How to Conduct Root Cause Analysis in Manufacturing

Critical to Lean manufacturing, root cause analysis (RCA) is the formal process of tracing a disruption or issue to its source. RCA seeks to treat not simply the symptoms of an issue, but to eradicate symptoms altogether by finding and addressing the specific cause or causes. In treating problems at their roots, the intention is to create a “ripple” effect down the entire process, resulting in a chain of improvements.

While some manufacturing issues can be forecast, it’s not always possible to predict problems before they occur, which makes preventative planning a challenge. Though RCA is reactive, it provides a standard structure for problem-solving, and therefore streamlines the time it takes to identify the root of a problem. Once established and found to be successful, RCA can enable proactive measures on the factory floor.

Identifying the root cause of a problem to develop a sustainable solution carries widespread benefits for an entire organization.

Establishes and improves realistic processes.
Once a team performs RCA, they begin to establish a standard operating procedure for addressing issues company-wide. While specific steps can differ across issues, RCA solidifies a standard, practical approach to solving any problem, in any department, on any team.

Reveals inefficiencies and vulnerabilities.
While RCA is not meant to send teams “looking for problems,” it can uncover issues that may have gone unnoticed without a closer look. Performing RCA can sometimes result in the workplace equivalent of killing two birds with one stone.

Cuts costs.
Since RCA treats the source and not the symptoms, chances are that eradicating the cause of a problem prevents further effects. Therefore, RCA can save organizations time and money spent on repeatedly addressing symptomatic issues, and can shorten downtime, reduce defects and improve processes in the long term.

Enables and encourages proactivity.
Once teams are able to identify root causes of problems, they will begin to look for other areas for improvement. This mindset can vastly improve an organization-wide approach to safety, maintenance and quality.

Multiplies improvement across departments.
If one department experiences success with RCA, they can communicate and transfer the process to other departments, creating a network of continuous improvement. The data gathered during one RCA process can be communicated to other teams, who can use this information to understand and address some of their own challenges.

Benefits of Root Cause Analysis for Manufacturers

In manufacturing, RCA is frequently used to find the source of machine breakdowns, malfunctions, degraded product quality or accidents. RCA is especially critical in manufacturing when it comes to safety; maintaining a safe, healthy environment free from hazards improves the employee experience, keeps costs stable and ensures products reach customers on time and in the optimal condition.

Chances are, if RCA is not deployed to fix a problem in a manufacturing setting, the problem will likely occur again, with potentially dangerous consequences.

As we’ll discuss below, there are multiple approaches to conducting RCA, depending on the complexity or scale of the problem, the availability of resources or the learning styles of the problem solvers themselves. While some organizations tend only to focus on the mechanical or equipment-related aspects of a problem, it’s critical to acknowledge any human elements that may have contributed to an issue, so that team members can recognize and learn from their mistakes.

No matter the technique, RCA comprises four distinct steps (from TWI Problem Solving):

1. Isolate and state the problem.
The problem can be general or specific, cosmetic or systemic, but all team members involved must understand what it is and why it is an issue. All parties must identify the problem as such without bias — i.e., the problem must be objectively stated and observed.

2. Prepare for the solution, collect evidence and assess impact.
This is where active problem solving begins. Using any number of RCA tools and techniques, team members list as many symptoms and associated causes as possible and record all factors that may have led to the issue at hand. It’s important not to confuse symptoms and causes — if an issue can be attributed to anything at all, it’s likely a symptom of a deeper problem. In the case of a mechanical malfunction, factors like lubrication, cleanliness of the environment, age of the equipment, floor layout and operator training should all be accounted for.

3. Correct the problem: Improve skills, modify behaviors and improve methods.
This step can include updating standards, developing new processes, implementing new training programs or technology, or establishing new channels of communication.

4. Check and evaluate the results.
A process for auditing and assessing changes must be established. Results must validate the effectiveness of the solution. The solution can always be adjusted to improve the results, as long as the auditing process is adjusted as well to account for any updates.

Once an RCA is completed, problem solvers may find that the root cause can be applied to other areas within an organization, and therefore may provide a standard solution to multiple problems.

Many organizations and teams find that a manual approach to RCA is most helpful for the largest number of people. This means literally writing down or diagramming causes and effects, so that all parties can visualize exactly where the problem started, and how different symptoms connect to each other. Making the theoretical visual or tactile also helps the human brain retain information.

RCA tools are many and varied, but what follows are some of the most common and effective.

The Five Ways
This is typically the first approach taken to address an issue, since it is straightforward and anyone can execute it.

Initially developed by inventor Sakichi Toyoda (father of the founder of the Toyota Motor Corporation), the Five Whys encourages asking “why” a problem occurred repeatedly until the root of the solution is uncovered. Toyoda likened it to a curious child — young children often ask adults “why” until there are no more answers to give. In manufacturing, each successive round of questioning should reveal more information about the source of the problem.

Using the Five Why approach to RCA may take more or fewer than five steps, but the methodology facilitates critical thinking until all barriers to the answer are removed. This technique is often enough to solve most issues.

Fishbone Diagram
When members of a team are telling multiple and varied stories about one issue, a more powerful technique is required.

Popular in the manual approach to RCA, a fishbone diagram is a visual chart illustrating cause and effect. The “head” of the fish represents the problem (or symptom) and the “bones” are the smaller causes that contributed to the problem. A fishbone diagram is better suited to more complex problems than the Five Whys approach, as it helps problem solvers see that an issue can have multiple causes. However, the Five Whys can be used to identify and list causes within a fishbone diagram.

Fishbone diagrams are popular at the management level, especially for strategic planning. Seeing where and how problems developed in the past can help leadership take preventative measures and fill in gaps moving forward.

Pareto Chart
A combination of a line graph and a bar graph, a Pareto chart is a visual representation of the frequency of issues, essentially ranking issues so teams know what to address first. Other RCA techniques can then be applied to individual issues, since there can be different causes for each. Problem solvers may discover that, once they find solutions for the most pressing issues, those same solutions may be applied to each successive, less frequent issue.

Is/Is Not Analysis
This is another visual tool that splits a problem into “is” or “is not” categories. This approach helps teams identify which conditions contributed to a problem and which did not, and helps teams avoid conjecture. The Is/Is Not analysis is often used when multiple rounds of previous RCA have been ineffective in preventing a problem from recurring.

The Five Whys Example
This example of a Five Why approach comes from Taiichi Ohno, who pioneered the Toyota Production System:

1. Why did the robot stop?
The circuit has overloaded, causing a fuse to blow.

2. Why is the circuit overloaded?
There was insufficient lubrication on the bearings, so they locked up.

3. Why was there insufficient lubrication on the bearings? 
The oil pump on the robot is not circulating sufficient oil.

4. Why is the pump not circulating sufficient oil?
The pump intake is clogged with metal shavings.

5. Why is the intake clogged with metal shavings? 
Because there is no filter on the pump.

Fishbone Diagram Example

Using a fishbone diagram, here is an example straight from the shop floor of a mechanical engineering facility:

1. A belt breaks on a lathe and is replaced by a technician.
2. A short time later, the belt breaks again. Analysis reveals that there is a misaligned spindle shaft causing the belt to overheat.
3. It is also discovered that the technician did not know to examine the spindle for runout.
4. Two contributing root causes emerge:
   a. The spindle shaft needs to be replaced.
   b. The technician who changed the belt needs further training on lathe spindle maintenance.
5. Once these two root causes are addressed, the belt will last longer and the technician will be better equipped to assess all parts of the lathe regularly.

RCA can be used to address almost any type of problem in any industry, specially issues with gray areas or many moving parts. Other industry applications that may utilize RCA include:

• Accident and risk analysis
• Disaster management
• Food processing industry (ex. tracking bacterial outbreaks)
• Industrial engineering
• Industrial process and quality control
• Information technology
• Medical fields
• Pharmaceutical production and research
• Robotics

Though RCA tools and techniques can be applied to almost any problem, large or small, there are some issues for which RCA isn’t necessary. For example, simple issues with an easily identifiable cause do not require an RCA; the process of diagramming and analyzing can be complicated, and may create more work than is necessary for problem solvers.

Root cause analysis is typically used to uncover three types of problem sources, which sometimes occur in combination:

• Physical causes, such as a malfunctioning part or environmental influences
• Human causes, such as an incorrectly installed part or operational error
• Organizational causes, such as a poorly-designed process or underserved team

Whatever the cause or causes, RCA is recommended for addressing the following three types of problems:

• Persistent or recurring issues
• Critical failures that pose safety hazards
• Single failures that impact a larger operation or timeline

Since the cause(s) of any of these issues may not be clear-cut or attributable to one single source, RCA can help shine a light in the “gray areas.” However, doing so can require an investment — of time, money, personnel and even software for data collection and analysis. This is why formal RCA is recommended for more complex problems, since using RCA techniques on black-and-white issues can cause further disruptions to production.

RCA is a fundamental component of TWI Problem Solving, in which frontline supervisors and their teams learn to recognize (and even foresee) problems that may negatively impact production, workflow, worker safety, product quality, communication and customer satisfaction. How TWI Problem Solving (PS) differs from “a la carte” RCA is its acknowledgment and involvement of the people behind the work:

• Did a machine malfunction because the operator lacked the knowledge or training to operate it safely?
• Is production slow because workers are disengaged or frustrated?
• Do workers understand the importance of specific tasks?

TWI PS focuses on addressing the human element of root causes, looking past the cold and mechanical to the technicians and operators actually making decisions on the factory floor.

When people are actively involved in the problem solving process, they take ownership of their part in any disruptions, and learn to address and prevent future issues through hands-on training. Built on a foundation of Training Within Industry (TWI) methodologies including Job Instruction, Job Methods and Job Relations, TWI Problem Solving provides a structured approach to embedding RCA into the organizational culture — soon becoming “just the way we do things.”

Do I need specific software to perform RCA?
While there is technology out there to help teams conduct RCA, you rarely need more sophisticated tools than a pencil and paper. Many RCA techniques rely on a visual element to help problem solvers literally see how cause leads to effect. What’s more, the tactile act of putting pencil to paper or marker to whiteboard helps most people retain information better.