Review of A Case Study on Weld Spatter and Pinholes, Part 2
In my last post, I continued with a problem-solving case study on a company that manufactures stainless steel pressurized vessels. In Part 2, we completed steps 2, 3, and 4 from the problem-solving roadmap.
To review, the team’s problem statement was as follows:
Pinholes and weld spatter are occurring on 100 percent of the stainless steel tanks at a rate of approximately eleven hours per day, creating significant amounts of rework. Based upon a recent study, as many as 100 hours per week of rework time have been observed for these two problems, and the trend is constant.
A step-by-step method
In this post, I will continue with the step-by-step method for solving the problem involving weld spatter and pinholes. As you will see, we will often realize additional benefits in addition to solving problems by following this method.
5.0 Record known changes
The team searched to discover any changes that might have occurred which could have impacted the level of weld spatter or pinholes. Since no hard data had been recorded, the team was forced to interview other employees that had worked in the welding area for some time. The only known change was that several years prior, the company had changed both the anti-spatter material and the method of dispensing it. According to the employees, the anti-spatter material had changed from a water-based material that was brushed onto the tanks, to the material they were using.
When asked if they remembered the impact on weld spatter, it was clear that some preferred the brush-on material, which they claimed resulted in less spatter. Still others believed that the new material was superior. With this split in opinions, the team elected to test both types and application methods for the anti-spatter material. Testing revealed no difference between the two materials.
6.0 List Defect-Free Configurations (DFCs)
You will recall that a Defect-Free Configuration, or DFC, is found by asking where or when you would expect to see the problem. You may see the problem occur in such instances, at a significantly lower rate, or you may not see the problem occur. The team evaluated the process and information they had collected and concluded that welding areas away from the structural rings could be considered DFCs on the basis of the smaller amount of weld spatter and pinholes present in those locations. Since the team was convinced that there was a Defect-Free Configuration available, the next step was to search for and record any distinctions.
7.0 Record distinctions
The team carefully considered each item on the list of symptoms and concluded that the gap between the tank and the structural rings was a clear distinction. They noted that when there was a gap present, the weld operator was required to fill in the gap with weld wire. No other noticeable distinctions were found.
8.0 Record possible causes
The team was now ready to develop a list of potential causes for the weld spatter. I gave them a choice of using a cause and effect diagram or causal chains to generate this list. After explaining how to use both tools, the team elected to use the causal chain technique.
Coming in the next post
In Part 4 of this series, we will continue working our way through the various steps in our problem-solving roadmap and present the causal chain the team had developed.
Until next time,
 Bob Sproull, The Problem-Solving, Problem-Prevention, and Decision-Making Guide, CRC Press, Taylor & Francis Group, 2018
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