Stepper Motors vs. Servo Motors: Achieving Precision and Quality when Laser Cutting and Engraving

20. November 2023 •

The unmatched precision and versatility of laser cutting and engraving have revolutionised production across industries. Laser systems offer efficient and precise ways to cut, engrave, and mark a wide range of materials. There are many considerations when selecting the optimal laser machine for your requirements, with the motion control system, in particular, playing a pivotal role in determining the quality and outcome of these laser applications. 

This article delves into two of the most common types of motors used in laser systems - stepper motors and servo motors. By understanding the differences and advantages of each, we can gain valuable insights into their impact on laser cutting and engraving processes. 

What is a Motion Control System? 

Before diving into the comparison between stepper and servo motors, let's briefly explain what a motion control system is. 

A motion control system in a laser machine is responsible for controlling the movement of the laser head, ensuring accurate positioning and path following during the cutting and engraving process. This system manages the motion of the laser in multiple axes (usually X, Y, and Z) and governs factors including speed, acceleration, and deceleration to achieve the desired results on the material being processed. 

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Understanding stepper motors and their limitations

Stepper motors are a simple and cost-effective option often found in entry-level laser systems due to their easy set up, which are popular choices for smaller businesses or companies with budget constraints. Operating by dividing a full rotation into discrete steps, these motors offer control over positioning, though the precision is dependent on factors including the motor's step angle and the mechanical build of the laser system. Typically, stepper motors operate in an open-loop operation, meaning the motor operates without feedback from the mechanism to monitor its actual position.  

Certain applications benefit from the simplicity of stepper motors. For basic laser cutting and engraving projects, where precise motion control isn’t paramount, stepper motors can deliver satisfactory results. These motors excel for lower-speed applications, offering a stable and consistent performance. Examples of applications are cutting basic shapes and engraving straightforward designs. 

Limitations of stepper motors

Particularly for highly detailed and intricate laser cutting and engraving tasks, stepper motors can negatively impact the finished quality. As stepper motors move in discrete steps, jagged edges can occur along the cut lines. As the laser cutter follows curves in the design, the stepper motor's step size may not perfectly match the required movement, which results in visible stair-stepping patterns along the edges. This is more pronounced at higher laser-cutting speeds  when working with intricate designs and when cutting curves. 

Stepper motors experience a reduction in torque as speed increases, leading to inaccuracies in the cut and engraving, which is particularly noticeable for complex designs or fine details during high speed laser processing. 

They are also susceptible to resonance and vibration issues, causing the system to lose synchronisation and jeopardise the precision required for intricate designs. The open-loop operation of the motor can result in slower dynamic response times, making it less suitable for high-speed laser engraving or cutting applications that require rapid changes in direction and power output. 

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Understanding Servo Motors in Laser Applications 

Servo motors are known for their exceptional precision and dynamic response and are the preferred choice for high-quality laser cutting and engraving applications. These motors are found in premium, production laser systems such as Trotec’s Speedy laser engravers. Historically, servo motors were more expensive than stepper motors, however, as their cost has decreased they have become increasingly common in laser systems.   

In contrast to stepper motors, which operate in an open-loop system without feedback, servo motors operate in a closed-loop system, meaning they continuously receive feedback from position sensors. The feedback loop allows the controller to compare the desired position of the laser head with the actual position and make real-time adjustments, ensuring accurate motion control and therefore accurate cutting and engraving results. 

With this superior precision and accuracy, servo motors ensure intricate designs and fine details are faithfully reproduced on the material, even at high speeds. The closed-loop control system minimises resonance and vibration issues, delivering a stable and reliable performance even in demanding applications. This also helps to reduce wasted materials due to processing accuracy.  

In contrast to stepper motors, servo motors maintain a consistent torque output at high speeds, guaranteeing smooth and uninterrupted motion throughout the process. The motors respond swiftly to changes in load or operating conditions, enabling rapid adjustments and precise control during intricate cutting and engraving tasks.  

The control electronics behind servo motors are an important consideration, as they affect the overall performance. Unlike the majority of equipment available, Trotec systems use our advanced electronics system to control the motors. This allows for much greater control of the setup and path planning, delivering real world benefits when compared to other servo motor systems in the marketplace, who are constrained by their suppliers limitations.  

Trotec continues to push ahead in real time modelling of the complete laser system and path planning to deliver accuracy and speed benefits compared to other manufacturers. 

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Striking the Balance 

When it comes to investing in a laser system for your business, there are many considerations. Whilst entry-level systems with stepper motors offer a low-cost investment and are suitable for basic laser cutting and engraving, the motor system presents a significant barrier to more advanced or higher throughput designs. Even on basic cutting jobs, the edges will often be imperfect, while the decrease in torque at higher speeds can result in inconsistent results.  

Advanced systems with servo motors present a superior investment for companies thanks to their exceptional precision, dynamic response, and reduced material waste. In contrast to stepper motors, servo motors offer a faster response and higher acceleration capabilities, optimising the systems for applications where rapid and precise movements are required.  Servo motors generally produce fewer vibrations and noise compared to stepper motors, which play an essential role in maintaining even cuts and engraving. The higher investment required for servo motor-based laser systems pays off with superior cut quality, faster acceleration, versatility in material handling and long-term cost savings through increased efficiency. 

Ultimately both systems have their place in production, with many companies often including a mix of laser systems in their workshops to allow for higher throughput.  

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Conclusion 

In laser cutting and engraving applications, the choice of motion control system plays a crucial role in determining the quality and precision of the finished product. While stepper motors appear to offer cost-effectiveness and simplicity for certain tasks, servo motors emerge as the clear winner when it comes to achieving detailed and high-quality laser application results as well as the ability to meet high-volume production demands with a fast turnaround. 

For businesses and individuals seeking to excel in the laser cutting and engraving industry, investing in a premium laser system with servo motors can lead to unparalleled precision, reduced errors, and increased efficiency. As technology advances and costs continue to become more competitive, servo motors are becoming more accessible, enabling businesses to elevate their capabilities and offer superior products in this dynamic and ever-evolving market. 

Where can I try both a servo and stepper motor laser system? 

Trotec offers a range of laser systems to meet varying applications and business needs. The leading Speedy series laser cutting and engraving machines are all built with servo motors, but the laser manufacturer also supplies a range of more basic laser cutters featuring stepper motors. These models are all available for demonstration at Trotec laser showrooms, giving you the advantage of trying out both, before you decide to invest in new laser equipment. To book a no-obligation laser demonstration at your local showroom, visit www.troteclaser.com or call +44 (0) 191 580 1182.  

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