Methods and tools for problem solving
Problems are at the heart of the Lean culture and are part of the daily life of production sites. A structured problem-solving approach that is followed in the field allows for sustainable improvements in industrial performance.
In this article, we propose you to review together the techniques and philosophy around industrial problem solving:
- The process of solving a problem
- How to analyse the causes of a problem
- Which method to use to carry out this approach (8D method, PDCA, DMAIC, QRQC, CARRE D'AS,)
- The most commonly used specific tools (5 Whys, QQOCCCP, is/is not analysis, yamazumi, Ishikawa diagram, pareto diagram, checklist...)
What are the steps to solve a problem in the factory? 🏭
First of all, it is necessary to clarify the basis of reasoning: what is a problem?
From an industrial point of view, a problem is defined as a gap between a given situation and the expected standard (Source: Wikipedia).
Problem-solving consists in finding the cause of this situation which is not in line with the expected results and putting in place lasting solutions.
Toyota has formalised the process very well for decades:
Let's go through the different stages of this process:
- Initial perception of the problem: This first step usually consists of describing the problem.
- Clarify the problem: Here, we try to reduce the search area as much as possible and to document the problem in order to find the best solution.
> What was the expected result? What information can be extracted from the field? Can the problem be broken down into simple entities? This brainstorming step allows to understand the symptoms in order to solve the problem in an efficient way.
- Locate the area/Point of Cause: Here you have to go back in the process to understand where the problem started.
> For example, if a part is defective, the problem may be due to an anomaly in the raw material or because of a defect in the machining stage.
- Searching for the root cause: Generally, this step is done using the 5 Whys method. The aim is to identify the source of the problem in order to solve it in a sustainable way and not in a superficial way. This questioning is essential.
- Think about solutions: Once the root cause has been identified, sustainable solutions can be thought of. (brainstorming)
- Test the solutions: This step is important, it simply validates the hypotheses and solutions considered in step 5. Only a real test can validate the solutions in a sustainable way.
- Standardize and generalize to similar problems.
Once the approach has been set, there are methods that make it possible to respect this approach by following a predefined framework. We will see right away.
What methods should be used for the problem-solving process?
Structured methods make it possible to identify and solve a problem in a sustainable way. They usually follow the problem-solving approach mentioned above and are divided into several steps. The best known are:
La méthode 8D: Artillerie lourde de la résolution de problème, le 8D se compose en 8 étapes
- D1: Team building
- D2: Describe the problem
- D3: Identify and implement immediate actions/Security
- D4: Determine the causes of the problem
- D5: Determine definitive and permanent corrective actions
- D6: Implementation of solutions
- D7: Preventing the problem from recurring elsewhere
- D8: Congratulations from the teams
La méthode PDCA ou Roue de Deming qui se décompose en 4 étapes:
- Plan: This step consists of analysing the data/problems and planning the actions to be implemented.
- Do: Deploy/implement the actions defined in step 1.
- Check: Check the result of the actions performed. Compare the results with those expected
- Act: Here either the results are as expected, or we have to adapt the solution and go back to the "Do" stage.
La méthode DMAIC
La méthode QRQC (Quick Response Quality Control):
More than a method, it's a state of mind. This method guarantees a quick response (Quick response) and also a thorough resolution of the problem (Quality control). Below is a schematization of the process.
The CARRE D'ASmethod
- Choose an issue
- Analyse the problem
- Search for causes
- Search for solutions
- Trying / Testing solutions
- Decide which solution to implement
- Apply the solution and monitor the results
These seven steps can be summarized in four phases:
- Choosing a problem
- Search for causes
- Search for solutions
- Decision / Implementation / Monitoring
The specific tools most used in the factory
Some tools may be necessary to structure the different steps of the above methodologies, for example, for the search of the root cause (8D and DMAIC), using the "5Why" tool allows to push the analysis of the causes.
To characterize the problem during the QRQC, the use of the QQOQCCP and the is/isn't analysis is sometimes essential.
Here is a non-exhaustive list of the most commonly used tools for problem solving:
La méthode des 5 Pourquoi
Used mainly to identify the root cause, this method consists of asking "Why?" until you get to the source of the problem. For example:
- Why was the part defective? Answer: A machining defect
- Why has a machining defect occurred? Answer: The machine was not set up correctly.
- Why weren't the settings correct? Answer: The instructions were ambiguous for the given situation.
- Etc. back to the source of the problem.
The QQOCCCP (Who, What, Where, When, How Much, How and Why)
The aim here is to characterise the problem by asking these 7 questions. This method can be combined with is/is not.
Analysis is/is not
It also helps to define the scope of the problem, which is why it can be combined with the QQOCCCP. This tool allows the elements to be sorted into two categories: those related to the phenomenon under study and those not related to it.
Le diagramme de Yamazumi
Workstationgraph: Each step is represented by a block and the associated time. This tool allows you to identify non-value added steps with their associated time. Here is an example:
Le Diagramme d'Ishikawa (ou Diagramme Causes-Effet):
It helps to identify the causes of a certain situation.
- Define the effect to be observed: defect phenomenon, characteristic of the product or process.
- Draw an arrow from left to right in the direction of the effect.
- Describe the main factors that are the potential causes of what is observed
- Generally the 5M below (+eventually Management and Financial Means)
Probably the simplest tool but not without usefulness, the Check-List allows of course to list the important steps.
There are actually a multitude of tools that can be used to solve complex problems in the plant: affinity diagram, pareto diagram, tree diagram...
We would be delighted to hear your views on our selection of problem solving methodologies so please email us at email@example.com. We will get back to you as soon as possible.