Skilled CNC spindle operators know that excessive heat is the biggest challenge to effective spindle machining. An overheated spindle requires shutting down the machine, interrupting production, and inspecting the finished product for defects caused by the excess heat. However, excessive heat doesn’t always have to be a problem for your CNC operation, especially if you know how to maximize the benefits of spindle cooling.

CNC spindles rotate tools at extremely high speeds—as fast as 250,000 RPM—to achieve the intricate machining requirements of today’s manufacturing environment. At those speeds, things can quickly start to heat up. A hot piece of metal,perhaps a tool or the workpiece, will expand and negatively affect machining accuracy. Excessive heat also affects components within the CNC spindle. If you exceed the limits of the lubrication, you start to see damage to internal spindle components, especially bearings. If left unchecked, damage occurs quickly, and repairs are costly. This doesn’t even account for lost production time, the inability to meet client deadlines, and the potential damage to your company’s reputation.

There are several telltale signs that the spindle is overheating:

• Overheated spindles often cause new sounds and vibrations. Immediately stop the spindle if you hear or feel something strange.
• Tools will become discolored. Look for darkening of the tool at the point of contact with the work material.
• When a spindle starts to overheat, it will produce less accurate work and will be unable to hold tight tolerances.  
• The spindle will not be able to reach higher RPMs.

Overheated spindles can cause serious problems, some of which can be devastating to the spindle assembly.

• Severe overheating can cause bearing failure, leading to damage to the shaft.
• Thermal expansion may result in misalignment, broken components, and broken tools.
• Premature wear from excessive heat reduces the lifespan of your spindle.
• Motor burnout due to excessive heat, leading to costly repairs and downtime

Need a second opinion? The experts at GMN USA are knowledgeable in identifying spindle overheating issues.

Fortunately, the engineers who design spindles recognize the challenge of overheating and have incorporated efficient cooling systems into these essential machines. Spindle cooling systems allow operators to control heat and keep production going while maintaining the quality and level of intricacy demanded by the marketplace.

There are two types of spindle cooling systems, and they have their distinct advantages and disadvantages:

Left unattended, a hot cup of coffee will give up its heat, but when you blow across the surface, you accelerate the process. Air-cooled spindles incorporate the same concept, but in this case, they use electric fans to direct air across the spindle assembly to direct heat away from the spindle. 

Air-cooled spindles have their advantages:

• They typically have a smaller footprint, which can be vital in factories where every square inch of floor space is essential.
• Air-cooled spindles are more self-contained, whereas water-cooled spindles might require a remote water source and a chiller.
• Air-cooled spindles are, to some operators, easier to maintain with fewer components to monitor. If the fans are running, the system is operating.

Air-cooled spindles also have disadvantages:

• They require space for proper airflow, which is often hard to monitor on a busy factory floor.
• Air-cooled spindles are less adjustable whereas water-cooled spindles lend themselves to fine-tuning.
• The fans make the air-cooled system noisier, adding to the noise pollution of the factory floor.

Water-cooled spindles use a coolant fluid to help manage the temperature of the spindle. They typically involve a reservoir for the coolant, and an external chiller that is usually next to the machine. The fluid circulates through channels in the spindle cooling system, which run adjacent to the shaft and other high-temperature areas. Higher-end spindles allow you to channel water or coolant directly through the tool bit to the work site. Systems that use water are often preferable.

Advantages of water-cooled spindles include:

• Water has excellent thermal capabilities, allowing you to convey heat away from the spindle efficiently.
• They can be adjusted to a specific temperature, which is crucial when working with tight tolerances.
• They can use various cooling media. Water-cooled spindles typically use water, but some models use a mixture of water and glycol (antifreeze), while others allow for oil.You can tailor the coolant to match the work your CNC machine shop performs.
• Because water-cooled spindles are more efficient, they enable the operator to run the spindle at higher speeds, which allows for a wider variety of work materials and faster production times.
• Water-cooled spindles are typically quiet compared to their air-cooled counterparts.

Disadvantages of water-cooled spindles include:

• Water-cooled spindles have a larger footprint, including a reservoir and a spindle chiller next to the machine that holds as much as 50 gallons of coolant.
• Water-cooled systems require more maintenance. Operators must regularly check fluid levels and monitor coolant mixtures for the correct balance.

The ability to fine-tune the operating temperature of your CNC spindle is a significant benefit of water-cooled spindles which far outshines any drawbacks. This is especially important given the variety of work done by CNC spindle machine shops. Manufacturers in all industries use spindles to machine numerous components and devices, including medical equipment and devices, aerospace components, and more. Quite often, spindle-machined components save lives, and just as often, they are also a vital part of keeping the economy moving forward. Additionally, airflow is often a challenge in manufacturing spaces, which makes air-cooled spindles problematic. Another advantage of water-cooled spindles is the ability to attain the higher speeds needed for today’s machine projects.

Looking for answers to your spindle cooling questions? GMN USA can help!

Many machine shops use chillers to facilitate spindle cooling. Chillers are standalone units that work by cooling water through the evaporation process. After cooling the spindle, the heat-bearing water travels to the chiller, passing through an exchange plate. The system returns the cooled water to the spindle, repeating the process. A good spindle chiller can enable you to control the temperature of the water to within one degree. GMN USA carries a selection of industrial chillers from Pfannenberg. Features of Pfannenberg chillers include:

• A wide range of temperature capabilities so that you can handle the temperature requirements for any project.
• Non-ferrous construction, which guards against corrosion in the system.
• Eco-friendly construction features so that you can reduce your environmental impact.

Water-cooled spindle systems require regular maintenance, but extending the lifespan of your spindle its capabilities far outweighs the extra work. Here are a few maintenance tips for water-cooled spindle upkeep:

• Check the coolant level regularly.
• Check the coolant mixture, especially if you combine water and glycol.
• Check the OEM guidelines of the spindle for how often you should flush the system. Water is corrosive and can cause build-up and clog lines if not tended to regularly. Use coolants that contain anti-corrosive additives. 
• Regularly check all connections in and around the spindle assembly for leaks.

GMN USA repairs, maintains, and upgrades all brands of spindles. Contact GMN USA for all your spindle cooling questions.

You can take other measures to facilitate spindle cooling and control overheating:

• Keep spindle operations within safe limits. Don’t push spindles past their parameters, especially when working with difficult materials and demanding machining requirements.
• Monitor all spindle operations closely. Use a spindle monitoring system like GMN’s IDEA-4S to review spindle performance. Look at your spindle operating history for patterns.
• Ensure that all tools are balanced. Unbalanced tools are a significant cause of spindle overheating, and you can remedy this situation quickly.
• Service your lubricators and make sure they are set up properly.
• Ensure that spindles receive periodic service as indicated by the OEM.

At GMN USA, our personnel are experts in all things spindles, especially the GMN line of water-cooled spindles. We are ready to help you with all your spindle cooling questions from cooling fluid choice to chiller capabilities and beyond.

Contact GMN USA today to find the right solution for your spindle cooling needs.