Development and application of pneumatic and hydraulic transmission
In recent 20 years, with the development of modern manufacturing technology, sealing technology, etc The hydraulic transmission technology has made great progress in high pressure, high speed, high power, low noise, reading ability, high efficiency and improving the service life, and has made beneficial exploration in AC hydraulic technology, machine day pack one fluid combination transmission, logic design of hydraulic system, computerization of hydraulic technology, etc., and has achieved certain results. The well has begun to be applied and popularized in engineering practice.
At present, pneumatic technology has developed into an independent technical field, and its application scope in all aspects is also expanding. In recent years, the pneumatic technology has become miniaturized, integrated and oil-free (a system composed of non oil lubricated and non lubricated components), improved the reliability and service life of components and systems, developed energy-saving technology, integrated electricity and gas (such as pressure proportional valve, flow proportional valve, digital control cylinder and other adaptive control pneumatic components), and improved the mechanical performance of pneumatic systems
Electric integration and automation level (such as PLC control pneumatic system)·
Because of the above characteristics, pneumatic and hydraulic systems have been widely used in industry since the middle of the 20th century Especially since the 1960s, with the development of electronic technology, computer technology, atomic energy and space technology, gas and hydraulic technology has developed into a complete automation technology including transmission, control and inspection. At present, it has been widely used in military, machine tools, engineering machinery, metallurgical machinery, mining machinery, agricultural and forestry machinery, vehicles, ships, automatic production lines, robots, door movement detection and other fields.
At present, pneumatic and hydraulic technologies are constantly developing and their application scope is expanding, and there is a new trend of mutual and coordinated development between them.
There are many aspects in which pneumatic and hydraulic technologies are used on machine tools, but mainly the advantages of pneumatic and hydraulic transmission, such as stepless speed change, easy door actuation and frequent reversing, are used. Generally, hydraulic and pneumatic transmission are often used in the following devices of machine tools
1. Feed motion transmission machine tools have different types, and the characteristics of feed motion are also different. For example, the grinding wheel rack of the lung machine, the tool rest of the grinder, the worktable or the upper axle box of the grinder, the drilling machine, the milling machine, the planer, and the power slide of the modular machine tools, some require slow movement, and some require fast movement Some require both fast and slow speed, some require a large speed range, and some require good frequent reversing performance. Hydraulic and pneumatic transmissions can meet these requirements.
Linear or rotary feed of worktable of CNC machine tool It can also be realized by electric signal controlling the electro-hydraulic servo system. If a closed-loop control system is formed by adding the corresponding depth detecting device, the feed transmission with high precision and large feed force or torque can be realized
2. Reciprocating linear motion table of planer and ram of shaper High speed reciprocating linear motion is required during operation. The former can reach the speed of 60-90 ml min, while the latter can reach the speed of 30-50 M/min In this case, F adopts hydraulic transmission, which is very beneficial in reducing reversing impact, reducing energy consumption, shortening reversing time, etc.
3. Rotary motion and profiling motion The rotary motion with stepless speed change can improve the quality of a when the load of the machine tool changes and improve the machining accuracy through hydraulic transmission. The hydraulic servo system can realize profiling processing on turning, milling and planing machines, and the processing accuracy is 0.01-0.02mm
4. Auxiliary device Workpiece clamping, control mechanism, m elimination device, dead weight balance of vertical moving parts, indexing device, loading and unloading, conveying and storage of workpieces and tools on the machine tool. It is generally realized by hydraulic and pneumatic devices. It not only simplifies the structure of the Royal L bed, but also improves the automation of the machine tool. It also saves space and volume
5. Hydrostatic bearing is required to improve the working stability and movement degree of machine tools Bearing, guide rail and screw nut mechanism supported by gas or liquid hydrostatic pressure have been widely developed and applied in heavy machine tools, high-speed machine tools and high-precision machine tools
As far as numerical control machine tools are concerned The application of pneumatic and hydraulic transmission is mainly in the realization of hydrostatic support and auxiliary movement. Such as spindle hydrostatic bearing, hydrostatic guide rail, workpiece clamping, loading and unloading. The replacement of the cutter, the self weight balance of the vertical moving parts, the exchange of the pallet, the rotary indexing of the workbench, etc., and sometimes the cleaning and cooling of the machine tool and workpiece are also applied to the hydraulic and pneumatic systems
In fact, it is difficult to solve the problem of whether a three-axis CNC machining center is better or a four-axis machining center is better. There is only a problem that is not suitable for machining some kinds of parts. Basically, all three-axis machining centers can process the parts that can be processed by a four axis machining center, while the parts that can be processed by a four axis machining center may not be processed by a three-axis machining center.
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