Induction Heat-Treating Developments
Rotating inductors are used for hardening bores of large parts that cannot be easily rotated (Fig. 1). This patented system avoids the need for parts to be mechanically handled and turned. Parts are fixed while the inductor rotates along the Z axis, and the hardening quality and process speed increase dramatically. Other benefits are that the machine design becomes lighter, less floor space is consumed and the operation is safer.
A multi-axis CNC machine combined with special twin-centered inductors (Fig. 2) is designed to efficiently harden small and large diameters on the same part. Using a single inductor with different diameters (twin-centered inductor) is a convenient solution when the part has different cross sections (e.g., camshafts). The design permits improved relationship between part and inductor with just one heat station/inductor for the heat treatment of the whole part. The direct benefit is to produce a complete part (no batches), simplifying the process. In addition, because the inductor fits the part, the consumed energy is much lower and the quality is improved.
Parts such as CV-joint components are induction tempered in a tunnel installation. This represents an advantageous alternative to conventional furnaces mainly because of the reduction of the intermediate stock of parts, integration in the automatic production line and the reduced footprint.
The automatic, high-production starter rings installation (Fig. 4 – lead photo) shows the capacity to develop challenging solutions. Hardening, tempering, marking and drying are carried out in a 7-second cycle time. The short cycle time, the different type of parts, the quick changeover time and the input ring stack buffer maximize the production.
In Europe, GH Group is offering a curing system that provides complete and spot heating on structural-adhesive material on automotive panels – door, hood, lift gate, trunk lid, fender and roof. The main customer benefit is to obtain a high-quality finish via fixation of inner and outer panels in the hem flange borderline, corrosion protection (sealing) and polymerization of the adhesive. All German car manufacturers like Audi, VW, Mercedes, BMW and Porsche are employing this application.
Solutions exist using multi-axis CNC machines for hardening large gears and raceways – GTH and GTV. In addition to the automotive sector, GH Group has been working with other industrial sectors with contributions in wind energy, cranes or handling vehicles using large slewing bearings (Fig. 5).
Other versatile installations have been developed to harden any combination of raceways and gears – inner or outer – adjusted to the customer volumes and type of production (Fig. 6).
Detailed Description of Unique SolutionsGH Tempering Tunnel
Tempering by induction represents an advantageous alternative to conventional furnaces:
- Small dimension (surface less than 6 m2) instead of big furnaces
- Reduction of the intermediate stock of parts, with a maximum of 15 parts in process at the same time
- Ease of incorporation in an automatic production line
- Immediate availability of parts
- Part-by-part control
The parts pass on a chain conveyor through the tunnel. At the exit, a pyrometer controls the output temperature and selects acceptable parts to pass through the cooling tunnel. A configuration based on a 50-KW generator can achieve a production greater than 300 parts per hour. Tempering-tunnel installation main process characteristics:
- Power – 50 KW
- Frequency – 2-5 kHz
- Production – 300 parts/hour (12 seconds/part)
- Maximum part length – 275 mm
- Maximum part diameter – 150 mm
Edge-Tracking Inductors - EdgeTrack SystemThe machine equipped with this system is composed of four servo-controlled axes – X, Y and Z for the inductor table and the rotation of the vertically positioned camshaft. The inductor is designed to ensure a close distance between the part surface and inductor and at the same time allow both cams and bearings/supports to be treated in one station.
By synchronizing movement of the inductor with the rotation of the camshaft, hardening profiles are achieved that are not possible with traditional machines. This method also avoids the problem of overheating the cam top while trying to harden the whole perimeter of the cam.
Combining the two systems (EdgeTrack System and twin-centered inductor) incorporates the benefits of both.
Large Gear/Raceway MachinesGTH (horizontal) and GTV (vertical) machines are commonly used in industries with low production and short series but with a wide range of part sizes.
Parts are slewing bearings and large rings composed of a combination of inner or outer gears (teeth) and inner or outer raceways (single or double). Teeth hardening is by scanning, tooth-by-tooth (some machines are able to treat two teeth at same time), and raceway hardening is performed by scanning or single shot in some cases (Fig. 6). The two basic formulas used in these treatments are:
- GTH-type, manual-loading machine where the part is treated in horizontal position. Depending on the diameter and the section of the part, the table is composed of three arms or six arms.
- GTV-type, manual-loading machine where the part is treated in vertical position.
These systems include mostly two inverters to perform multiple heating (preheating and heating) of large raceways and sometimes the treatment of teeth two by two. The GTH and GTV machines use one or two inverters at 150-200 KW and single or multiple frequencies depending on the treatment specifications. IH
For more information: Contact Frank Wilson, GH Induction Group, 1840 Roslyn Road, Grosse Pointe Woods, MI 48236; tel: 313-432-1602; e-mail: email@example.com; web: www.ghe-usa.com
Additional related information may be found by searching for these (and other) key words/terms via BNP Media SEARCH at www.industrialheating.com: induction, tempering, inductor, frequency, tunnel furnace
SIDEBAR: GH History and ExperienceGH Induction Group is young in North America. However, the GH tradition of service to different industries using low-, medium- and high-frequency induction goes back for decades. Over 4,000 systems supplied since 1961 to over 50 countries form a well-established experience base.
Automotive manufacturers and suppliers are among GH’s customer base: Audi, GKN, Mercedes, Chrysler, BMW, Citroen, Nissan, DANA, Delphi, Peugeot, Eaton, Ford, TRW, Honda, John Deere, Kia, VW, etc.
GH’s philosophy involves working closely with customers to find customized solutions for their needs. Special focus is given to complete solutions and turnkey projects.
Constantly increasing the local presence, it has sales representation and technical service in almost every country in Europe, U.S., South America and Asia. Its production facilities are located in Germany, Spain, China, India, Korea and Brazil.