Spindles

In the structure of metal processing machinery, the precision spindle is the rotating unit of the machine, the center of the spindle is a shaft, but the concept of the spindle includes the central shaft, sleeve, bearing and surrounding components. 
 
From this point of view, the built-in spindle is one of the most complicated spindle types. Due to its power driving characteristics, it is self-powered, and the precision spindle motor is placed in the spindle sleeve. It is often installed with several spindles on one machine, such as the spindle in headstock and tailstock for bench lathe, or primary spindle and secondary spindle on machining centers. The spindle is usually the biggest one installed at the primary machining unit.

Multiple spindles

In practical applications, some machine tools dedicated to mass production are equipped with a set of four, five or even six spindles. Such a machine tool is called a multi-spindle machine tool. For example, gang drills and many screw machines are multi-spindle machines that can process simultaneously. Although the bench lathe has several spindles, it does not belong to the category of multi-spindle machine tools due to its structure and application purpose.

 

Installation of the built-in spindle

The lathe spindle is the center of the headstock or tailstock, which is used to clamp the work piece. In the milling machines, the spindle is used to clamp the cutting tool. There are many types of spindles, including electric spindles, grinding spindles, machine tool spindles, low-speed spindles, high speed spindles, high torque spindle, and many other variants.

 

Speed ranges

RPM (Revolutions per minute) is the calculation unit of spindle speed. Generally, high-speed spindles are strictly used in specialized metal processing machine tools, such as CNC milling machines. High-speed spindles can be divided into two types according to the drive mode:

 

Belt-driven

The belt-driven spindle is powered by a pulley and a precision spindle motor connected outside the spindle. 

 

Direct drive spindle and Gear spindle

In these two categories, the motor output power and torque are significantly higher, so many heavy machinery need to use this type of spindle.

 

External power source

The above mentioned spindle types are all applied external motor sources, sometimes higher power and torque can be created by changing a few parts of spindle, and the possible speed range is from 12,000 RPM to 15,000 RPM. The advantage of this type of spindle is that the speed switching is flexible and cost-effective, while the disadvantage is that the maximum speed is limited, which in turn limits the possibility of machine processing.

 

Integrated design

The integrated motor precision spindle: In this design, the key component of the spindle is the motor, which is placed in the spindle sleeve. Due to the limited internal space of the spindle sleeve, the type and size of the motor will be limited, and the output power and torque will also be limited.

 

Other custom applications

In the field of built-in spindles, the main application is not heavy-duty machining, but high-end machining, such as 3C and other vulnerable work piece processing, finishing, aerospace propeller cutting, engine cylinder processing, car chassis processing, gearbox joint grinding, etc. 

 

Common feature

Manufacturers always demand fast and flexible processing. This appeal made them tend to choose motorized spindles. Compared with other spindle types, the motorized spindle can achieve excellent processing quality through high speed and fast switching.
 
In addition, its torque performance is much more stable and stronger than belt drive spindles. For example, a traditional CNC lathe can be equipped with a belt drive spindle, but a turning and milling center that requires high machining accuracy is not. Since the work piece is fixed on the chuck, the spindle is usually used to control the cutting tool. If the precision spindle is driven by a belt, the teeth and gears on the belt are prone to mechanical failure and reduce the output quality.

 

Applications onto machining centers

In the field of machining centers, more and more machining centers are equipped with motorized spindles for multi-task machining. A precision spindle motor is equipped in spindle sleeve, so the multi-axis head can rotate more freely and work at a faster speed, which means that many curve machining and complex cutting can be realized.
Therefore, compared with other spindle types, vertical machining centers, horizontal machining centers, double-column machining centers, and moving-column machining centers install motorized spindles in order to achieve perfect production efficiency and quality.

 

Conclusion

All metal cutting tasks need to be performed through the spindle, so the precision spindle is regarded as the core of the machine tool, which controls the ultimate cutting speed, machining torque, and work productivity of the machine tool and even the entire production line. The research on the machining spindle is a lot and in-depth, which provides workers and engineers with more smart maintenance methods, which can more efficiently check and overcome the spindle problem.

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