I having being saying for long time that 80% of quality issue on products comes from design and 20% only of quality related issue comes from manufacturing and procurement causes. On behalf of my clients I have been performing Root Cause Analysis on defectives products for a while now, and I have to admit that very frequently problems initiate from design, conception, engineering and lack of planning more than from manufacturing itself. This is where DFMEA take all its importance.
When performing New Product Development, there are typically different ways to operate:
The amateurs will start developing straight away their product and will adjust on the fly the design and engineering, and this mass production after mass production while catching fire like a firemen.
The most professional one will plan and spend time at the beginning of the process to attempt to anticipate all the problems that can be identified before they finally occur. The professional will supply with solutions to all those failures even before the design start.
In this article, I explain how a design / engineering process can be optimized, made more reliable and how it can anticipate product failure even before the design and engineering start by using a DFMEA process.
# What is DFMEA
DFMEA stand for Design Failure Mode and Effect Analysis. I think the denomination already easily translate in what it is but for those who have no quality engineering background, the DFMEA is an organized methodology allowing to identify cause of risks and potential failure which can happen on a new or modified design products and what are the effect of those failure on its environment (user, regulation, related process or product). In short, it identify what can cause failure, what will be the effect of those failure and help to establish patch to avoid those failure. DFMEA is a sub-section of FMEA .
The methodology particularly establish a scale related to risk criticality, risk prioritization so the designers and engineers know on which problem, cause and risk they should focus their effort first.
This methodology was invented in the 1960 during the space race when rocket were exploding without any possibility to perform a root cause analysis post explosion (as all the product was spreader into small piece). Scientists decided to work the way around by attempting to identify potentiel risk or failure during design in a proactive way before problem happens and not just in a reactive way after the rocket exploded.
DFMEA is a methodical and organized approach allowing to anticipate a maximum of potential failure due to design and conception very early in the New Product Development design and engineering process.
# Why using DFMEA
DFMEA can be considered as an investment. An investment in time, ressources and effort allowing later to avoid having to manage with non quality cost such as fixing, maintenance, recall etc… I don’t know any buyer, importer, retailer or even manufacturer willing to deal with recall, repair and maintenance of the products they sell or manufacture.
The DFMEA process allow to drastically reduce those non quality cost by anticipating issue and by supplying with solution, corrective action and patches during the hardware product development process and not after it. Remember that at the Product Development stage of an hardware product we are still nearby the white sheet of paper so change and correction are still made at lower cost than later on when the product development phase is achieved, even worse than when product is in manufacturing stage or distribution stage.
Modifying a product when it is already in manufacturing stage will involve to perform again some engineering, to perform a validation prototype, potentially to certify again the product (as it is has been modified), potentially to modify tooling, jig or fixture, potentially scrap some stored material, reorganize part of a production line etc… All of this involve a lot of costs and waste.
Modifying a product which is already on the market in distribution mode will be even worse because on the top of the all the modification which have to be made on manufacturing and engineering, on the top of this, some recall, repair or replacement of product to customer might be necessary. In this case the non quality cost increase drastically and may even eat up all the margin generated by the sale of the product.
From what I see, many factories and manufacturers who design (or pretend to design) products in Asia just skip or botch this process of DFMEA. Most of time, they don’t even know what is is. it is still actually an important one when you consider mass production of a physical product as non-quality cost scale quickly when mass production is considered.
If you are about to develop a new products and are not yet entered into mass production phase, and if you have not perform DFMEA yet, then I highly recommend you to stop everything you are doing now and to perform a DFMEA before going further.
# How to perform DFMEA
The DFMEA process work as follow:
Step 1: Identify the stake holders which may have an influence on design, engineering, manufacturing, usage, and maintenance of your product. Take all those people and lock them in a room one or more day to brain storm all the possibile failure which may happen using the next steps below
Step 2: Establish the scope of the DFMEA.
Step 3: List all the functions of your products in a table
Step 4: Establish all the potential failure possible on each function of your product and list them in your table face to each function
Step 5: For each failure establish the list of all the consequences of those failures on the product, user, environment, regulation and other related third party product or other systems around. List them in your table face to each failure.
Step 6: Establish the severity S of each failure with a rating for this severity from 1 to 10, where 1 is the less significant and 10 is the more catastrophic, and report it to the table in a new column face to each failure type.
Step 7: Establish all the potential cause of those potential failure and list them in the table in front of each failure.
Step 8: Establish the occurence rating O for each potential cause from 1 to 10, where 1 is very unlikely and 10 is the most inevitable to occur, and report it in the table in a new column
Step 9: For each cause list the current process control in place and associated and report it in the table in a new column aligning with each cause.
Step 10: For each control establish the detection rating D from 1 to 10, where 1 is the control has the maximum chance of detecting the failure or the cause and 10 has no chance to detect the failure or the cause, and report it in the table in a new column aligning with each cause.
Step 11: Calculate the Risk Priority Number (RPN) by multiplying S by O by D, and report it in the table in front of each cause in a new column
Step 12: Calculate Criticality by multiplying S by O, and report it in the table in front of each cause in a new column
Step 13: Identify and list recommended actions to prevent those failures by starting with item which got highest RPN and highest criticality.
Step 14: For each actions, identify and list who is responsible for it and the expected target completion dates
Step 15: Implement the actions and update the FMEA table to update S, O, D , RPN and Criticality. Normally all of those should have lowered in number.
# When to implement DFMEA
Ideally the DFMEA should be implemented during the design phase and as soon as possible as the product development phase is started but in this case it should be continually implemented at different stage of the process. If you implement it to early, then the engineering is not yet established. If you implement it too late then the product development moved forward too much yet and will imply a higher modification cost.
# Working with an example
An electronic product such as a DVR product is supposed to be installed in a fleet of vehicle such as bus. The vehicle is going to be used in Alaska for transporting school kids from remote location to city. Bus number : 200. Expected unit cost of the system : 500 USD. Expected setup fees to install the system : 500 USD. Expected maintenance cost : 200 USD / year.
Total expected fix cost: 200 bus x 1200 = 240 000 USD. The client think to spend around 1 to 2% (around 5000 USD) of this budget on DFMEA process to avoid to inflate maintenance cost which if the system fail will cost him to have someone to fix to around 500 USD / day. If 200 pieces fail, it will generate an extra cost of 100 000 USD.
Hence, during the design phase, instead of just relying on his asian manufacturer, he decided to conduct a DFMEA by appointing a consultant to lead the DFMEA. The consultant setup several days meeting with engineers, designers, manufacturers and customers, sit them on a table in order to optimize the design before anything else.
As the product is an electronic product and is setup in a vehicle riding in a very cold region of the USA, already a few potential failures and causes are identified: life cycle of components, temperature and humidity range acceptance of electronic, reaction of the assembly to the vibration of the engine (unsoldering of component), temperature reaction for cable, etc….
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Let’s take as example the failure of component due to cold temperature.
Function: recording function of camera
Failure 1: the camera doesn’t see anything on his sensor
Cause: sensor has not been chosen properly face to environmental condition
Patch: choose a sensor capable to handle low cold temperature
I will add a full excel table soon indicating how I filled it. If you want to receive it just subscribe to the newsletter on the right part of the page.