By replacing the old drives, replacing the cables is an easy solution that can make a significant difference on the reliability, noise reduction, and uptime of the machine, and can be done without the cost of replacing the entire system. A large number of older CNCs, packaging lines, and automation cells continue to use the original cables that were not designed for the modern drive systems and the more demanding conditions within the plant. Here at Hulk Electric we have assisted many maintenance teams and retrofit specialists to help prolong the life of valuable legacy equipment by servicing the cables to match existing drives and motors.
The purpose of this guide is to discuss the timing of a servo cable upgrade, the actual advantages of such an upgrade, and performing the upgrade correctly with full compatibility.
Why Legacy Machines Often Need Servo Cable Attention
Older equipment was manufactured in a time when the technology of drives and operating requirements were very different than those of today. Original cables are frequently the weak link as plants strive to go faster and become more automated.
Older Cables Were Not Designed for Today’s Noise and Speed
The early servo installations were on basic motor and feedback cables that were not necessarily well shielded and had low flex ratings. The modern servo drives use PWM switching of switching frequency, which produces more electromagnetic interference (EMI) in the power and encoder lines. Legacy cable jackets and insulation are also unable to withstand the constant effects of coolants, oils, and harsh cleaning agents used in industrial settings today.
Symptoms That Point Toward Cable Limitations
The following are common warning symptoms of an encoder or feedback alarm, position glitch, unexpected servo trips and noise sensitivity. Some of the most common causes for the frequent replacement of cables are cracking of the cable jackets, degradation of the cable insulation in cable carriers, and chafing in areas with high cable motion. If the symptoms are caused by several factors, but diagnostics point to EMI or mechanical fatigue, it may be the result of outdated cabling.
What “Modern Servo Cables” Actually Offer
The servo cables used today have over a decade of engineering advances specific to challenging motion control applications.
Enhanced Shielding and Noise Immunity
Feedback signals are individually shielded or foil + braid combinations of cables for modern servos. Proper twisted pairs and EMC optimized constructions significantly reduce EMC from drive switching, resulting in cleaner encoder feedback, and more stable operation in electrically noisy environments.
Better Flex Life and Power-Chain Performance
High flex cables are servo cables that are designed to move continuously in cable chains and drag chains. They operate at electrical performance well beyond that of static or low-cycle legacy cables, even when repeatedly bent, subjected to high acceleration and travel distances.
Improved Environmental Resistance
Advanced jacket materials like PUR and special TPE mixes offer greater resistance to oils, coolants, chemicals, moisture and UV. This longevity also means less early failure and maintenance requirements in challenging production environments.
When a Cable Change Can Improve Performance (And When It Won’t)
In many older installations, a well-thought-out upgrade to the servo cables can provide measurable benefits, however, not all installations require such an upgrade.
Realistic Performance Gains From a Cable Upgrade
Modern shielded servo cables frequently reduce the number of encoder failures, sensitivity to electrical noise and improve the performance of the servo system and contribute to lower unplanned downtime due to cable failures. A higher flex life translates to longer time between replacements in applications with high-motion.
Limits of What Cables Can Fix
Cables will not solve such mechanical issues as backlash, worn bearings, misaligned gears, etc. and will not fix underpowered motors or bad drive tuning. The improvements in accuracy are more due to more reliable feedback signals than to actual changes in system resolution.
Cases Where a Cable Upgrade Is Worth Considering
- Legacy CNC axes equipped with the newer, high-speed modern drives and the original low flex cables in carriers.
- Food processing or packaging machines that are subject to frequent coolants or washdown induced jacket degradation.
- Heavy EMI from new drives on lightweight unshielded legacy cables in high-speed robotic lines.
Compatibility First: Match New Cables to Legacy Drives and Motors
All upgrades are always done with the utmost care for exact compatibility with the existing system.
Respect OEM Voltage, Current and Connector Requirements
New cables should have the same voltage and current ratings as the originals (e.g., 300V, 600V, or 1kV) as the drive and motor manufacturer specified. Connectors and pinouts should be followed according to the OEM documentation to avoid any hassles of plug and play installation.
Feedback Interface and Maximum Length
There are certain limitations on length and capacitance for encoder and resolver cables. Select constructions that will maintain signal integrity of your feedback protocol with distances within the recommended limits.
Designing a Cable Upgrade Plan for Legacy Machines
The best results are achieved with a systematic approach.
Step 1 – Document the Existing System
Document the types of drive and motor models, existing cable types (power, feedback, brake), routing paths, conditions of cable carrier, environmental exposures, and any observed faults.
Step 2 – Characterize Noise and Mechanical Duty
Evaluate temperature, chemical exposure, motion parameters and EMI sources. This information helps to determine the type of shielding and jacket material to choose.
Step 3 – Select Cables Based on Modern Criteria
Understand electrical ratings, shielding effectiveness, flex rating and bend radius, environmental resistance, and necessary certifications (UL, CE, RoHS, etc.). For retrofit applications, Hulk Electric’s servo and motor cables are specifically designed.
Implementation: Routing, Termination and Testing on the First Upgraded Machine
When new cables are installed, it’s important to install them correctly to gain the maximum benefit.
Proper Assembly and Strain Relief
Apply proper stripping, crimping and strain relief techniques. Sharp bends or over-tightened ties should be avoided as they may affect flex life and/or shielding.
Routing and EMC Practices
Provide clean power and signal installation practices—signals must be installed and routed away from power cables, maintained to ensure proper grounding and kept under 90 degrees for crossing power cables to reduce noise and ground loops.
Validate the Upgrade
Check the drive diagnostics, fault logs and cable condition post-installation. Make pre-and post-performance comparisons to determine reliability and uptime improvements.
When symptoms match the cable limitations, upgrading the older machine with new servo cables can be a cost effective solution to improve the performance and reliability of the machine. Plant selection of high quality and compatible solutions from an experienced manufacturer, such as Hulk Electric, who specialize in high-flex servo cables, strong shielding and customization, will allow plants to keep their valuable equipment in production longer while still meeting today’s stringent industrial requirements.
Contact our team and let them know about your legacy machine; from there they can give you the best suggestions for servo cables to fit your needs.