Shrink fit a steel gear onto a steel gear motor shaft

Objective

Heat the bore of a hardened spur steel gear to shrink fit onto a gear motor shaft. This is part of a chair for the disabled.

End Product

wheel chair

Equipment

Ambrell 2 kW induction heating system, equipped with a remote workhead containing two 0.66 µF capacitors for a total of 1.32 µF

An induction heating coil designed and developed specifically for this application.

Materials

Steel gear 2.5” (63.5mm) OD, .75” (19mm) ID x .625” (16mm) thick, temperature indicating paint

Temperature

400 ºF (204 ºC)

Frequency

300 kHz

Testing

A four turn helical internal coil is used to heat the gear bore. The coil is inserted into the gear bore and power is applied for 90 seconds to reach the required 400 ºF (204 ºC) and expand the gear bore. The gear is then placed on the shaft and allowed to cool, creating the shrink fit between the gear and the shaft.

Benefits

Induction heating provides:

• No pre-heat cycle, heat is available on demand

• Energy efficient, heats only the part, not the atmosphere around it

• Controlled, even distribution of heating

• Faster production times

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