Today, copper bushings are critical for ensuring the optimal performance of equipment. It allows them to carry heavy loads and move at high speed without having to worry about safety issues or risk failures. To achieve this, in-depth knowledge of copper bushings is required. As a result, we have curated the most comprehensive guide on copper bushing for more understanding and knowledge.
What are Copper Bushings?
Copper bushings which are also known as plain bearings or sleeve bearings are mostly cylindrical with no moving parts. The sleeve bearing or copper bushings feature a sliding action and as a result, they are mostly self-lubricating. They function to provide a reliable and smooth operation of machine parts. Copper bushing comes in standard configurations including:
- Cylindrical Bushings or bearings
- Flanged Bearing or Bushings
- Thrust Washers & Flanged Thrust Washer
- Sliding Plates
Aside from the standard configuration, copper bushings can be made into custom designs such as special shapes with features including holes, grooves, notches, tabs, different dimensions, and many more. Copper bushings are used for rotating, sliding, reciprocating or oscillating motion in CNC machine parts.
The Manufacturing Process of Copper Bushings
The manufacturing process is much more complex than one can imagine with varieties of machining operations. However, these operations can be reduced by doing multiple operations simultaneously using the CNC machining process. The process includes the following
- A deformable metallic cylinder with an interior cylindrically shaped surface is produced at first from copper and its alloy using sintering metallic granules.
- Then followed by forming a concave-convex portion on the cylindrically shaped surface of the deformable metallic cylinder
- The deformable metallic cylinder in the first step is inserted into a mold where a fused resin is injected. This forms a resinous cylinder.
- Then followed by the insertion of a core pin into the resinous cylinder and passing it through a die to deform the metallic cylinder to produce a copper bushing.
- Copper bushing movement suitability
The copper bushing is used for rotating, sliding, reciprocating or oscillating motion. In rotating applications, movement involves one or two-directional travel of cylindrical surface. Reciprocating and oscillating applications involve cylindrical or flat surfaces, but with bi-directional travel. For sliding applications, copper bushings serve as bearing trips, slide bearings, and wear plates. The movement in slide application is always linear rather than rotating.
Copper Alloys for Bushing Materials
There are vast varieties of copper alloys available as bushing materials. The majority of these materials can be grouped into about 5 groups which include copper-tin, copper lead or tin bronze, aluminum bronze, leaded bronze, and beryllium copper
1. Copper Lead
A cast copper-lead microstructure features lead pockets in a copper matrix. This is possible because lead is practically insoluble in copper. The pockets of lead function as reservoirs for the maintenance of a continuous film of lead on the surface of the bushings. A steel backing is then used with copper-lead bushing to increase its strength. This is done either by powder-metallurgy or casting techniques. This type of copper alloys’ hardness is similar to that of babbitt at room temperature. However, when the temperature approaches 300oC the hardness of the bushing made with this alloy becomes higher. To reduce corrosion of either copper or lead components, additives can be used such as high-quality industrial and automotive lubricating oils.
2. Leaded Bronze
This type of alloy is used in the industry for manufacturing bushings. They contain about 4 – 10% tin content. The presence of tin helps to increase the strength, fatigue resistance hardness, and load capacity of the bushings. These properties are slightly above the ratings of the simple copper lead bushings. For corrosion resistance, you can use zinc as a replacement for tin. Also, silver or nickel is added to improve the toughness and corrosion resistance.
3. Beryllium Copper
Bushings made from copper-beryllium alloy features relatively high strength with thermal and electrical conductivity. These alloys are used when strength and conductivity are required. They do not tolerate dirty lubricants or misalignment and are generally used against hardened steel shafts. Bushings made of this alloy are specified for aircraft landing gear, other airframe sliding surfaces, and electrically conducting applications.
4. Tin Bronze
Bushing manufacture from Tin bronze features high hardness. As a result, they require good alignment, reliable lubrication, and a minimum of Brinell’s shaft harness within the range of 300 and 400. They function perfectly and do not require a separate overlay or a steel backing. This type of bushings offers good casting, low cost, high load capacity, impressive structural properties, easy machining characteristics, good compatibility, and many more.
5. Aluminum Bronze
Bushings made from this alloy are of high strength. This is because this alloy is made from aluminum, manganese, iron, nickel, and silicon. In combination, they work to offer excellent resistance to wear and shock. At high temperatures, they retain high strength and are used in machines that operate at above 5000C. While bushings made from aluminum bronze offer low embeddability, conformability, and poor compatibility, they are best suited for heavy-duty, low-speed functions with enough lubrication.
Signs of Bushing Failure and How to Fix them
There various signs of bushing failures. They include
1. Peeling
Insufficient lubrication or foreign matter infiltration may cause peeling. It is a small area of peeling or flaking caused by hairline cracks. This can be resolved by re-evaluating the type of lubrication and methods used. Ensure that the bushings operate smoothly and enhance the sealing to prevent infiltration of foreign materials.
2. Flaking
Flaking occurs mostly as a result of improper handling, heavy loads, rust, contamination, or low lubrication. A reduction in hardness of materials, improper mounting, and inadequate shaft precision can all result in flaking. The remedy to this is to evaluate whether the right type of bush is used followed by re-evaluating the conditions inherent in the application, the design of the bushings area, lubrication, lubrication methods, and the clearance.
3. Scuffing & Smearing
This occurs when the surface of the bushings becomes rough and it produces deposits. Typically, scuffing means roughness on the race collar. This is caused by inadequate lubrication and entrapment of foreign particles. Large axial loadings can cause bare spot and in turn, leads to scuffing and smearing. This can be resolved by re-evaluating the lubrication methods and lubricant with the service conditions and preload.
4. Spalling
Spalling is a result of poor mounting or removal practices. It can be caused by oil film discontinuation due to a radial load that is excessive for the design of the bearing. Poor lubrication or slippage can cause spalling. This can be easily fixed by correcting the preload, the re-evaluating system used, and improving operating conditions. Lubrication methods, as well as the lubricant, must be addressed while mounting and removal methods must be effectively addressed.
Application of Copper Bushings
Copper bushings are applicable in vast varieties of space. They include turbomachines such as compressors operating in critical pipeline applications, power plant steam turbines, and many more. They are also frequently used in the low-speed shafting application including ship propeller shafts. Due to their low cost and simplicity, bushings are well suited to intermittent motion applications.
Bushings (Sleeve Bearing) Vs Bearings (Rolling Bearing): Is There Any Difference?
Bushing and bearings are usually used interchangeably. However, there are important factors that differentiate the two groups of bushings. These differences make either of the two preferable for specific applications. The table below shows the differences between the two.
Bushings Bearings Mostly designed and manufactured purposefully Are mostly readily available Are mostly cost-effective (Less costly) Larger bearings have lower overall cost while small bearings may have a higher relative cost Life span is not predictable, life span is unlimited Are statistically predictable with a finite life span Offer more versatility, design flexibility, and a broader spectrum of materials Are limited by available configurations, standard size, and materials May require periodic maintenance because they are more abuse tolerant Requires minimal maintenance and are very sensitive to abuse Wear can approach zero under favorable conditions. Feature higher friction Feature generally low wear and low friction Requires little help for installation Requires experts for its installation
Conclusion
Conclusively, Copper Bushings are used to reduce friction between stationary support members and rotating shafts. They rely on oil film or lubricant to support the rotating shaft on the hardened shaft journal. They offer quite a vast variety of applications and can be found virtually from household appliances to industrial machinery.
RapidDone is the machined part expert who has a rich base of expertise and experience for this type of product. If your products contain copper bushings, then you should utilize our services. Consult with our quotation team for manufacturing advice or a quotation.