Downtime statistics were divided into two groups: 1) downtime occurring before the graders' station; and 2) downtime occurring after the graders' station.
Downtime duration before the graders was modeled by using three different distributions: 1) 89 percent having a uniform distribution between 60 seconds and 240 seconds; 2) 8 percent having a triangular distribution with a minimum value of 60 seconds, a mode of 60 seconds, and a maximum duration of 240 seconds; and 3) 3 percent having a uniform distribution between 240 and 600 seconds.
Downtime as a function of length and number of graders (line speed) is shown in Table 2 for two graders and in Table 3 for three graders.
This disruption in operation was included in the statistics used for estimation of downtime before the graders, although some of the downtime was actually caused by set-up after the graders' station.
Information for molding machines is obtained through the IMAC data acquisition unit, which performs three functions: it continually monitors up to 32 production/process parameters and reports any deviations that exceed established limits; it provides an interface which allows downtime and defect codes to be entered, production and engineering data to be reviewed, and the addition of stacklights for additional status information on the plant floor; and it furnishes an interface to quality control instruments such as digital scales, digital calipers and digital micrometers.
The ProHelp system is a process quality control and real-time production monitoring system, which includes among its functions production counts, shift production reports, scrap and downtime reports and machine efficiency reports.
The network monitors production quantities, rejects, operators, and downtime from up to 100 machines.