Pacemaker

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. This happens when 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.

A pacemaker process simplifies production oversight. It allows the schedule to be given to just one point on the value stream, and that process then controls the model mix and the flow of production. It reduces the chance of mix-ups where different processes building off separate lists get out of sync.

A pacemaker system needs to make sure that other production processes receive the information they need to proceed. The pull signals from the pacemaker controls upstream work, and information contained on the item controls work downstream. This is commonly done with a traveler sheet that rides on the product through production. Generally, this is only needed for customized products.

Upstream control is often done with supermarkets in a sequence, where the items that the pacemaker pulls dictates what is built next upstream. That process pulls from its upstream supermarket, and so on.

Downstream work is generally done with FIFO lanes, where the first work in is the first item worked on. These lanes should have a specified number of spaces, though, to prevent overproduction.

The Pacemaker Process

1. The production schedule is planned according to takt time and is sent to the pacemaker process. It pulls from the upstream processes.
2. Upstream processes ONLY produce when the pacemaker sends its signal. If there are multiple products, supermarkets are used.
3. Continuous flow is used downstream from the pacemaker to manage production. In many cases, when there is not a moving assembly line, this is done with production squares that act as a kanban.

There are several things to consider when selecting a pacemaker.

1. The pacemaker should be reliable. If it is frequently down for maintenance, it wreaks havoc on the rest of the value stream.
2. It should have minimal setup time to prevent surges.
3. 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.
4. 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 process would determine the sequence of production rather than when shifts occur.

When using a pacemaker, there is a tradeoff, though. If it is further upstream, there is less need for supermarkets or other systems that require more inventory to respond to pull signals for different models. But, depending on how long the lead time is, this also means that there is less flexibility. Once the product specifics are assigned to the queue, you can no longer adjust to meet actual demand.

Before attempting to use a pacemaker to regulate production, you must have a solid foundation in place. A pacemaker will only work if there is a system to link it to the rest of your production processes. This means that you have to master kanban, pull, and flow first. You will also have to get at least rudimentary standard work in place or the signals could vary wildly.

Once you’ve established the foundation, select your pacemaker. The location will depend upon the degree of configuration you have in your products. The earlier a specific item is designated for a specific customer, the earlier your pacemaker will likely be.