The rotary table of machine tool usually has two types: indexing table and CNC rotary table. Swing table bearing
NC rotary table is usually used for circular feed motion of machine tool, and can also complete indexing motion. It is referred to as CNC turntable for short, while the indexing worktable can only rotate the workpiece and change the surface, usually in cooperation with the automatic tool change device.
There is not much difference in the shape of the two, but there are obvious differences in the internal structure. The structure of the CNC turntable is similar to the feed drive mechanism of the CNC machine tool; The difference is that the machine tool driver mainly provides linear feed, while the CNC turntable mainly provides circular feed.
The rotary table is widely used in various types of machine tools such as CNC milling machines, boring machines, vertical lathe, and end milling. It is required to be able to bear the weight of the workpiece well and have high rotation accuracy. Therefore, the turntable bearing must not only have high bearing capacity, but also have high slewing accuracy, high overturning resistance and high speed capacity. The types of bearings used for the rotary table are roughly divided into:
Thrust ball bearing+cylindrical roller bearing combination
Thrust ball bearing mainly bears axial force, while cylindrical roller bearing mainly bears radial positioning and external radial force. This design combination has low application cost, but its axial bearing capacity is relatively limited, so it is mainly used in small or medium-sized machine tools.
Hydrostatic bearing+precision cylindrical roller bearing combination
Hydrostatic bearings are always under the protection of liquid lubrication during operation, so they have no wear, long service life, small starting power, high accuracy, high stiffness, and can inhibit oil film oscillation. The precision cylindrical roller bearing can well bear the radial load and provide high rotation accuracy. This combination can provide higher axial load bearing, but it must be equipped with a special oil supply system, and the maintenance cost is high.
Cross roller bearing
In the application of turntable, cross roller bearing is also widely used. It has two raceways and two rows of cross-arranged rollers. The machine tool turntable with cross roller bearing can obtain more compact structure, smaller volume and lower cost.