Over the years, I’ve described a number of techniques to identify opportunities for reducing waste while improving customer satisfaction. One such technique is Value Stream Mapping, which uses quantities of inventory throughout the process to illustrate the relationship between value-added and non-value added activities. Another option is Process Mapping, which we’ll discuss in further detail.
A process map can be used to describe any process in manufacturing or the administrative side of the business. Instead of employing a measure of inventory, it relies on process durations and system quality measures to uncover waste. Although a range of information can be included in a process map, I typically focus on several key topics:
Process time– the time required to complete the process. This can also be described as “touch time,” or the time spent actually doing the work required of the process.
Elapsed time or lead-time–the duration of time from the point at which the process is ready to begin until the time the process is completed. This elapsed time consists of the process time itself and any delays that occur before the process can begin, or that prevent the process from being finished after it is started.
||Activity||Process Time (min)||
|2||Get/load tools into machine||4||20||98%|
|3||Get/load material into machine||1||20||97%|
Percent Complete and Accurate–a measure of the quality of the input to the process. A complete and accurate figure of 90 percent would indicate that nine times out of ten, information is complete and accurate enough to start and finish the process. Relating this measure to the prior examples cited, if a print or process sheet did not have sufficient information, then the machining process could not be completed. If two out of ten machining jobs are delayed because of incomplete or inaccurate information, then the percent complete and accurate for this machining process would be 80 percent.
The process map is a listing of every step in the process, along with each step’s process time, elapsed time, and percent complete and accurate measure.
It can be quite revealing when process times and elapsed times are totaled and then compared. In the example shown to the right, there are 13.5 minutes of process time (or value added time) and 182 minutes of elapsed time. The difference between the Total Process Time and the Total Elapsed Time represents the waste in the process. Put another way, it takes a little over 3 hours to complete 13.5 minutes of work. If just a portion of this time could be reduced, then the result would be faster part throughput, and more importantly, improved customer satisfaction. The Total Percent Complete and Accurate figure measures the overall quality of the process. This figure is arrived at by multiplying all of the individual process measures. The 93 percent Complete and Accurate measure in step 1 is multiplied by the 98 percent Complete and Accurate measure in step 2, then the 97 percent Complete and Accurate measure in step 3 and so forth. The result is an overall Percent Complete and Accurate measure of 80 percent (eight out of ten jobs go through the entire process without the problem of incomplete or inaccurate information).
Don’t discount the value of a simple process map when looking for improvement opportunities in your organization.