Does any of the following sound familiar in your business?
· Product flow needs improvement
· Nothing flows as easily as it should
· We don’t have consistent flow
Lean manufacturing addresses the issue of flow with the concept of takt time and designing processes to meet it. Takt time is the pace of customer demand. The work pace requires that the production schedules are leveled or smoothed over a period of time- 1 month, 3 months, or longer.
Using takt time to design processes that improve flow
It’s unlikely that customer demand is smooth enough to meet the requirements of takt time. So, some method of smoothing the production schedule is required. That is a topic of its own that requires more in depth coverage than I will go into here.
1. For the sake of this discussion, we’ll assume that the schedules are leveled and takt time can be determined. Great! Now there’s a pace that can be used to establish smooth flow in the operation.
2. The next step is to evaluate the work content of the processes involved so that they can be arranged to meet the required flow rate. Work content is measured by timing each step in the process, manual processes and automatic or machine processes combined with manual processes.
3. If we know the required pace and the cycle times of the processes, we can design the work to meet the required pace. For strictly manual processes, we can calculate the number of people required by dividing the total cycle time (or work content) by takt time. When machines are involved, we can determine if the available machines have the capacity required to meet takt time.
The end result is standardized work, which defines each processing step, the amount of cycle time required for each step, and the total time (equal to or slightly less than takt time). It also defines which station or operation executes each processing step and the required sequence of operations.
When takt time is established and an operation tries to run at the required pace, you’ll discover many pre-existing problems that have been preventing good flow all along. All of these problems will occur as they always have, but now the problems are exposed. Exposing the problems so that they can be solved is a fundamental concept of lean manufacturing.
What traditional manufacturing does wrong
Traditional manufacturing approaches hide problems by adding people, equipment, plants, overtime, outsourcing, etc. All of these countermeasures add cost and also hide waste. Unfortunately, whatever waste exists is being increased by adding resources. For example, when you double capacity to meet demand for a process that contains 25% waste, the new capacity will also contain 25% waste. You have just doubled the waste in the system.
Once pace is established and processes arranged to meet the pace (with a pacing mechanism), we would need to work with the teams to establish what they need to do on a continuous basis to achieve the required pace through problem solving. These issues may be quality related, shortages, scheduling and synchronization issues, etc.
One of the many objectives of lean manufacturing is to create an environment where the shop floor can ‘manage itself.’ When this happens, people are freed up to make further improvements. The goal is to move away from daily firefighting to a condition of constant improvement. It begins with takt time.
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