R. L. Lankford implemented in his Otis Engineering plant in Texas, making oil well drilling tools, a finite scheduling technique he called "operation sequencing." His definition was "simulating in advance in our computer the sequence in which manufacturing jobs will flow through the various work centers of the plant." Figure 11 compares proposed actions for work schedules in work center 37 using infinite capacity scheduling and operation sequencing. The uppermost section headed Planned shows three weeks with load/capacity ratios of 120 percent in week 1, 50 percent in week 2, and 150 percent in week 3. The proposed actions are, "Work six days in week 1, work halftime in week 2, and work 10-hour days in week 3." These are feasible if people can be shifted and their work hours varied.
The simulated actual data for upstream work centers show that work planned for this work center will not arrive; the revised actions are, "Work halftime in week 1, work a normal schedule in week 2, and work five 10-hour days in week 3." What a difference! Operation sequencing could be run again in week 1 for the next three weeks and repeated each week to get the latest information. This technique was implemented successfully in the early 1970s using homemade software.
PROBLEMS IN EXECUTION
The major problem in execution is unrealistic, overloaded plans. Uncertain demand leads managers to make master production schedules "wish lists" in hopes of getting better customer service. To get new business, large orders are stuffed into already loaded plants. Poor capacity planning fails to alert people to the real problem. Capacity must be adequate for sound planning.
Also major problems are data errors and omissions in routings, work standards, and work-in-process. These are the poorest records in industry. Proliferating changes in product designs and processing methods are compounding these problems today. Few are solving these well.
Excessive work-in-process results from lack of effective control of work input and output. This causes long and erratic lead times and poor priority control. A basic manufacturing strategy, "Don't commit flexible resources (i.e., money, materials, machinery, and people) to specific items until the last possible moment" is the core of Just-in-Time activities.
Other problems include late or defective supplier materials and services, poor quality materials, machine breakdowns, tooling failures, design delays and errors, and poor processing methods. These, long thought to be unavoidable, cause upsets hamstringing execution.
At the heart of these problems are underqualified people who don't understand how manufacturing works and how to make it work better. Instead of attacking these problems, they seek a silver bullet in computer software. They neglect today's accepted goals of improving customer service, eliminating waste and non-value activities, zero defects, short lead times, flexibility, supplier and customer partnerships, and teamwork among their people. They view the needed education to fully qualify people as an unaffordable expense.
To Be Continued
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