This article discusses two different ways that infrared (IR) heating can be used. One is a high-heat process requiring preheating of the tools/dies, and the other is a lower-temperature process where IR is cleaner and more efficient. Can infrared be used in your process to improve energy efficiency?
Written by Ian Bartley, Heraeus Noblelight Ltd.
Short-wave infrared emitters have allowed Mettis Aerospace to reduce the time required for the heating of tools and dies used in the manufacture of high-specification titanium aircraft components to one-seventh of the heating times required by a previous gas system. This has provided significant energy savings and improved controllability, as well as improved forging practices, at the company’s Redditch (U.K.) site.
Mettis Aerospace has decades of experience in the production of highly complex, forged and machined, safety-critical aircraft components. This extends from manufacturing the majority of Britain’s aero-engine pistons during WWII to pioneering the use of titanium in jet engines to developing alloys for use in Concorde’s structure and skin. Today, Mettis is an important global supplier of complex alloy components to industry giants such as Rolls-Royce, Boeing and Airbus.
The manufacture of titanium components involves heating titanium preforms to above 900°C (1652°F) and then transferring the heated material into molding tools. However, it is essential that the tools are preheated to above 200°C (392°F) to allow better material flow and avoid die wear. Previously, die heating had been carried out by an open-flame gas system, which directed its heat onto support plates. The gas system remained switched on for 24 hours to ensure that the plates were at the correct temperature before the tools were loaded into position. Heating by this method could take up to 10 hours, with limited control of the heat transfer.
When modernization work was carried out in the Redditch facility, particular attention was paid to the tool-heating system, and Heraeus Noblelight was asked to provide an alternative infrared solution. The short-wave system installed consists of two 72-kW infrared cassettes, each mounted on an aluminum vertical profile frame. The two frames are positioned on either side of the table used to support the tools, which can be heated in pairs or individually with heat applied from one side only or from both sides. During heating, a pair of thermocouples measures the temperature of each tool face, and this measurement is then used to automatically regulate each cassette’s emitters constantly from 0-100% to maintain the set temperature with optimum energy consumption, maximizing the system’s efficiency.
Since installation, the new system has allowed significant energy savings because it is now only switched on when required. Tool heating times have been reduced,in some cases, from 10 hours to just 90 minutes.
As Dr. Xenofon Gogouvitis,the R&D lead at Mettis,reports,“Implementation of an IR heating solution has been a very important step toward an eco-friendly factory. The system’s efficiency has allowed us tor educe energy and time consumption during the preheating stage of the dies while improving overall control of the process.In addition, the absence of any open flames means that we now have a safer and more comfortable working environment.”
Aerospace applications are just one example of the use of infrared heating technology. A variety of high-quality energy sources covering the electromagnetic spectrum from ultraviolet to infrared are available. With over 40 years of experience in infrared technology, Heraeus provides efficient and effective solutions to drying, heating and curing problems throughout the thermal-processing industry. IH
For more information: Contac tIan Bartley, Heraeus Noblelight Ltd, Unit 1, Millennium Court, Clayhill Industrial Estate, Buildwas Rd., Neston, Cheshire CH64 3UZ; tel: 0151 353 2710; fax: 0151 353 2719; e-mail: firstname.lastname@example.org
SIDEBAR: Controlling White-Metal Bearing Manufacture with Infrared
Michell Bearings, located in Newcastle upon Tyne (U.K.) for more than 80 years, is the premier designer and manufacturer of self-contained white-metal (babbit) bearings for a wide range of marine and industrial applications, such as gearboxes, turbines, pumps and fans.
One of the most important production stages in the manufacture of a white-metal bearing is the coating of the parent metal of the bearing surface with the white metal itself. Generally, white-metal alloys are composed of tin, copper and antimony. There are various methods of applying the white metal, including dipping the parent-metal shell in a hot tinning bath. However, all coating methods require the application of heat to ensure good fluxing and adhesion of the white metal.
Directing a naked gas flame onto the parent metal as well as hot tinning can cause a dirty and often hazardous working environment. In an effort to solve the environmental problems and to achieve greater control over the coating process, Michell has installed an infrared oven at their Newcastle plant. It has been installed over an existing flat coating bed and is fitted to an overhead track system.
In operation, the shot-blasted steel parent-metal bearing is loaded onto an existing spinning mechanism on the bed. The infrared oven is then manually moved in place over the bearing before the emitters are switched on. The temperature of the parent-metal surface is checked. When this reaches 280°C (536°F), the IR emitters are switched off and the hood is moved away. At this point, the spinning mechanism is activated and the white metal is poured in to be evenly distributed over the required bearing surface by the centrifugal force. The coated bearing is then cooled by an atomized spray of air and water.
Apart from being significantly cleaner and less hazardous than conventional coating methods, the new system has also allowed the coating process to be more controllable, with corresponding improvements in coating quality. Moreover, since the heat is applied only when necessary and is precisely focused onto the bearing surface, the infrared oven has proven to be more energy-efficient.