New structure of spindle design of the hottest CNC

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A new structure designed for the main water-resistant shaft of CNC lathe

for the high-speed rotating machine tool spindle, the front and rear ends of the spindle extend out of the spindle box, and there is a gap between the spindle shaft diameter and the box hole. In order to prevent the leakage of oil in the box and the entry of air containing dust outside the box, many machine tools use radial or end face labyrinth seals. This sealing form has the advantages of simple structure and good processability. At present, it is widely used in various types of horizontal lathes, milling machines and drilling machines. This structure is preferred when designing the spindle of CNC lathe. However, in the use of machine tools, it is found that due to the temperature rise and cooling of the spindle box, the air volume in the box expands or contracts. The air flow phenomenon occurs in the clearance of the labyrinth seal, which makes the dust in the surrounding air, such as debris particles, enter the main shaft bearing and the main shaft box, causing the main shaft bearing and other parts in the box to enter the sill and cause serious wear, which leads to the reduction of the spindle rotation accuracy and affects the machining performance of the machine tool

our company has developed a structure called air isolation gas seal. After use inspection, it is proved that this structure has the advantages of simple structure and good manufacturability. At the same time, it can better overcome the shortcomings of labyrinth seal which is widely used in hull, aircraft, bicycle tires, military helmets and bulletproof vests. In the bidding for the gear and shaft processing project of FAW Volkswagen with an annual output of 300000 cars, our machine tool won the bid with this air tight seal structure, winning the market for machine tool products

the principle of air isolation gas seal, that is, on the basis of labyrinth seal, increase the air pressure in the box, so that the air in the gap of the sealing area always flows from the box to the outside of the box. This not only prevents dust and other debris from entering the box, but also blows away the residual dirt in the gap and keeps the box clean, as shown in Figure 1

1,7. Outward gas ring 2,9 Inward gas ring 3,5 Bearing 4 Machine tool spindle 6 Front inner spacer ring 8 Nose shield 10 Outer pressure ring 11 Rear bearing pressure ring

Figure 1 CL-20 high speed full function CNC lathe spindle air isolation gas seal

when using air isolation gas seal, the following points should be paid attention to:

when the front end of the spindle adopts labyrinth seal, the rear end of the spindle should also adopt labyrinth seal or similar structure. When other parts of the box are closed, the front and rear ends of the main shaft should also be sealed with air isolation gas to ensure the reliability of the main shaft seal. As the gas pressure is increased at the front and rear ends of the spindle at the same time, under the action of this gas pressure, the pressure in the spindle box is in equilibrium or close to equilibrium, and there will be no air convection with large flow rate in the box

it should be considered in the design that the air resistance on the inner gas ring should be greater than that on the outer gas ring; The clearance of the inner gas ring should be 0.08 ~ 0.12mm, and the clearance of the outer gas ring should be 0.15 ~ 0.20mm, so as to ensure that the gas pressure at the main shaft seal is greater than the pressure outside the box. In this way, dust and other debris in the air will not enter the main shaft seal ring under the action of air pressure

the purification and drying of compressed air should be considered in the design. Label making

in general, the gas pressure acting on the gas isolation ring is 0.2 ~ 0.4MPa

the establishment of air pressure in the box and the rotation start of the spindle should be interlocked synchronously to ensure that the pressure in the box is higher than the pressure outside the box during the operation of the machine tool

since the general machining site is equipped with compressed air source interface, it is easy to carry out maintenance from these aspects: the fixture used to fix the product on the machine is sealed with air isolation gas

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