Our Production Manager, John, is heading out to the production floor. He sees that his highest priority line is down again. “What is it this time?” he asks. His top mechanic replies, “I can’t believe we are down for a conveyor. We’ll be back up before long, if we have the right sprocket.”
John decides to do a 5 Why analysis even though this appears to be a simple fix. In the old days they might have been satisfied with replacing the sprocket. Today, John wants to make sure that the replacement does not fail prematurely. He wants to address the root cause.
We have already looked at simple 5 Why’s. Several readers commented that many real life examples are not that simple and do not have straight-line answers. Today we’ll look at a complex, multiple path 5 Why.
You will still go through the same basic 7 Steps of an Effective 5 Why as addressed in a previous post. The difference with the Multiple Path 5 Why is that there will be more than one answer to some or all of the why’s. My suggestion is that you only include the answers that you believe are contributing to the issue. The 5 Why can spin out of control and become too complex if you include every conceivable possibility. If you are unsure, you can capture the idea and verify if the condition exists. For example, if someone says, “maybe the bearings have not been properly lubricated.” Capture the idea and verify the condition of the bearing. If the bearing hasn’t been lubricated properly, include it in your Root Cause Analysis. There are situations where you may want to include all options which we’ll discuss next time. Today, we will only include the conditions that we believe exist. Let’s look at the sprocket and do a thorough Root Cause Analysis (RCA):
Problem Statement: Conveyor stops due to a broken sprocket
Why #1: Why did the sprocket break?
Answer: [a] excessive stress [b] wrong sprocket
Why 2a: Why is there excessive stress?
Answer:  dirty conveyor  worn bearings  line speed exceeds conveyor design
Why 2b: Why is the wrong sprocket on the conveyor?
Answer: Correct sprocket was not in stock when replaced last time.
Why 3a : Why is the conveyor dirty?
Answer: Not on cleaning schedule
Why 3a : Why are there worn bearings?
Answer: Bearings have not been PM’d
Why 3a : Why isn’t the conveyor designed for the actual line speed?
Answer: Conveyor was taken from the bone yard to finish an in-house line modification
Why 3b: Why wasn’t the right sprocket in stock?
Answer: Inaccurate inventory
Why 4a : Why isn’t the conveyor on the cleaning schedule?
Answer: New conveyor was not added to the cleaning schedule
Why 4a : Why haven’t the bearings been PM’d?
Answer: Mechanic didn’t know about these bearings
Why 4a : Why was the conveyor taken from the bone yard?
Answer: Management/Engineering decision to manage the cost of the project
Why 4b: Why wasn’t the inventory accurate?
Answer:  parts usage is not consistently documented  parts inventory is overdue
Why 5a : Why weren’t the new conveyors added to the cleaning schedule
Answer: Early management failure
Countermeasure: Add sanitation requirements to the project management checklist. Update the sanitation schedule to reflect the new conveyor.
Why 5a : Why didn’t the mechanic know about the bearings?
Answer: [2.1] New mechanic that is unfamiliar with the line changes [2.2] Conveyor section pulled from the bone yard was not added to the PM system
Why 6a [2.1] Why wasn’t the new mechanic familiar?
Answer: See 5a [2.2]
Why 6a [2.2]: Why wasn’t this section of conveyor added to the PM system?
Answer: PM’s had already been updated when the decision was made to use conveyor from the bone yard.
Countermeasure: Modify the post project review procedure. Changes to reflect the need for full analysis of the impact of project changes on Safety, Sanitation, PM’s, etc. Update the PM’s to include the new conveyor.
Why 5b : Why isn’t parts usage documented properly?
Answer: No system when the parts clerk is not on site.
Countermeasure: Implement parts usage form to be used on all shifts. Order sprockets as needed to re-establish minimum quantities.
Why 5b : Why is the parts inventory overdue?
Answer: Overtime production prevented completing as scheduled.
Countermeasure: Schedule parts inventory as soon as possible.
John and his team have invested much more time performing a thorough RCA than if they had just replaced the sprocket. You can see though that the team has been able to identify several root causes that need to be addressed. What would happen if they did not address these root causes? They would likely have another premature sprocket failure. This premature failure would be the result of the same conditions that led to the first failure.
The great John Wooden said, “If you don’t have time to do it right, when will you have time to do it over?” If you don’t have the time to address the root causes now, you will likely be dealing with the same issues again. What issue is your plant facing today that warrants a good 5 Why Root Cause Analysis?
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