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High-speed machining in the middle of multi-axis control
Source: China Bearing Network Time: 2013-03-06
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Multi-axis control knows the fundamental concept. The multi-axis control usually refers to the control of more than 4 axes. The representative one is the 5-axis control machining middle. This machining can process the messy shape that can not be processed by the 3-axis control machine. Workpiece. If it is used to machine a workpiece that can be machined by a 3-axis control machine; that can improve machining accuracy and power.
For the relative orientation of the tool and the workpiece; today's multi-axis machining can set up 6 axes in the middle; that is, 3 axes of X, Y, Z that move forward, backward, left and right or up and down along the straight line; The B axis of the viewpoint and the C axis that manipulates the spindle to reverse the viewpoint. When the reverse tool is used, the spindle that is reversed by the Z axis is moved up and down or back and forth; it becomes a 5-axis control. For 6-axis control.
Usually, the reversing tool is used to improve the machining power; however, it is also constrained by the reversing tool; there are parts and shapes that can not be processed. Nowadays, not only can the reversing tool be used; but also the non-reverse tool can be used and the counter can be manipulated. Turning point; so it can be machined for any shape; usually with non-reverse tools, there are planing and smoothing on the XY plane. Now we have developed an improved tool and integrated 6-axis control combined with new machining in the middle.
The machining feature in the middle of the 5-axis machining process is because the tool in the middle of the 5-axis machining can process the workpiece in a comfortable posture; therefore, the image with zero cutting speed can be avoided; and the most suitable tool and the posture related to the workpiece can be selected efficiently. Processing; and processing the concave shape with a tool skewed posture; these are conditions that are favorable for processing.
Commonly used when machining with 5 axes; in order to avoid the tool and the workpiece with two reversal axes, it is necessary to generate the tool path. But it is very troublesome to generate NC data. Now it has developed versatility. The 5-axis control software; that is, the tool path that can avoid the occurrence of the attack between the tool and the workpiece. At this time, the software entity model is used as the middle; the tool path (ie, CL data) can be generated by using the algorithm to avoid the onset of the attack. The tool path is independent of the layout in the 5-axis control process; it is a neutral data. This disposal software is called the main handler.
In addition to this; it is also necessary to set the layout and composition that can be used in accordance with the rules; the post-processor that actively generates NC data from the generated tool path. If the generated tool path is used as it is, it will not work. The same mechanical layout and layout of the 5-axis control machining intermediate work. It is necessary to adopt various methods to transform the CL data into NC data suitable for the middle of different layout processing.
The primary layout method in the middle of 5-axis machining can be divided into three categories according to the two reverse axes of the workbench and the various setting methods of one spindle. Because the relative orientation of each axis has various layout patterns, it is also necessary. Set up a generalized postprocessor that can get used to a variety of layout styles.
After setting up the processor, it is not only to change the tool path to avoid the dry and the NC data suitable for the different layout processing; also to linearly change the feed speed and minimize the error of the moving path.
There is one point to note about the machining characteristics in the middle of 6-axis machining; it is possible to use 6-axis control when using the reverse tool. However, because the cutting speed and the feed speed are flat, the machining power is high; therefore, the 5-axis is used. Manipulating the blank for one-time clamping can also be processed in a variety of ways. It is precisely because the cutting speed and the tool feeding speed are appropriate; therefore, it is necessary to use the processing of the high-rigid layout. The cutting amount of the finishing is very good. Also requires the machine tool to have high positioning accuracy.
The 6-axis control features are as follows:
1. Smooth processing on planes and surfaces: because it is processed by line touch; so there is no residual feed mark on the processed surface.
2. Machining the groove of the profiled section on the plane and the surface: that is, the groove capable of machining at right angles to the direction in which the tool advances; any shape that can be symmetrical with respect to the wrong direction. This profiled groove can not be machined with the reverse tool.
3. The characteristic line at the intersection of the two curved surfaces is processed: this is to use a fixed tool to touch the surface along the intersection line. Under the condition, the moving tool is used for planing. This feature line cannot be processed by the reverse tool.
4, corner processing: because the reverse tool is circular; so can not form a right angle at the corner. With 6-axis control can process the corner.
5, pit processing: the ridge line formed by the plane and the surface of the pit can be clearly processed. This is the expansion of the feature line processing.
The 6-axis control and the 5-axis control set the main processor and the post-processor. But because the relationship between the tool and the workpiece makes 6 degrees of freedom. To do this, try to avoid the onset of the attack; Unable to continue processing. After this, it is necessary to generate NC data in the middle of the 6-axis manipulation processing of the different types by the post-processor based on the generated CL data.
NURBS interpolation for the 5-axis manipulation process is carried out because the NC data for the finishing of the free-form surface is expressed by successive small line segments; therefore, the amount of NC data that starts to be messy is very large. Now, because the price of the memory is cheap; It can be used for large-capacity storage; it can also transfer data at high speed in combination with FA-LAN's DNC operation. However, in today's high-speed machining, the transmission speed of NC data can't keep up with the feed rate of the tool; Then the quality of the processing is reduced. For this reason, 5-axis control using a lot of data is necessary to further improve the speed.
Nowadays, the shape method for interpolating the 3-dimensional point group with the free curve is used. The NURBS shows that the free curve can supply more appropriate information for the NC data; then the data volume is greatly reduced. On the other hand; The NURBS expression for 3-axis manipulation has been extended to 5-axis maneuvers; then the 5-axis maneuver has been cut; then the orientation of the NC data has been reduced.
Using a quadrifilar end mill for 5-axis manipulating machining Using a ball end mill to finish a free-form surface; there is no need to exchange tools with a tool; therefore, there is no problem with tool engagement; It is necessary to select a small-diameter ball-end end mill that is accustomed to the maximum radius of curvature of the machined surface. If it is to obtain an excellent machined surface with a low concave height formed by machining, it is necessary to reduce the set feed interval; Then the cutting interval and machining time are smashed. One of the ways to deal with this problem is to use a common shape tool called a quadric surface end mill for 5-axis control cutting.
The so-called quadric surface end mill is a kind of milling cutter which is formed by conical curve around the intermediate axis to form the shape of the head. The head shape has three types: inverted paraboloid, inverted hyperboloid and inverted elliptical surface. There are many cutting edges on the rotating surface; but its cutting edge is different from the ball end mill; it has various curvatures that change successively. Their curvature can be obtained from the formula of each conic curve.
When cutting with this type of milling cutter, it does not require a curvature like a ball end mill; instead, it can select the curvature that corresponds to the machined surface. Named as some of the curvatures on the machined surface are somewhat adjacent to the cutter head. Edge processing; some of the curvature can be processed by the cutting edge on the side of the milling cutter; this will increase the feed interval; shorten the processing moments.
It can actively generate CAM software for 5-axis control high-power machining of free-form surfaces using quadric surface end mills; it has been developed. 6-axis control processing with ultrasonic oscillation.
When the 6-axis manipulation of soft metals such as aluminum is carried out under customary conditions; there is a defect that the surface roughness is very effective. Now there is a method of ultrasonically arranging the tool on the tool holder for 6-axis manipulation; Apparently the cutting speed is accelerated; it can also significantly improve the roughness of the machined surface; it is a desirable approach.
Ultra-high-speed machining was about 10 years ago; after the super-high-speed CNC milling machine with a spindle speed of 100,000 rpm was introduced, the skill of high-speed milling was used to process the messy shape parts of the mold and other products. Then there was hardness. HRC60's sintered cubic boron nitride ball end mills are available. This high-hardness tool not only can perform ultra-high-speed machining beyond 1000m per minute; it also has a long service life.
After that; because of the success of high-speed milling of molds and other products with disorganized shape parts; this skill has received everyone's attention. At the same time, high-speed machining intermediates, tools, auxiliary things and CAD/XAM have also been developed and market-oriented.å“Ÿ èŸ¾å’šåŒ èŸ¾å’šåŒ èŸ¾å’šåŒ èŸ¾å’šåŒ é†¯ 醯 醯 æ… æ… æ… æ… æ… æ… æ… æ… æ… æ… æ… æ… æ… æ… æ… æƒ´
Ultra-high speed machining of the dm of the super high speed spindle of the super high speed spindle. The value of n exceeds 2 million; during which dm is the diameter of the bearing scale; the unit is mm; n is the maximum speed per minute; the unit is rpm. For this purpose, the radial thrust bearing of ceramic ball has been specially developed; through the suitable suitable ceramic ball The small diameter is used to reduce the centrifugal force and reduce the heat; and the smooth method under the seat ring is used to complete the high-speed reversal.
In addition, non-touch oil and aerostatic bearings, which are different from ball bearings, and new bearings such as aerostatic bearings and magnetic bearings have been developed. The hydrostatic bearings have been successfully used in ultra-high-speed CNC milling machines. It is useful. The ultra-high-speed machine tool equipped with this kind of bearing is characterized by the spindle jumping pole. It is 0.005um; it is suitable for small-diameter end mills or tools for high-speed and high-precision cutting. Its other feature is easy to grasp. Only need to be operated by short-term training; deal with time-consuming training problems. After adding active interchangeable tool equipment; constitute a good machining middle. Start to reach the useful high-speed machining middle spindle speed is 8 per minute 10,000 revolutions. The diameter of the tool used for the test is m. If it is later introduced, the equipment with the same method is introduced in the middle of the ultra-high speed machining of 150,000 spindles per minute; the diameter of the tool used for the test is φ6m.
Found in the test; when the spindle speed exceeds 100,000 revolutions per minute; centrifugal force makes the spindle diameter swell; for this reason, it is necessary to have an excellent connection between the spindle and the knife; the most suitable method has been developed now. Until now; In the ultra-high-speed cutting test; the spindles are all equipped with built-in tension spring chuck equipment and a method of clamping the double sides by a short taper.
Others; in the middle of machining for high-speed machining; both need to reach high power; also need to reach high precision; so it is necessary to use tools with long life. The fundamental method is to reduce the beating of the tool tip in the machining process. The spindle is beating under high-speed cutting conditions; therefore, it is necessary to consider the development of a spindle with good dynamic dispersion characteristics.
Ultra-high-speed feed and acceleration and deceleration equipment This is a layout that uses two threads of high-precision guide ball screw; it makes it a new type of feed device for high-speed machining with high rigidity and less inertia. In addition, the newly developed small inertia output servo motor and the high rigidity layout of the machine body; the high-speed feed drive machining that makes the feed speed reach 60m and 1G acceleration per minute.
In addition, a workbench feed system has been developed. It is a common intervening feed drive system with a U-axis attached to the X-axis and Y-axis. The U-axis is located under the workbench; the drive table can be driven. Parallel to the X-axis. The high-precision guide ball screw used has a feed rate of 100m and 2g acceleration per minute. It is driven by a linear motor; the first is to focus on the progressive feed drive system. High-speed acceleration and deceleration characteristics. Now some machining centers have chosen this method to drive.
For the middle of machining used in mold processing; it also has to deal with the problem of thermal displacement. This can be an important research topic in the future.
Ultra-high cutting tools have been developed for ultra-high-speed cutting; negative-angle super-high-speed end mills have been developed from dynamic balancing characteristics and rigid-cutting of cutting edges; now they are produced by various tool manufacturers and market-oriented. The following various problems:
1, to make the tip of the blade tipping pole. Yue (11) car pocket scorpion venom lemon sac 蛩刂 å ‘ å ‘ å ‘ å•¡ å•¡ å•¡ å•¡ å•¡ 庵痔 庵痔 庵痔 庵痔 庵痔 庵痔 庵痔 庵痔 庵痔 庵痔 庵痔 庵痔The beating of the blade tip is also related to the accuracy of the surface of the machined surface; if the runout is slightly larger, the machined surface with excellent roughness can not be obtained. In common, the end mill with high speed and high precision machining is under the condition of L/D=3. The ambition of the blade tip should be less than 5um.
2, the tool's high rigidity, high power depiction: in the case of suitable use of high-speed reverse machining such as end mill; in the drawing should ensure that the blade length of the tool reaches the shortest, multi-blade and maximum cross-sectional area; then it can fully promote this High precision of tools; high power machining characteristics.
3. Depicting the tool as suitable for CNC machining: In the process of drawing the tool, it is only necessary to use a small number of tools to make a variety of composite machining. That is, a tool has multiple functions. For example, using a tool It can complete the functions of total sinking, drilling and cutting internal thread; this can improve the working power.
4. Depicting the tool as a shape that facilitates the supply of coolant: primarily with respect to the drill bit; usually during drilling; it is difficult to supply coolant to the hole. A through hole is now opened in the middle of the drill bit; coolant is supplied from the hole. The coolant is sent directly to the cutting part of the quality product; thus extending the service life of the drill bit; it can also assist in the discharge of the chips when the coolant is discharged outward. Currently, cooling air and mist coolant are used to meet the needs of environmental protection; The newly depicted tool shape also helps supply both cooling media.
5. The tool is depicted as an interchangeable cutter type suitable for high-speed reversal: the body of the interchangeable cutter head is usually made of lightweight materials such as aluminum alloy; this can reduce the centrifugal force during high-speed reversal. The tool will be used after reaching the maximum speed. 6. Select the applicable tool data: Tool materials with very good high temperature hardness and stable operation should be selected; for example, carbide coating and metal with high density coating Ceramic coating.
7, fully promote the role of cubic boron nitride: cubic boron nitride data has an outstanding cutting function; therefore, the high-power, high-precision machining skills of cubic boron nitride sintered body tools should be established.
8, the development of small-diameter cubic boron nitride tools: in order to carry forward the outstanding characteristics of cubic boron nitride; so the development of small-diameter cubic boron nitride sintered body tools; such as right-angle end mills, ball end mills and reamers.
Tool holders suitable for ultra-high speeds are advancing with high-speed, high-precision cutting skills; tool holders will also undergo major changes for cooperation.
Under the current conditions of continuous development in the direction of ultra-high speed reversal; a new type of connection between the intermediate spindle and the tool holder will be discussed and developed. In the middle of high-speed machining with a speed exceeding 30,000 revolutions per minute; The tool holder is ambition. Nowadays, the holder has been put into practical use; the user can fully carry out the function of the small diameter cutting tool.
The skill of rapid exchange of tools should be based on the intention of use to select the habitual approach. From the current situation; the piercing tension spring collet has a higher rigidity; and the beating is also very strong. Strong fan> capsule.
It is known from the test; under the same cutting conditions; the use of the tool anti-vibration gripper with O-ring can achieve excellent surface roughness; because this gripper can effectively absorb the annual occurrence of cutting Oscillation; then the cutting edge of the tool is reduced. The tool anti-vibration gripper without O-ring has a slightly worse effect; the conventional tool holder has the worst surface roughness.
There is also a tool holder for the hot-sleeve method. This type of holder has an outstanding effect in reducing the edge of the tool and the rigidity of the tool. However, when the clamping method is used to process the work with the table; Because the diameter of the holder is large and the proximity is poor. The processing speed is constantly improving; it is estimated that all kinds of new methods of clamping the tool will be introduced in the future.
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