Coupling
At Faizeal, we are the leading supplier of custom magnetic couplings to the magnet industry. We offer three types of couplings: synchronous couplings, eddy current couplings and hysteresis couplings.
A magnetic coupler is a device that transmits force through space without physical contact. Uses attractive and repulsive magnetic forces to perform work in a linear or rotational manner.
About magnetic couplings
The simplest magnetic coupling consists of two components: the driver and the follower.
The drive is the part of the mechanism connected to the prime mover (electric machine). Through magnetic interaction, the follower reacts to the movement of the driver, resulting in a contactless transmission of mechanical energy. This contactless power transmission offers several advantages:
Component isolation, which minimizes or eliminates mechanical vibration through magnetic damping and allows a mechanical barrier to be inserted between the driver and follower to isolate the environment and allow operation at pressure differentials.
High tolerance for axial, radial and angular misalignment between prime mover and load.
Speed changes and regulation between prime mover and load are allowed.
Rapid prototyping of magnetic couplers
Coupling prototyping is a critical step in ensuring that the magnetic solution meets your needs and requirements. At Faizeal, our rapid prototyping services combine deep expertise and ingenuity with purpose-built equipment to give you what you need, when you need it.
Orders for custom couplings are divided into two phases: feasibility and engineering.
During the feasibility phase, we discuss the necessary design/manufacturing information with you (if a confidentiality agreement is required for the transfer of information, we will initiate a confidentiality agreement). At the end of the feasibility phase, you will have technical suitability and cost estimates.
If the estimates provided in the feasibility study are suitable, a formal quote will be created for you which includes the cost of the works (sometimes this is assessed before starting the design process). The design process is interactive and requires regular communication with our engineers to ensure compliance with your needs.
Once the feasibility process is complete, prototypes are created and tested in-house to ensure they meet dimensional specifications and force/torque requirements.
Please contact us to learn more about magnetic couplings and rapid prototyping services.
Synchronous (Category 1)
As the name suggests, this coupling is a version of synchronization that essentially results in a 1:1 relationship between the motion of the driver and follower. As taught in grade school, just as the magnetic poles (north and south) repel each other and the opposite poles (north and south) attract each other, synchronous coupling exploits these "attractive" and "repulsive" properties to produce motion. By placing an array of alternating pole permanent magnets (NSNS) on the driver and an equivalent array of alternating pole permanent magnets on the follower, a "coupled" magnetic circuit is created, with each north and south pole in the driver being connected to its respective The south pole is connected to the north pole of the follower.
As the driver moves relative to the follower, the magnetic poles begin to overlap each other, creating a "push-pull" effect and consequent movement. The magnitude of the resultant force depends not only on the amount of overlap, but also on the properties of the chosen magnetic material and the separation distance between the driver and follower.
However, at a certain displacement, the coupling can achieve peak force-generating capabilities. Displacement beyond this point can cause decoupling. This decoupling manifests itself as a ratcheting effect caused by similar magnetic poles of the driver and slave repelling each other. However, unlike the mechanical equivalent, decoupling usually does not cause permanent damage; and synchronization is restarted at the next pole coupling point.
Advantages: Maximum body force density.
Cons: Limited to 1:1 motion ratio
Purpose: Equipment requiring direct coupling and no slip during operation.
Eddy Current (Level 2)
This coupling is an asynchronous version that relies on a speed mismatch between the driver and follower to generate force. An array of alternating pole permanent magnets (NSNS) is placed on the driver or follower, and a conductive material (usually aluminum or copper) is placed on the mating component.
As the driver translates relative to the follower, a current is induced in the conductive material, creating a magnetic field that opposes the permanent magnet and "couples" the two components. Ampere's law governs the relationship between induced electric fields and resultant magnetic fields. The size of the resultant force is directly related to the following factors:
The speed difference between the two parts
Magnetic material properties
resistivity of conductive media
Separation distance between driver and follower.
Unlike synchronous coupling (Class 1), this asynchronous version is a "lossy" device, prone to ohmic losses and heating due to induced electric fields.
Advantages: Speed mismatch between driver and follower.
Disadvantages: "lossy" - may require active cooling, reduced volumetric force density
Purpose: For asynchronous motion or where force/torque changes with speed (braking device)
Hysteresis (Level 3)
As a hybrid of Type 1 and Type 2 techniques, this coupling is typically used asynchronously as a force limiter, but can also be used in a synchronous state. An array of alternating pole permanent magnets (NSNS) is placed on the driver or follower, and an easily magnetized/demagnetized material called Hysterloy is placed on the mating component. In the stationary state, the permanent magnet array is designed to magnetize Hysterloy, thus forming a synchronously coupled magnetic circuit*. If these forces are sufficient for the application, the coupling will operate in a synchronous state.
*Due to the magnetic properties of Hysterloy, the volumetric force density may be orders of magnitude lower than a stage 1 coupling.
However, if the force induced by the prime mover exceeds this synchronous operating state, the driver separates from the follower and begins to move relative to the follower. This movement causes the Hysterloy to cycle through its magnetization circuit (magnetize-demagnetize-magnetize) via the permanent magnet on the mating component, which now translates relative to it. As with type 2 eddy current coupling, the magnetic field generated by permanent magnets is also utilized and converted. However, unlike eddy current coupling, where the energy from the magnetic field is converted into flowing electric current (and heat), the cyclic processes around the Hysterloy's magnetized loop (the hysteresis loop) use magnetic energy to convert the magnetized state of the Hysterloy's material from north to south pole.
Unlike a fully synchronous coupling, which experiences a "ratcheting effect" when its synchronous force threshold is exceeded, this coupling continues to operate smoothly at asynchronous speed while maintaining the force threshold. This is done without the ohmic heating inherent in Class 2 coupling. Therefore, this type 3 coupling provides a synchronous solution that can be decoupled and run in an asynchronous state.
Advantages: No ratchet during asynchronous operation, minimal heat generation during asynchronous operation.
Disadvantages: low volume force density. Hysterloy materials are available in limited sizes.
Purpose: For asynchronous motion or force/torque limitation, such as capping machines and tensioning devices.
Type of coupling
Magnetic couplings are capable of transmitting force both linearly and rotationally. Therefore, in addition to selecting the desired coupling category (synchronous, eddy current, or hysteresis), you also need to specify the coupling type.
There are two types of couplings: torque couplings and linear couplings. As the name suggests, torque couplings are used to transmit force rotationally, while linear couplings are used to transmit force linearly. As one would expect, each coupling type also has a variety of geometric topologies that can be used to meet design intent. Details of these configurations are below.
Torque Coupling – Coaxial
Coaxial magnetic couplings are configured so that one part of the coupling is completely nested within the inner diameter of the second part. The two components share a common axis around which both rotate.
Axial misalignment – very forgiving. In fact, it can easily be designed to accommodate very large axial misalignments if required.
Radial misalignment - tolerable. The tolerance size is based on the spacing between the driver and follower. The greater the spacing, the greater the tolerance for radial misalignment. Large radial misalignments in closely spaced couplings can cause excessive radial loads on the bearings.
Angle misalignment - tolerated. The tolerance size is based on the spacing between the driver and follower. The greater the spacing, the greater the tolerance for angular deviations.
Torque coupling – face to face
The face-to-face magnetic coupling is configured so that magnetic flux is transferred around the flat end of the cylindrical component. The two components are axially attracted to each other and often require additional thrust bearing support for proper integration.
Axial misalignment – mildly tolerated. The amount of torque transmitted is directly proportional to the axial spacing and number of magnets used in the design. Small changes in air gap can result in huge changes in torque
Radial misalignment – highly tolerable.
Angle misalignment - tolerated. Due to the relationship between torque output and axial spacing, larger angular misalignments may result in unexpected reductions in torque
Linear Coupling – Tube Type
The tubular magnetic coupling is configured such that one member of the coupling is completely nested within the inner diameter of the second member. The two components share a common axis around which both translate.
Axial misalignment - tolerable. Essentially, linear couplings are axially aligned. Therefore, any misalignment will cause the driver to pull the follower into position.
Radial misalignment - tolerable. The tolerance size is based on the spacing between the driver and follower. The greater the spacing, the greater the tolerance for radial misalignment. Large radial misalignments in closely spaced couplings can cause excessive radial loads on the bearings or shafts.
Angle misalignment - tolerated. The size of the tolerance depends on the spacing between the driver and the follower. The greater the spacing, the greater the tolerance for angular deviations.
Linear Coupling – Flat
Planar magnetic coupling is configured such that magnetic flux is transferred around the flat end face of the magnetic assembly. The two components are attracted to each other and often require additional thrust bearing support for proper integration.
Plane (direction of motion) misalignment – tolerated. Essentially, linear couplings are axially aligned. Therefore, any misalignment will cause the driver to pull the follower into position.
Plane (perpendicular to the direction of movement) misalignment – very forgiving. Designs can be made to constrain 2-DOF if desired.
Angular deviation - tolerable. The amount of angular misalignment depends on the air gap between the two components.
Design help
1.What type of coupling is required?
•Linear
•Torque
2.What topology are you considering?
•Face to face (torque coupling)
•Coaxial (torque coupling)
•Tubular type (linear coupling)
•planar (linear coupling)
3.How much force or torque do you want to transmit?
4.What type of coupling are you considering?
•Category I – Synchronous
•Category II – Eddy Current
•Class III – Hysteresis
5.What is the traveling speed of the coupling? (Speed or RPM)
6.Is there a need for a barrier between the driver and the follower? If so, what pressure differentials would you like the design to be able to accommodate?
7.What is the operating temperature range of this coupling?
8.Are there corrosive elements or liquids to consider? If so, what types are they?
9.Geometric requirements:
•driver
（1）Shaft size
（2）Installation type
•Fixing screws and keys
•Compression (threaded shaft end)
•Taper Lock (not available in all sizes)
（3）MAX. OD
（4）MAX. Length
•followers
（1）Shaft size
（2）Installation type
•Set screws and keys
•Compression (threaded shaft end)
•Taper Lock (not available in all sizes)
（3）MAX. Length
10.Bearing supports (radial and axial) are usually provided external to the coupling system but can be accommodated in the design. Is it necessary to design bearing supports in the coupling?
11.Is dynamic balancing required (for rotating systems)?
Material
Magnetic materials – dependent on application. Usually based on heat and corrosion resistance requirements.
NdFeB – Temperatures up to 150°C. Corrosion protection is required.
Samarium Cobalt - Temperatures up to 350°C. Optional corrosion protection.
Ceramic – Temperatures up to 250°C. No corrosion protection is required.
Hysterlloy (Type III - Hysteresis Coupling) - Temperatures up to 350C. No corrosion protection is required.
Conductive materials – usually based on cost and size constraints.
Aluminum – low cost. Medium to high conductivity.
Copper – Moderate cost. High conductivity.
Driver and slave construction – application dependent. Typically based on corrosion resistance and cost constraints.
Cold rolled steel (1018, 1045, etc.) – Low cost magnetic material. Corrosion protection is recommended. Low-medium intensity.
Alloy steel (4140, 4340, etc.) - medium and low-cost magnetic materials. Optional corrosion protection. high strength.
Non-magnetic stainless steel (316, 304, etc.) – Moderate cost. No corrosion protection is required. Typically used in airtight seals. Low intensity.
Magnetic Stainless Steel (416, 430, 17-4PH, etc.) – Medium to high cost. Optional corrosion protection. Low-high strength depends on heat treatment.
Nickel Superalloys (Inconel, Hastelloy, Monel, etc.) – very expensive. The intensity is very high. No corrosion protection is required.
Beryllium Copper – Very expensive. The intensity is very high. No corrosion protection is required.
Aluminum – very low cost. Low intensity. No corrosion protection is required.
Obstacles – Typically based on pressure and speed requirements.
Non-magnetic stainless steel for medium pressure and medium speed applications. – Moderate cost. No corrosion protection is required. Low intensity. Conductivity is low.
Nickel superalloys (Inconel, Hastelloy, Monel, etc.) for high pressure and high speed applications. – The cost is very high and the strength is very high. No corrosion protection is required. The conductivity is extremely low.
Plastics (Nylon, Teflon, Delrin, Super Plastics, etc.) High speed, low pressure and precise force application. Costs range from low to high. Low intensity. No corrosion protection is required. Non-conductive.
Can process ceramics with high speed, medium pressure and precise force application. Cost is medium to high. Low to medium intensity. No corrosion protection is required. Non-conductive.
Frequently Asked Questions
1.How to install magnetic coupling?
Installation of a magnetic coupling usually requires positioning it correctly between the input and output shafts and ensuring proper alignment of the magnetic source (usually a permanent magnet). Tighten the screws to secure the coupling and make sure there is no play. Please refer to the manufacturer's installation instructions before installation.
2.Do magnetic couplings require maintenance?
Magnetic couplings generally require less maintenance because they have no physical contact. However, regularly checking the performance of your magnetic source to ensure it is clean and that there is no loss of magnetism is part of maintenance.
3.Why is my magnetic coupling not transmitting torque?
If your magnetic coupling is unable to transmit torque, it may be due to demagnetization or damage to the magnetic source. Check the performance of the magnetic sources to make sure they are not disturbed by external magnetic fields.
4.Can magnetic couplings be used in high temperature or corrosive environments?
Magnetic couplings typically operate within an appropriate temperature range, and high temperatures or corrosive environments may affect their performance. Under these conditions, it is important to select suitable protective measures or materials.
5.How to choose a suitable magnetic coupling?
Selecting a suitable magnetic coupling requires consideration of application needs such as torque requirements, working environment, installation space and quality standards. Working with a manufacturer to tailor a solution to your specific needs is the best option.
6.What are the application fields of magnetic couplings?
Magnetic couplings are widely used in engineering, manufacturing, wind power generation, medical equipment and other fields. They are used to transmit torque, reduce vibration, isolate equipment and provide reliable transmission.
7.How to maintain the performance of magnetic couplings?
Periodic inspection the performance of the magnetic source, ensuring cleanliness, and avoiding exposure to external magnetic fields are key to maintaining the performance of magnetic couplings. Perform regular maintenance according to manufacturer's recommendations.
I hope the above answers will help you better understand the use and maintenance of magnetic couplings. If you encounter problems in actual use, it is recommended to consult with a professional magnetic coupling manufacturer or engineer for more specific support and advice.
