Calculating cycle time consequences

Someone famous once said that injection molders don’t really sell parts—they sell time. And with all that money tied up in time, finding ways here and there to save, hoard, scrimp, and otherwise economize seconds and minutes is a constant job in many molders’ lives.

Of course the number one target of time savings on the plant floor is the molding cycle. Much lives and dies by cycle time, and the conscientious molder running a job at a longer cycle time than quoted to the customer can almost see the money flying out the door. Still, even when the cycle time is running less than quoted, and you know you’re making money, it’s hard to quantify the savings. Without pulling out a calculator and doing some quick math each time, it’s difficult for a molder to know on the spot just how much incremental savings or losses of time are worth.

To help put these fluctuations in cycle time in perspective, molding industry veteran Paul Allen, president of Logic Corp., based in Sandy Hook, CT, has developed this cycle time savings chart. A molder can use it to compare quoted cycle time to the actual cycle time and derive a savings or loss in hours/week.

Using the chart is relatively simple, but we’ll run through an example. First, the three columns on the left are used to select the quoted cycle time; the three rows at the bottom are used to select the actual cycle time. Numbers in the tan cells above the purple cells denote the gain in hours; the numbers in the blue cells below the purple cells denote the loss in hours. You use it like a mileage chart, selecting the intersecting columns and rows of the same color.

Say, for instance, the quoted cycle time is 24 seconds, but your engineering staff optimizes the job to run at 23 seconds. The intersection of 24 seconds quoted and 23 seconds actual produces 5 hours saved per week, based on a 120-hour week.

If you know how much your machine costs each hour it runs, you can view that 5 hours gained as money saved on the current job, or an opportunity to make more money on other jobs, thanks to the increased efficiency.