Before you understand CNC machines, you need to understand spindles!
A machine tool's spindle has the ability to rotate the tool or workpiece. The majority of machine tools contain spindle components, with the exception of those whose primary motion is linear motion, like planers and broaching machines. Spindles are used
The spindle on a machine tool can drive the workpiece or tool to rotate, in addition to planers, broaching machines, and other machine tools whose main motion is linear, most machine tools have spindle components. Even many small desktop CNC engraving machines use spindles as cutting tools. Lunyee's spindle CNC engraving machine will not be able to run without the spindle.
What conditions should a good spindle fulfill?
The motion accuracy and structural rigidity of spindle parts are important factors in determining machining quality and cutting efficiency. For CNC machine tools, spindle parts not only need to meet the requirements of high fineness in the finishing process but also have the cutting ability in the roughing process. At the same time, CNC machine tool spindle parts should have high stiffness and resistance to thermal deformation.
Specifically, the spindle components of CNC machine tools should mainly meet the following five requirements:
- Accuracy durability: spindle assembly accuracy durability refers to the ability of the spindle to maintain the original manufacturing accuracy over time. Due to the high price of CNC machine tools, to speed up its return on investment, CNC machine tools tend to start higher. But at the same time, to extend the service life, to reduce the number of repairs, which requires CNC machine tools spindle components with good accuracy and durability.
- Higher stiffness: machine tools in the operation of high-speed cutting are usually used, which requires the spindle motor assembly to have a high degree of stiffness, otherwise the spindle in the external force will produce a large elastic deformation, thus causing vibration and vibration. This will affect the accuracy and surface roughness of the processed parts.
- Strong thermal stability: the thermal stability of the assembly refers to the ability of the spindle bearing to resist changes in shape and position caused by heat generation. CNC machine tools in the process of operation, due to friction, oil churning, and other reasons will produce heat, resulting in spindle component temperature imbalance, and deformation when affecting the shape and direction of the spindle components, which in turn affects the machining accuracy.
- High reversal accuracy: the same rotational accuracy of the machine tool spindle components, refers to the no load, in the spindle front end of the workpiece, fixtures, or tools on the positioning surface of the radial runout, low speed, and axial runout measured with a percentage table. Its height directly affects the geometric accuracy and surface quality of machined parts. Therefore, the reversal accuracy of CNC lathe spindle parts should be high.
- Good vibration resistance: the vibration resistance of the spindle components of the CNC machine tool refers to the ability of the spindle components to resist vibration and maintain balanced operation during the CNC machining process. Once the CNC machine tool vibration, it will affect the quality of the surface of the workpiece, the durability of the tool, and the life of the spindle bearings, and at the same time, it will also produce noise, affecting the working environment.
Precautions for spindle use
Since the spindle components for CNC machine performance are so important, in the daily use and maintenance process, what should we focus on?
Good lubrication can reduce the working temperature of the bearing and prolong the service life. Therefore, in the operation and use should pay attention to low-speed, the use of grease, oil circulation lubrication; high-speed use of oil mist, and oil and gas lubrication.
It should be noted that, in the use of grease lubrication, do not arbitrarily fill, because too much grease, will exacerbate the spindle heating. For oil circulation lubrication, the operation and use should be done every day to check the spindle lubrication thermostatic oil tank to see whether the oil volume is sufficient. If the oil quantity is not enough, then the lubricant should be added in time, and at the same time, pay attention to check whether the lubricant temperature range is appropriate.
There are usually two types of spindle lubrication: oil mist lubrication and spray lubrication. Oil-air lubrication is similar to oil mist lubrication, but oil mist lubrication is a continuous supply of oil mist, while oil-air lubrication is timed to send the oil mist into the bearing gap, so that both the realization of the oil mist lubrication, but also to avoid the oil mist too much and pollute the surrounding air. Spray lubrication is to use a larger flow of constant temperature oil (each bearing 3 ~ 4L / min) injected into the spindle bearings, to achieve the purpose of lubrication, and cooling. Here the larger flow injection of oil must rely on the oil pump to force oil discharge, rather than natural reflux. At the same time, but also the use of a special large-capacity high-precision thermostatic oil tank, oil temperature change control in ± 0.5 ℃.
The sealing of the spindle parts should not only prevent dust, chips, and cutting fluid from entering the spindle parts but also prevent the leakage of lubricating oil.
There are two types of sealing for spindle parts: contact and non-contact sealing. For the use of linoleum ring and oil-resistant rubber sealing ring contact sealing, pay attention to check if it is aging and breakage; and for non-contact sealing, to prevent leakage, it is important to ensure that the return oil can be drained as soon as possible to ensure that the oil return hole is smooth.
In summary, the spindle components of the lubrication, cooling, and sealing of these three points are a CNC machine tool in the daily use and maintenance process of the top priority.