Bottlenecks & the 5 Focusing Steps
Just as a liquid gets slowed down at the narrow neck of a bottle, process bottlenecks - or constraints - are the part of a process that takes the longest time, often also taking the most work.
The capacity of a process is limited by its bottlenecks, which affect the entire Cycle Time. Bottlenecks can be reduced with targeted action plans, e.g. the 5 focusing steps, resulting in improved process throughput.
Why do bottlenecks occur?
Bottlenecks develop simply because in any process - be it a manufacturing line or business process - different activities take different amounts of time, or various stages have different capacity, due to uneven numbers of resources.
Factories often compensate for that by overproducing an item, which in turn leads to exacerbation of the bottleneck. Bottlenecks can also be a result of bad planning and poor coordination.
The reason they are so predominant in the supply chain is a good phenomenon having gone bad. In the 1970s, computerized material planning became successful - those systems had high accuracy and managers loved them, but sometimes they were not updated and teams would trust the machines completely, rather than seeing what was happening on their production floor, which led to an oversupply of material.
Finally, bottlenecks occur also because of batch processing. Some machines and people are only available at limited times of the day or week, and so to drive efficiency, raw materials are organized into batches, so that machines can run less frequently. The problem with this is that it assumes inventory being held at the preceding step, creating a bottleneck.
In a traditional batch and queue system, steps 1 and 2 will quickly form an overload of inventory occurring at step 3, making it the bottleneck, with steps 4 and 5 standing idle waiting for step 3 to complete.
Bottlenecks not only cause waste through overproduction but also lead to the steps down the line from them to continuous periods of standing idle.
How to solve bottlenecks with the 5 focusing steps?
In Lean, we analyze the value stream to reduce waste, and bottlenecks leading to additional waste deem them bad, correct? Not necessarily. Bottlenecks are like the neighborhood watch of your production line, they often point to problems in the process, but it’s rare for them to be their root cause. Bottlenecks cause slow Takt time - the time it takes to honor your client requests, but if you understand how to deal with them, you can improve your overall process.
One of the thinkers, that the Lean movement borrowed from, was Eliyahu Goldratt. He introduced a methodology known as the 5 focusing steps, which worked specifically on improving throughput, driving down Takt times, and elevating customer satisfaction. The 5 steps are introducing positive changes through ..bottlenecks!
Step 1: Identify the bottleneck
Goldratt’s theory of constraints stipulated, that if you improved throughput anywhere else other than the point of the bottleneck, you’d cause even further losses. It can be seen in the above table - if we improve the throughput of steps 1 and 2, even more items will pile up in front of step 3. If step 5’s throughput was improved, this too would be a waste, because its new improved speed could never be tried, since step 3 is not able to supply it at a speed that it’d need to reach its full capacity.
Leaders going on a Gemba walk should be on an outlook for people or machines that are always busy, while other people stand idly. It’s quite common for the person or machine, that has a large pile of work in front, to be the bottleneck.
Did you know?
Kanban Tool® visualizes process stages as columns, making bottleneck identification effortless. Try out this simple but brilliant approach, and take advantage of other virtual process board perks, e.g. WIP limits, Process Automation, Time Tracking & Reporting.
Step 2: Exploit/honor the bottleneck
To exploit a bottleneck, we first need to establish whether the bottleneck is a valid part of the process - be careful that the constraint is not an unnecessary step, i.e. management oversight.
If the bottleneck is a necessary, value-generating part of the process, then make sure that it’s only doing the work that is required. For example, in a development team, you may have reason to think one of the developers to be the bottleneck, but when you go talk to him, you may find out, that he had to deal with really poor requirements documentation. So besides coding itself, he had to spend the time, that he did not have, chasing down actual requirements. Once you make sure that he has all the information he needs, his development time can be significantly reduced.
Step 3: Subordinate the rest of the processes to the bottleneck
Meaning, that the bottleneck drives the speed of delivery. So, steps 1 and 2 should deliver at a speed that will generate a supply of work that the bottleneck can deal with. The Theory of Constraints calls this a drum buffer rope approach, wherein a metaphorical rope is tied to the constraint, causing the rest of the supply line to keep up with it. The rope ensures that the line does not supply the bottleneck too fast, nor too slowly, causing it to stand idly. The rope takes the role of a buffer, ensuring the team knows when it’s running out of slack.
Step 4: Elevate the bottleneck
At this stage, you look at how the rest of the production process can help out the bottleneck. For example, maybe steps 4 and 5 in our table can help out in step 3, if they find it overloaded. In Kanban, this process is known as swarming - the entire team looks to remove the bottleneck and get the throughput moving again. Of course, you can also look at improving the capacity of the constraint point: maybe more resources need to be allocated to that step, perhaps faster machines or automation of a kind will do the trick.
Step 5: Restart the process, re-check the bottleneck
The last step in the Theory is to ensure that you restart the process at the new speed, and observe how things are flowing through the bottleneck. If needed, start again from the beginning. You no longer need to target the constraint, once you realize that no matter the improvement you make, the bottleneck no longer improves your Takt time. When that happens, it means the meaningful bottleneck has moved to another area of your line.
Set up your process to deal with bottlenecks
Bottlenecks are always going to occur and you need to keep an eye out for them. Organizing your teams, or process lines in U-shaped cells can quickly let team members have oversight of the entire line. This way, team members can immediately notice bottlenecks occurring, and help out. Having Andons as part of the line can allow team members to stop the line when needed, or at least inform of the current flow.
For teams that don’t share an office, but collaborate on a virtual Kanban board, an effective solution to visualizing and dealing with bottlenecks is adding queuing lanes to the process. Each step of the board should be divided into work waiting, ongoing, and completed, or at least to “doing/done”. This way, if a bottleneck builds up, it will be clear within seconds where and for what reason it has developed - either a step is processing items too slowly or too quickly, or a step is being overloaded with tickets arriving from a preceding stage.
Additional ways to help resolve bottlenecks
Problem-solving techniques are also helpful when dealing with bottlenecks. Eliyahu Goldratt developed a technique called the Evaporating Cloud: often, bottlenecks occur because manufacturing processes deal with assumptions that are just not accurate. Evaporating Cloud looks at interdependencies in the process, at what needs changing, and to what ends. The occurrence of bottlenecks often hides the root cause of undesirable effects in production. This is why working with Lean methods is beneficial - the techniques help to ask the right questions to get to the root cause of your process’ bottlenecks.
Using the 5S, keeping the process lines clean, and going on Gemba all help to easily identify bottlenecks. Finally, inspecting the Cumulative Flow diagram lets you check the impact of the improvement initiatives on your bottlenecks, and on your process’ Cycle Time.
Key benefits of addressing and working with process bottlenecks:
- Increased productivity and shorter Cycle Times, with less stalling and production hiccups
- A standardized way to deal with process congestion & process change
- Contained overproduction - less waste in teams’ time and effort
- A more predictable and stable process throughput - leading to happier teams and satisfied customers