Numerical control machine tools have developed into a wide variety of products for a wide range of choices. The simpler the model selection should be under the premise of meeting the requirements of the processing technology. For example, turning centers and CNC lathes can process shaft parts, but a turning center that meets the same processing specifications is several times more expensive than a CNC lathe. If there is no further process requirement, it should be reasonable to choose a CNC lathe. In processing cavity mold parts, CNC milling machines and machining centers of the same specifications can meet the basic processing requirements, but the price difference between the two machine tools is 20% to 50%, so the process of frequently changing tools can be arranged in mold processing. Machining center, and a CNC milling machine can be used for long-term milling with a fixed tool.
The main specifications of CNC machine tools are the stroke range of several CNC axes and the power of the spindle motor. The three basic linear coordinate (X, Y, Z) strokes of the machine tool reflect the processing space allowed by the machine tool, and the two coordinates (X, Z) in the lathe reflect the size of the allowable rotating body. In general, the contour size of the workpiece to be processed should be within the processing space of the machine tool. For example, if the typical workpiece is a box of 450 mm × 450 mm × 450 mm, a machining center with a table size of 500 mm × 500 mm should be selected. The choice of work surface is slightly larger than the typical work piece because of the consideration of the installation fixture. There is a certain proportional relationship between the table size of the machine tool and the three linear coordinate strokes. For example, the machine tool with the above table (500 mm × 500 mm), the x-axis stroke is generally (700～800) mm, and the y-axis is (500～700). )Mm, z-axis is about (500～600)mm. Therefore, the size of the work surface basically determines the size of the processing space. In individual cases, the size of the workpiece is allowed to be larger than the coordinate stroke. At this time, the processing area on the part must be within the stroke range, and the allowable load-bearing capacity of the machine table and whether the workpiece interferes with the space of the machine tool exchange tool, Interference with machine tool guards and other accessories.
The main motor power of the CNC machine tool can also have various configurations on the machine of the same specification, which generally reflects the cutting rigidity of the machine tool and the high-speed performance of the spindle. For example, the spindle motor power of a light-duty machine tool may be 1 to 2 levels lower than that of a standard machine tool. At present, the spindle speed of the general machining center is (4000～8000) r/min, the high-speed machine tool can reach (20000～70000) r/min, and the horizontal machine tool (10000～20000) r/min, the power of the spindle motor is also Multiplied. The power of the spindle motor reflects the cutting efficiency of the machine tool, and from the other side also reflects the cutting rigidity and the overall rigidity of the machine tool. In modern small and medium-sized CNC machine tools, the mechanical speed change of the spindle box has been seldom used, and the AC adjustable speed motor with larger power is often used to directly connect the spindle, and even the electric spindle structure is adopted. The torque of this structure is limited at low speed, that is, the output power of the speed-regulating motor decreases at low speed. In order to ensure the low-speed output torque, a high-power motor must be used. Therefore, the spindle motor of the CNC machine tool of the same specification is several times larger than that of the ordinary machine tool. When there are a lot of low-speed machining on some typical workpieces of the unit, the low-speed output torque of the selected machine tool must also be checked. Light-duty machine tools are definitely cheap in price, and users are required to comprehensively choose machine tools based on their typical workpiece blank allowance, cutting ability (metal removal per unit time), required machining accuracy, and what kind of tools can actually be configured.
In recent years, the high-speed trend of CNC machine tools has developed rapidly. The spindle has changed from several thousand to tens of thousands of revolutions per minute, and the rapid moving speed of linear coordinates has increased from (10-20) m/min to more than 80m/min. Of course, the price of machine tools is also corresponding. As a result, user units must make reasonable choices based on their own technical capabilities and supporting capabilities. For example, the maximum speed of the spindle on a vertical machining center can reach (50,000 to 80,000) r/min. Except for some special processing cases, the matching tools are generally very expensive. Some high-speed lathes can reach (6000～8000) r/min or more, and the configuration requirements of turning tools are also very high.
For a small number of special workpieces, only three linear coordinates can not meet the requirements. It is necessary to increase the rotation coordinates (A, B, C) or additional work coordinates (U, V, W), etc. These requirements can be met in the machine tool market. However, the price of machine tools will increase a lot, especially for some requirements that require multi-axis machining, such as four-axis and five-axis machining, it is necessary to comprehensively consider and arrange the corresponding programming software and measurement methods.