Structure and characteristics of CNC lathe
The structure of CNC lathe CNC lathe is also composed of spindle box, tool rest, feed transmission system, bed, hydraulic system, cooling system, lubrication system, etc., only the feed system of CNC lathe and the feed system of horizontal lathe There are essential differences in structure. Figure 1-12 shows the mechanical structure of a typical CNC lathe. The movement of the main shaft of the horizontal lathe is transmitted to the tool rest through the hanging wheel frame, the feed box and the slide box to realize the longitudinal and transverse feed movement. The CNC lathe uses a servo motor, which is transmitted to the slide plate and the tool holder through the ball screw to realize the z-direction (longitudinal) and set-direction (horizontal) feed movement. The CNC lathe also has the function of various threads, and the motion relationship between the rotation of the spindle and the movement of the tool rest is controlled by the CNC system. A pulse encoder is installed in the spindle box of the CNC lathe, and the movement of the main shaft is transmitted to the pulse encoder 11 through the synchronous toothed belt. When the spindle rotates, the pulse encoder sends a detection pulse signal to the numerical control system, so that the rotation of the spindle motor and the cutting feed of the tool holder maintain the motion relationship required for thread milling machining, that is, when the thread is machined, the spindle rotates once, and the tool holder rotates. Move the workpiece one lead in the z direction.
The layout of the CNC lathe The layout of the spindle, tailstock and other components of the CNC lathe relative to the bed is basically the same as that of the horizontal lathe, while the layout of the tool rest and guide rails has fundamentally changed. This is because the layout of the tool rest and guide rails It directly affects the performance and appearance of the CNC lathe. In addition, CNC lathes are equipped with closed guards.
(1) The layout of the bed and guide rails.
The relative position of the CNC lathe bed guide rail and the horizontal plane is shown in Figure 1-13, and there are 4 layouts.
The horizontal bed has good craftsmanship, which is convenient for the processing of the guide rail surface. The horizontal bed with the horizontally configured tool lance can improve the movement speed of the tool holder, which can generally be used for the layout of large CNC lathes or small precision CNC lathes. However, the space under the horizontal bed is small, which makes chip evacuation difficult. In terms of structural dimensions, the horizontal placement of the tool rest makes the lateral dimension of the slide plate longer, thereby increasing the structural dimension in the width direction of the machine tool.
The horizontal bed is equipped with an inclined sliding plate and is equipped with an inclined guide rail protective cover. On the one hand, the horizontal bed has the characteristics of good craftsmanship; And chip removal is convenient.
The horizontal bed with inclined sliding plate and the inclined bed with inclined sliding plate are widely used in small and medium-sized CNC turning lathes. This is because the two layout forms are easy to remove chips, the chips will not accumulate on the guide rail, and it is also easy to install the automatic chip conveyor; the operation is convenient, and the manipulator is easy to install to achieve stand-alone automation; the machine tool occupies a small area, and has a simple and beautiful appearance , easy to achieve closed protection.
The angle of inclination of the inclined bed guide rail can be 30 degrees. , 45. , 60. , 75. and 90. (called vertical bed) and so on. If the angle of inclination is small, chip removal is inconvenient; if the angle of inclination is large, the guiding of the guide rail is poor, and the stress is also poor. The size of the inclination angle of the guide rail also directly affects the ratio of the height and width of the machine tool dimensions. Taking into account the above factors, the inclination of the bed of small and medium-sized CNC lathes is 60. appropriate.
(2) The layout of the tool holder.
The tool holder of the CNC lathe is an important part of the machine tool. The tool holder is used to clamp the cutting tool. Therefore, its structure directly affects the cutting performance and cutting efficiency of the machine tool. To a certain extent, the tool holder structure and performance reflect the CNC Lathe design and manufacturing level. With the continuous development of CNC lathes, the structure of the tool holder is constantly innovating, but in general, it can be roughly divided into two categories, namely the row tool holder and the turret type tool holder. Some turning centers also use automatic tool changers with tool magazines.
The arranging tool holder is generally used in small CNC lathes. Various tools are arranged and clamped on a movable sliding plate, and automatic positioning can be realized when changing tools.
The turret type tool holder is also called a turret or a tool table, and there are two types of structures: vertical and horizontal. It has a multi-tool position automatic positioning device, and realizes the automatic tool change action of the machine tool through the rotation, indexing and positioning of the turret head. The turret-type tool post should have accurate indexing, reliable positioning, high repeat positioning accuracy, fast indexing speed, and good clamping performance to ensure the high precision and high efficiency of the CNC lathe. Some turret-type tool holders can not only achieve automatic positioning, but also transmit power. At present, two-coordinate linkage lathes mostly use 12-station turret-type tool holders, and some also use 6-station, 8-station, and 10-station turret-type tool holders. There are two layouts of turret-type tool post on the machine tool: one is a turret-type tool post used for processing disc parts, and its rotary axis is perpendicular to the main shaft; the other is used for processing shafts and discs A turret-type tool holder for a part whose axis of rotation is parallel to the main shaft.
The bed of the CNC lathe with four-coordinate control is equipped with two independent slide plates and a turret-type tool post, so it is called a double-tool post four-coordinate CNC lathe. Among them, the cutting feed amount of each tool rest is controlled separately, therefore, the two tool rests can cut different parts of the same workpiece at the same time, which not only expands the processing range, but also improves the processing efficiency. The four-coordinate CNC lathe has a complex structure and needs to be equipped with a special CNC system to realize the control of two independent tool holders. It is suitable for processing crankshafts, aircraft parts and other parts with complex shapes and large batches.