1. What is DFMEA?
Design Failure Mode and Effects Analysis (DFMEA) is a risk assessment method used to evaluate potential failure mode of product design and drive corrective actions to prevent or reduce the chance of defects occur before production launch.
DFMEA focuses on product failure while PFMEA focuses on process failure
2. Which area should be applied?
DFMEA is a great risk assessment tool for product designers. Base on DFMEA, designers can ensure that all design requirements are completely met before start the production.
3. Why DFMEA?
Quality is critical to satisfying your customers and retaining their loyalty and keep them continue buying the product. A lot of scandals recently with many companies show the fact that serious design problems can ruin the reputation of any company or put them out of business.
Less serious design problems can dissatisfy customers, delay launching of new product and place a substantial financial burden on the company.
Properly conducting DFMEA can help a company prevent the costly design problems before product launching. However, it’s never been easy to apply DFMEA effectively in any company, to make DFMEA work effectively; the company must conduct it by the right team at the right time with the right way.
#1 FMEA Creator for Excel
4. Team Members
A good DFMEA performance needs knowledge and experience of many departments in a company. So it should be handled by a cross-functional team and led by the responsible product designer. The involved departments should include but are not limited to Design, Production, Supplier Quality, Product Quality, Service and Logistic.
5. When to conduct DFMEA
For a new product, creating DFMEA should start with product design and before prototype manufacturing.
After DFMEA is created, the team should continuously review and update in the events of product changes:
• Change of Product Design: Change product dimension, the material could be the reason to review DFMEA. In this case, the change point and effected points should be focused.
• Quality Problem caused by product design: New internal defects or customer return should be reflected in DFMEA to re-analyze and re-evaluation and consider for corrective action.
DFMEA should reflect the current status of product design, and that is why it is called a living document. However, keep DFMEA “living” is not easy. That’s because of a complicacy of DFMEA and its linkage to other documents, maintaining DFMEA living is much easier if we use proper DFMEA software.
6. How to make a DFMEA
Below documents should be considered as input resources for the team when starting a DFMEA:
• Block (Boundary) Diagrams: The block diagram of the product shows the physical and logical relationships between the components of the product. Block Diagram can be used to determine the item included in the DFMEA.
• Parameter (P) Diagrams: The P-Diagram is a structured tool used to describe the physics related to the functions of the design by listing input, output, control, and noise factor of the objective.
• Quality History: Can be used to find the potential failure mode and confirm the effectiveness of preventive action in new design.
• Drawing, Engineering Specification: Can be used to determine the function and requirements.
• Bill of Materials: List of component/part of the product.
Below example, we use a common DFMEA form. You can add, remove or modify the information to be suitable for your risk assessment process.
6.3 DFMEA Steps
1st Step: Define Product Requirements
Item Name and Number: List all product’s parts/assemblies/components (from now on referred to as Item) name and number into these columns. This information can be obtained from the Build of Material.
In our example, each item has only one function. If an item has more than one function, each function should be listed separately but still align with its item.
In the Requirement column, list all requirements of each part/function. Each requirement should be list separately but still aligned with its process/function.
Excel Quick Tips: In Excel worksheet, one Item has one Requirement. To add more requirement item without merging cell, select the current requirement and press Enter. See FMEA Excel Quick Tips for more details.
2nd Step: Brainstorming Potential Failure Mode
In the Potential Failure Mode column, list all potential failure mode of each requirement. Each potential failure mode should be list separately but still aligned with its requirement.
3rd Step: Analyze Effects
In Effects column, input the potential effects on customers of each failure mode. The customers here can be an internal customer or external customer.
In Severity column, input the ranking number reflecting the most severe potential effect of a failure mode. Severity ranks on a 1 to 10 scale, 10 is the most severe risk.
4th Step: Finding Potential Cause
In the Potential Cause column, list all potential causes of each failure mode. The causes should be listed separately. However, if two causes have to occur at the same time to generate the failure, they should be listed together.
5th Step: Describe Current Control for the potential causes
In the Prevention Control and Detection Control column, input the current prevention control methods and detection control method for the respective potential cause.
Prevention Controls are control methods for preventing the cause of the occurrence. Detection Controls are control methods for detecting the cause or failure if it occurs.
6th Step: Evaluate Occurrence /Detection of Current Status
In the Occurrence (C) column input the ranking number reflecting the possibility of occurrence of the Failure. Occurrence ranks on a 1 to 10 scale, 10 means the highest possibility of occurrence.
In the Detection (D) column, input the ranking number reflects the best detection control method. Detection ranks on a 1 to 10 scale, 10 means worst detection capability.
7th Step: Calculate RPN and Evaluate Risk
RPN is risk assessment number used to evaluate the risk level of failure modes. This number is the product of Severity, Occurrence and Detection ranking.
RPN = S X O X D
Excel Tips for quick generate RPN formula: in the top item of RPN column, Input the formula for the first cause, then click Copy Formula in ABC ribbon tab; the RPN formula will be deployed to all PFMEA worksheet.
8th Step: Corrective Action Plan
The team should decide to conduct corrective action to address the failure with the highest RPN and severity. For details of Corrective Action Plan, input corrective actions, responsible personnel, the planned date and then the complete date when the corrective action is finished.
9th Step: Re-rating RPN after Corrective Action
After actions completed, re-rate the Severity, Occurrence and Detection ranking based on new status. Then input the S, O, D ranking number in the corresponding column and re-calculate the RPN.
Easy to edit FMEA right inside Excel
6.4 Linkage of DFMEA
DFMEA is not a standalone document in product and process development process. To make your DFMEA consistency with each other, the information in DFMEA must link with the respective information in other documents:
The connection of PFMEA and DFMEA may not be obvious because PFMEA focuses on process failure mode and DFMA focuses on product failure mode. However, below linkage should be maintained:
• Characteristics of product and process mentioned in PFMEA should be consistent with respective items in DFMEA.
• Sometimes, DFMEA and PFMEA failure modes have a same potential effect. Severity rankings that associate with the same effects should be equal in both PFMEA and DFMEA. Otherwise, the company should have a clear reason why they have different ranking systems for the same kind of risk.
• Potential failure modes of PFMEA leads to product-related effect should appear in Potential Cause of Failure in DFMEA. Vice versa, Potential Failure Mode in DFMEA that cause by process should appear in PFMEA Potential Failure Effects.
6.4.2 Design Verification Plan and Report (DVP&R)
Design Verification Plan and Report is a plan and report used to confirm a system, product or component meets the design requirements. At the minimum, DVP&R should have test items, criteria, procedure, and sample size. DFMEA prevention and detection control are the input of the test item included in the Design Verification Plan.
6.5 Lesson Learn & Knowledge Reuse
To save time, current DFMEA should be re-used in the new project if the new product is similar to the existing product. However, the DFMEA team needs to focus only on the changing point of the new product.