Linear motors can achieve high acceleration and long strokes, with excellent thrust force and extremely high positioning accuracy. In contrast, other drive mechanisms—such as belts, screws, or rack-and-pinion systems—must sacrifice at least one of these performance attributes to achieve the others. This is why linear motors are the preferred choice for high-dynamic applications like metrology and semiconductor manufacturing.

In fact, based on their performance specifications, linear motors seem to be the perfect solution for addressing the conflicting requirements commonly seen in linear motion applications. But this raises a question: "Why haven’t linear motors been more widely adopted?"

To understand why the adoption rate of linear motors still lags behind that of other drive technologies (e.g., belt, screw, or rack-and-pinion drives), let’s examine some advantages and disadvantages of linear motor design.

When sizing and selecting a motor—whether rotational or linear—one of the key considerations is heat. In fact, the torque (or force) vs. speed curve, which outlines the continuous and intermittent operating ranges of a given motor-drive combination, is based on the motor’s ability to dissipate heat under specific operating conditions.

Heat-related issues can be more severe in linear motors than in rotational motors because the load is mounted on the mover, which contains the motor windings. (In some linear motor designs, the load can be mounted on the magnetic track, though this is typically only feasible for short strokes.) In ironless linear motors, the windings are encapsulated in epoxy, which does not conduct heat as efficiently as metals like iron or aluminum.

This means heat is easily transferred to the load and surrounding components, leading to thermal expansion, degradation, or in extreme cases, damage or failure. Even if the load remains unaffected, heat buildup reduces the motor’s continuous force output. To address this issue, some applications require forced air or liquid cooling, which increases cost, footprint, and complexity.

Due to their open design and exposed magnets, flat iron-core linear motors and U-channel ironless designs can be challenging to protect against contamination. While various off-the-shelf seals and scrapers can be used to protect the supporting linear guides, the exposed magnets of linear motors may attract ferrous particles from machining operations or simply from the airborne contaminants common in manufacturing and factory environments. Liquid contamination can damage sensitive electronics or disrupt feedback systems.

Of course, covers and external structures can be designed to prevent contamination, but they make it harder for the motor to dissipate heat—exacerbating the heat-related issues discussed earlier.

One of the main selling points of linear motor solutions is that they eliminate the need for mechanical power transmission components (e.g., screws, belts, gearboxes, and couplings) between the motor and the load. This means linear motors are not affected by backlash, windup, or compliance—key factors that enable them to achieve extremely high positioning accuracy, perform high-dynamic motions, and maintain rapid acceleration and deceleration rates.

However, mechanical transmission components can be beneficial in motion systems: they provide a damping mechanism for oscillating and attenuating disturbances, such as reaction forces from machining operations or vibrations caused by load movement. Without this "built-in" damping effect, oscillations and vibrations can prevent linear motors from reaching the desired positioning accuracy or settling time.

To ensure the system can respond to and correct for the effects of these undamped vibrations and oscillations, linear motor systems typically require higher-frequency control loops for speed, position, and current (force), as well as higher current loop bandwidth. Position feedback systems (usually optical or magnetic linear encoders) also need higher resolution to allow the controller to track the position of the motor and load more accurately. Even the machine frame or support structure must be sufficiently rigid (with a high natural frequency) to remain relatively insensitive to shocks and vibrations and to withstand the forces generated by the linear motor.

In other words, because there are fewer components to help compensate for vibrations and disturbances, the feedback and control loops must communicate faster and more accurately to enable the system to achieve dynamic, high-precision performance.

Finally, one of the key barriers to widespread linear motor adoption remains upfront cost. While numerous comparisons show that the TCO of linear motor solutions is lower than that of traditional belt, screw, or rack-and-pinion solutions in some applications, the upfront cost of linear motor systems still discourages engineers and designers tasked with meeting performance specifications within limited budgets. A case in point: for applications requiring very long strokes (one area where linear motor solutions excel), the cost of magnets and high-resolution linear encoders needed to meet stroke requirements can make the price of a linear motor solution prohibitive.

Despite the potential challenges posed by heat generation, contamination protection, high-bandwidth control, and cost, the adoption of linear motors is on the rise. Once considered niche solutions for semiconductor, metrology, and heavy-duty machining applications, iron-core, ironless, and tubular linear motors are now used in automotive, food and packaging, and printing applications. In these fields, motion may be less challenging or precision requirements less demanding, but the benefits—fewer components, less downtime, and higher throughput—justify the additional cost and design considerations.