Definition and Purpose
Process FMEA helps eliminate failures that result from changes in process variables, i.e., out-of-spec conditions such as wrong size, texture, color, hardness, and so on. The goal of manufacturing is to produce a product that meets all specifications every time. A process-related failure mode is any deviation of the product from specification; it is caused by a change in process variables. For example, The process is finishing the cage of a roller bearing. The failure mode is cage is not completely formed. The cause is low hydraulic pressure in the cut-and-carry press. A process FMEA identifies potential deviations from specification, and eliminates or minimizes them by preventing or detecting changes in the process variables.
Benefits
- Identifies potential problems before bad product is manufactured
- Helps avoid scrap and rework
- Reduces the number of product failures expreienced by the customer
- Ensures a smoother start-up
Basic Steps
Draft Stage
- The manufacturing engineer reviews product specifications with the product design engineer to:
- Help ensure the feasibility of the product design
- Help avoid start-up problems
- The manufacturing engineer then drafts the following portions of the process FMEA form:
- Description, Specification, and Part(s)
- Potential Failure Modes
- Potential Causes of Failure Modes
- In-place and Planned Cause Preventions or Detections
Team review stage
- The manufacturing engineer assembles a team to review the draft. Team members may include:
- Line operators
- Tooling and set-up people
- Electricians
- Plumbers
- OEMs
- Process consultants
- A start-up meeting is held to:
- Update team members on the product's development.
- Explain the proposed process design.
- Review the process FMEA procedure.
- Distribute copies of the draft FMEA form, product engineering drawing, spec sheet, process flowchart, and other supporting documentation.
- Working independently or in small groups, team members review the draft and:
- Identify additional failure modes, effects, causes, and prevention or detection methods.
- Recommend corrective actions to eliminate the cause, or to enhance the prevention or detection methods.
- Rank the effectiveness of the prevention and detection methods identified by the manufacturing engineer.
- Team members submit their comments to the manufacturing engineer who:
- Combines their comments with his original entries into a composite process FMEA form.
- Reviews the composite with his/her supervisor to determine which corrective actions (if any) should be implemented and who will be responsible for them.
Implementation stage
- The manufacturing engineer follows up with people assigned responsibility for implementing corrective actions to check on their progress.
- Completed actions are noted on the composite FMEA form.
- A copy of the composite form is given to the FMEA facilitator for the files.
In-service stage
- Any changes made to the product design or manufacturing process which could impact product reliability undergo another Failure Mode and Effect Analysis.
- The existing FMEA form is revised as needed to reflect the changes.