There are two main types of linear motors: ironcore and ironless, referring to whether the windings of the primary part (similar to the stator in a rotating machine) are installed in a laminated stack of iron layers or in epoxy. Determining whether the application requires an iron core or an ironless linear motor is usually the first step in design and selection. Linear motors with iron cores are best suited for applications requiring extremely high thrust. This is because the lamination of the primary part contains "teeth" (protrusions) that concentrate the magnetic flux to the magnets of the secondary part (similar to the rotor in a rotating electrical machine). This magnetic force between the iron core of the primary part and the permanent magnets of the secondary part enables the motor to provide a higher thrust.

Ironless linear motors usually have low thrust, so they are not suitable for applications with extremely high thrust requirements such as stamping, machining or forming, but are better at high-speed assembly and transportation.

Coreless linear motors are sometimes referred to as "U-shaped" linear motors because their secondary parts are shaped like a "U" with two magnetic plates mounted opposite each other. The main part (also called "thruster") is located in the U-groove between the two magnetic plates.

A disadvantage of a core design is cogging, which reduces the smoothness of the motion. Cogging occurs because the slotted design of the primary part causes it to have a "preferred" position when moving along the rows of magnets of the secondary part. In order to overcome the tendency of the primary and secondary magnets to align, the motor must generate more force to counteract the tendency, which causes fluctuations in speed, called cogging. This change in force and speed fluctuations will reduce the smoothness of the movement, which can be a major problem in applications where the quality of the movement (not just the final positioning accuracy) within the stroke is very demanding.

Manufacturers use a variety of methods to reduce cogging. A common method is to arrange the position of the magnets (teeth) obliquely, which is smoother as the primary moves through the secondary magnets. A similar effect can also be achieved when the shape of the magnet is changed to an elongated octagon.

Another method of reducing cogging is called segmented winding. In this design, the primary coil has more laminated teeth than the magnets in the secondary, and the laminated stack has a special shape. Together, these two designs counteract cogging forces. In addition, this problem can be solved by software solutions. The algorithm to reduce cogging allows the servo driver and controller to adjust the current provided to the primary coil, thereby minimizing force and speed changes.

Coreless linear motors do not have cogging because their primary coils are encapsulated in epoxy instead of being wound around the iron core. The low mass of the coreless linear motor (epoxy is lighter than the iron core, but less stiff) enables the highest acceleration, deceleration and operating speed in the electromechanical system. The settling time of an ironless motor is generally better (lower) than an ironless motor. The absence of an iron core for the primary coil, and the associated absence of cogging or speed ripple, also means that ironless linear motors can provide very low-speed, stable motion, typically with a speed fluctuation of less than 0.01 percent.

How integrated is the linear motor?

Like a rotary motor, a linear motor is only one component of a motion system. Complete linear motor systems additionally require bearings (rails) to support and guide the load, cable management, feedback (usually linear encoders), servo drives, and controllers. Experienced equipment manufacturers and machine builders, or those with very unique design or performance requirements, can build complete systems with internal functions and off-the-shelf components from different manufacturers.

Linear motor system designs are arguably simpler than belt, rack-and-pinion, or screw-based system designs, with fewer components and fewer labor-intensive assembly steps (no need to align ball screw mounts or tension belts). Linear motors are non-contact, so designers do not have to worry about preparing for the lubrication, adjustment or other maintenance of the drive unit. But for OEMs and machine builders looking for turnkey solutions, complete linear motor-driven actuators, high-precision stages, and even Cartesian and gantry systems have countless options.

When choosing a suitable linear guide for a linear motor with iron core, it is necessary to consider the attractive force between the primary and secondary components, which may increase the load on the linear guide. But ironless linear motors do not have this problem, because the primary part does not use iron core means that there is no attraction between the primary and secondary.

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