Job shop capacity and schedule management

December 22, 2015

Each and every one of the dozens of job shops and high mix low volume (HMLV) manufacturers I’ve visited over the years has been unique: different customers, machinery, expertise, sales strategies, management styles, business philosophies, profit levels and debt levels, among others. There is, however, one thing most have in common: problems managing capacity and scheduling.

Problems in job shop planning and scheduling:

  1. Capacity is unknown—or known only through a hunch in the mind of a key individual who is intimately familiar with everything that happens in the shop.
  2. The day-to-day, hour-by-hour operation of the shop floor is so dynamic that a traditional material requirements planning/enterprise resource planning (MRP/ERP) system cannot possibly keep pace.
  3. Flow is nearly impossible to achieve on a consistent basis, not because of the wide variety of work scope, operations and lead times, but because of the lack of information and visibility of orders.
  4. Because capacity is unknown or ignored, and flow is inconsistent, lead times are impossible to predict. Of course, lead times for individual orders can be shortened by expediting the order through the shop, although at an unidentified expense to other orders and overall efficiency of the shop.

How did we get here?

Most job shops start with a couple guys and a few machine tools. Planning and scheduling are pretty simple. “Hey Joe, which customer is screaming the loudest for their parts? Do you want to run them or should I?” But as shops add people and machines, scheduling is often done by a guy running around with a stack of paper work, telling everybody what to work on.

At some point, the owner decides his company needs to “grow up” and purchase a reputable ERP system to manage the ever growing chaos. Months later, he realizes he bought a program that does a decent job of accounting, order entry, purchasing, bill of materials (BOM) and more, but is ineffective at real life planning and scheduling. Instead of reaching scheduling nirvana, the company is stuck with a computer-dictated schedule that everyone knows isn’t accurate or realistic.

The problem, in my opinion, is most computerized scheduling systems are to the manufacturing environment what a stop (and go... as we say in Wisconsin) light is to the traffic world. In the world of traffic flow, a central computer sets the timing of the lights to control traffic. Control may be arbitrarily timed, or it may sense traffic volume and movement. Either way, a central computer is controlling your commute… and your shop. If you’re thinking there must be a better way, you are correct.

A non-traditional approach to job shop planning and scheduling

I realize that many drivers are not great fans of roundabouts, although studies have shown that roundabouts do indeed improve traffic flow and reduce accidents. In contrast to a stop light, a roundabout provides a framework (such as lanes and exits), sets some guidelines (such as lane markers and signs) and gives people the freedom to choose when to yield or when to go for it. Out of self-preservation and some regard for their fellow motorists, people generally will make good decisions... at least once they understand the rules.

By combining key principles of Lean, Quick Response Manufacturing (QRM) and Theory of Constraints (TOC), we can develop a planning and scheduling system that is the manufacturing equivalent of a roundabout, improving flow by using a framework and guidelines to de-centralize control.

I’ve worked with several manufacturers to develop more effective systems for planning and scheduling. If you’re tired of being stuck in traffic, give us a call.