This section provides an overview for oilless bushings as well as their applications and principles. Also, please take a look at the list of 8 oilless bushing manufacturers and their company rankings.
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An oilless bush is a bush bearing that does not require lubrication when compared to a regular bush.
It is a component used as a sliding bearing among machine bearings, sometimes called an oilless bearing by some companies.
Without lubrication, a normal bushing will consume kinetic energy due to friction, and wear will occur. Oilless bushings, as the name suggests, do not consume kinetic energy and cause little wear even without lubrication, thus reducing the frequency of equipment maintenance.
As the name implies, oilless bushings are used as bearing components in machinery.
They are especially used in machinery that cannot be used in an oiled condition, such as in food machinery where they are in direct contact with food or where it is difficult to supply oil.
In addition, the use of oilless bushings can reduce the cost of oil changes and oil recycling costs.
Similarly, the design of lubrication-related components is eliminated, which reduces design time and simplifies the machine itself.
Oilless bushings can be used oillessly because of the materials they are made of. Most can be divided into two main types. The first is the use of solid lubricants or engineering plastics with a low coefficient of friction.
For example, by blending metals with lubricants such as molybdenum disulfide, metallic saponite, or soft metals, it is possible to create metals with a much lower coefficient of friction than normal warm metals. If this metal is molded into the shape of a bushing, it becomes an oilless bushing.
Oilless bushings can also be made from a plastic called engineering plastic. The most commonly used engineering plastics are those that have a low coefficient of friction, are well-balanced in strength, and do not cause major problems for the human body if they should get mixed in with food.
In particular, oilless bushings are manufactured using materials such as Teflon (PTFE), polyacetal resin Duracon, Delrin, and the very expensive polyether ether ketone (otherwise known as PEEK).
Oilless bushings can be made of resinous, multi-layered, or metallic materials.
Resinous materials are generally made of polyacetal, tetrafluoroethylene, polyamide, or other materials to which fillers and lubricants are added. Although resin-based materials are less strong than metal-based materials, they have advantages such as low coefficient of friction, light weight, and low cost, and are also used to support soft materials such as aluminum.
The multi-layer type has a back metal, sintered layer, and surface layer, with resin-based materials or solid lubricant materials used for the surface layer. The thin wall and excellent mechanical strength allow for compact design. Since it is an oilless bushing, it can be used without lubrication, but it exhibits even better characteristics when used in combination with lubricating oil.
The metallic type is generally a copper alloy or aluminum alloy embedded with solid lubricant. They are used in high-load bearings and are considered high-strength, long-life bearing materials. Graphite is often used as a solid lubricant.
There are other types with solid lubricant dispersed in sintered metal, which are often used in high-temperature environments.
The life of an oilless bushing is the time it takes for the bushing to wear out due to sliding and for the gap between the shaft and bushing to become larger than the design gap, resulting in rattling in the sliding parts.
Although there is no definite value for life, there is a method of determining the amount of wear based on a theoretical formula and setting the life as the time until the amount of wear becomes larger than the design clearance.
The estimated wear rate is calculated by multiplying the specific wear rate (mm/(N/mm^2-m/s-hr)), design surface pressure (N/mm^2), design speed (m/s), and friction time (hr). Based on experimental data, the specific wear rate is 0.0006 to 0.003 in the unlubricated condition.
When designing oilless bushings, the design surface pressure is calculated by setting the friction time as the required life, the allowable bearing clearance as the estimated wear volume, and the design speed as the operating speed. Once the design surface pressure is determined, the shaft diameter and bushing length are selected so that the surface pressure is less than or equal to the design surface pressure.
*Including some distributors, etc.
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