Separator — detail of the bearing structure, whose task is to divide the direction of the rolling elements. This increases the speed of rotation of the bearing compared with the full complement this. In addition separator provides space for additional lubrication, which is also a positive effect on bearing life as a whole. separator material brings its own characteristics in the bearing characteristics.
Contrary to popular opinion, the separator itself does not carry the load bearing, its task is to hold the rolling elements. That is why the bearing type change does not affect static and dynamic bearing capacity. The load on the separator may be, for example, in the case of damage to the raceways.
The most common material for the bearing cage — steel. They are divided into two types — pressed steel cages and machined steel cages.
Steel pressed cages made of low-carbon hot-rolled steel sheet according to the standard (DIN) EN 10111: 1998. Advantages — low weight, relatively high strength. Also, they can be further processed to reduce friction and wear.
Pressed cages in the bearings of stainless steel is usually made from stainless steel X5CrNi18-10 according to the standard EN 10088-1: 1995.
Machined steel cages
Machined separators are usually made of S355GT (St 52) carbon steel grade according to EN 10025: 1990 + A: 1993. They are used for large bearings or in cases where there is a risk of destruction of the separator brass, for example due to a chemical reaction. Steel separators are not exposed to the mineral or synthetic lubricants or organic solvents. They can be used in temperature ranges up to 300 ºC.
The second most common material for separators — brass. This material is heavier than steel and much softer, which makes it possible to operate in heavy conditions when there are shock loads.
This type of separator is also divided into two types — stamped from sheet brass cages (used for some bearings of small and medium-sized) and machined brass cages.
For the manufacture of stamped Brass separators, according to EN 1652: 1997.
Machined brass cage
Most of machined brass cages are made of cast or go brand CW612N brass according to EN 1652: 1997. Brass cages should not be used at temperatures above + 250 ºC.
Polymer separators are also common and increasingly replace steel. Taken together, the properties of polyamide is comparable with steel for strength, durability, though lighter than steel and nylon bearings with polyamide cage work is generally quieter. However, the temperature range for the polyamide hard-coded and must not go beyond it. This imposes restrictions on the use and installation of such bearings. For example, heating the bearings with polyamide cage in oil is strictly prohibited. In addition, the degree of aggressiveness of the environment also plays an important role.
As for operation at low operating temperatures, there may be a limit as polyamide separator loses its elasticity and can collapse. Therefore, separators made of for example glass fiber reinforced polyamide 6.6, should not be operated under constant operating temperatures below — 40 ° C.
Polyamide 6.6 — used for most manufactured by injection molding separators. May or may not have glass fiber reinforcement and thus has a favorable combination of strength and elasticity.
Polyetheretherketone — durable and flexible material, with a wide operating temperature range, high chemical resistance and wear resistance, high workability, it has become central to the separators vysokooborotisty precision spindle ball and roller bearings.
This material shows no signs of aging at temperatures up to +200 ° C in the lubricant additives. However, the maximum temperature for operation at high speeds is +150 ° C, as this temperature is a softening of the polymer.
Separators of the PCB (lightweight reinforced fabric separators of phenol-formaldehyde plastics) are able to withstand heavy loads and centrifugal acceleration, but can not work in high temperature conditions.
Heating phenol formaldehyde leads to the formation of volatile toxic compounds. In addition the material brittle and fragile to strong shock loads. Previously, these separators used in conventional precision angular contact ball bearings. However, such a construction is found less and less, gradually replacing PEEK.
In addition to the foregoing materials, the bearings can be equipped with special purpose separators made of other polymeric materials, light alloys or special cast iron.
The correct separator material leads to an increase in the resource node, it is very important in the selection of the bearing.