An unlinked production environment is like an accordion. Some processes move faster than the average and some operate more slowly. As a result, parts move through the system at varying speeds, only to end up in piles of inventory scattered along the value stream.
Even with a takt time in place, there can still be some fluctuation in the actual performance of processes, if they are not somehow linked together. This fluctuation gets even more complicated when scheduling is done at multiple places in a value stream. For this reason, a pacemaker is often established. A pacemaker is the single point where a production process is scheduled. The upstream processes don’t produce without a pull signal originating from the pacemaker.
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The pacemaker simplifies production oversight. Having only one scheduling point greatly reduces the need for coordination. The benefit is amplified when there is mixed-model production in a value stream. The actual demand determines the mix, and the pull signals generated by the pacemaker ensure that only the types of products that are needed are produced.
The Pacemaker Process
The production schedule is planned according to takt time, and is sent to the pacemaker process. It pulls from the upstream processes.
Upstream processes ONLY produce when the pacemaker sends its signal. If there are multiple products, supermarkets are used.
Continuous flow is used downstream from the pacemaker to manage production.
There are several things to consider when selecting a pacemaker.
The pacemaker should be reliable. If it is frequently down for maintenance, it wreaks havoc on the rest of the value stream.
It should have minimal setup times to prevent surges.
The closer it is to the end of production, the more linked it is to the customer. The downside is that it might drive more inventory into supermarkets on the upstream processes.
Branches in production processes need to be upstream of the pacemaker, or have a supermarket.
Don’t let a pacemaker process override a takt time. You don’t want wild fluctuations in production rates. When a process is well refined and tightly linked the pacemaker becomes more of a scheduling point than a way to manage the actual pace. Consider an assembly line. The shifts occur at prescribed intervals, or the line moves at a constant pace. The pacemaker simple determines the sequence of production.