Cable routing is an important aspect of servo system performance that is often overlooked. Even the highest quality servo cable can cause EMI problems, encoder failure, wear and tear or maintenance problems if the routing has not taken into consideration power-signal separation, shield integrity, bend radius or mechanical protection. Thoughtful routing helps to facilitate electromagnetic compatibility, long cable life, thermal control and serviceability in control cabinets and machine frames for OEM builders, panel shops and service personnel.
This guide provides direction on how to route servo power, feedback, encoder, and brake cable types, as well as other cables. It focuses on classification, layout planning, the EMC practices, the handling of motion and the design of services for reliable operation in industrial automation.
Start by Classifying Every Cable Path
The first step in making the cable routing correct is to know what each cable does before you install it. Classify according to functionality, voltage, sensitivity to noise, motion specifications and environment exposure.
Servo Power Cables Carry High-Energy Switching Noise
The cables that carry the power to the drive for the servo motors are high current power cables which can produce electromagnetic interference if the motors are pulsed. Minimize coupling by routing as separate as possible from sensitive circuits. Distinguish them from incoming AC mains, feedback lines, analog signals and communication networks.
Feedback, Encoder and Communication Cables Need a Quiet Route
Low frequency or high frequency signals using encoder feedback, resolver, fieldbus or Ethernet cables are easily vulnerable to noise. Provide them with separate roads or physical separation from power lines. Please always refer to the specific drive, motor and encoder documentation for protocol specific routing and grounding requirements.
Brake, Thermal and Auxiliary Circuits Must Be Identified Too
A brake conductor, a temperature sensor or hybrid parts are commonly provided in servo assemblies. Do not treat these devices as all being the same voltage class, or having the same safety function as power cables. Check OEM drawings to set up routing treatments.
Plan the Control Cabinet Layout Before Routing Cable
Clean routing is built on component placement. Locate drives, PLCs, filters and terminals to minimize runs and crossing between noisy and sensitive areas.
Separate Power and Control Zones
Isolate the group motor drives, contactors and power components from the motion controllers, analog I/O and communication gear. If possible use separate enclosures or clear physical divisions within the panel.
Create Dedicated Ducts, Trays or Wireways
Use different wireways for motor power, AC supply, DC control and signal wires. Avoid intersections where possible, cross power and signal paths at right angles to each other when intersections are unavoidable. This way, the number of parallel runs is reduced that could raise the risk for interference.
Protect Airflow and Thermal Margin
Do not obstruct ventilation around drives, resistors, and power supplies. Consider heat build-up and leave duct clearance for cooling and future access when choosing cable bundling.
Route Servo Power and Feedback Cables for EMC Control
With the correct choice of cables, termination, and shielding strategies and grounding best practices, routing has a direct impact on electromagnetic compatibility.
Keep Motor Power Away From Sensitive Paths
Avoid long parallel runs of servo power cables to encoder and/or network cables. If space allows, separate trays and/or barriers.
Use Shielded Cable and Preserve Shield Continuity
Maintain shield integrity from drive to motor as part of effective EMI and noise control in custom cables. Avoid crushed sections, long unshielded pigtails, or improper glands that compromise performance.
Terminate Shields According to OEM Instructions
Ensure drive to the motor is covered with shields. Do not use crushed sections or long unshielded pigtails or improper glands that interfere with performance.
Protect Servo Cables Through Machine Frames and Moving Sections
Outside the cabinet, cables face vibration, abrasion, and motion stresses that demand extra protection.
Use Correct Cable Support and Entry Protection
Cables in Use Outside the Cabinet are subjected to added vibration, abrasion and motion stresses that require additional protection.
Respect Bend Radius at Every Transition
Use appropriate clamps, grommets and glands to prevent sharp edges. Don’t tie a knot too tightly – this can hurt jackets or shields.
Use Cable Carriers and Dress Packs Correctly
When servo cables run through moving carriers, follow best practices for installing cables in drag chains, including the required bend radius at exits, turns and service loops — both static and dynamic. Fatigue of conductors and insulation happens faster at tight bends.
Design for Serviceability, Identification and Troubleshooting
Good routing supports long-term operation and maintenance.
Label Both Ends and Maintain Accurate Documentation
Use durable labels matching schematics on every cable. Keep route drawings and pinout records up to date.
Provide Service Loops and Removal Paths
Include appropriate slack for component replacement without stressing cables or disturbing neighbors.
Keep Cable Routes Accessible
Design so technicians can inspect critical sections, clamps, and carriers without major disassembly.
Common Routing Mistakes That Create Servo Problems
Common problems that occur are a combination of power and feedback over long distances, incorrect termination of the shields, inadequate bends for wear, and routes that interfere with the cooling or access. These result in sporadic failures, alarms or cable shorting. Handle them early by planning and verifying them.
Practical Servo Cable Routing Checklist
Include this checklist in the design, construction, commissioning, and audit of servo cables for static, flexing, and torsional applications:
Before Powering the Machine
- Group all the cables together by their purpose (power, feedback, brakes, etc.)
- Check cable requirements to application requirements
- Verify Separation of Power and Sensitive Circuits in accordance with OEM guidelines
- Make sure that shields are terminated and grounded properly.
- Examine bend radius, strain relief, edge protection
- Verify cable carrier configuration for movements.
- Ducts don’t block air circulation
- Check labels and paperwork
- Make sure the access to inspect and replace is safe.
- Obey lockout/tagout and manufacturer guidelines
Hulk Electric’s specialty products include high-flex servo cables, hybrid assemblies, and custom cables for high-precision servo and motion control systems designed for challenging routing applications. Let our team know your machine parameters, motion profiles, and environment. You can also use our servo cable selection checklist for new machine designs before contacting us, and we’ll help you choose or design cables that deliver reliable performance from cabinet to the end effector.
