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More and more processors are looking for greater precision from their feeding equipment. Here's what some are doing about it. How Low Can Low-Rate Feeders Go? Eschewing pre-compounded resins, processors in certain markets are increasingly asking their material-handling equipment suppliers to dial in ever more precise feeding—down to indi- vidual pellets and grams of additives—for applica- tions in which being off by one pellet of colorant, for instance, is the difference between a good part and a scrap one. Roger Hultquist recounts a recent medical job to illustrate his point. The customer in question wanted exactly three cylindrical colorant pellets to be fed into the injection molding machine's feed throat during screw- recovery time, which clocked in at about 3 sec. "It's not like feeding 100 lb/ hr," says Hultquist, co-founder and president of sales and marketing at feeding, blending, and material-handling equip- ment supplier Orbetron, Hudson, Wis. (orbetron.com). "When you're feeding two pellets in a shot, one pellet makes a huge difference in the accuracy, and that becomes more of an issue, especially on the medical side and especially when you're making translucent product." Simply stated: As feeding-rate requirements have gone lower, the need for precision has reached higher. Orbetron, which specializes in low-rate bulk feeders, has applied in plastics a tech- nology originally deployed in the pharmaceutical industry to feed powders. (see Hultquist's July '17 feature on the subject). A handful of equipment suppliers are targeting this niche of processors who utilize the precision and flexibility of low-rate feeding to compound material at the machine and in other areas where maximum accuracy is requisite. For a processor feeding additives at rates of 0.5 lb to 1 lb/hr, high precision isn't as key, but as that number goes lower accuracy becomes paramount. "On a wire and cable project where you're feeding 15 g/hr, it becomes very important that those pellets go right where they're supposed to go," Hultquist says. "At low rates, it becomes critical, especially in color—the color consistency of that product is one of the big things that we look at." For instances like the wire and cable job Hultquist referred to, Orbetron feeds material directly into the throat of the extruders, helping address what Hultquist calls a two-pronged challenge with pellets. "You can feed material, but once you do, now you have to make sure it gets dispersed correctly into your process," Hultquist explains. In addition to precision, players in this niche require high flexibility, notes Hultquist. "For custom molding houses that do quick color changes and may change color 10, 12, 15 times per day, it becomes very important that they can stop and change out colors in a matter of minutes." Orbetron's feeders are designed so that the entire feed section can be pulled off the unit, allowing processors to switch one for another as they change colors. By Tony Deligio Senior Editor "When you're feeding two pellets in a shot, one pellet makes a huge difference in the accuracy." 54 SEPTEMBER 2017 Plastics Technology PTonline.com Tips and Techniques