How to view the difference and connection between DFMEA and PFMEA?
● DFMEA and PFMEA use different objects
DFMEA is mainly completed by design engineers in the design stage. The object of analysis is the function of the product. The analysis method is mainly used to find failures through simulation and theoretical inference.
The main task of DFMEA is to find the functional failure of the design process, so as to give a design method and guide the design engineer to carry out the design.
PFMEA is mainly completed by process engineers in the process development stage. The object of analysis is the manufacturing process flow. The analysis method mainly relies on the experience of engineers, lessons from past failures, and customer feedback to find failures.
The main task of PFMEA is to find the process failure of the manufacturing process, so as to give process guidance and guide the process engineer to start the preparation of process documents and inspection documents.
● Both DFMEA and PFMEA should figure out the requirements to start
Any process starts from input and goes through activities to output, and the process of compiling FMEA is no exception.
Before compiling DFMEA, enterprises often understand the needs of customers and convert them into technical requirements through tools such as QFD, and then carry out DFMEA analysis.
However, such identification is often insufficient, and requires us to fully understand the needs (customer, legal, internal, logistics, etc.) before conducting DFMEA analysis. Therefore, in the AIAG manual, the scope of customers is relatively wide, and the design cannot Only meet the needs of users or OEMs.
u End user: The person or organization that uses the product. For example: durability, safety.
uOEM assembly or manufacturing center: such as: assembly, stamping, etc. in automobile factories.
u Supply chain manufacturing: it can be any follow-up operation, such as: electroplating, heat treatment, etc.
uGovernment regulatory agencies: especially local laws and regulations
uOther related parties: for example, local residents, internal employees, shareholders, logistics industry, etc.
PFMEA analysis, everyone has a weaker grasp of the demand, and the PFMEA analysis should also fully analyze the demand, especially the production demand:
For example: ergonomic requirements, requirements for new auxiliary materials, safety requirements, error-proofing requirements, quality goal realization requirements, etc.
●Link between DFMEA and PFMEA
The DFMEA is very important as an input to the PFMEA. The AIAG manual gives the relationship between DFMEA and DVP, and the relationship between PFMEA and control plan, but there is no good link between DFMEA and PFMEA.
Logical Reasoning of PFMEA:
The failure of the D feature leads to the failure of the A feature of the finished product, then the A feature fails, resulting in the failure mode of the system or subsystem.
The failure mode of the system or subsystem causes the failure effect to be bad for the customer, let’s say we have a score of 5 here.
Then, the effect of failure transmitted to the D characteristic is also 5 points.
At that time, not all feature failures in process 1 affected feature A, and failures of features that may not have any effect on the finished product would not be passed on to the DFMEA, which is the second sentence, the impact of the process FMEA must be re-evaluated.
Last words
The transfer between DFMEA and PFMEA, and the transfer of FMEA between customers and suppliers, is a concept that is particularly emphasized in the new version of FMEA. Therefore, in our actual operation, we should develop more platforms for communication between design and process personnel.
