The spindle is the rotating axis in a machine used for executing operations on metals. The spindle is a vital part of the machine and is generally a combined unit containing a Mandrel. It contains a sleeve, a tool holder, bearings, fluid for cutting through the metal, and a coolant circuit. The inner composition of the spindle is a complicated structure. There are different types of spindles, but an electric spindle has high power and precision since it is motorised.
Because of automation and the need for speed in metal works, electric spindles are becoming more popular, especially in high-speed machining. They are also useful in precision milling equipment as their operation is simpler and more accurate. However, one of the drawbacks associated with electric spindles lies in the use of induction motors. In times of heavy usage, high rotor losses cause the heat to accumulate and increase inside the spindle shaft, making it expand. As a result, shaft heat then flows to the bearings, axials and other parts of the spindle reducing their service life.
Owing to the above drawback associated with induction motors, machine tool creators have started using synchronous magnet motors instead. As opposed to induction motors, they are not subject to rotor losses. As a result, the rotor draws no electric power, and all losses happen in the stator. The heat can then be easily removed using water cooling or other methods.
What to Consider When Choosing Electric Spindles
● Oil lubrication—Electric spindles usually use ceramic ball bearing because they are resistant to corrosion, high temperatures and repeated usage and have a long life span. The rotation produces heat owing to the friction between the oil lubrication and the bearings, which will cause the oil to dry. Therefore, lubrication is needed.
● Coolant— Electric spindle cooling devices should be configured with an appropriate coolant- be it water or oil. Water-cooled spindles carry the benefit that they are faster, though rust inhibitors are needed to ensure that the spindle does not accumulate rust over time. This challenge does not arise in oil-cooled spindles, though they are slower in cooling down the machine.
● Spindle speed—depending upon the usage time, the spindle speed needs to be determined and appropriately configured. The actual processing speed to attain high cutting force is generally 80% of the maximum speed. If the requirement is for low-speed processing, it falls not less than 10% of the maximum speed.
Just like many other mechanical parts, the spindle too can be customised. These customised motor spindles can be used for different functions in high-end machinings, such as aircraft propeller cutting, car chassis machining, engine cylinder machining etc.
Electric spindles are used widely in machining centres for accomplishing multitasking. Machine efficiency is greater, and precision machining can easily be performed. For this reason, electric spindles are used in horizontal, vertical, double-column and moving column machine centres.