Schaeffler Singapore

Extruder Gearbox

Design solution


The high axial loads induced in the screw drive shafts by the extrusion process are transmitted into the housing by the tandem bearing F-81660. A tandem bearing consists of several axial cylindrical roller bearings arranged in line. A sprung system of specially matched rings and washers ensures that all stages of the tandem bearing are always equally loaded regardless of the ratio between the basic load rating C and the axial load F. The rings and washers in the tandem bearing are made from hardened steel. It is generally fitted with standard axial cylindrical roller and cage assemblies.

The advantages of a tandem bearing come to the fore particularly when the following requirements must be fulfilled:

  • low radial space requirement
  • high axial load carrying capacity
  • long operating life
  • low friction.

Distributor shaft

The two parts of the distributor shaft (b) are each supported radially in two cylindrical roller bearings SL 183040. They are installed such that they act as non-locating bearings. Each shaft section is supported by a four point contact bearing acting as a locating bearing. Each bearing is axially preloaded and has a radial release.

Intermediate shaft

On the intermediate shaft one intermediate gear (c) has a helical tooth set while the other intermediate gear (c) has a straight tooth set. Both intermediate gears are supported in cylindrical roller bearings SL 192328 C3.

Screw drive shafts

The bearings selected for the screw drive shafts are two double row semi-locating bearings NNCF 140x225x105 and two double row semi-locating bearings SL1850 26 C3. The shafts are additionally supported in a radial direction on the tandem bearings by ball bearings 6309. A needle roller bearing NA 4824 C3 is also used to guide a shaft.
Tandem bearings are generally preloaded. The preload is achieved in this bearing by means of disc spring assemblies. During zero load running, the disc spring assemblies are supported by two axial cylindrical roller bearings 81224 TN.


The whole gearbox is lubricated and cooled using oil. Dissipation of heat is very important in a gearbox characterized by power levels of this magnitude. Particular attention was therefore paid to the design of the oil feed system.

The direction and quantity of lubricant flow is particularly important in tandem bearings.

INA/FAG products used

  • (1) Semi-locating bearing SL 183040
  • (2) Semi-locating bearing SL 192328 C3
  • (3) Semi-locating bearing NNCF 4824 C3
  • (4) Semi-locating bearing SL 185026 C3
  • (5) Axial cylindrical roller bearing 812 24 TN
  • (6) Needle roller bearing NA 4824 C3
  • (7) Radial ball bearing 6309 C3
  • (8) Tandem bearing F-81660
  • (9) Four-point bearing QJ324N2MPA

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