Processing method of thin wall parts
Thin-walled parts are widely used in the industrial sector, but their rigidity is weak, the processing of deformation is difficult to control, through the improvement of traditional cutting methods and the application of CNC compensation cutting, high-speed cutting and vibration cutting, are able to play well to better processing accuracy requirements.
The characteristics of thin-walled parts
Thin zero-walled parts with light quality, material saving, compact structure and other characteristics, in the aviation, automotive, machinery and other industrial sectors have been widely used. But the thin-walled parts of its poor rigidity, weak strength, deformation in the processing is difficult to control, but also produce cutting vibration, so that the quality of machining parts is difficult to ensure.
Anti-deformation clamping technology and clamping appropriate clamping
Parts clamping can be divided into positioning and clamping. Positioning so that the part is in a stable state, for the plane should be adopted 3-point positioning. In the positioning point should generally bear a certain clamping force, and should have a certain strength and rigidity. From the positioning stability and positioning accuracy, the smaller the contact surface is the better; and from the clamping force function, the larger the contact surface needs to be the better, the smallest unit area pressure can be used to obtain the maximum friction force. In precision machining, it is the clamping mechanism and the size of the clamping force that are determined by the small cutting force. Therefore, the positioning and clamping mechanism of the part should be carefully analyzed, as well as the force applied by the tool to the part, the budget causes the size of the part of the deformation force and the direction of action. The best machining condition for thin-walled annular workpieces is if there is no force in the radial direction. In the processing of thin-walled sleeve parts, the relationship between the clamping point and the amount of deformation, according to the West Germany Falkart International Clamping Technology Company on the clamping point and the amount of deformation of the test shows that; in the same clamping conditions, such as 3-point clamping of the part deformation is 1, the uniform 6-point clamping deformation is only 1/16 of the 3-point. 12-point clamping deformation is almost 0, it can be seen that the uniform multi-point clamping will greatly reduce the part The clamping deformation, that is, to increase the contact area of the jaws and parts is an important way to reduce the amount of clamping deformation. This is also the reason why the soft jaw chuck and open seam sleeve is commonly used in the processing of thin-walled sleeve parts.
The processing process requirements
Rough machining, finish machining separate
For thin-walled parts, the processing stages should be separated. Roughing and finishing are separated to avoid the elastic deformation of the clamping force and cutting heat deformation caused by rough machining, eliminating the internal stress caused by rough machining, cutting force, cutting heat, clamping force on the processing accuracy, to maintain the accuracy of the parts. In addition, rough and finish machining separately, machine tools and equipment can also be used reasonably, that is, rough machining machine tools can give full play to its efficiency, finish machining machine tools can maintain long-term machine accuracy and maintain the service life.
Roughing and finishing machining between the increased stress relief process
In the process of processing thin-walled parts, due to thermal expansion and contraction of various parts of the workpiece is not uniform or changes in metallurgical organization, so that the internal blank produced a considerable internal stress. The more complex the structure of the blank, the more uneven the wall thickness of each part, the greater the difference in thermal conditions, the greater the internal stresses generated within the blank. A blank with internal stress is not visible for a short period of time, and the internal stress is temporarily in a relatively balanced state, but when a layer of metal is removed, this balance is broken, the internal stress is redistributed, and the workpiece is significantly deformed. Therefore, between rough and finish machining, it is best to increase the stress relief process to eliminate the internal stress of the workpiece.
Control quenching medium to prevent parts heat treatment deformation
Quenching is one of the most important processes to strengthen the parts, the workpiece in quenching before the size and geometric accuracy are basically achieved, even if left with little grinding margin, so quenching not only to ensure good organization and performance, but also to maintain its dimensional accuracy, by controlling the quenching medium to change the cooling characteristics. In short, for small size parts, thin-walled parts and good hardenability parts, the cooling rate, especially the boiling period of the cooling rate is critical to improve the convection start temperature, so that the quenching medium is more suitable for thin-walled parts quenching, so as to effectively control the heat treatment deformation, improve the quality of heat treatment.
Cutting amount, cutting fluid
The cutting amount of requirements
Back draft, feed, cutting speed is the cutting amount of the three elements. After a large number of tests we have proved that: back draft and feed increase at the same time, the cutting force also increases, deformation is also large, the turning of thin-walled parts is extremely unfavorable. In the processing of thin-walled parts with high accuracy requirements, generally take symmetric processing, so that the relative two sides of the stress balance, to achieve a stable state, after processing the workpiece flat. When the back of a process to eat a large amount of tool, the stress will be out of balance, the workpiece will produce deformation.
The requirements of cutting fluid
The reasonable choice of cutting fluid can reduce the friction in the cutting process, improve the heat dissipation conditions, thus reducing the cutting force, cutting power, cutting temperature, reduce tool wear, improve the quality of the machined surface. Rough machining cutting volume, generating a lot of cutting heat, tool wear, especially high-speed steel, should be selected for cooling-based cutting fluid, such as emulsion or water solution. And carbide tools can be used without cutting fluid, such as to use must be continuous and sufficient pouring, so as not to produce cracks. Finishing cutting fluid is mainly lubrication to improve the surface accuracy and surface roughness of the workpiece, to use extreme pressure cutting oil or ionic cutting fluid.
The use of advanced processing methods
CNC machining line cutting machine tools to solve the traditional processing difficult to solve the problem, it is not affected by material hardness, heat treatment conditions, especially in the sharp angle, small r and taper cutting products more advantageous in the process of processing. Such as packaging machine tobacco library of a thin-walled parts, the inner and outer surfaces of the part taper direction, such as the use of fixed taper, can not be processed all of the corridor at once, if the use of up and down shaped variable taper method of programming, resulting in a large amount of program, for this reason, combined with the fixed taper programming method, the inner and outer surfaces using the method of taper reversal in a program to complete the processing of the inner and outer surfaces at the same time, in This ensures the quality of the product and improves the efficiency of machining.
High-speed machining technology is a high-efficiency, high-quality, low-consumption manufacturing technology developed in recent years. In high-speed cutting processing, because the balance of the blank material is not yet fully deformed in an instant cut away from the workpiece, the residual stress on the surface of the workpiece is very small, the vast majority of heat generated during the cutting process is quickly taken away by the cutting, thereby reducing the thermal deformation of thin-walled parts to achieve surface finish quality.
Currently used high-precision, thin-walled cavity class parts, many varieties, small batches, and the structure of the parts are constantly changing, but the basic formation of high-speed cutting machining optimization process. At the same time, according to the specific structure of the thin wall parts, different process measures and means, such as process arrangement, tool route, cutting parameters optimization, clamping methods, etc., basically can meet the existing design and manufacturing needs of similar parts.
Source: China Thin Wall Parts Manufacturer – Yaang Pipe Industry (www.pipelinedubai.com)