Picture-perfect manufacturing: the vision of a production process with little or no waste is the inspiration behind lean manufacturing. Value stream mapping is a graphical tool that this contract manufacturer uses to create that vision

Modern Machine Shop, July, 2004 by Mark Albert

Of course, a future state map becomes a current state map as soon as changes and improvements are made. "You go back and make a new future state map," Mr. Andries says. "That's one of the beauties of value stream mapping. Ultimately, it puts your whole organization on a future-becomes-present cycle that keeps customer satisfaction in the forefront."

The Value Stream Mindset

"Value stream mapping made us conscious of the concepts and principles of lean manufacturing" Mr. Andries continues. "Value stream mapping helped us to start thinking lean as a habit."

This "value stream mindset" has been especially beneficial for Stremel's short-run contract work. Mr. Andries explains: "For one thing, we created a set of genetic value streams that emphasize opportunities for continuous flow rather than hatching. So we estimate and quote jobs with savings from lean manufacturing built in."

A more specific and formal application of value stream mapping is then undertaken to fine-tune the process plan when the contract is awarded. "We create a process plan, then scrutinize it as if it were a current state map of an existing process. Next we develop a future state map to tweak the process and make it leaner," Mr. Andties says.

For example, one of the key concepts in value stream mapping is takt time. Takt time indicates how often a total process must produce a finished part in the work time available to meet customer demand. Ideally, the cycle time of the downstream process nearest to customer delivery should be close to takt time. This process (often referred to as the "pacemaker") sets the pace for upstream processes from which the pacemaker process pulls work.

"Takt time helps us determine if a process will be effective or not," Mr. Andries says. "We can look at the process plan for apart and make sound decisions about which machine to use, how much change-over time is acceptable and how many change-overs to allow."

According to Mr.Andries, the value stream mindset guards against a high-production mentality--the conventional thinking that making as many parts as possible in the least amount of time with the fewest changeovers is always the most cost-effective way to make a part. In fact, thinking about the value stream may reveal that a smaller, slower, less-expensive-to-operate machine will be more than adequate. Meanwhile, as order quantities increase, a different future state can be visualized for changing the production strategy to keep up.

The value stream mindset may also encourage planners at Stremel to look for opportunities that integrate operations other than CNC machining. For example, by bringing assembly, inspection, marking or finishing operations in house, the company offers the customer additional value while taking advantage of continuous flow to create shared savings. Likewise, the value stream mindset can help focus on how suppliers can contribute to waste reduction. For example, Stremel routinely looks for ways a supplier can deliver material directly to a workstation. When the company added a 40,000-square-foot facility for its expanded CNC machining operations in 2003, designated areas were laid out at each machine for incoming and finished outgoing workpieces, allowing pallets loaded in a preset manner by the supplier to be dropped off at the machine.