Top 5 Common Power Problems Faced by CNC Machines

CNC machines play an essential role in shaping many products, equipment, and infrastructure people commonly use. Like other manufacturing systems, CNC machines offer precision, speed, and versatility in meeting evolving demands. However, these machines’ ability to operate efficiently relies on their received power supply, which is rarely ideal in real-world scenarios.


Manufacturing plants and facilities with installed CNC machines often experience severe power quality issues. If your CNC machines suffer frequent disruption, a noisy incoming power supply could be the culprit.


In this article, we’ll explore how CNC machines are affected by different power issues and propose an ideal solution.



What are CNC Machines? 


CNC machines are industrial equipment designed to automatically cut, bore, drill, or bend steel, wood, plastic, or other materials for products. Instead of manually aligning the tooling mechanism, operators input the coordinates and dimensions in a computer language the CNC machine understands to automate the process. This saves companies precious time producing parts and allows industrial designers to work with complex geometry. 





Companies use these machines to manufacture many products we’re familiar with. For example, CNC machines are instrumental in creating road signage, engines, and consumer electronics. They can support a wide range of tooling operations – from large cuts to micrometre-precision drills. Not only do CNC machines improve productivity, but they also eliminate human errors in manual processes. 


While the machine’s output is mainly mechanical, they are driven by sophisticated electronic hardware and software. Hence, power stability is pivotal in ensuring the precision and consistency of CNC machines. A slight fluctuation can be the difference between a clean cut, and one jarred with deformed lines. 




Top 5 Common Power Problems 


CNC machines operate optimally in their specified power ratings. However, that’s often not the case in most installations, as they are subjected to power irregularities. 




Brownouts are a phenomenon when the incoming mains dip below the nominal rating for a prolonged period. The sudden voltage drop is often unintentional and caused by different factors, including increased load exceeding the supply capacity. Because of their duration, brownouts usually cause notable effects. For example, lamps might dim, and computers may suffer in the long run when your building experiences a brownout. 


In industrial facilities, brownouts might destabilise operations and damage equipment if they are not mitigated in the long run. Electronics chips driving CNC machines are sensitive to sudden drops in voltage, and brownouts could cause them to behave erratically. 



Voltage sags


Voltage sags are power quality incidents that cause a momentary voltage drop on the power supply line. However, it is not as long-lasting as a brownout event. The IEC 61000-4-30 standard defines a sag as a voltage reduction exceeding 10% of the nominal rating and lasting between 8 milliseconds and 1 minute. Such incidents are often attributed to abrupt switching on electrical loads, inrush current, and faults in the incoming supply. 


The effect of voltage sags on machines varies. Most electrical devices will be unaffected by shallow and short sags, but some electronics might not be able to sustain the disruption that stretches beyond seconds. Due to its unpredictable nature, voltage sags cause gradual degradation of electronic parts in the long run. 



Harmonic distortion


Harmonic distortion occurs as a disturbance caused by the presence of frequencies multiple times of the AC mains on the power distribution line. This happens in industrial systems with non-linear electrical loads, such as high-frequency AC-DC converters and variable-frequency drives. Depending on their order, the presence of voltage harmonics induces varying effects. For example, the 2nd harmonic order creates a negative torque sequence which motors must compensate, while a 3rd harmonic causes more current to flow on the neutral line. 


When left unmitigated, harmonic distortion can result in costly damages. Motors, transformers, and power cables may overheat as the harmonics interfere with the fundamental voltage frequency of the system. 



Voltage spikes




Voltage spikes are sudden increases in voltage amplitude beyond the safe operating threshold of equipment. Spikes happen for several reasons, including lighting surges, inductive loads, and wiring faults. Often, voltage spikes cause widespread damage in an unprotected system as electrical parts cannot absorb the excessive electrical charge channelled through conductive terminals. 







Electrical noise


Electrical noise is the undesired presence of high-frequency disturbance of varying amplitude on the power or signal lines. The fluctuation might originate from the system itself or external sources. For example, a switching regulator may induce electromagnetic disturbance into an adjacent signal path, which travels to the connected loads.


While not as destructive as voltage spikes, electrical noise poses problems of its own. For example, noise can interfere with data signals, affecting machining precision and consistency.






Which type of CNC machines are most affected? 


CNC technology powers modern manufacturing machines for different machining tasks. CNC machines are engineered with electrical parts, which makes them susceptible to prolonged voltage irregularities. Some machines also contribute to such disturbances when in use. As a result, they suffer from self-inflicted power disturbances and voltage irregularities from external sources. 


Here’s a deeper look at different types of CNC machines.


CNC milling machines


CNC milling machines are equipped with servo motors that automatically cut and shape different materials with high precision. They are commonly used in the automotive, manufacturing, and engineering sectors, which require capabilities to produce parts with complex geometries. When operating, these machines consume immense electrical power and may cause brownouts or sags in facilities with near-maximum power capacity. 






CNC machines that use variable frequency drives 


Variable frequency drives (VFD) are electrical device that controls an electric motor’s speed. It does so by altering the voltage and frequency supplied to the motor. Many types of CNC machines consist of VFDs to enable versatile machining operations. For example, you’ll find VFDs in CNC milling machines, lathes, and laser cutters. 


VFDs are, as a matter of fact, non-linear loads that contribute to harmonic problems. They also contain sensitive electronics prone to harmonic issues. Therefore, such machines might cause and also suffer from harmonic distortion.



CNC Turning Centres


CNC turning centres, also known as CNC lathes, enable manufacturers to produce cylindrical parts with high precision. The machine has a spindle motor connected to a motor drive, which rotates the material through a cutting tool. When operating, the motor and drive may generate electrical noise, affecting its control board and nearby systems. 







CNC routers


CNC routers are similar to their milling counterparts, except the former works on less rigid materials. For example, manufacturers use CNC routers to carve wood, plastics and foams into 2D or 3D geometries. These machines run on stepper or servo motors to provide much-needed accuracy and undesired electrical disturbance.



CNC Drilling Machines


CNC drilling machines provides drill automation with computer-controlled machining mechanism. They create precise holes in different materials at varying sizes and depths. These machines require substantial power and may cause voltage sags or brownouts if the incoming supply struggles to sustain the total load. 










How AVR helps overcome power issues in CNC machines 


CNC machines require adequate protection to prolong their lifespan and produce top-quality deliverables amidst power quality issues. This is where installing an automatic voltage regulator (AVR) helps.


The AVR is an electrical device capable of suppressing voltage anomalies and protecting the CNC machine from direct or indirect consequences. By installing an AVR, the CNC machine receives a consistent voltage at the nominal rating throughout the operation. Whether spike, sag, or electrical noises, the AVR kicks in, stabilises the power line and stops the fluctuation from affecting critical components. 


Most AVRs consist of an autotransformer. The AVR alters the transformer’s winding ratio to compensate for ongoing changes in the incoming voltage. To do that, the AVR actively compares the output voltage with a predefined configuration and changes the winding ratio by moving the servo motor as required. Well-designed AVRs remain functional and can tolerate substantial fluctuations from incoming mains. This way, the electrical load receives a stable and clean power supply despite a noisy incoming power supply. 


AVR in the CNC industry


AVRs proved a reliable solution for mitigating power quality issues affecting CNC machines. Often, industry clients reported premature machine breakdowns when performing CNC tasks in challenging electrical environments. Consequently, companies face costly downtime as they hasten to repair or replace damaged machines. 


Installing an AVR on the facility or with the machine reduces the risks of negative implications. Instead of making frequent repair calls, manufacturers enjoy better productivity in their production pipeline. Moreover, AVRs increase the lifespan of CNC machines and provide companies with better investment returns. 




That said, not all AVRs are designed with equal reliability and accuracy. For example, static AVRs are prone to damage from inrush currents and lack accuracy. Instead, servo or magnetic induction AVRs are better options to safeguard your CNC machines. At Ashley Edison, we build AVRs capable of regulating the voltage at ±0.5%, ten times above the industry average. 


Here’s how a leading CNC machine manufacturer uses Ashley Edison AVRs to improve operational uptime. 




CNC machines are an indispensable part of the manufacturing ecosystem. Still, they face power quality issues that need to be resolved or risk affecting productivity, safety and profitability. Installing an AVR is the logical solution to persistent problems caused by challenging electrical environments. We’ve shown how CNC machine manufacturers help their clients achieve stability by installing an AVR.


Don’t let power issues jeopardise your CNC operations. Talk to our team to get professional help. 

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