Three major skills of workpiece clamping in CNC lathe

Clamping is an important part of workpiece clamping process. After the workpiece location must be through a certain mechanism to produce clamping force, the workpiece pressure on the positioning element, so as to maintain accurate positioning position, will not be due to the cutting force, workpiece gravity, CNC lathe centrifugal force or inertia force and other effects of position change and vibration, to ensure the processing accuracy and safe operation. The mechanism that produces the clamping force is called the clamping device. (1) clamping device should have the basic requirements (1) clamping process is reliable, do not change the workpiece after the location of the correct position. (2) the size of clamping force is appropriate, not only to ensure that the workpiece in the process of processing its position is stable and unchanged, vibration is small, but also to make the workpiece will not produce too large clamping deformation. (3) simple and convenient operation, labor saving and safety. (4) good structure, clamping device knot CNC lathe plant structure to simple, compact, easy to manufacture and maintenance. (2) selection of clamping force direction and operating point (1) clamping force should be oriented to the main positioning datum. The workpiece is boring with / 4 surface vertical requirements, so when processing with surface A as the main positioning base, clamping force F, direction should be oriented to / 4 surface. If the clamping force is shifted to side B, because of the included Angle error between side / 4 and bottom surface B of the CNC lathe, the positioning position of the workpiece is destroyed during clamping, which affects the vertical requirement of the hole and side / 4. The application point of clamping force in nc lathe (2) should be within the supporting range of positioning element and close to the geometric center of supporting element. The clamping force acting outside the supporting surface causes the tilt and movement of the workpiece, which damages the positioning of the workpiece. (3) the direction of clamping force should be conducive to reducing the size of clamping force. When drilling hole A, the clamping force rej and the axial cutting force F. , the direction of the workpiece gravity C is the same, the clamping force required in the processing process is the minimum. (4) the direction and operating point of clamping force should be applied in the direction and position of the rigid parts of the CNC lathe. The axial rigidity of thin-wall sleeve workpiece is better than that of radial shaft, so clamping force should be applied along axial direction. When the thin-wall box is clamped, it should be applied to the flange of the CNC lathe with good properties. When there is no flange, single point clamping can be changed to three point clamping. (5) clamping force should be used as close as possible to the workpiece processing surface. In order to improve the rigidity of the workpiece and prevent or reduce the vibration of the workpiece, the clamping force should be applied as close as possible to the processing surface. When the fork is clamped, the main clamping force F: ACTS on the main positioning base plane vertically, sets auxiliary supports near the machining surface, and applies appropriate auxiliary clamping force to improve the installation stiffness of the workpiece. The size of clamping force has a great relationship with the reliability of workpiece installation, the deformation of CNC lathe of workpiece and fixture, and the complexity of clamping mechanism. During processing, the workpiece is affected by cutting force, centrifugal force, inertia force and the workpiece's own gravity. Generally, the cutting force (moment) plays a decisive role in machining small and medium-sized workpiece in CNC lathe factory. When processing heavy and large workpiece, the effect of the workpiece gravity must be considered. The effect of centrifugal force or inertia force on clamping action cannot be ignored when the workpiece is processed at high speed. In addition, the cutting force itself is a dynamic load, in the process of machining is also changing. The degree of clamping force is also related to the stiffness of process system and transmission efficiency of clamping mechanism. Therefore, the calculation of clamping force is a very complicated problem, which can only be roughly estimated. For simplicity, in the low speed processing to determine the clamping force, can only consider cutting force (torque) influence on clamping, and assumes that the numerical control lathe process system is rigid, the cutting process is stable, according to the process of the instantaneous state of clamping the worst, according to the principle of static equilibrium and the size of the clamping force, and then multiplied by the factor of safety as the actual required clamping force CNC lathe factory, namely Fj type = kF Fj - in the actual required clamping force; F -- clamping force calculated by static equilibrium under certain conditions; K -- safety factor. Considering the change of cutting force and deformation of process system and other factors, A 2 1 is generally adopted. 5 to 3. In practical application, it is not necessary to calculate the clamping force when there is a CNC lathe. The manual clamping mechanism usually determines the clamping force according to experience or analogy method. If it is necessary to calculate the clamping force accurately, the above method can be used to calculate the clamping force.