Machine tool fixture design 5 major considerations
With the rapid development of science and technology, the changing needs of the market and the increasingly fierce competition for goods, so that the cycle of renewal of mechanical products is getting shorter and shorter, the proportion of multi-species, small batch production is getting higher and higher. In order to apply the needs of this situation, there are a variety of new CNC machine tool fixtures. The same machine tool, why the difference in production efficiency is several times? The conclusion is: CNC machine tool selection fixture is not suitable, so that the production efficiency of CNC machine tools significantly reduced. How to improve the utilization of CNC machine tools? Through technical analysis, the use of fixtures has a great deal to do with it.
Components of machine tool fixtures 1, positioning elements and positioning devices: used to determine the position of the workpiece in the fixture, by making the workpiece processing relative to the tool and cutting and shaping movement in the correct position. Commonly used positioning elements: positioning mandrel, support plate, support nail, V-shaped block, etc. 2、Clamping device: used to maintain the workpiece in the fixture in the established position, so that under the action of gravity, inertial force and cutting force does not produce displacement. Clamping device in the fixture by the power unit (cylinder, cylinder, etc.), intermediate force transfer mechanism (lever, thread, ramp, etc.) and clamping components (jaws, pressure plate, etc.) device. 3, tool setting and guiding elements: used to determine the correct position of the tool relative to the positioning elements. Note: milling machine fixture (tooling block), drilling machine fixture (drilling set), boring machine fixture (boring set) must be designed on the tooling elements. 4、Clamp specific: used to connect the components and devices of the jig, so that it becomes a whole of the basic parts. 5, its components and devices: orientation keys, indexing indexing devices used to determine the direction of the fixture in the relevant part of the machine tool or to achieve the workpiece in the fixture in the same installation indexing indexing and other special functions of the components or devices. The following is an introduction to several modern CNC machine tool fixtures. First, adjustable fixture adjustable fixture is divided into general adjustable fixture and group fixture (also known as special adjustable fixture) two categories. Their common feature is that as long as the replacement or adjustment of individual positioning, clamping or guiding components, can be used for the processing of a variety of parts, so that a variety of small batch production of single parts into a group of parts in the same fixture “batch production”. After the product is updated, as long as it belongs to the same type of parts, it can still be processed on this fixture. Because the adjustable fixture has strong adaptability and good inheritance, so the use of adjustable fixture can greatly reduce the number of special fixtures, shorten the production preparation cycle and reduce costs.
Combination fixture is also called “building block fixture”, which consists of a series of standardized design, different functions and different sizes of machine tool fixture components, customers can quickly assemble various types of machine tool fixtures according to the processing requirements, like “building blocks”. Customers can quickly assemble various types of machine tool jigs like “building blocks” according to their machining requirements. As the combination jig eliminates the time of designing and manufacturing special jigs, it greatly shortens the production preparation time, thus effectively shortening the cycle time of small batch production, i.e. improving the production efficiency. In addition, the combination fixture also has the advantages of high positioning accuracy, clamping flexibility, recycling, manufacturing energy and material saving, low cost of use, etc.. Therefore, small batch processing, especially when the product shape is more complex, can give priority to the use of combination fixture. Third, the precision combination of flat nose pliers precision combination of flat nose pliers actually belongs to the combination of fixtures in the “combined”, compared with other combination of fixture components, its greater versatility, higher degree of standardization, easier to use, more reliable clamping, so it has been widely used in the world. Precision combination flat jaws have the advantages of fast installation (disassembly), fast clamping, etc., so it can shorten the production preparation time and improve the efficiency of small batch production. At present, the international common precision combination of flat vise clamping range is generally within 1000mm, the clamping force is generally within 5000Kgf. It should be noted that the precision combination of vise here is not the old machine vise, the old machine vise single function, low manufacturing accuracy, can not be used in groups, short life, not suitable for use in CNC machine tools, machining centers. Fourth, the electric permanent magnet jig Electric permanent magnet jig is a new type of jig designed by using the modern magnetic circuit principle with the new permanent magnet material such as neodymium iron boron as the magnetic force source. A large number of machining practice shows that the electric permanent magnet fixture can significantly improve the comprehensive machining efficiency of CNC machine tools and machining centers. The clamping and unclamping process of electric permanent magnet clamps only takes about 1 second, so significantly shorten the clamping time; conventional CNC machine tool clamps positioning elements and clamping elements take up more space, while the electric permanent magnet clamps do not have these space-occupying components, so compared with conventional CNC machine tool clamps, the clamping range of electric permanent magnet clamps is greater, which is conducive to making full use of the CNC machine tool working table and processing stroke, which is conducive to improving the overall machining efficiency of CNC machine tools. This is conducive to the full use of CNC machine tools and machining stroke, which is conducive to improving the overall processing efficiency of CNC machine tools. The suction force of the electric permanent magnetic clamps are generally 15 to 18Kgf/cm2, so it must ensure that the suction force (clamping force) is sufficient to resist the cutting force, in general, the adsorption area should not be less than 30cm2, that is, the clamping force is not less than 450Kgf. In modern automated production, the application of CNC machine tools has become more and more widespread. CNC machine tool processing, the tool or table movement is controlled by the program, according to a certain coordinate position.
CNC machine tool fixture design should pay attention to the following points: 1. CNC machine tool fixture should be set on the origin (tooling point). 2. CNC machine tool fixture does not need to set the tool guide. This is because the CNC machine tool processing, machine tools, fixtures, tools and workpieces always maintain a strict coordinate relationship between the tool and the workpiece without guide elements to determine the position. 3. CNC machine tools are often required in several directions on the workpiece processing, so the CNC machine tool fixture should be open. 4. CNC machine tools should try to use adjustable fixtures, assembling fixtures and combination fixtures. Because the workpiece processed on CNC machine tools, often a single piece of small batch production, must use good flexibility, short preparation time fixture. 5. CNC machine clamping fixtures should be solid and reliable, easy to operate. Clamping components should be fixed in position to prevent the automatic processing process, components and tools touch.