Machining Parts
Machining refers to the process of removing material through precise machining to finally change the shape or performance of the workpiece
According to the difference in processing method, it can be divided into cutting processing and pressure processing.
1) Cutting refers to the processing method of using cutting tools (including cutting tools, grinding tools and abrasives) to cut off the excess material layer on the blank or workpiece into chips, so that the workpiece can obtain the specified geometric shape, size and surface quality.
2) Pressure processing is a production method that uses the plastic deformation of metal under the action of external force to obtain raw materials, blanks or parts with certain shape, size and mechanical properties. It is called metal pressure processing, also known as metal plastic processing.
According to precision, it can be divided into precision machining, high precision machining and ultra-high precision machining
Machining accuracy includes the following three aspects at the same time:
1. Dimensional accuracy: refers to the degree of conformity between the actual size of the processed part and the center of the tolerance zone of the part size, in order to limit the dimensional error between the processed surface and its reference within a certain range.
2. Geometric shape accuracy: that is, the degree of conformity between the actual geometric shape of the processed part surface and the ideal geometric shape, which is used to limit the macroscopic geometric shape error of the processed surface, such as roundness, cylindricity, straightness and flatness
3. Mutual position accuracy: refers to the actual position accuracy difference between the relevant surfaces of the processed parts, which is used to limit the mutual position error between the processed surface and its reference, such as parallelism, perpendicularity and coaxiality.
Relationship between dimensional accuracy, shape accuracy and positional accuracy:
There is a relationship between the dimensional accuracy, shape accuracy and positional accuracy of part processing. In general, shape errors should be limited within positional tolerances, and positional errors should be limited within dimensional tolerances.
According to the temperature state of the processed workpiece, it can be divided into cold processing and hot processing.
1. Generally, it is processed at room temperature and does not cause chemical or phase changes of the workpiece, which is called cold processing.
2. Generally, processing at higher or lower than normal temperature will cause chemical or physical phase changes of the workpiece, which is called thermal processing.
ccording to the classification of processing procedures, it can be divided into two categories: boring and milling and turning and milling. Turning and milling can be divided into the following three categories according to the number of control axes:
1. Three-axis turning and milling machining center
2. Four-axis turning and milling machining center
3. Five-axis turning and milling machining center.
Classified according to the posture of the processing machine
(1) Horizontal machining center: refers to the machining center with the spindle axis parallel to the workbench, and is mainly suitable for machining box-type parts. The horizontal machining center generally has an indexing turntable or a numerical control turntable, which can process all sides of the workpiece; it can also perform joint movement of multiple coordinates in order to process complex spatial surfaces.
2) Vertical machining center: refers to the machining center where the spindle axis is perpendicular to the workbench, and is mainly suitable for processing complex parts such as plates, discs, molds and small shells. Vertical machining centers generally do not have a turntable and are only used for top surface processing. In addition, there are compound machining centers with vertical and horizontal spindles, and vertical and horizontal adjustable machining centers with spindles that can be adjusted to horizontal or vertical axes, which can process five sides of the workpiece.
(3) Universal machining center (also known as multi-axis linkage machining center): refers to a machining center that can control the linkage change through the angle between the axis of the machining spindle and the axis of rotation of the table to complete the machining of complex spatial surfaces. It is suitable for processing impeller rotors, molds, cutting tools and other workpieces with complex spatial surfaces. The form of multi-process centralized processing has been extended to other types of CNC machine tools, such as turning centers, which are equipped with multiple automatic tool changers on CNC lathes, which can control more than three coordinates. In addition to turning, the spindle can be stopped or indexed , and the milling, drilling, reaming and tapping processes performed by the tool rotation are suitable for processing complex rotating parts.
According to the type of processing
(1) Boring and milling machining center Boring and milling machining center is a machining center that was developed earlier and is currently used a lot, so what people usually call a machining center generally refers to a boring and milling machining center. Each feed axis can realize stepless speed change, and can realize multi-axis linkage control, the spindle can also realize stepless speed change, can realize automatic clamping and loosening of tools (knife loading and unloading), with automatic chip removal and Automatic tool changer. Its main technological capability is mainly boring and milling, and it can also perform drilling, expanding, reaming, countersinking, tapping and other processing. Its processing objects mainly include: planar parts with a fixed angle (constant) between the processing surface and the horizontal plane, such as discs, sleeves, and plate parts; variable-angle parts with a continuously changing angle between the processing surface and the horizontal plane; Box parts; complex curved surfaces (cams, integral impellers, molds, spherical surfaces, etc.); special-shaped parts with irregular shapes, most of which require point, line, and surface multi-station mixed processing).
(2) Turning center The turning center is based on the CNC lathe, equipped with a tool magazine and a manipulator, so that the number of tools that can be used is greatly increased. The turning center mainly focuses on turning, and can also perform milling, drilling, expanding, reaming, tapping and other processing. Its processing objects mainly include: the conical surface of complex parts, and the rotary body with complex curve as the generatrix. Drilling radial holes, milling keyways, milling cam grooves and spiral grooves, tapered threads and variable pitch threads can also be performed on the turning center. Turning centers generally also have the following two advanced functions. 1) Power tool function, that is, some or all tool positions on the tool holder can use rotary tools (such as milling cutters, drills) to rotate these tools through the power in the tool holder. 2) The c-axis position control function can realize the arbitrary position control of the spindle circumference. Realize X-C, Z-C linkage. In addition, some turning centers also have a Y-axis function.
3) Five-sided machining center In addition to the functions of general machining centers, the five-sided machining center is characterized by a spindle head that can be converted from vertical to horizontal. With the support of CNC indexing table or CNC rotary table, it can realize For one clamping of hexahedral parts (such as box parts), five surfaces are processed. This type of machining center can not only greatly reduce the auxiliary time of machining, but also reduce the influence of positioning errors due to multiple clamping on the accuracy of parts.
(4) Turning and milling compound processing equipment As the name suggests, turning and milling compound processing equipment refers to processing equipment that has both turning and milling functions. In this sense, the above-mentioned turning center also belongs to this type of processing equipment. But what is mentioned here generally refers to large-scale and heavy-duty turning-milling compound processing equipment, in which the turning and milling functions are equally powerful, and can realize the processing of multiple surfaces in one clamping of some large and complex parts (such as the integral propeller for large ships). The surface processing accuracy of the parts and the mutual position accuracy of each processed surface (such as the mutual position accuracy of the propeller blade profile, positioning hole, installation positioning surface, etc.) are guaranteed by the accuracy of the equipment. Due to the high technical content of this type of equipment, not only the price is high, but also because of its obvious military application background, it is listed as a national strategic material by various countries.