Cause of Failure because it is not actionable.
Processes must be designed to expect that operators wish to do the correct thing. Training and providing Work Instructions and Procedures are not robust enough for repetitive processes. Poor Training and / or Work Instructions are inadequate secondary choices to Operator Error. The real issue is the operator discovers errors made in the process design. The process designer / engineer must strive to engage operators into the process and help reduce the number of possible errors available for operators to find.
Quality-One approaches Operator Error by considering the interfaces of the process that the operator is engaged in. The process should be designed to permit communication between the process and the operator.
Processes designed with operators provide feedback to the process status. This process interface can be passive or active. Passive interfaces use visual cues, such as seeing parts remaining in a kitted bin or tactile feedback when installing a part or engaging a clamp. Active interfaces use logic, sounds, lights, process interruption or lockouts as feedback. Ultimately, Error and Mistake Proofing are deployed in order to eliminate or reduce errors discovered by operators.
With the process interface in mind, there is a cascade from Operator Error (Level 1), down to specific actionable topics (Level 2 and 3 Causes).
- Work Station Design
- Documentation and Training
- Assists and Tool Design
- Cognitive Attention and Concentration
Operator Error is not an acceptable Cause of Failure because there is no direct action that can be taken. Level 2 and/or 3 Causes of Operator Error can be addressed directly through process or product change.