Tubular Linear Motor Magnets
About Tubular Linear Motor Magnets
Halbach array in tubular linear motor is made of radially oriented magnets and axial magnetized magnets which arranged in a certain order, then obtain much stronger sinusoidal distributed magnetic field on the working side and keeping the field to a very low value on the other side. Actually, halbach array has broad prospects in tubular linear motor, and there is no doubt that both technical difficulty and cost of radially oriented magnets are significantly higher than regular axial magnetized magnets, therefore, the vast majority of tubular linear motor manufacturers are all adopts axial magnetized magnet array in their products. For large-sized tubular linear motor, HSMAG can make radially magnetized magnet by several pieces of diametrically magnetized arc magnet, in the meanwhile, fabricate ultra-small radially oriented tubular linear motor magnets by hot-pressed and hot-pressed process to meet the requirement of motor’s miniaturization.
A tubular linear motor is a type of linear electric motor with a forcer consisting of a series of solenoids wrapped around a cylinder enclosing a movable rod that contains a number of strong cylindrical permanent magnets aligned in alternating and opposing directions. Tubular linear motors are used in applications requiring linear actuators with performance that cannot be met by other forms of linear actuators such as pneumatic cylinders or lead screw linear actuators. Either the forcer (the part containing the coils) or the rod (the part containing the magnets) may be the moving part, depending on the application.
Early linear motion driving is achieved by the transformation from rotation to linear motion, by contrast, linear motor driving system has many advantages including high efficiency, control accuracy, dynamic performance, simple structure and also easy to maintain. Compared to traditional linear motor, tubular linear motor possess relatively higher power density and free of end winding, thus endow distinct technology advantage and promotion value in industrial automation, mechanical and military applications. As an essential component, tubular linear motor magnets have also got a lot of attention.
Tubular linear motor can be classified to radial magnetized type, axial magnetized type and halbach type according to the internal magnet array pattern.
Linear motors are often thought of as either flat or U-channel designs. But tubular, or shaft-type, linear motors have a construction principle that provides higher efficiency and makes them especially well-suited for gantry applications.
Benefits of cylindrical design
Tubular linear motors consist of a thrust rod (or tube) with permanent magnets and a stator (sometimes referred to as a forcer) with coils. The most common configuration is a fixed thrust rod with a moving stator, to which the load or tooling can be attached. But some manufacturers offer configurations in which the rod extends and retracts from a housing that encloses the stator. This design provides an alternative to pneumatic or screw-driven rod-type actuators. In rod-style thrust applications, linear motors provide high speed and acceleration, the ability to withstand high duty cycles, and precise positioning.
The primary benefit of tubular linear motors over flat and U-channel types is their high efficiency. Linear motors work on the principle of the Lorentz Force, which states that when a conductor with current (the stator) is placed in a magnetic field that is perpendicular to the current, a force is generated on the conductor. The direction of the force is perpendicular to both the magnetic field and the current. The key for tubular linear motors is that their design allows the entire coil (not just a portion of the coil, as in flat and U-channel designs) to be perpendicular to the magnetic flux, so all of the current is used to generate force in the direction of travel, maximizing their efficiency.
High efficiency devices generate less heat, so less cooling is needed. Less heat also means less expansion and contraction of components due to thermal effects, and more importantly, less heat transferred to the external load or work environment. The result is better positioning accuracy, which is especially important for cutting, machining, or dispensing applications. Although some designs are available with iron core stators for higher force production, most tubular motors are ironless, so they have no cogging effects and produce very smooth motion.
The air gap, or space between the thrust rod and the stator, is relatively large, at 0.5 mm to 2 mm, and the round design balances the attractive forces between the rod and stator. Together, these features make installation and assembly of tubular linear motors easier than for other linear motor types.