Workpiece refers to the processing object in the process of mechanical processing. It can be a single part or a combination of several parts fixed together. The processing methods of workpieces are various, such as turning, milling, planer, grinding, casting, forging and so on. The working procedure of the workpiece varies with the change of the processing mode.
The causes of deformation in workpiece processing - deep hole processing manufacturers come to tell you:
First aspect: deformation caused by workpiece clamping
When clamping a workpiece, the correct clamping point should be selected first, and then the appropriate clamping force should be selected according to the position of the clamping point. Therefore, the clamping point should be as close as possible to the processing surface, and the position where the force is not easy to cause the clamping deformation should be selected so that the clamping force acts on the support.
When there are clamping forces acting in several directions on the workpiece, the sequence of clamping forces should be considered. For the clamping force in the contact between the workpiece and the support, it should first act and not be too large. For the main clamping force in balancing the cutting force, it should act at the back.
Secondly, the contact area between workpiece and fixture should be enlarged or the axial clamping force should be adopted. Increasing the rigidity of parts is an effective way to solve the clamping deformation, but due to the shape and structure characteristics of thin-walled parts, it has lower rigidity. In this way, under the action of clamping force, deformation will occur.
Increasing the contact area between workpiece and fixture can effectively reduce the deformation of workpiece during clamping. For example, when Milling Thin-walled parts, a large number of elastic pressing plates are used to increase the force area of the contact parts; when turning the inner diameter and outer circle of the thin-walled sleeve, whether using simple open transition rings, or using elastic mandrels, arc clamps, etc., the contact area is increased when the workpiece is clamped. This method is conducive to bearing clamping force, thus avoiding the deformation of parts. Axial clamping force is also widely used in production. The clamping force can be applied on the end surface by designing and manufacturing special clamps, which can solve the bending deformation of the workpiece caused by thin wall and poor rigidity of the workpiece.
Second aspect: deformation caused by workpiece processing
In the process of cutting, the workpiece is subjected to the action of cutting force, resulting in elastic deformation in the direction of force, which is what we often call the knife-let phenomenon. Corresponding measures should be taken to deal with this kind of deformation on the cutter. The cutter should be sharp when finishing. On the one hand, it can reduce the resistance caused by friction between the cutter and the workpiece, on the other hand, it can improve the heat dissipation ability of the cutter when cutting the workpiece, so as to reduce the residual internal stress on the workpiece.
For example, when milling the large plane of thin-walled parts, using single-edge milling method, the tool parameters are selected with larger principal deviation angle and larger rake angle, in order to reduce cutting resistance. Because of its light cutting speed, the tool reduces the deformation of thin-walled parts and is widely used in production.
In the turning of thin-walled parts, the reasonable tool angle is very important to the cutting force, the thermal deformation and the micro-quality of the workpiece surface. The cutting deformation and the sharpness of tool rake angle are determined by the size of tool rake angle. Large rake angle reduces cutting deformation and friction, but too large rake angle reduces the wedge angle of the tool, reduces the strength of the tool, reduces the heat dissipation of the tool and accelerates wear. Therefore, when turning thin-walled steel parts, high-speed cutters are usually used, with a rake angle of 6 ~30 and carbide cutters, with a rake angle of 5 ~20.
The cutting force decreases when the tool's back angle is large and friction is small, but too large back angle will also weaken the strength of the tool. When turning thin-walled parts, high-speed steel turning tool is used, the tool's rear angle is 6 12 and carbide tool is used. The rear angle is 4 12 while finishing, the larger rear angle is taken, while roughing, the smaller rear angle is taken. When the inner and outer circles of the thin-walled parts of the car are round, the main deflection angle should be large. Correct tool selection is a necessary condition to deal with workpiece deformation.