There are 6 steps in process FMEA as per VDA & AIAG. These 6 steps provide a systematic approach to do failure mode and effect analysis.
1. Scope Definition & Project Planning :
Purpose of the process scope definition is to decide what product / process to include / exclude for review in the PFMEA project. Below are the main objective of defining the scope definition:
- Project identification
- Project plan
- Define the boundary of the analysis
- Identify lesson learning sheet.
During the scope definition PFMEA header should be filled as below:
2. Structure Analysis:
Purpose of process structure analysis is to identify and categorize the production system in to
- Process Item
- Process Step
- Process Work Element.
Main objective of Process structure analysis:
- System structure for a product or element of a process.
- Visualization of the scope of the analysis
- Identification of the process steps
- Basis for the function analysis steps
A Process flow diagram or Structure tree helps to define the process and provide the basis for structure analysis.
3. Function Analysis :
The purpose of the process function analysis is to ensure that intended functions of the product / process are defined adequately.
Main objective of the function analysis :
- Check the functionality of the process
- Visualization of the process function using process flow diagram.
- Association to characteristics to function
- Basis for failure analysis
A function describes what the process item or process step is intended to do.
A requirement is related to performance of the function and can be measured. Requirement falls in to 2 categories :
- Product characteristics
- Process characteristics.
A product characteristics like geometry,material specification and surface finish etc. A process characteristics is shown on manufacturing operation standard or work instruction. A process characteristics like pressure, temperature, current, voltage etc.
4. Failure Analysis :
The purpose of the process failure analysis is to identify failure causes, mode and effect.
Main objective of the Process failure analysis :
- Establishment of the failure for each function of process item
- Identification of the possible failure to process element or step.
- Visualization of the failure relationship
- Effect may be shared by the customer to their supplier.
Failure of a process step are non conformity to product or process characteristics. For a specific failure there are three categories:
- Failure effect
- Failure mode
- Failure cause
5. Risk Analysis :
Purpose of the risk analysis is to estimate risk by evaluating severity, occurrence and detection and prioritize the need for action.
Main objective of the risk analysis :
- Identify prevention control
- Identify detection control
- Rating of severity, occurrence and detection
- Communication between customer and supplier on severity.
There are two different control groups :
- Current prevention control
- Current detection control
Action Priority (AP) :
In this new FMEA Action Priority (AP) replaced the RPN. The AP table provide the logic detail for the FMEA team for all 1000 combination of S,O and D. It includes the logic based description of each action priority level.There are 3 types of action priority in AP table as below :
Priority High (H) :
The team must take or identify action to improve prevention or detection control. or Justify that current control is OK.
Priority Medium (M) :
The team should take or identify action to improve prevention or detection control or justify that current control is OK.
Priority Low (L) :
There is low priority for action. It means no need to take any action.
6. Optimization :
Purpose of the process optimization step is to determine action to mitigate risk and access the effectiveness of these actions.
Main objective of the process optimization :
- Identification of the action necessary to reduce risk
- Assignment of the action and target completion time for action implementation
- Implementation and documentation of the action taken
- Confirmation of the effectiveness of the action taken
- Continues improvement of the process
FMEA result documentation :
The scope and result of a FMEA should be summarized in a report.The report can be used for communication purpose in the company or to customer.
Reference : AIAG VDA FMEA