1、 Spindle structure and characteristics

Belt driven spindle; Direct spindle; Built in spindle (motorized spindle), double contact (equipped with HSK, BBT and NBT tool handles) taper hole spindle; The spindle with the same speed has many different characteristics, which should be reasonably selected. For example, the size, specification and position of the bearing are different; The rigidity of spindle has different indexes; The length of the front end of the spindle has different specifications; There are different additional functions (nail pulling type, spindle cooling, medium spray, air curtain protection, nozzle with cutting fluid, tool loosening reverse buckle, etc.).

2、 Spindle selection elements

Machine tool design generally takes meeting the maximum cutting force of the machine tool as the first element. At the same time, factors such as maximum cutting speed, maximum cutting torque, spindle rotation accuracy, machine tool structure requirements, processing materials, cutting conditions and so on should be considered comprehensively.

If the spindle design calculation is not skilled, it can be roughly calculated from the tool tension force on the spindle sample to ensure that the spindle can bear the maximum cutting force. Generally, the tool tension force is about twice greater than the maximum axial cutting force borne by the spindle.

The commonly used maximum speed during processing shall not be higher than 80% of the maximum speed provided on the sample.

Selection of pulling nail type: the steel ball tensioning device is generally selected for the spindle with speed below 6000 rpm, and it can also be selected for those with small cutting force; Four jaw tensioning device shall be selected for high-speed spindle above 8000rpm and strong cutting.

Selection of spindle cooling: the spindle diameter less than 70mm and the maximum speed of 8000rpm (discontinuous operation) can not be selected, and the machine tool of high-precision machining center must be selected. The selection and definition of cooling should be based on the consideration of accuracy rather than damage.

Selection of intermediate spraying function: it is recommended to select the machine tool for processing aluminum alloy, titanium alloy and stainless steel materials, and the machine tool for processing small holes and deep holes.

Selection of air curtain protection function: generally, it should be selected, especially the machine tool for processing graphite materials, plastic materials and aluminum alloy materials. The compressed air of the machine tool with this function must be dry, otherwise it will rust inside the spindle.

Selection of tool loosening reverse buckle function: this function can protect the spindle shaft from the impact of tool loosening force, reduce and prolong the service life of the bearing.

For spindles with the same taper hole specification, spindles with large outer diameter are often equipped with large steel ball or ceramic ball bearings, which have high rigidity, stable cutting and can bear large cutting force. They are generally selected on high-power and strong cutting machine tools.

When purchasing the spindle, it is best for the supplier to provide the transmission parts and basic installation size requirements at the same time, so as to realize the complete supply and avoid errors.

Try to select the spindle with standard specifications of the company, with relatively low price and short delivery time.

3、 Precautions for selection and use

Belt drive type: the belt drive type has no gear. It can be used at high speed for vibration and noise problems, but the spindle is subject to large lateral force vibration. At low speed, the belt drive efficiency is almost suitable for low-speed heavy cutting. At high speed, the friction noise between belt and air is quite large. When the DMN value exceeds 1000000mm / rpm, other transmission methods should be used.

Built in type: it is most widely used in high-speed machining, with light weight and is most suitable for high-speed movement. At the same time, it has a small number of parts, easy dynamic balance correction and centering, and low vibration.

Motor direct connection type: in order to reduce the vibration caused by the lateral force on the spindle, the motor and the main shaft are connected by a coupling. The speed can be higher than the belt driven main shaft, with heavy weight and large volume, but the cost is cheaper than the inner main shaft, and the speed can reach 20000 rpm.

Speed: the speed required for high-speed cutting is mainly determined by the material of the workpiece, the material of the cutting tool and the diameter of the cutting tool. The high-speed spindle speed of BT40 specification is mostly below 15000 rpm, up to 10000 rpm and 12000 rpm, and the high-speed spindle speed of BT50 specification is mostly below 12000 rpm and up to 1000 rpm. It is used in high-speed cutting spindle of light alloy and other materials. The spindle speed is mostly above 20000 rpm. Hsk-a63 is commonly used for tool handle specification, and hsk-a100 is used for large workpiece processing.

Horsepower: in the goal of improving the processing energy rate, we are also concerned about whether the horse country of the main shaft is enough. In the pursuit of high removal rate in high-speed cutting, the horsepower of the high-speed main shaft is much higher than that of the traditional main shaft, but the rigidity of the machine should also be matched, otherwise we can give full play to part of the horsepower to reduce the vibration of the machine structure. In domestic tool machine factories, some machine products are directly replaced with high-speed spindles. Its main goal is to improve the cutting speed and process light alloy or soft materials. It does not need high removal rate, and small horsepower can be used.

Rigidity: if the rigidity of the spindle is insufficient, the machining accuracy will be affected, but if the rigidity exceeds the functional requirements, the service life of the spindle bearing will be reduced. When the DMN value is low, the positioning preloading can be used. When rotating at high speed, the preloading is aggravated due to temperature rise. The bearing spacer ring can be used for cooling? And preloading increase has a good effect. When DMN value is high, constant pressure preloading can be used to ensure the preloading value. When the DMN value is low, grease lubrication can be used, and its rigidity value must be lower than that of oil-gas lubrication, so as to avoid accelerating grease deterioration and shortening the service life of the main shaft due to excessive preloading and temperature rise.