Views:0 Author:Site Editor Publish Time: 2021-02-22 Origin:Site
Shaft couplings have many types with different functions so that how to choose a suitable shaft coupling is a problem for the user. Some shaft couplings have been standardized. When selecting, you should first select the appropriate type according to the work requirements. Then calculate the torque and speed according to the diameter of the shaft. Next find the applicable model from the relevant manual. Finally, make the necessary check calculations for some key parts.
What is the difference between rigid coupling and flexible coupling?
What are the advantages and disadvantages of rigid couplings and flexible couplings?
How to choose the shaft couplings?
Rigid shaft coupling cannot compensate for the axial displacement and radial displacement between the connecting transmission shafts.
Flexible shaft coupling can compensate for the axial displacement and radial displacement between the connecting shafts.
The main difference between rigid couplings and flexible couplings is the connection they provide. Rigid coupling provides a rigid connection, that is, two shafts are firmly connected, and the rigid coupling can transmit torque smoothly in the entire system. A flexible coupling can form a flexible connection, and the components may lose some torque through interaction.
Other important differences between rigid couplings and flexible couplings are:
Alignment requirements: Flexible couplings can handle shafts that are slightly misaligned. The rigid coupling has torsional rigidity and cannot withstand any misalignment. This applies to two shafts that are misaligned at rest, and parts that may be misaligned during operation due to thermal changes.
Backlash: Rigid couplings, especially newer aluminum rigid couplings, can significantly reduce backlash to zero or close to zero. Flexible couplings cannot provide the same protection.
Maintenance requirements: Since rigid couplings are very hard, they cannot absorb vibrations, which can cause premature wear of parts that are not aligned properly. The operator should routinely check the wear and alignment of the rigid coupling, and lubricate it routinely. The flexible coupling can withstand vibration and shock without causing adverse wear.
Complexity: Flexible couplings usually have more components or more complexity. This makes operation and maintenance more complicated. In contrast, rigid couplings are simpler and more straightforward.
Application: Flexible couplings can be used in servo systems that have low or medium torque levels and may cause shaft misalignment, including applications such as processing tools, semiconductor manufacturing and packaging equipment. Rigid couplings are best suited for high torque requirements, shaft support applications and push-pull use cases.
Cost: Rigid couplings are cheaper than flexible couplings.
Advantages and disadvantages of rigid couplings:
Excellent torque transmission: Rigid couplings can efficiently transfer torque from one shaft to the other connected shaft.
Low cost of production: Manufacturers can produce standard and custom rigid couplings at cost-effective rates.
Precision, with nearly zero windup and zero backlash
Torsional stiffness: High torsional stiffness allows for better positioning.
Alignment capabilities: Rigid couplings can be used to establish shaft alignment between the motor and connected components.
Suitability for push-pull and support applications
Easy assembly, disassembly, and maintenance operations throughout the life of the coupling
It is difficult to assemble or dismantle.
Since it is a rigid coupling so it cannot accommodate any misalignment.
Due to the absence of flexible elements it cannot absorbs shocks and vibrations
Advantages and Limitations of flexible coupling:
No lubrication or maintenance
Good vibration damping and shock absorbing qualities
Less expensive than metallic couplings
More misalignment allowable than most metallic couplings
Sensitive to chemicals and high temperatures
Usually not torsionally stiff enough for positive displacement
Larger in outside diameter than metallic coupling
Difficult to balance as an assembly
According to the size of the transferred load, the speed of the shaft, and the installation accuracy of the two parts to be connected, choose a suitable shaft coupling, together with referring to the characteristics of various couplings. The following points can be considered when selecting:
The size and nature of the torque to be transmitted and the requirements for the cushioning function. For example, for high-power and heavy-duty transmissions, gear couplings can be selected. For transmissions that require severe impact loads or to eliminate shaft torsional vibration, tire couplings and other couplings with high elasticity can be selected.
The working speed of the shaft coupling and the centrifugal force. For high-speed transmission shafts, shaft couplings with high balance accuracy, such as diaphragm couplings should be selected, rather than slider couplings which has eccentricity.
The magnitude and direction of the relative displacement of the two axes. When it is difficult to maintain strict and precise alignment of the two shafts after installation and adjustment, or when the two shafts will have a large additional relative displacement during the working process, a flexible coupling should be used. For example, when the radial displacement is large, the slider coupling can be used. The universal coupling can be used for the connection of large angular displacement or intersecting two shafts.
The reliability and working environment of the shaft coupling. Shaft coupling usually made of metal elements that do not require lubrication are more reliable. The performance of shaft coupling is easily affected by the perfect degree of lubrication and may pollute the environment. Shaft coupling containing non-metallic components such as rubber are sensitive to temperature, corrosive media and strong light, and are prone to aging. The surrounding working environment of shaft coupling is more complicated. Temperature, humidity, water, steam, dust, sand, oil, acid, alkali, corrosive media, salt water, and radiation are all should be taken into consideration when choosing a shaft coupling. For the working quality of high or low temperature, oil, acid and alkali medium, it is not suitable to choose the flexible coupling with the general rubber as the elastic element material.
The manufacturing, installation, maintenance and cost of the shaft coupling. Under the premise of meeting the convenience performance, shaft coupling that are easy to install and unload, simple to maintain, and low-cost should be selected. For example, the rigid coupling has simple structure and convenient assembly and disassembly, and can be used for low-speed, high-rigidity drive shafts. General non-metal element couplings are widely used in general medium and small power transmissions due to their good comprehensive capabilities.
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