No matter the industry, manufacturing processes can sometimes fail in thousands of different ways. This makes it difficult to determine the exact cause of a failure when it occurs.
Luckily, there are comprehensive methods of tracking and investigating failures for more reliable manufacturing. While you can never fully eliminate the possibility of failure, conducting a proper failure analysis can help put you back on track to continuous improvement.
Let’s break down the elements of failure analysis.
What Counts As Failure in Manufacturing?
If you truly think about it, there are nearly infinite possibilities for a manufacturing failure, from miscalculating a measurement to a meteor falling on your production line (although we acknowledge that last possibility is very, very unlikely).
In fact, failure doesn’t have to be disastrous, like a machine breaking down and pouring smoke. Failure can also include a final product that doesn’t quite pass final quality checks. That being said, we should try to find some way of classifying types of failures in a very elementary sense so that they can be examined in more depth as you conduct your failure analysis.
Internal Causes of Failure
Internal causes of failure are factors that are within your control. This doesn’t mean that they are necessarily anyone’s fault or mistake – just that they are potentially fixable within your immediate environment.
Examples of internal causes of failure include:
- Misusing industrial equipment
- Incorrect assembly
- Incorrect measurements or temperatures during processing
- Misreading output values
External Causes of Failure
External causes of failure are factors that are outside of your control as a manufacturer.
Examples include:
- Inadequate sub-components from other contractors
- Weather conditions or natural disasters near your factory
- Absenteeism and labor shortages
- Damages during shipping
Oftentimes internal causes of failure are more easily addressed than external causes of failure. The main thing to take into account is that all of these factors can interplay with each other to various degrees, and it is crucial to acknowledge the full extent of possibilities when conducting your failure analysis.
For example, there are tried and true ways to reduce the potential for human error, just as there are incident report metrics to track the overall rate of error. You will probably need a combination of both tools.
Don’t worry about trying to label your potential failures as internal or external just yet. You don’t have all the pieces of the puzzle, which is why we’re going to introduce several tools to help you gather all the evidence for your failure analysis.
Key Mindsets & Skills For Analyzing Failure
In order to uncover root causes of failure, you have to think like an investigator. Tools alone aren’t going to do the hard work of analyzing your workflows, so don’t just go through the motions. Remember to be diligent and fully observe all the working parts of your manufacturing business.
Experts in failure analysis nurture the following skills to help in truly revelatory failure analysis:
- High attention to detail when conducting visual inspections such as Gemba Walks
- Knowledge of Lean & Six Sigma best practices
- Scientific mindset when drafting hypotheses and isolating key variables in testing
- Meticulous evidence collecting
- Patience when implementing new procedures
- Awareness of and adherence to current Good Manufacturing Practices (cGMP)
Try reminding yourself of the DMAIC approach to improve your analytical reasoning skills.
Setting Up an Example Failure Mode & Effects Analysis (FMEA)
The industry standard for assessing modes of failure is a tool called FMEA, which stands for Failure Mode and Effects Analysis.
There are 10 steps in a Failure Mode and Effects Analysis (FMEA):
- Review – the assessment begins with an introductory critical overview
- Identify potential failure modes – participants will mark areas where they suspect failures could occur, whether or not there is evidence of failure
- Identify potential failure effects – the effects of certain mechanism failures can have far greater impact for use and safety than failures themselves, so these effects are anticipated in the report
- Identify potential causes of failure – different than effects, pinpointing potential causes of that failure is a way of identifying a trigger or catalyst that may be the culprit of later problems
- Assign severity ranking – A number from 1 (negligible effect) to 5 (catastrophic failure) is assigned, depending on the results of the type of failure and whether only parts of the product are damaged or rendered irreparable
- Assign occurrence (probability) ranking – A number from 1 (extremely unlikely) to 5 (inevitable, frequent failure) is assigned to represent a range of the frequency of failures
- Assign detection ranking – A number from 1 (certainty of fault detection) to 5 (undetected by operators) is assigned to indicate the probability that failures will be caught and corrected by real-time operators, and is helpful for assessing the maintainability of a production system
- Calculate Risk Priority Number (RPN) – The RPN is calculated using the S, P, and D rankings above using the following formula:
RPN = Severity (of failure) × probability (of failure happening) × detection (the chance that the failure would go undetected before correction) - Outline action plan – at this stage, engineers will draw up a plan to correct the design risks in order to start testing their concluded hypothesis
- Recalculate RPN – finally, the RPN is redone to see the anticipated impact of the changed plan
Here are a couple of templates you can use for your own FMEA:
Other Tools for Process Analysis of Failure
You can use several other tools in combination with an FMEA chart to help with analyzing potential manufacturing failures.
This is just a small overview. If you want more detailed information about any of the below tools, be sure to click on the included hyperlinks to read our other articles about how and when to use them in your failure analysis.
Root Cause Analysis
Root cause analysis is the practice of uncovering the core issue – the root cause – of a problem or error in a process. It is a collaborative process of problem-solving by interrogating the situation at hand. There are many types of root cause analysis, and the two most commonly used, Ishikawa diagrams and the 5 Whys, are described below in more detail.
Quality Function Deployment
Quality Function Deployment is a comprehensive plan for setting up lean operations, with blueprints for production processes, marketing and sales, distribution, etc.
It is common for FMEA charts and QFD blueprints to co-exist as a master plan for lean-ifying manufacturing plants. In fact, it is recommended that FMEA charts are applied after setting up your factory for QFD.
5 Whys
The 5 Whys is a root cause analysis tool that uses questioning as a way of uncovering more detail about a situation. It works due to its repetition: by asking the question “Why” 5 times, you examine deeper issues at play that contribute to failure, as opposed to focusing on the surface problems. Here is an example:
- Why #1: Our manufacturing job order was canceled
- Why #2: We didn’t have the finished product ready in time
- Why #3: The required material components we needed arrived late
- Why #4: Our parts supplier misinterpreted our order request
- Why #5: Our supply chain system is not streamlined and user-friendly
Ishikawa Diagram
Ishikawa diagrams, also known as Fishbone diagrams, are charts that aid in root cause analysis by separating and classifying any potential problems on a line diagram. It is an orderly method of cataloging many issues that contribute to an eventual failure. When completed, the diagram resembles a fish skeleton:
