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Choosing the right cable for your industrial automation system is not as simple as picking a random part from a catalog.
As an engineer purchaser who has worked with servo systems for years, I can tell you that the type of cable you use—specifically whether it’s shielded or unshielded—can make a huge difference in performance, reliability, and long-term costs.
In this article, we’ll break down the key differences between shielded and unshielded servo cables, how to choose the right one for your system, and provide some real-world examples based on years of experience.
By the end of it, you’ll have a clear understanding of which type of servo motor cable is best for your needs.
What Are Servo Cables?
Servo cables are used in industrial automation systems to provide power, control, and feedback to servo motors.
These cables are crucial for precise motion control, which is why you see them in CNC machines, robotics, packaging lines, and any application requiring high-precision movement.
In these systems, servo cables typically perform three main functions:
- Power transmission – Delivering electricity to the servo motor.
- Signal transmission – Communicating feedback from the motor to the controller (position, speed, torque).
- Control signal – Ensuring the motor operates in sync with the system commands.
The key differentiating factor in servo cables is whether they are shielded or unshielded, which significantly impacts their ability to handle noise, interference, and environmental stress.
Shielded vs. Unshielded: What’s the Difference?
To put it simply, shielded cables are designed to protect against electromagnetic interference (EMI) and radio frequency interference (RFI).
They have an additional layer of protection (the “shield”) that helps keep unwanted signals from corrupting the data or power transmitted through the cable.
Unshielded cables, on the other hand, lack this protective layer, making them lighter and more cost-effective, but also more vulnerable to interference in noisy environments.
What Is Shielding and Why Does It Matter?
The purpose of shielding is to maintain signal integrity by preventing external electromagnetic fields from affecting the signals traveling through the cables.
This becomes especially important in industrial environments where motors, electrical equipment, and heavy machinery create high levels of electromagnetic interference (EMI).
Think about it this way: Imagine you’re trying to listen to your favorite music on your phone while walking through a busy construction site.
Without your headphones’ noise-canceling feature (the “shield”), all you’ll hear is the roar of machinery, traffic, and clanking tools.
Shielding in cables works the same way—it helps keep the “noise” out and ensures that the signals from your servo motor remain clear and precise.
Why You Might Choose Unshielded Servo Cables
Unshielded servo cables are typically used in environments where electromagnetic interference (EMI) is low or non-existent.
If your industrial setting is relatively quiet, electrically speaking, you might not need the extra protection that a shielded cable provides.
Cost-Effective and Lightweight
In my experience, unshielded cables are the go-to choice for small-scale or less demanding applications.
I’ve seen several smaller automation projects where the systems didn’t require any special shielding because they were used in clean rooms or areas with little to no electrical noise.
In these cases, using unshielded cables helped to keep costs down without compromising performance.
For example, a client of mine needed cables for a small, local robotic arm that worked in a low-EMI environment—an assembly line with minimal electrical interference.
Using unshielded servo cables made perfect sense. The cost savings were significant, and the cables still performed well in the setup.
Best Use Cases for Unshielded Cables:
- Short cable runs: If the servo motor is relatively close to the controller or power supply, the signal is less likely to degrade.
- Low-electrical noise environments: Areas with minimal machinery and electrical equipment that won’t interfere with the signal.
- Simple systems: For smaller applications like basic robotic arms or small motors where high-speed feedback isn’t critical.
Why Shielded Servo Cables Are Essential in Certain Applications
While unshielded cables may work well in certain conditions, there are plenty of situations where the added protection of shielding is crucial.
High EMI environments are one of the most common reasons to opt for shielded servo cables.
These cables feature an additional layer of braided copper or foil that shields the signals from external interference.
Reducing EMI and RFI for Reliable Performance
I remember working on a project in a large manufacturing facility where motors, welding machines, and power supplies were running constantly.
The environment was full of electrical noise, and any unshielded servo cables would have experienced signal degradation, leading to erratic motor behavior and unreliable feedback.
By switching to shielded servo cables, we were able to minimize EMI, improve data transmission, and maintain system stability.
The motors performed better, with fewer errors or lag, and the feedback signals were much clearer.
When to Choose Shielded Cables:
- High EMI environments: Factory floors, control panels, and other settings with heavy electrical machinery.
- Long cable runs: Over long distances, the signal is more vulnerable to degradation, especially when interference is present.
- Critical applications: CNC machines, robotics, and motion control systems that require precise positioning and minimal signal loss.
Key Factors to Consider When Choosing Between Shielded and Unshielded Servo Cables
Now that you understand the basic differences, let’s take a deeper dive into the factors that should influence your decision between shielded and unshielded servo cables.
Environmental Considerations
Electrical Noise: If your equipment operates in a high-noise environment—think motors, induction heaters, or other heavy-duty machinery—shielded cables are your best option.
On the other hand, if you’re working in a relatively quiet setting, unshielded cables may be just fine.
I’ve worked with various clients who’ve had to deal with significant EMI from nearby welding machines or large motors, and in these cases, the right shielded cables saved a lot of headaches down the road.
Cable Length and Routing
The longer the cable run, the more susceptible the signal becomes to interference. If you need to run cables across long distances, it’s better to use shielded cables to maintain signal integrity.
Shorter cables, especially when the servo motor and controller are close together, can often get by without shielding.
Cost and Budget Constraints
Shielded cables are more expensive due to the added layers of protection, so if you’re on a tight budget, you might lean towards unshielded cables.
However, it’s important to weigh the potential cost of malfunctioning equipment or downtime against the savings of using cheaper cables.
System Complexity
In highly complex automation systems where precision is key—such as CNC machines or robotic arms—shielded cables are worth the investment.
For less complex setups or systems where signal integrity isn’t as critical, unshielded cables will likely do the job.
Shielded vs. Unshielded Servo Cables: A Quick Comparison
To make things easier, here’s a quick comparison table summarizing the key factors:
| Factor | Shielded Cables | Unshielded Cables |
|---|---|---|
| Cost | Higher due to shielding layer | Lower, more affordable |
| Protection from EMI/RFI | Excellent, prevents signal degradation | Minimal, susceptible to interference |
| Best for | High-noise environments, long runs, critical systems | Low-noise environments, short runs, simple systems |
| Signal Integrity | High, maintains quality over distance and noise | Lower, especially in noisy environments |
| Durability | More robust, designed for industrial use | Lighter and simpler, less protection from external forces |
| Application Examples | CNC, industrial robots, factory floors with heavy equipment | Simple machinery, short-distance control, basic robots |
Conclusion
Whether you choose shielded or unshielded servo cables will depend on the specific requirements of your automation system.
If you’re working in a noisy environment or need to maintain precise signal transmission over long distances, shielded cables are the way to go.
On the other hand, if you’re working in a low-interference environment with shorter cable runs, unshielded cables will suffice and save you some budget.
At the end of the day, it all comes down to balancing your needs for performance, cost, and reliability.
As an experienced engineer purchaser, I can tell you that the right choice of cable will make all the difference in ensuring your system operates smoothly and efficiently.
Need help deciding? Don’t hesitate to reach out to a cable supplier or an automation expert to guide you through your specific needs and help you make the right decision.