ETEL IL+/LM Linear Motor Selection and Integration Guide

Complete Guide to Selection and Integrated Application of ETEL IL+/LM Series Linear Motor Technology

In the field of precision motion control, linear motors are gradually replacing the traditional "rotary motor+screw/belt" transmission scheme, becoming the preferred power source for high acceleration, high precision, and long-life applications. As a pioneer in direct drive technology, ETEL has been focusing on the research and development of linear motors and torque motors since 1994. Its IL+(ironless) and LM (iron core) series cover a wide range of applications from nanoscale positioning to high-density heavy-duty drives. However, faced with a plethora of model parameters such as sustained force, peak force, magnetic pole period, heat dissipation method, voltage level, etc., engineers often find it difficult to quickly identify the most suitable model for specific application scenarios. This article combines the core selection framework of the ETEL IL+/LM series product manual, systematically sorts out the differences and selection points between the two technologies, and provides integrated debugging suggestions with the ETEL DSC series servo controller.

Core advantages of direct drive technology

Before delving into the selection process, it is necessary to clarify the fundamental changes brought about by "direct drive". In traditional transmission chains, motors convert rotational motion into linear motion through screws, belts, or gears. These intermediate links introduce problems such as elastic deformation, backlash, friction, and inertia matching, which limit the system bandwidth and positioning accuracy. Direct drive couples the load directly with the motor rotor, eliminating all mechanical transmission components. Its advantages include:

Zero backlash: There is no backlash of the screw nut or gear, and the repeatability of positioning is significantly improved.

High stiffness: The air gap between the rotor and stator forms an "air cushion spring", and the electrical stiffness is much higher than that of the mechanical transmission chain.

High acceleration: The load is directly subjected to force, without the need to overcome the inertia and friction of transmission components, and can achieve acceleration of tens of grams.

Maintenance free: No wear parts (such as screws and belts), with an extremely long lifespan in clean environments or high demand industrial applications.

Simplify mechanical design: reduce the number of parts, lower the overall size and weight of the machine.

ETEL's linear motor products are based on the above concept and have been widely used in fields such as semiconductor manufacturing, flat panel display inspection, laser processing, precision measurement, and biomedicine.

Two major technological routes: IL+(coreless) vs LM (coreless)

The ETEL linear motor product line is divided into two major camps, with the core difference being whether the actuator uses ferromagnetic materials as the magnetic circuit.

2.1 LM Series - Iron Core Linear Motor

The rotor of the iron core motor is made of stacked silicon steel sheets, and the winding is embedded in the slot, which interacts with the permanent magnet stator (magnetic track) to generate thrust.

Core advantages:

High force density: The thrust generated per unit volume or unit current is much higher than that of ironless motors. The LM series includes sub series such as LMS (standard force density) and LMG (high force density), with a maximum continuous thrust of several thousand newtons.

High voltage compatibility: Supports bus voltages up to 340Vdc (or even higher), matched with the high-voltage version of the ETEL DSC series controllers, suitable for heavy-duty and high-speed applications.

Extremely low force ripple: ETEL adopts a patented magnetic circuit design (inclined groove or special magnetic pole shape) to minimize cogging and force ripple, ensuring smooth positioning.

Typical applications: CNC machine tool feed axis, large-scale flat printing, heavy-duty material handling, electrode cutting in battery manufacturing, and other scenarios that require high thrust and medium low speed accuracy.

2.2 IL+Series - Ironless Motor

The rotor of the ironless motor does not contain ferromagnetic materials, and the winding is directly encapsulated in a non-magnetic skeleton. The stator is a double row of permanent magnets forming an air gap magnetic field.

Core advantages:

Zero cogging effect: There is no magnetic resistance change in the coreless structure, and the thrust position curve is theoretically completely straight, achieving "zero force fluctuation".

Extremely low inertia: The mass of the rotor is extremely light (usually only 30%~50% of the same thrust iron core motor), and can achieve ultra-high acceleration and velocity (>5m/s or even 10m/s).

No magnetic attraction: There is no attractive force between the rotor and stator, simplifying the design of mechanical guide rails and reducing friction and wear.

Excellent speed stability: Due to the absence of cogging force and low inertia, the speed ripple is extremely low, making it very suitable for high-precision uniform scanning applications such as wafer inspection and flat panel display AOI.