DFMEA is a Design FMEA performed on the product design
PFMEA is a Process FMEA performed on the manufacturing process.
Both are very useful and both techniques should be utilized.
There is correlation between the two – one analysis could definitely influence the other, and often times a mitigation for a Design FMEA may be doing something different in the manufacturing process if it cannot be fixed by design alone.
There are many other forms of FMEA such as User FMEA, Software FMEA, Functional FMEA and others. FMEA is a very powerful tool and you choose the type of FMEA based on the particular circumstance. Here is a short summary of my favorite 6 types:
Design FMEAs are performed on the product or system at the design level.
The purpose is to analyze how failure modes affect the system, and to minimize failure effects upon the system. Design FMEAs are used before products are released to the manufacturing operation. All anticipated design deficiencies will have been detected and corrected by the end of this process.
Process FMEAs are performed on the manufacturing processes.
They are conducted through the quality planning phase as an aid during production.
The possible failure modes in the manufacturing process, limitations in equipment, tooling, gauges, operator training, or potential sources of error are highlighted, and corrective action taken.
System FMEAs comprise part level FMEAs.
All of the part level FMEAs will tie together to form the system.
As a FMEA goes into more detail, more failure modes will be considered.
A system FMEA needs only go down to the appropriate level of detail as needed.
Functional FMEAs are also known as “Black Box” FMEAs.
This type of FMEA focuses on the performance of the intended part or device rather than on the specific characteristic of the individual parts.
As an example, if a project is in the early design stages, a Black Box analysis would focus on the function of the device rather than on the exact specifications (color must be blue-gray, knob is 2.15 mm to the left, etc.)
A subset of the Design FMEA that focuses specifically on the customer and how they will use/mis-use the product
An input to the User FMEA is the user manual
The User FMEA will look at installation, use, and end-of-life situations.
All of the FMEA methods (Design, Process, System, Functional, User) can also be applied to software.
In a Software FMEA, we are not only interested in potential software bugs but errors in interfaces and errors in boundary conditions.
Excellent tool to use if you have a set of bugs and are trying to determine the likely cause.