CNC machine tools commonly used in rotary table partakers of the table and CNC rotary table . CNC machine tools in the processing of certain parts , apart from the straight line need X, Y, Z three axes feed motion , but sometimes also need to have X, Y, Z three axes around in a circular motion , called A, B, C axis.

 

NC rotary table can be used to achieve the circumference feed movement , in addition, you can also complete the indexing movement . The indexing table indexing function just changing the workpiece surface , and with the use of automatic tool changer , the installation can be completed to achieve a workpiece several faces a variety of processes , thus , greatly improving the work efficiency. Not much difference in the shape and NC rotary indexing table , but it has a series of structural features. Since the NC rotary table enables feed movement , so it is structurally and CNC machine feed drive mechanism have much in common . The difference is that the drive mechanism to achieve is linear feed movement, and NC rotary table to achieve is the circumference of the feed movement .

 

Rotary table is widely used in a variety of CNC milling machines, boring machines, vertical lathe and milling a variety of other machine tools . In addition to requiring rotary table can well withstand the weight of the workpiece , but also the need to ensure the accuracy of its rotation under load . Turntable bearing , as the core component of the turntable , the turntable is running, only to have a high load carrying capacity , the need to have a high rotational accuracy , high resistance to overturning capacity, and high speed capability.

 

A thrust ball bearing + cylindrical roller bearings

 

Thrust ball bearings can withstand axial force , so that the bearings are mainly used to bear the weight of the workpiece ; and cylindrical roller bearings are mainly used to locate the radial and radial withstand external forces ( such as cutting force , milling force, etc. ) . Wide application of such design , and the cost is relatively low . Because a point contact thrust ball bearing , so it's axial capacity is relatively limited , mainly for small or medium-sized machine tool rotary table . Thrust ball lubrication is also difficult .

 

2 hydrostatic bearing + Precision Cylindrical Roller Bearings

 

A hydrostatic bearing by the pressure oil supplied from the outside , in order to achieve the establishment of hydrostatic fluid film bearing lubricated slide bearing in the bearing . Hydrostatic bearings from start to stop always work under liquid lubrication, so there is no wear, long life, start small power ; addition, this bearing also has a high rotational accuracy , film rigidity, can inhibit oil whip advantages. Precision Cylindrical Roller Bearings has a good radial bearing capacity , and thanks to the precision bearings , rotary precision rotary table can be guaranteed. The use of such design rotary table can withstand high axial force , the weight of some of the work over more than 200t , turntable diameter of more than 10m. But such design also has some shortcomings , because the hydrostatic bearing must be accompanied by a dedicated supply system to supply pressure oil , maintenance is more complex , and the cost is relatively high.

 

3 cross roller bearings

 

Cross roller bearings in the turntable is relatively common . Cross roller bearing is characterized by two roller bearings , roller two rows of staggered . With conventional thrust bearing and radial bearing assembly compared centered , cross roller bearings, compact structure , small size, and simplifies the design table , thereby reducing the cost of the turntable.

 

Further , the use of optimized preload such bearings having high stiffness , rigidity and precision turntable thus also guaranteed. Thanks to the two rows of cross roller design , the effective span of the bearing can be significantly improved , so these bearings have a high resistance to overturning moment. In cross roller bearings , divided into two types: the first is a cylindrical cross roller bearings , and the second is a conical cross roller bearings. Typically , cylindrical cross- price ratio tapered roller bearings Crossed roller bearings low for a relatively low speed rotary applications ; while tapered cross roller bearings tapered roller rolling pure design , with high running accuracy , speed capability strong , reducing the shaft length and processing costs and other advantages . Crossed roller bearings are suitable for all types of vertical or horizontal boring machine, as well as vertical mill , vertical lathe and large gear milling applications.

 

All in all, a machine tool spindle bearing turntable and the core components of the operating performance of the machine has played a pivotal role. In order to choose the right size and type of bearings , we need to consider various operating conditions , such as running speed , lubrication, installation type , shaft stiffness, precision requirements. On the bearing itself, the only fully understand its design features and the advantages and disadvantages resulting , in order to achieve the best performance out of the bearing.