Latest Hot Runners Have Plenty For Every Need

There’s no doubt that hot runners improve the quality and profitability of many molded parts. But with the average use rate of hot runners in industrialized countries at 25 to 35% of molds, and much less in developing nations, there is still considerable potential for growth for their use in molds with large or multiple cavities.

One way of making the case for hot runners is to load the products with desirable features and target them at specific end-uses. For instance, the product featured on this month’s cover and this page, the 3 Series SFT from Günther Hot Runner Technology, is for micromolding. Joseph F. Podge, general manager of the German company’s U.S. operation in Buffalo Grove, IL, claims it’s among the slimmest hot runners available and can be easily stacked within the smallest molds.

And that’s just one example. Suppliers overall are providing systems with high performance, easy assembly and maintenance, and in many cases innovative molding capabilities.

The value of hot runners is most evident in markets, notably those producing high-volume, cost-sensitive products, where they can improve product quality and reduce scrap. In pet bottle preforms, the figure for hot-runner use is almost 100%, while in closures it is probably well over 90%.

Suppliers are also making hot runners more reliable and better adapted to processing diverse resins, from commodity grades to heat-sensitive engineering thermoplastics. There is also a growing number of cold-runner systems for processing thermoset resins, especially liquid silicone rubber.

All this development is complemented by a trend to shorter delivery times — in some cases, delivery is under one month for complete systems. Aiding this capability is the presence of supplier locations worldwide that not only provide a ready source of hot runners, but the design, engineering, and troubleshooting capabilities necessary to meet virtually any process need.

If industrialized countries still offer plenty of growth, developing countries are bonanzas for hot-runner use, especially as offshore oems specify them and as domestic moldmaking and molding capabilities advance.

Reasons for using hot runners vary by region. At the heart is cost, but while machine-time and cycle-time savings are seen as the primary benefit in the West, it’s material savings in Asia, since labor is less expensive there.

Despite the economic slowdown in many countries around the world, hot-runner suppliers are experiencing solid annual growth rates — around 20% in the U.S., 10% in Europe, and above 20% in Asia. But competition is increasing and performance differences between suppliers are closing, so service is becoming more critical.

The prospects for hot-runner sales are adding to the supply pool, with new suppliers continuing to emerge. Some are hardly neophytes. MHS, Georgetown, ON, Canada, for example, started up a year ago and is headed by Harald Schmidt, who previously held development and engineering positions at Dynisco, Husky Injection Molding Systems, and Mold-Masters. MHS has an alliance with pet moldmaker MHT, Wiesbaden, Germany, which was set up several years ago by former Husky engineers, and it is concentrating on custom-engineered solutions for complex applications, including stack molds and coinjection and cascade molds.

Schmidt says the company’s program has been engineered to measure up with new resins and demanding molding applications. Installation ease and serviceability, as well as a high cost-performance ratio, are found in all of its hot-runner design elements, he says.

Another new player is HRS Flow, a division of Incos, a major producer of molds for multicolor automotive lenses based in San Polo di Piave, Italy. According to HRS North American sales manager Diano Bontorin, in Windsor, ON, the company is concentrating on standard nozzles and manifolds. Special features include “fail-safe” heaters and thermocouples; if one fails, a pre-installed replacement minimizes downtime. Despite the extra components, Bontorin says HRS quotes several notches below competitors’ prices.

Design features aim to differentiate products

Suppliers continue to strive for product differentiation. Flex Dura nozzles for large parts from Mold-Masters Ltd. have evolved since their introduction six years ago, says Andreas Thunich in the company’s Baden-Baden, Germany, facility. He notes that the electrical wiring channel, for example, has been bulked up for added stability, and the hydraulic and pneumatic systems are now fully wired and tested prior to consignment. There are new options, such as position indicators for valve pins, and manifold heater plates have been redesigned for improved localized heating.

Pre-wired systems are, in fact, offered by numerous suppliers. Incoe Corp., Troy, MI, for example, touts what business development vp. John Blundy calls its unitized manifold system. Such systems allow moldmakers to concentrate on where they add value, i.e., the mold, he explains.

Husky says its Ultra line has gained swift market acceptance. The basic design is the same across the size range, and the nozzles handle nearly all thermoplastics. Before Husky launched the Ultra nozzles in 2001, “We could do systems for difficult materials, but it was always a compromise,” says product manager Stefan Schmitt. “We were aiming more at the closures and packaging market, in the way we did with our injection machines.” Now, most growth is in technical applications.

In the U.S., Peabody, ma-based Synventive Molding Solutions is one of the top suppliers for large automotive molds in the U.S., thanks to heat pipe technology developed by Kona Corp. (Synventive is an amalgamation of Dynisco HotRunners, Eurotool, and Kona.) It uses the phenomena of evaporation, condensation, and surface-tension pumping of liquid in a wick to transfer latent heat of vaporization continuously from one region to another. Bart-Jan Jongenotter at Synventive’s ‘s-Gravendeel, Netherlands, office, says U.S. processors like the system because it is simple, requires little maintenance, and is ideal for long nozzles as it provides an even heat profile. But the technology has not caught on in Europe because heat pipes are made for limited temperature ranges and, once in place, can’t be changed like heater bands.

In Europe, Synventive introduced a valve gate cylinder said to be easy to assemble and maintain. The cylinder, made up of several components assembled into a compact unit, can be used with a variety of nozzle types. The service engineer can disassemble the needle independently from the oil chamber. Because the oil chamber is separated and sealed, there is less chance of leakage.

To make systems more compact, several companies, including Günther, Frankenberg, Germany, and Thermo-play, Pont St. Martin, Italy, offer ejector plate-type systems to activate multiple valve gates, rather than having individual cylinders on each nozzle. Synchronization is improved, units take up less space, and maintenance is reduced, the companies claim.

Plasthing, Turin, Italy, best known for high-end systems, launched an economy range of hot runners last October. Owner John Donovan says the range will give it access to markets it has not been able to reach with tailored systems. “In the past, no more than 30% of the market was open to us,” Donovan says, particularly in Italy and the Far East.

“We do a fair amount in packaging and caps, but we have been missing out on a large section of the market,” he explains. “Our established open-flow bushing for automotive has 12 pieces. You couldn’t use a low-cost version for that sort of application.” By contrast, a new design it developed will have four parts — body, tip, heater, and thermocouple — which Donovan says can be high-speed machined. The price for a hot-half with 32 feeds is around two-thirds that of a standard Plasthing hot-half.

Trade expositions are important launch venues

Fast Heat, Elmhurst, il, will launch its Precision Series valve-gate nozzle at NPE in Chicago, June 23-27. The product features a guided tip design, patented sleeve-heating technology, and modular construction. A new cylindrical pin requires less shut-off force than earlier designs. Nozzles are designed to run commodity and engineering resins. All tips, thermocouples, and heaters can be easily replaced while inside the press, according to the company.

D-M-E product manager Ken Kurtz says an important trend is the use of stack molds to increase productivity, and the hot-runner system is a vital part of the stack mold assembly. D-M-E, Madison Heights, MI, and its parent, injection machine maker Milacron Inc., are jointly developing technology for stack molds.

Guzzini Engineering, located in Recanati, Italy, will use the Plast exposition in Milan next month to unveil multipoint torpedo nozzles — the TP/M2, TP/M3, and TP/M4 — which have a stainless steel body and torpedoes made of a beryllium-free conductive material. Marketing manager Andrea Guzzini says that many customers are shifting back from valve-gate to torpedo nozzles, citing an injection point quality nearly as good as with valve gates, no moving parts, and no material stripping from the gate.

In development at Günther is an innovative manifold heater. The thick-film manifold heating elements are high-tensile steel plates that can be fixed on the outer surface of the hot-runner manifold. The key advantage is even heat distribution. Günther says that because the form of the heater element can be easily adapted to any hot-runner geometry, design flexibility is raised. And, the simplified fixing technology of the manifold heater element means that manifolds can be made smaller and thus heat up faster.

In testing is a new nozzle heater technology. “This would facilitate the making of nozzles for low voltage and 230V in the same small outer measurements a reality,” according to spokesman Maik Weishaupt.

Ewikon, also in Frankenberg, Germany, offers HPS III-MH2 externally heated multitip nozzles for direct horizontal gating. It says they are especially suitable for processing materials used in packaging and medical parts. It notes that in these sectors, many applications need long nozzles to pass by nozzle-sided core seats of long slim articles, or nozzle-sided ejector mechanisms. “The thermal expansion of the nozzle can cause problems,” says spokesman Henning Becker. In the worst case, the tip dislocates behind the gate, resulting in poor vestige quality.

The HPS III-MH2 multitip nozzles consist of two components. The heat-conducting tip insert is fixed in a split mold insert and allows for sliding vertical movement of the nozzle shaft. This compensates for thermal expansion of the shaft and does not influence the position of the tips.

Valve gates from Japanese supplier Fisa, in Tokyo, are spring-loaded, using melt pressure to open and close. Since they don’t have actuators, they are compact. The company has been selling the system for almost 30 years, usually for molds with six cavities or less. Its latest nozzle has a 12-mm gate, which is claimed to be among the world’s largest.

High-performance equipment must be delivered quickly and on time, with a full-service package, or it will fail to meet the needs of many time-sensitive applications. At Husky’s hot-runner operation in Dudelange, Luxembourg, general manager Keith Carlton says the company is beginning to reap the rewards of a drive in recent months to reduce lead times via investments in production equipment and efficiency improvements.

Over a year ago, lead time for a low-cavitation system was around 10 weeks, Carlton says, and for a high-cavitation system it was as much as 14 weeks. Today, the respective lead times are 6-8 weeks and under 10 weeks.

For its modular Pronto system, standard delivery time is four weeks worldwide, and even lower in some areas. Carlton says that Husky has further ambitious lead-time targets, though he would not elaborate on what these are or when they may be realized.

“The moldmakers’ ability is driving our lead times,” says Bill Gunn, Husky’s product manager who is based at the company’s campus in Milton, VT. “The speed [in delivery] demanded from Asia is making hot-runner suppliers rethink their operations.”

Incoe’s Blundy concurs with this assessment. “The industry has cut delivery times in half over the past few years,” he acknowledges, adding, “In a down economy, everyone is trying to get more for less.”

The emphasis on speed is driven by “a different way of operating by moldmakers in Asia,” says D-M-E’s business development director, Larry Navarre. Whereas in North America, moldmakers design tools in one or two shifts with extensive overtime, Asian moldmakers have shifts around the clock. To meet this need, D-M-E’s Meteor system can be delivered in basic form in a single day, while a complete system takes three weeks, Navarre notes.