Magnetic Torque Coupler and Linear Couplers for Sale

Torque and Linear Couplers

Stanford Magnets Official

A magnetic coupling is a coupling that transfers force, using a magnetic field rather than a physical mechanical connection. Both torque coupler and linear magnetic couplers are very helpful when one assembly needs a separated operating environment.

Typically, the cost of a torque coupling or linear coupling exceeds the cost of common mechanical solutions, so couplers are often used in an aggressive environment where mechanical linkages are not feasible, such as:

High pressure
Temperature Extremes
Caustic liquids or gasses
High degree of particulates or fouling agent

Linear Couplers

A linear coupler is simpler compared with a torque couplers. It can be two magnets or comprised of engineered arrays containing multiple magnets of various configurations. The required coupling force and the operating environment are the prime design variables.

There are many variations of Linear Couplers. The fundamental similarity is that the coupler’s "halves" are "linked" through a gap. One "half" can propagate the other "half" without contact. All of the common and unique designs for Linear Couplers try to minimize cost, increase performance, and make use of the application-specific geometry.

One common style of Linear Couplers is simple magnets on a backing-plate. The magnets are sized based on the gap and desired force to be transferred.

Which Magnet Should Be Chosen for Linear Couplers?

Choose bonded NdFeB. If the application requires moderate torque/thrust and operates in a moderate temperature environment (e.g., below 150°C), bonded NdFeB is an excellent choice. It offers good design flexibility.
Choose sintered NdFeB. For precision positioning systems that require high thrust, fast response, and high performance within a compact space, sintered NdFeB is the ideal choice.
Choose samarium cobalt (SmCo). When a linear coupler needs to operate in a high-temperature environment or requires penetrating a relatively thick isolation wall (e.g., a container wall) to drive an internal valve, SmCo magnets—with their exceptional temperature stability (low temperature coefficient) and strong demagnetization resistance—are key to ensuring long-term reliable operation.

Torque Coupling

Two versions of the synchronous style of torque coupling: "Face to Face" and "Coaxial".

Face-to-Face: Face-to-Face torque coupling is comprised of disc-shaped assemblies. This torque coupling is a good low-cost solution when the required torque, speed, and size restraints are moderate.
Coaxial: Coaxial torque coupling is comprised of an inner assembly (half) and an outer assembly (half). It usually costs more than Face to Face torque coupling but requires less space.

Which Magnet Should Be Chosen for Torque Coupling?

Torque coupling is primarily used to transmit rotational torque, with typical examples being magnetic drive pumps and stirred reactors. When selecting magnets, the choice depends on the operating temperature.

For moderate operating temperatures (below 150°C) with high torque density requirements, sintered NdFeB is the preferred choice. NdFeB has the highest maximum energy product ((BH)max) of all permanent magnet materials, reaching over 50 MGOe. This means it can generate the highest torque in a given volume, making it ideal for space-constrained applications that require high torque transmission.

For higher operating temperatures (150°C to 350°C), samarium cobalt (SmCo, such as Sm₂Co₁₇ type) is recommended. Although SmCo has a slightly lower energy product than NdFeB (typically around 26–32 MGOe), it offers excellent temperature stability and demagnetization resistance, allowing it to operate reliably within this temperature range.

For extremely high operating temperatures (above 350°C, up to 550°C), high-temperature SmCo must be chosen. This type of magnet is the only commercially available permanent magnet material that can maintain effective driving force at such high temperatures.