Hot assembly systems

The experience and know-how acquired by ATE in the production of numerous systems and equipment for the hot coupling of mechanical parts has allowed them to propose valid solutions with induction systems for the following applications.


Heating of cage rotors for asynchronous motors

It is well-known that heating the rotors of die-casted asynchronous motors (being already complete with aluminium “squirrel cage”) at around 430-450 °C and the subsequent natural air cooling (in particular cases, in water), produces a significant overall improvement of the electric efficiency of the motor. With this treatment, the aluminium cage is in fact detached from the rotor core plates, which significantly reduces the rotor losses and increases the coupling work.

Heating of aluminium frames for asynchronous motors

For some types of asynchronous motors, the operation of housing the stator wound in its frame can be carried out after having suitably heated and then dilated the frame itself. This allows easy insertion while ensuring high mechanical interference and therefore, great coupling stability.

Heating of rotors for synchronous alternators

Like asynchronous motor rotors, also synchronous alternator rotors can be induction treated at around 400 °C, making them pass through a circular sector “saddle type” inductor. Given the specific shape of the pole pieces, the support pins are made in such a way that the rotors keep a given angular position within the inductor, to ensure good heating homogeneity, A surface contact thermocouple is positioned at the furnace outlet measuring the temperature of each rotor, signalling any anomalies in the event the temperatures are not within the pre-set value range.

Heating of motor bodies of special machines

Quite often, special machines as pumps, compressors, blowers, etc., are manufactured, which for encumbrance reasons, but not only, include the operating machine and driving motor in a single unit. The body of these single units is sometimes non-homogeneous in shape and volume and the assembly of the “wound stator unit” of the asynchronous motor requires case and precision. The local heating of the motor housing area considerably favours the operations described above and simultaneously ensures the coupling stability. The induction heating system of the single units carried out by ATE allows heat to be localised in the specific area, reducing processing times and curbing the energy used.

Hot insertion of the shaft of electric motor rotors

The dilation of the rotor hole, caused by the temperature increase, can be profitably used to perform the hot driving of the shaft. For this purpose, ATE has integrated the rotor induction heating system in completely automated lines, which perform the rotor heating and then the hot insertion of the shaft on the rotors. The heating temperature for correct insertion depends on the mechanical interference between the rotor hole and shaft. Generally, a temperature of 300 – 350°C is sufficient. It is possible to combine the heat treatment with the driving operation by heating the rotor to a higher temperature of around 430 °C.

Hot shrinking-on and shrinking-off of roll bearings

The system includes the frequency converter in a mobile version and the heating “head”, which in this case can be directly integrated in the mobile unit or separated in the portable version. The heating inductor for the shrinking-on of the bearings is a “pin”, externally insulated in epoxy resin with a copper pipe solenoid inside.

PFor shrinking-off, the inductor is made up of a coil with an appropriate diameter that the operator inserts by embracing the bearing to be disassembled. Also in this case, when the desired temperature is reached, heating is interrupted, and the bearing can be easily removed from the hub, without having to overcome a mechanical contrast.

Hot driving of shafts of gear pumps

The system includes a frequency converter and a heating unit with two alternatively operating work stations Each work station can have one or two pieces being heated.

According to the shape and dimensions of the workpieces to be heated, the inductor can be provided to heat from the outside or from the inside. For the application in question, the workpieces to be heated are the chain drives of gear pumps for automotive use. The system ensures a high production pace and can be inserted in robotised work islands.

Assembly of planetary gear boxes

The system includes a frequency converter in a mobile version and a series of heating “heads”, (inductors) for the various sizes of gear boxes to be heated.

The inductor caries out the localised heating of the planetary gear holder body, resulting in a dilation of the holes and relative bearings, which enable the insertion without friction of the coupling pin. Once it is cooled, coupling with high interference and high safety margin is carried out.

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