New low-mass heater technologies at Watlow Electric Manufacturing Co. include a thermal-spray/laser-etching combination that the firm contends offers certain advantages over thick-film heaters it introduced four years ago.
At K 2004, Watlow was pointing the new technology at hot-runner nozzles and manifolds. But it is also looking at other markets. It cited ``several innovative packaging applications'' but provided no details. The firm said the low-mass heaters are much less bound by restrictions on size, shape and substrate than traditional heaters.
While thick-film heaters are very good at providing even heat distribution over the surface of hot-runner nozzles and manifolds, their thermal expansion has to be matched exactly to that of the substrate to stop them from delaminating, Watlow said. This problem does not arise with spray coatings. A further advantage is that sprayed-on heaters take up minimum space. Total thickness is around 17 mils.
The heaters are manufactured by first spraying the nozzle with an insulating ceramic, followed by a layer of an aluminum oxide. A laser is used to etch a spiral circuit around the nozzle.
The electrical resistance of spray-on heaters rises rapidly with their temperature, making them ideal at distributing power evenly over the nozzle. If the nozzle is cooler at the front, more power is diverted there.
``It's like you're using a fine-tuning knob,'' said Watlow director of plastics marketing James McMillin. ``It doesn't compensate for a bad design, but it has the potential to make a good design great.''
Because the resistance of the coating is a function of its temperature, thermocouples are no longer needed in the nozzle. ``If you know the resistance, you know the temperature,'' he said in an interview at K 2004 in Dusseldorf.
Watlow said the technology is at an advanced development stage, and it has done field tests at a couple of locations. ``Results are good,'' McMillin said.
Watlow obtained the technology through its recent acquisition of Austrian firm RSG Heizungsproduktions-Vertriebs GmbH. RSG, based near Salzburg, was in bankruptcy. Renamed Watlow Plasmatech, it will serve as a development hub. McMillin will head the operation, splitting his time between Salzburg and Watlow's Batavia, Ill., headquarters.
Thermal spray is one of several technologies Watlow is exploring to expand its portfolio of layered heater products, McMillin said. Others are in a less-advanced state of development.
But there also is plenty of room for growth for thick-film heaters, he said: ``We've only scratched the surface of the potential hot-runner applications that can benefit from these heater designs.''
Hot-runner companies using Watlow's thick-film heaters include Gunther Hot Runner Systems Inc., Kortec Inc. and Osco Inc. Husky Injection Molding Systems Ltd. introduced hot runners incorporating its own thick-film heaters at NPE 2003 in Chicago.
Husky is gradually introducing thick-film technology on its hot runners but is still in the process of optimizing the manufacturing process, the Bolton, Ontario, firm said in a news release.
``Until we do, Husky has taken the precautious step of slowing down the product launch of this new technology. We are working aggressively to improve the manufacturing process and are planning to ramp up production of UltraHeaters again in mid-2005,'' the company said.