F-87920.T8AR Roller bearing for plastics extruder gearbox shaft

F-87920.T8AR Roller bearing for plastics extruder gearbox shaft

F-87920.T8AR f-87920.t8ar BEARINGS specification as following::

:

Tandem Bearings Type:

1. Basic Type: The bearing adopts elastic spacer to connect the shaft washer,housing washer, roller and cage assembly. The components of this Thrust Bearings are demountable. The user should assemble or dismount the bearing meticulously according to our guide book.

2. Shaft Type: The bearing is made by penetrating an axis through the inner bore of basic type bearing and fastening the bearing to the axis by locking collar/snap ring. The components of this type bearing are inseparable. Shaft type tandem bearing is variational structure of basic type.

3. Multi-stage cylindrical roller thrust bearing (sleeve type) locking collar is made by covering a sleeve to the external of the basic type multi-stage cylindrical roller thrust bearing. It is also inseparable,and is assembled and disassembled as a whole.

There are two major types of extruders; single and twin screw (co-rotating and counter rotating). These come with a wide range of screw diameters (D), lengths (L), and designs. The single screw and co-rotating twin screw are inherently axially open-channel extruders. They can be regarded as drag flow pumps. Their output or degree of fill (if not running at maximum volumetric rate) can be impacted by the pressure flow within the extruder. Closely intermeshing counter-rotating twin screw extruders form closed channels in the intermeshing region. Their output is less vulnerable to the pressure flow within the extruder. As such, they can be considered as positive displacement pumps.

How to choose the tandem cylindrical roller bearing type:

Three pieces of information are necessary when selecting a suitable tandem bearing:
– the maximum possible bearing OD
– the desired calculated rating life under operating load and speed
– the maximum screw pressure.
The maximum possible bearing OD results from the intermeshing of two screws in the case of twin screw extruders. In the process, the crest diameter of one screw contacts the root diameter of the other screw. The resulting tight center distance and the output shaft near the
tandem bearing limit the radial design space. The length of a tandem bearing is normally not a crucial factor in bearing selection. For this limited envelope, tandem bearings are available in the 31.5 to 900 mm OD range.

How to Mount Tandem Bearings:

Tandem bearings are mounted with a loose F7 fit for the housing and f6 for the
tandem bearing shaft. A loose fit is necessary to allow the axial shifting (deflection) of the washers, rings and sleeves. The seating surface of the adjacent structure (housing and shaft) should be designed to have a perpendicularity tolerance to DIN ISO 1101 and qualities IT4 to IT7
(depending on the diameter range). For the mating structure, care should also be taken to ensure that the contact diameter indicated on the delivery drawing is maintained. The contact diameter
(support diameter) for the shaft shoulder may not be lower than the diameter indicated, and the contact diameter for the housing must not be exceeded. Insufficient support will not only cause an unequal load distribution but also an increased washer deformation (washers GS 0 and WS 0), which in turn will result in increased strain on the components.

Tandem bearings offer an optimum solution wherever the following requirements apply:
■ small radial design envelope
■ high axial forces
■ long operating life
■ low frictional energy.
Tandem bearings have proven effective principally in gearboxes for single and twin screw extruders in the rubber and plastics industry.
Other possible applications include:
■ deep hole drilling equipment
■ friction welding machines.