Flexible Tubular Heater, Heating Elements with Power Distribution: Full Range

Since the early 1970s, hotset has been supplying the plastics industry with industrial heating systems, including temperature-control technology. In production plants in Lüdenscheid, of Germany's Sauerland area, and in Malta, over 300 employees produce not only high-quality standard heating elements, but also specialized constructions tailored to customers' needs. SCOPE editor Michael Stöcker presents the company and its current solutions.

The heating elements produced by hotset are used wherever heat is required in industrial production processes or where a constant temperature level is required in certain components — such as in injection molding, the castings industry, and the packaging industry. Plastics manufacturers, in particular, rely on the company's knowhow.

In Lüdenscheid, hotset currently employs 240 people, mainly in the production of individual pieces and small batches according to customers' individual specifications. This involves a large proportion of handiwork in a manufacturing operation the likes of which one rarely finds in this country today. The company produces larger batches in its own production plant in Malta. The portfolio currently consists of cartridge heaters, coil heaters, flexible tubular heaters, and sealed heaters, as well as machine nozzles with compatible temperature sensors and controllers.

The heating elements must be tailored to the plastics manufacturers' machines and tools. This has substantial consequences for the company's production. Over 80 percent of the heating elements are produced according to customer specifications; their manufacture therefore requires a great deal of manpower. Managing director Ralf Schwarzkopf says: "It is only as a result of our firm roots in the region and the close bond between the company and its employees that we can, as a family business, react flexibly to the different requirements of our clients, who operate across the globe."

The regular development of innovative solutions plays a central role for the company. "If we want to continue to grow and to secure our location in Lüdenscheid, we must improve our products continuously," explains Schwarzkopf. This philosophy is also reflected in the workforce. Nine employees in the development department attend to future development of existing products and innovation management.

The company already achieved innovative leaps: In 1980 it produced the first round hotspring coil-heaters (type WRP). Further bright ideas followed, such as the patented hotflex flexible tubular heater, which can be bent by hand in all three dimensions. It can therefore be adapted to best match the shape of the machine tool that is to be heated. "Imagine that the customer needs to heat a metal block with a rigid tubular heater. In order to replace the tubular heater, they have to have another one individually produced. That takes time. If the customer is abroad, it can take weeks until the machine is back in operation. The hotflex can simply be bought off the shelf, kept in stock, and bent into shape as required for the respective tool", says Schwarzkopf, explaining the advantages of the flexible tubular heater.

The hotflex is frequently used for heating hot-runner manifolds for injection-molding plastics. The tubular heater can be precisely press-fitted into a milled slot or manually hammered in with a plastic hammer and without special tools. By taking into account the recommended slot dimensions, a contact surface of up to 75 percent can be achieved for optimum heat transfer — for both round and square formats.

Using hotflex allows the heat energy to be delivered, for example, directly to a melt channel or heated outline. The tool dimensions can be correspondingly small, resulting in energy savings. Storage is another of the heater's strong points: Stored flat and in the corresponding length, the flexible tubular heater can be used for a range of different slot geometries. Many dimensions are available off the shelf, removing the waiting time associated with a conventional preformed tubular heater. The hotflex is also optionally available with flexible unheated zones — for narrow connection areas, for example.

The company has also made a name for itself in the plastics hot-runner industry with the innovation of the hotslot, a heating element with individually specifiable power distribution for heating hot-runner nozzles for injection-molding plastics. It consists of a coil heater that is press-fitted into a brass supporting tube. Because of its thin wall thickness, this heating element allows minimal cavity spacing. As well as the connection configurations, the hotslot also allows selection of the run of the slot for the press-fitted heater. The power distribution is therefore absolutely precise and reproducible, in order to guarantee targeted and uniform temperature control in the production process. Low-power zones can be included in the construction of the brass support, which would not be feasible with a simple coil heater. Serpentine coils, cut-outs, openings, and boreholes are also possible, as is the use as a flat heating element. To facilitate disassembly at a later stage, the supporting tube can be nickel-plated.

Thermocouples are integrated with an additional slot and can also be positioned individually. If desired, hotset can produce the hotslot with a slotted or partially slotted supporting tube with serpentine coiling. This offers the advantage that the thermocouple can easily be swapped when required. Besides the customer-specific options, hotset also offers several varieties of the hotslot with a thermocouple as a standard stock item.

However, regardless of whether an individual heating element is needed or system solutions are to be realized: For its customer projects, hotset develops complete solutions for sometimes highly complex challenges. The services spectrum ranges from heating elements to control and regulation electronics, to isolation technology, and to comprehensive tool concepts. Customer-project development is currently one of the company's booming areas of business. Many hotset customers are considered to be Hidden Champions in their field, and focus their efforts on their core competency. Keeping in-house specialists in heating technology is becoming an increasingly unattractive situation. "We can offer our customers a one-off production today and a large batch of 100,000 units tomorrow — or individual system solutions as a development service. It's precisely this diversity that makes us strong," Schwarzkopf is convinced.

This fundamental attitude may also explain why hotset no longer wants to position itself only as a manufacturer, but rather as an engineering service provider with its new division, Customer Project Engineering (C Pro). Ingo Brückner, responsible for Marketing and Product Management, says: "Particularly in terms of energy savings, it is important in a production process to deliver the right amount of heat in the right place. For this, we offer our development competency."