1. Basic requirements for clamping devices
During machining, in order to maintain the correct position determined when the workpiece is positioned and prevent the workpiece from displacement and vibration under the action of cutting force, inertial force, centrifugal force and gravity, the machine tool fixture should be equipped with The clamping device presses and clamps the workpiece firmly. Whether the clamping device is reasonable, reliable and safe has a significant impact on the accuracy, productivity and labor conditions of the workpiece. For this reason, the following basic requirements are proposed:
1) During the clamping process, the correct position of the workpiece after positioning cannot be changed .
2) The size of the clamping force should be appropriate, not only to ensure that the position of the workpiece is stable and the vibration is small during the entire processing process, but also to prevent the workpiece from causing excessive clamping deformation.
3) The automation and complexity of the clamping device should be compatible with the rich production type. Under the premise of ensuring production efficiency, its structure should be simple and easy to manufacture and maintain.
4) The operation of the clamping device should be convenient, safe and labor-saving.
5) The clamping device should have good self-locking performance to ensure that the clamping state can still be maintained after the source power riots or disappears.
The purpose of clamping is to ensure the positioning of the workpiece in the fixture, so that it will not move or vibrate due to cutting force, gravity or associated centrifugal force, inertial force, thermal stress, etc. during work.
The clamping device is an important and indispensable part of the clamping function of the fixture. Unless the various forces on the workpiece during processing will not cause it to leave the position that needs to be determined during positioning, it can be installed Clamping device.
he design of the clamping device has a great influence on improving the accuracy of clamping, increasing work efficiency, and reducing labor intensity. Analyzing the basic functional requirements of various types of fixtures can be summarized into two types of clamping devices: the first type is performance requirements, mainly designated position uniqueness, positioning stability, clamping stability and overall constraints; the second type of requirements is fixtures Structural rigidity, cost and ease of operation, ease of maintenance and other requirements.
When designing the clamping device, the following main requirements should be met:
1. The clamping device should not damage the positioning of the workpiece when clamping the workpiece. For this reason, the direction of the clamping force and the focus point must be selected correctly.
2. The clamping force should be reliable and appropriate. It is necessary to ensure that the deformation of the workpiece after clamping and the damage of the pressure surface will not exceed the allowable range.
3. The structure of the clamping device is simple and reasonable, the clamping action should be rapid, the operation is convenient, labor-saving and safe.
4. The clamping force or clamping stroke can be adjusted and compensated within a certain range.
2. Determination of the clamping force
When determining the direction, point of action and magnitude of the clamping force, it should be determined according to the structural characteristics and processing requirements of the workpiece, combined with the force status in the processing of the workpiece, and the structure and multiple methods of the positioning element.
The direction of the clamping force The direction of the clamping force should be at the top and the main clamping force should face the main limit base.
The point of action of the clamping force After the direction of the clamping force is determined, the location of the point of action should be determined according to the following principles:
1) The point of action of the clamping force should fall within the support range of the positioning element.
2) The point of action of the clamping force should fall in the direction and position of the workpiece with good rigidity.
3) The point of application of the clamping force should be close to the processing surface of the workpiece.