Fishbone Diagram
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In a case that our experts came across, the project called for ACC (Autoclaved Aerated Concrete) blocks to be used for building walls.
Now, concrete blocks have various densities and hence the desired strength is specified as per this factor. However in this case the grade with required strength was not mentioned in the specifications and thus the right ACC blocks were not ordered. It so turned out that the blocks were not strong enough, and ended up breaking while cutting during the construction. Upon delving into the problem, the root cause was found and addressed. But this kind of oversight leads to wastages of material and time and increases the workload of the contractor.
In all it leads to an undesirable, stressful situation. If one considers any construction material there are various grades that are available in the market. In the absence of clear specifications, the contractors end up using materials of various grades that result in quality control issues.
When an issue is identified, it is important that the root cause is investigated as well. What usually happens on site are just rectification jobs whenever problems arise but this is not enough. Unless project managers plug the root cause, they will never have confidence that the problem will not recur. For this purpose Quality Control teams use a scientific method called the Fishbone Diagram.
A Japanese quality control expert, Kaoru Ishikawa invented the fishbone diagram. QC professionals can use this tool to understand whether the potential causes of specific events in construction – so whether the issue is related to materials, supervision, methodology adopted, environment or supervision. One of the first steps in creating a fishbone diagram is determining the factors that contribute to variations within a process.
Ishikawa describes these contributing factors as the 6 Ms in the manufacturing world: man, machine, method, material, measurement and Mother Nature.
The fishbone diagram enables one to delve deep into the matter and thus resolve it.
Here’s an example that illustrates the need of the Fishbone diagram tool.
In a construction project, after laying marble flooring, the contractor proceeded with the other building works and covered the floor with protective plastic sheets that were provided.
However, the plastic cover was never in position and the new floor kept getting exposed and dirty. Upon delving into the issue it was found that the contractor had not used a particular tape that was also provided to stick the sheets in place so that they do not move and protect the expensive and delicate marble flooring.
So this shows that going to the root cause is an easier and sustainable way of solving issues on site.
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