ECSL (Extended Control and Simulation Language).
ECSL is a general purpose simulator for a third generation machine. It includes programming codes, standard format guides, a compiler package and a program test monitor.
With a union contract running thin and demand up, Powers Tool management boosted power tool production. Automated lines went to twenty hours per day; hand-run subassembly lines ran two twelve-hour shifts. A supervisor reported an alarming increase in queue length and frequency at the only fully automatic machine step on the subassembly line.
The production manager checked the machine station on the line. Two machines were used to mount circuit boards on the subassembly frames. Production workers were required to bring frames to the machines. With the circuit boards mounted, these people returned to work tables to continue assembling their units.
One machine could process a frame in six minutes. One hundred and eighty parts were processed through a typical twelve-hour shift. Machine availability during a shift then was 1440 minutes, while the demand for machine time each shift was only 1080 minutes. The machines sat idle for six hours total each shift. These figures, derived from production logs, obviously did not cover the queue problem.
KEY FACTOR SELECTION
It seemed to the Powers Tool computer manager that the problem, stemmed from frame arrival at random intervals. The mean time to process a part was six minutes per machine, and the arrival of parts occurred on the average every four minutes. As many as two hundred parts might be brought to the machine station in a single shift.
The company's computer manager built an abstract model of the machine station operation: a computer program written in Honeywell's Extended Control and Simulation Language. Powers Tool's Series 200 computer ran this program, processing information and simulating time in a manner similar to the operation of the actual machine station. A negative-exponential random number generator simulated part arrival times. This type of generator had proved useful for queuing problems. *
The model program was run and the results compared to observations from the actual production line. Since the program results compared favourably, the program was considered an acceptable model.
The model program was changed to reflect the addition of another machine to process parts. The actual program modification was minor: the station capacity of 2 was changed to 3, so that program line 002 read "3 is CP." The modified program was run; and the resultant histograms studied. A production worker is worth $12 per hour to Powers Tool Company. An additional machine added to the line costs Powers Tool $4 per hour. The histograms were used to determine the solution to the subassembly line queue problem.
* Additional random number generators built into the ECSL system include routines using random distribution, normal distribution, and arbitrary or empirical sample distribution tables.
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|Title Annotation:||SOFTWARE SURVEY 1969|
|Date:||Sep 1, 2009|
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