How to Eliminate Cogging in Linear Motors? The Advantages of Coreless Linear Motors in Semiconductor Micron-Level Positioning

In ultra-precision automation fields such as semiconductor manufacturing, advanced packaging, testing, and optical inspection, micron-level or even nanometer-level positioning accuracy determines equipment performance. However, mechanical and electrical engineers often hit a physical bottleneck when utilizing traditional iron-core linear motors: cogging effect. This phenomenon induces thrust ripples during movement, which severely disrupts the smoothness required for micron-level velocity control and positioning settling.

This article delivers a deep dive into the root causes of the cogging effect and demonstrates how the coreless design of GAOGONG INTELLIGENT TRANSMISSION’s GGUI Ironless Linear Motor Series completely eliminates cogging forces to achieve ultimate micron-level positioning in semiconductor applications.

1. What is the Cogging Effect in Linear Motors?

Traditional iron-core linear motors utilize silicon steel laminations within their moving parts (forcers). As the forcer travels across the permanent magnet track (stator), the presence of iron slots causes the magnetic reluctance within the magnetic circuit to vary periodically based on position. This variation generates an undesirable attractive force that pulls the forcer toward specific magnetic poles, known as cogging force.

The primary drawbacks of the cogging effect include:

• Thrust Ripple: It introduces noticeable velocity fluctuations and cogging disturbances, especially at low-speed scanning operations.

• Degraded Settling Performance: During micro-stepping or micron-level microscopic feeding, the cogging force disturbs the servo loop control, causing system overshoot, hunting, or residual oscillations.

2. The Ultimate Solution: GAOGONG INTELLIGENT TRANSMISSION GGUI Ironless Linear Motors

To eradicate the cogging effect fundamentally, the iron core structure within the moving part must be entirely removed.

The GGUI Coreless Type I Linear Motor Series independently developed by GAOGONG INTELLIGENT TRANSMISSION features a forcer encapsulated entirely in high-density epoxy resin, containing absolutely no iron core or silicon steel sheets.

Key Characteristics Achieved by Coreless Architecture:

• Zero Cogging: The magnetic reluctance remains perfectly constant at any position, ensuring exceptionally smooth motion profile execution.

• No Magnetic Attraction: There is zero net attraction force between the forcer and the magnetic tracks. This drastically reduces the structural preload and friction on the precision linear guideways, extending the mechanical lifecycle.

• Lightweight with High Acceleration: Eliminating the heavy iron core provides an outstanding thrust-to-mass ratio, facilitating ultra-high dynamic frequency response.

3. GGUI Series Hardcore Parameter Analysis: Enabling Micron-Level Stability

According to GAOGONG INTELLIGENT TRANSMISSION’s official engineering specifications, specific model parameters validate its superior motion control performance:

1. Exceptional Thrust Linearity and Control Sensitivity

Precise semiconductor die bonding or wafer inspection require highly linear force output. Take the GGUI3-S-S1 model as a benchmark:

• Continuous Force (Coil @ 100°C): Rated at 27.5 N.

• Peak Force: Reaches up to 105.5 N.

• Force Constant ($K_f$): Stands at 13.0 N/Arms in a series (S) connection wiring configuration.

  Consequently, even minimal current adjustments from the servo drive translate into instantaneous, perfectly linear thrust responses. Without cogging forces to counteract, micron-level micro-positioning becomes seamlessly straightforward.

2. High-Payload Precision Motion: GGUI4 & GGUI5 Series

For heavy-duty payloads on the X-Y gantries of semiconductor equipment, GAOGONG INTELLIGENT TRANSMISSION provides larger force density series:

• GGUI4-S/P-S4: Offers a continuous force of 223.6 N and a peak force of up to 1263.6 N.

• GGUI5-S/P-S4: Steps up the performance with a continuous force of 400.0 N and an impressive peak force of 1800.0 N.

  Despite these high force capabilities, their cogging force remains absolute zero due to the slotless, ironless architecture. This combination of "high thrust and zero ripple" serves as the ideal powertrain for long-stroke wafer dicing saws and lithography exposure systems.

3. Low Electrical Time Constant and Rapid Thermal Response

In high-frequency semiconductor pick-and-place applications demanding rapid come-and-go duty cycles, thermal management and responsiveness are critical. The GGUI3 series exhibits an electrical time constant as low as 0.59 ms and a motor constant ($K_m$) of 3.3 N/sqrt(W). This ensures high efficiency in electrical-to-kinetic energy conversion, keeping heat dissipation minimal and preventing thermal expansion from shifting micron-level mechanical alignments.

4. Flexible Forcer and Magnet Track Part Number Configuration

The GGUI series utilizes a highly standardized, modular part numbering system, allowing automation engineers to configure dimensions accurately based on machine envelopes:

• Forcer Configuration Example: GGUI3-S-S2-H-T-0.3-MR

• Model Series: Selectable among GGUI3, GGUI4, and GGUI5 force scales.

• Wiring Connection: Supports Series (S) or Parallel (P) configurations to match drive bus voltages and current limits.

• Forcer Size: Modular lengths scaled from S1 up to S6 (and extending to S9).

• Smart Integration: Integrates optional digital Hall effect sensors (H) and Thermal sensors (T) for closed-loop safety protection and commutation.

• Magnet Track Configuration Example: GGUI3-TL300

• Standardized track lengths are supplied in modular increments like TL120, TL180, TL240, TL300, and TL600. These modules support unlimited butt-joint splicing to achieve unrestricted travel distances, accommodating both compact desktop semiconductor tools and massive automated assembly lines.

Conclusion

For micron-level semiconductor applications with zero tolerance for velocity ripple, the cogging effect represents an inherent limitation of iron-core linear motors. GAOGONG INTELLIGENT TRANSMISSION’s GGUI Ironless Linear Motor Series successfully overcomes this barrier by delivering zero cogging force, rapid dynamic acceleration, and flawless force linearity up to an 1800.0 N peak threshold.

As a National High-Tech Enterprise, GAOGONG INTELLIGENT TRANSMISSION delivers more than just high-end linear components. We offer comprehensive "Linear Motor + Servo Drive Integration Tuning" packages. Our assemblies ship fully optimized and pre-tuned, empowering your intelligent equipment to enter the micro- and nano-positioning frontier effortlessly.