Objetivos específicos

Routing analysis is nothing more than the assessment of workflow patterns and volume/process variation. The first step in this analysis is the creation of a process matrix (Figure 6.6). This is accomplished by placing the routings for each part of a product on a grid. By identifying all manufacturing pro- cesses across the top and listing products down the side, a grid is created where each part routing can be physically drawn. By displaying the workflow in this manner, it is easy to see patterns of commonality, resource consump- tion, and reverse part flow activity. Each of these items is an important factor to consider when establishing cell configuration.

The purpose of a work content matrix (Figure 6.7) is to gather relevant man time, machine time, and setup time for a particular part population. After being collected, this baseline information should be loaded into a database as

Figure 6.6 Process Matrix

Manufacturing Flow Element 67

reference data for utilization during the cell design process. This database of information can be gathered in one of at least two different ways. The first is strictly a manual process in which an industrial engineer will conduct a work element analysis and complete a time observation form (TOF; Figure 6.8). The

Figure 6.7 Work Content Matrix

Figure 6.8 Time Observation Form

68 Lean Manufacturing: Tools, Techniques, and How To Use Them

engineer will walk the process map for each part and record the actual oper- ational data for each of the process steps. The engineer will need to keep track of both the individual operation time and the cumulative running total time. Depending on the operation, a series of five to ten recordings should be enough to accurately reflect the process. In addition to the time study, interviews with the process owners can provide valuable insight into the existing process flow. At times, with certain work environments, these “time studies” can be viewed in a negative light, and participation by the shop floor can be difficult to obtain. It should be explained that these observations are being used to try to understand the current process and are not being used to set pay rate. If there is still opposition, then try to reach a consensus utilizing the existing work element standards. In many cases, there is so much improvement opportunity available without being concerned with changes to the actual work content of the process that this is not an issue.

A second approach would be to capture data from the existing MRP II system. This approach is probably more acceptable when trying to address a large population of parts in a short period of time and information accuracy of 95% is not required. If, however, the root cause of a problem is critical or an accurate story is required, then it is recommended that the analysis be performed on data collected directly from the shop floor. This way the engi- neer can not only formally record what is seen but also record informally what is heard through conversations with shopfloor personnel.

At this point, the work content of the products has been recorded and some insight into the product process flow has been documented. Now it is time to understand the relationship between the two. By reflecting the prod- uct and process flow in a volume matrix (Figure 6.9), decisions about the cell design begin to evolve. The volume matrix reflects demand and process flow data in production units and minutes/hours. The placement of product groups on a matrix allows for the calculation of total volume by units and hours for each product and each process. Depending on the manufacturing process, the production rate could be calculated in days or weeks. The hours should reflect three major categories: man time, machine time, and setup time (the setup time being assumed at once per day). One of the objectives of a lean manufacturer is to be flexible and responsive; therefore, the goal is to make today what is sold today. This cannot be accomplished if changeovers are executed once per month.

Again referring to Costanza’s The Quantum Leap: In Speed to Market, the

author describes a similar process of searching for commonality: “Each prod- uct is reviewed to identify the particular processes or machine operations required to manufacture each product. The next step in cell design is to create Chapter 06 Page 68 Saturday, August 12, 2000 1:37 AM

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a cell configuration that is made up of the common machines or operations

identified in the process map.”5

There are two primary outcomes of the routing analysis exercise: (1) the segregation of high- and low-volume products based on a reflective view of the manufacturing process, and (2) an understanding of the degree of vari- ation in product volume/mix and work content as it relates to cell design. It is through an understanding of these two aspects that cell design decisions can be made relative to the use of:

1. Scheduling methodology — complex mix vs. segregated production 2. Rate-based, Kanban, make-to-order products

3. Kanban buffers for line imbalances and long setup times 4. Equipment workloads

5. Equipment needs 6. Staffing needs

7. Shift hour requirements