Three-axis, four-axis, five-axis machining centers, what is the difference between these types of machines?
The role and advantages of three-axis machining centers: Vertical machining centers (three-axis) the most effective machining surface is only the top surface of the workpiece, horizontal machining centers with the help of rotary table, can only complete the workpiece four-sided processing. At present, high-grade machining centers are moving towards the direction of five-axis control, the workpiece can be clamped once to complete the processing of five faces. Such as the configuration of five-axis linkage on the high-grade CNC system, but also for complex spatial surfaces for high-precision machining. Four-axis machining The so-called four-axis machining is generally added a rotary axis, usually called the fourth axis. General machine tools only three axes that is, the workpiece platform can be left and right (1-axis) before and after (2-axis) spindle head (3-axis) to move, for cutting the workpiece, the fourth axis is to move the platform to add a 360-degree rotation of the motorized indexing head! This can be automatically indexed to play oblique holes, milling beveled edges, etc., without the loss of precision of the second clamping.Four-axis machining features:
(1). Three-axis linkage machining machine can not be processed or need to be clamped too long(2). Improve the accuracy, quality and efficiency of free-space surfaces
(3). Difference between four-axis and three-axis; four-axis difference and three-axis more than one rotary axis four-axis coordinate establishment andThe representation of its code:
Determination of the Z-axis: the direction of the axis of the machine tool spindle or the vertical direction of the table for clamping the workpiece for the Z-axis X-axis determination: and the workpiece mounting surface parallel to the level of the horizontal surface or in the horizontal surface of the direction of the axis of rotation selected perpendicular to the workpiece for the X-axis, away from the direction of the spindle axis for the positive. The direction away from the spindle axis is the positive direction. Some people say that the first to learn three-axis, and then go to the four-axis, five-axis machining centers, what is the difference between these machines? Vertical five-axis machining centers There are two ways to rotate the rotary axis of this type of machining center, one is the table rotary axis. The table, set up on the bed, can rotate around the X-axis, defined as the A-axis, which typically has a range of +30 degrees to -120 degrees. The table also has a rotary table in the center of the table that rotates around the Z-axis in the position shown, defined as the C-axis, which is a 360-degree rotation. The combination of the A-axis and C-axis allows the vertical spindle to machine all five faces of the workpiece fixed to the table, except the bottom face, which can be machined by the vertical spindle. the minimum indexing value of the A-axis and C-axis is generally 0.001 degrees, which makes it possible to sub-divide the workpiece into any angle, and to machine tilted surfaces, tilted holes, and so on. The A-axis and C-axis, if linked with the XYZ linear axes, can process complex spatial surfaces, which of course requires high-grade CNC, servo system and software support. The advantage of this setup is that the structure of the spindle is relatively simple, the spindle rigidity is very good, and the manufacturing cost is relatively low. However, the general table can not be designed too large, the load bearing is also small, especially when the A-axis rotary greater than or equal to 90 degrees, the workpiece cutting will bring a lot of load-bearing moment on the table. The front of the spindle is a rotary head, can surround the Z-axis 360 degrees by itself, becoming the C-axis, rotary head also has a rotary head can be rotated around the X-axis A-axis, generally up to ± 90 degrees or more, to achieve the same function described above, this setup has the advantage of the spindle machining is very flexible, the worktable can be designed to be very large, airliners huge fuselage, a huge engine casing can be machined on this type of machining centers.This design also has a major advantage.
This design also has a major advantage: we use a spherical milling cutter processing surface, when the tool centerline perpendicular to the machining surface, due to the apex of the spherical milling cutter line speed is zero, the apex of the workpiece surface quality will be cut out very poorly, using the design of the spindle rotary spindle relative to the workpiece to turn an angle, so that the spherical milling cutter to avoid the apex of the cut to ensure that there is a certain line speed, can improve the surface processing quality. This structure is very welcome by the mold high-precision surface processing, which is difficult to do with the table rotary machining center. In order to achieve high precision rotary, high-grade rotary axis is also configured with a round scale feedback, indexing accuracy are within a few seconds, of course, this type of spindle rotary structure is more complex, manufacturing costs are also higher. Vertical five-axis machining center spindle rotary vertical machining center spindle gravity downward, bearing high-speed idling radial force is equal, rotary characteristics are very good, so you can increase the speed of the general high speed up to 1,2000r/min or more, the highest speed of the practical has reached 4,0000 rpm. The spindle system is equipped with a circulating cooling device. The circulating cooling oil takes away the heat generated by the high-speed rotation, and then flows back to the spindle system after being reduced to a suitable temperature by a chiller.The X, Y, and Z linear axes are also available with linear scale feedback for bi-directional positioning accuracy within the micron range. Due to the rapid feed of more than 40-60m/min, most of the ball screws of X, Y and Z axes are cooled by the center type, like the spindle system, by the cooled circulating oil flowing through the center of the ball screws to take away the heat.
Horizontal five-axis machining centers
There are also two ways of rotary axes in this type of machining centers, one is the horizontal spindle swing as a rotary axis, coupled with a rotary axis of the table, to achieve five-axis simultaneous machining. This setup is simple and flexible, such as the need for spindle vertical and horizontal conversion, the table only needs to be indexed and positioned, can be simply configured as a three-axis machining center with vertical and horizontal conversion. By the spindle vertical and horizontal conversion with the table indexing, the workpiece to realize five-sided machining, reducing manufacturing costs, but also very practical. The table can also be set up on the CNC axis, the minimum indexing value of 0.001 degrees, but do not linkage, become a vertical and horizontal conversion of four-axis machining centers to adapt to different processing requirements, the price is very competitive. Another traditional table rotary axis, set in the bed of the table A-axis general working range of +20 degrees to -100 degrees. The center of the table is also equipped with a rotary table B-axis, B-axis can be bi-directional 360-degree rotation. This type of horizontal 5-axis machining center has better linkage characteristics than the first type, and is often used for machining complex curved surfaces of large impellers. Rotary axis can also be configured with circular scale feedback, indexing accuracy of a few seconds, of course, this rotary axis structure is more complex, expensive. At present, the horizontal machining center table can do more than 1.25m2, the first five-axis setup has no impact. But the second five-axis setup is more difficult, because 1.25m2 of the table to do A-axis rotary, but also with the table in the middle of the B-axis rotary table linkage is really difficult. Horizontal machining center spindle speed is generally more than 10,000rpm, due to the horizontal setup of the spindle in the radial direction of the self-gravity, bearing high-speed idling radial force is not uniform, coupled with the use of larger BT50 shanks, generally up to 20,000rpm. Horizontal machining centers to reach the rapid feed 30 ~ 60m/min or more, the spindle motor power 22-40KW Above, the tool magazine capacity can be increased from 40 to 160 as needed, the machining capacity far exceeds the general vertical machining centers, is the first choice for heavy machining. Most of the machining centers can be designed as a double-table exchange, when a table running in the machining area, the other table is outside the machining area to replace the workpiece, in preparation for the processing of the next workpiece, the time to exchange the table depending on the size of the table, from a few seconds to dozens of seconds can be completed. The latest design of machining centers taking into account the structure to be suitable for the composition of modular manufacturing unit (FMC) and flexible production line (FMS), modular manufacturing unit generally at least two machining centers and four exchange table composition, machining centers are placed side by side, the exchange of workstations in front of the machine in a zigzag row, the exchange of workstations, and more can be lined up into two rows, or even double layer design. Each side of a workstation as the position of the upper and lower workpiece, the rest of the workstation on the exchange table mounted workpiece waiting for processing, there is a trolley will be in accordance with the system commands, the workpiece mounted exchange table into the machining center, or from the machining center to take out the completed processing of the exchange table, sent to the next workstation or sent directly to the lower material workstation, to complete the entire machining operation. Flexible production line in addition to trolleys, exchange table, there is a unified tool library, there will generally be hundreds of tools, in the system stored in the identity of the tool code information, and then through the tool conveyor system into the machining center, and the tool used up to retrieve the flexible production line often also need a FMS controller to direct the operation. The difference between a vertical machining center and a horizontal machining center : Obviously, because the table is made larger, it is changed to vertical, and obviously the vertical can process larger parts (in fact, all vertical machines have a greater capacity to accommodate the size of the workpiece than their horizontal counterparts, this is an inherent advantage of the vertical machines.) Horizontal machining centers and vertical machining centers is the main difference between : spindle (feed axis) a is parallel to the bottom surface is perpendicular to the ground vertical obviously spindle is perpendicular to the ground, horizontal spindle is parallel to the ground, the horizontal equivalent of a boring machine, just more features, high precision.