You've got a 100,000-part job on press.

You've got a 100,000-part job on press. You're halfway through the run and still on schedule. Suddenly the phone rings: The molding- room supervisor has bad news. You have just one more hour's worth of material in the silo. It will take days to get another bulk delivery from your regular supplier, meaning you will miss your delivery date. Or you could get an emergency shipment of bagged resin from a local distributor, but the price will eat up your profits.

If any of this sounds familiar, then our cover story this month is right up your alley. It gives you the lowdown on level sensors—small devices costing as little as a couple of hundred dollars, which can save you big headaches. Put one on top of a silo or bulk tank, and you'll never be caught short again.

"But I have one of those," you may say. If you're like most processors, you may even have two—one at the top of the silo to signal when it's full, and one at the bottom to warn when it's empty. But there's nothing in between to tell you how close you are to running out. Senior Editor Lilli Sherman's feature explains how a continuous level sensor can make up for that shortcoming of common point level sensors. She also reports on recent improvements that overcome limitations of earlier sensors.

This story has been a long time coming. I cannot remember another comprehensive article on the subject appearing in a plastics magazine in the last 30 years. Almost a decade ago, we looked into this topic and were waved off by suppliers of material-handling systems. They said level sensors were a minor detail that didn't much interest plastics customers and were hardly worth the ink. Nowadays, however, inventory management is recognized as a key element of cost control and customer satisfaction. And level sensors are looming large.