Portuguese Tire Manufacturer Saves Thousands Using DMAIC Methodology

A recent study of the implementation of Six Sigma at Continental Mabor, a tire manufacturing company located in Famalicao, Portugal, provides a step-by-step look at putting Six Sigma’s DMAIC methodology into place. The study, published at the 2017 Manufacturing Engineering Society International Conference, was written by F.J.G. Silva, a professor in the school of engineering at Polytechnic of Porto, Portugal.

Continental Mabor instituted Six Sigma because tire manufacturing is an intensely competitive business around the globe and “continuous flexibility and adaptation” is necessary, Silva wrote, adding that to achieve success, “it is crucial to seek operational excellence.”

Here is an overview of how Continental Mabor approached implementing the Six Sigma methodology of DMAIC, which stands for define, measure, analyze, improve and control.

The company focused on improvements in the rubber extrusion process, particularly the mixing, preparation and construction departments. The amount of material generated in the process – which is later reused for other purposes – is one of the indicators for the company on how efficient the operation is running. The focus is to limit the amount of extra material generated during the tread and sidewall extrusion process, called “work off.”

Define

To accurately define the problem areas in the process, the company drew up a project charter that identifies problems, establishes objectives and defines the scope of the project (including the employee teams involved). A project charter also:

Establishes the business case for how the project will impact overall organizational strategy

Measures the impact on the business of the current problem and measures the gap between where things are and the desired state

Creates a clear scope for the project with identification of the areas where teams will focus to prevent “scope creep” – moving into areas outside the defined perimeter of the project

To create the charter, the company used a Gantt chart, a horizontal chart that maps out a production schedule. They also used a SIPOC diagram to plot the extrusion process in greater detail. SIPOC stands for suppliers, inputs, processes, outputs, and customers. A SIPOC is a way to see an entire process in one graph and see the relationship between inputs and suppliers and the output for customers.

Measure

To get a handle on the current state of the extrusion process, Continental Mabor leaders then created a data collection plan. This included measuring the amount of rejected material during the extrusion process. Data was collected for 30 weeks. After this period of measurement, the company could determine the percentage of unused work off material generated in the tread and sidewall extrusion processes.

Analyze

With the amount of data collected, the focus then turned to find the root causes of the defects in the process that caused variation in the number of materials wasted. The company used an Ishikawa diagram to find the cause and effect relationship between various activities and inputs into the process and the problem of generating unused material. They then used a Pareto chart to prioritize which potential causes seemed to have the most unfavorable impact.

They discovered that one machine in the sidewall extrusion process was not performing as well as others, leading to a significant increase in extra material. In the tread extrusion process, they discovered that the method for feeding the machines was creating problems with machine stoppage and jamming.

Improve

In this phase, a list was made of all the problems and root causes, then the subsequent action taken to improve these issues. These include changes to the machinery itself and changes in the methods used by employees to feed material into the machine.

Control

With the improvements in place, data was then collected on the changes in the process. The company reduced the amount of work off material by five tons per day. After factoring in the cost of improvements to the machinery, the positive impact on the company’s bottom line was 165,000 euros per year, which translates to a little more than $200,000 U.S. dollars.

In his conclusion on the process improvement at Continental Mabor, Silva wrote that “the use of Six Sigma methodology played a decisive role in the achievement of the proposed goal, ensuring that there was a systematic and disciplined approach to the issues at hand through the DMAIC cycle.”

Productivity and Quality Office