To achieve high metal removal rates, spindle designers have been working on delivering high torque and speed. Traditional solutions involve connecting a drive motor to the spindle with a belt, which adds heat and vibration.
Air-powered turbines eliminate the belt drive and achieve the same speeds without the belt. In addition, they generate cold air, which can be used to cool the tool during machining.
Reduced Heat and Duty Cycle
Spindle motors can be powered and cooled through either water or air. Air-powered systems rely on the cooling capabilities of fans to carry heat away from the engine, keeping it cool and running smoothly. Air-cooled systems are generally easier to maintain, as routine cleaning of the fans should be sufficient to keep the system working efficiently.
High-speed spindles are often characterized by their power, but this number alone tells little about the machine’s cutting performance. Power is a function of speed and torque, and a single figure may not reflect the device’s capabilities. For example, a winding might produce 21 kW at 40,000 rpm, but power output drops significantly at higher speeds.
An air-powered high-speed CNC spindle motor provides governed constant high speed even under load, allowing them to deliver excellent cut quality and eliminate the need for frequent tool changes. This means a machine can be run 24 hours a day, seven days a week, for continuous production without costly downtime or retooling. This enables high-speed operation for mold manufacturing, fine detail work, MEP, stone, wood, and hardware machining. The patented governor control increases airflow CFM to match tool load while maintaining a consistent high-rated speed and eliminating excessive vibration or heat.
Reduced Vibration
A high-speed spindle can produce high levels of vibration that damage tools and workpieces and a safety hazard. Pulse is generated by a combination of factors, including friction between the shaft and bearings, high rotational speeds, and unbalanced tooling.
Adding an air-powered speeder to a CNC machine with low spindle speeds can reduce these vibrations, resulting in smooth, accurate machining and improving part quality. These motors can also deliver more torque than their electric counterparts at higher speeds, improving cutting performance and precision.
The type of motor used in a high-speed spindle also significantly impacts its ability to achieve high speeds. AC induction motors have more winding pairs in their stator, allowing them to reach higher rates than brushless DC motors.
When selecting a high-speed spindle, a shop must evaluate the materials it works with and the cutting tools it uses to determine an appropriate speed range. A shop must also consult machining guidelines and tool manufacturer recommendations to determine the optimum spindle speed for its application. For example, elongating the distance between the front and rear bearing sets on a 40,000 rpm spindle can lower its first natural frequency to a value too close to its maximum operating speed. This increases the risk of a sudden shutdown, which can damage the bearings and cause costly downtime.
Increased Durability
The spindle is a critical component of any machine tool. It allows the machining process to occur at high speeds and with precision. It also provides support for cutting tools or workpieces. This makes proper maintenance and care of the spindle vital to a machine’s performance and longevity. If properly maintained, a quality spindle can last decades, but the wrong care can lead to premature spindle failure.
A machine’s spindle is often the most expensive component of the overall system. This is especially true for CNC machines that operate 24 hours a day, seven days a week. As a result, the need to maximize efficiency and durability in a new design is critical.
One way to increase a spindle’s motor torque is by increasing the size of its stator windings. However, this can be expensive and not feasible in all applications. Another option is to elongate the motor’s diameter. However, this change will significantly alter the motor’s natural frequency.
A better alternative is to do away with the outer housing of an integral-motor spindle design. This change lets the designers eliminate the 10 to 15 mm of wall thickness typical of the outer housing and increase the stator diameter by this amount to improve torque significantly.
Increased Efficiency
Using a permanent air-powered motor in your machine can help you increase productivity and reduce downtime. These spindle motors have a built-in cooling system to manage heat, keeping them at an optimal temperature range to extend their lifespan. The built-in cooling system can combine coolant channels, heat exchangers, or air blowers.
A permanent lubricated bearing system helps keep maintenance costs and downtime low. Most air spindle models feature a herringbone-style belt that disperses trapped air to make the system quieter, especially at higher speeds.
The type of material you work with and your cutting tools will affect your spindle speed requirements. Always consult machining guidelines and tool manufacturers’ recommendations to ensure your spindle is set at the appropriate speed. Too high a rate will produce vibration that can damage the spindle, while operating at too low a speed may lead to poor cutting results and shortened tool life.
If you’re working with a high-speed application, consider a liquid-cooled spindle. This spindle type is more excellent than an air-cooled model and can offer the added benefit of thermal stability to prevent head growth.