NEW TECHNOLOGIES IN HOT RUNNER SYSTEMS By Liz Stevens, contributing writer, The American Mold Builder ven as they tout the enduring strengths of hot runner Ehandful systems, hot runner makers are not sitting still. We asked a of hot runner manufacturers to give a glimpse of the
improvements and new technologies unfolding in their systems, and to share their insight about the recent waves of change. We spoke with INCOE’s Jim Bott, business development manager – mobility/automotive/heavy truck; Robert Harvey, director of sales North America at HRSFlow; Brenda Clark, engineering manager at HASCO America; Mastip’s marketing manager, Steven McKinlay; and Greg Osborn, industrial sales manager – North America at Synventive Molding Solutions. WHY HOT RUNNER? To set the stage for discussing changes stemming from new technologies and the rise of automation in injection molding, we first asked the manufacturers to make the case for using a hot runner system as opposed to a conventional cold runner setup. “Making the decision whether or not to incorporate a hot runner in a build,” said HRSFlow’s Robert Harvey, “will depend on a variety of factors.” One factor is the anticipated production volumes because for very low volume runs, a hot runner’s price may be too rich. Other factors, he said, include “the material type to be used and its cost, and the impact of the cycle time difference between cold and hot runners.” The correct types of source material must be chosen for use in hot runners, and Harvey also pointed out that the amount of sprue or scrap material that can be eliminated by removing the cold runner, and the desirability and ability to reprocess scrap material also are important considerations for whether a hot runner is a good fit. INCOE’s Jim Bott approached the question by describing a given and then the few factors that, in his opinion, would rule out the use of a hot runner system. “Starting with Hot Runner 101: There is the given of reducing or eliminating the cold sprue of a cold runner by instead using a single hot nozzle,” he said. “There only are a few instances where hot runner technology cannot be value add, and what comes quickly to mind is low volume – but that would be an oversimplification.” Regardless of the production volume, many part designs require hot runner technology to properly fill the parts to meet
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the american MOLD BUILDER | Issue 2 2021
performance requirements. In the end, Bott narrowed down the poor candidates for hot runner systems to “perhaps very low cost, non-technical, low volume parts, and also, parts that need the cold runner for packaging purposes or conveying logistics. And certainly, some plastic materials – such as thermosets and liquid silicone rubber – cannot be processed with hot runner technology.” Greg Osborn, of Synventive, focused on production volume and part size, while also noting the scrap-reducing nature of hot runners. “Production levels and part size are important factors to consider,” he said, “when deciding between cold runner or hot runner conveying systems. The higher production volumes made possible with hot runner systems allow the added expense of a hot runner to be absorbed over the higher quantity of parts.” Osborn stressed that part size can play an important part in the decision. “Small parts being fed by a cold runner can often lead to increased cycle time because of the longer processing times required by the cold runner system,” he said. At the other end of the size spectrum, he said, “many large parts like automotive bumpers and fascia also lend themselves well to production on hot runner systems, thereby avoiding the complex or unfeasible three-plate design that a cold runner system would require to feed these large parts for filling.” HOT RUNNERS FOR FASTER PRODUCTION, LESS WASTE, BETTER QUALITY When asked how today’s new hot runner technologies address the demand for faster cycle times, reduced waste and improved part quality in plastics processing, Bott was happy to field the question. “From the inception of hot runner technology,” he said, “all of these ‘pain points’ have been the solution focal points of the technology.” Bott stated that these higher demands and requirements have presented hot runner solution providers with challenges that require ever-advancing technology. “The latest in technology includes advancing heater, sensing and heater controller technology,” Bott said. “It also includes upgrades to machining, cutting, probing and inspection technologies. There have been upgrades in flow simulation hardware and software, and there is continuing development of nozzle tip designs.”
