In mechanical processing, according to the material and requirements of mechanical processing workpiece can choose different processing methods, understand the common types of mechanical processing and mechanical processing knowledge, can let us choose a more appropriate mechanical processing methods and applicable scope, so how to choose the mechanical processing methods and applicable scope?
One, turning processing
The method of using lathe to process parts is called turning. In turning, the workpiece rotates to form the main cutting movement. When the cutter moves along the axis of parallel rotation, it forms an inner and outer cylinder. A cone is formed when a tool moves along an oblique line that intersects the axis. On a copying lathe or numerical control lathe, the cutting tool is fed along a curve to form a specific surface of rotation. Using a molding tool, transverse feed, can also be processed out of the rotating surface. Turning can also be processed thread surface, end plane and eccentric shaft. Turning accuracy is generally IT11 - IT6, surface roughness is 12.5-0.8 m. Finishing, up to IT6 - IT5, roughness up to 0.4-0.1 muon. The turning processing productivity is higher, the cutting process is more stable, the cutting tool is simpler.
Scope of application: drilling center hole, drilling hole, reaming hole, tapping thread, turning round, boring hole, turning end face, turning groove, turning surface, turning cone, knurling, turning thread
Second, milling processing
Milling is a method of machining the workpiece with a rotating multi-edge cutter (milling cutter) on the milling machine. The main cutting movement is the rotation of the cutter. In horizontal milling, the formation of a plane is formed by the edges on the outer surface of the milling cutter. In end milling, the plane is formed by the end face edge of the milling cutter. Higher cutting speed can be obtained by increasing the speed of milling cutter. But because the cutter teeth cut into, cut out, the formation of impact, the cutting process is easy to produce vibration, thus limiting the workpiece surface quality, this impact, also intensified the wear and damage of the tool. The milling accuracy is generally up to IT8 -- IT7, and the surface roughness is 6.3 -- 1.6 microns. General milling can only be processed plane, with the form milling cutter can also be processed a fixed surface. Numerical control milling machine can be controlled by software through the numerical control system several axis according to a certain relationship linkage, milling out a complex surface, then generally use ball head milling cutter. Nc milling machine is of great importance for machining the complicated workpiece such as the vane of turbomachinery, the mould core and the cavity. In the general time of cutting off the workpiece, a certain amount of cooling can be obtained, so the heat dissipation conditions are better. According to the direction of the main movement speed when milling and workpiece feed direction of the same or opposite, and is divided into shun milling and inverse milling.
The horizontal component of the milling force and the workpiece feed direction is the same, the workpiece table feed screw and the fixed nut between the clearance generally exists, so the cutting force is easy to cause the workpiece and the table to move forward together, make the feed suddenly increased, resulting in a knife. When milling parts with hard surface such as castings or forgings, the teeth of the milling cutter first contact the hard surface of the workpiece, which aggravates the wear of the milling cutter.
(2) inverse milling
It can avoid the phenomenon of channeling when milling. In reverse milling, the cutting thickness increases gradually from zero, thus the blade begins to experience a period of compression sliding on the machined surface hardened by cutting, accelerating the wear of the tool. At the same time, the inverse milling, milling force will be lifted, easy to cause vibration, this is the disadvantage of the inverse milling.
Scope of application: milling plane, milling step, milling groove, milling forming surface, milling spiral groove, milling gear, cutting
Three, planing processing
Planing generally refers to the use of planer on the planer relative to the workpiece to do reciprocating linear motion, cutting excess material processing method. When planing, the reciprocating linear motion of the cutter is the main motion of cutting. Therefore, planing processing speed is slow, low productivity. Planing processing is more stable than milling processing, planing processing belongs to rough processing, some cases can reach the degree of semi-finishing, its accuracy is lower than milling processing, the processing accuracy is generally up to IT8 -- IT7, the surface roughness of ra6.3-1.6 microns, planing planeness up to 0.02/1000, the surface roughness of 0.8 -- 0.4 microns. However, it has advantages for processing large castings.
Scope of application: planer plane, planer vertical plane, planer step plane, planer right Angle groove, planer inclined plane, planer doffing groove, planer v-groove, planer curved surface, planer keyway, planer rack, planer compound surface
Four, grinding processing
Grinding is a method of cutting workpiece surface by using high hardness artificial grinding wheel (grinding wheel) as cutter. Its main movement is the rotation of grinding wheel. The grinding process of grinding wheel is actually the comprehensive effect of three effects of abrasive particles on workpiece surface: cutting, cutting and sliding. In grinding, grinding grain itself also gradually blunt by sharp, so that the cutting effect become poor, cutting force. When the cutting force exceeds the strength of the adhesive, the round blunt abrasive grains fall off, exposing a new layer of abrasive grains, forming the "self-sharpness" of the grinding wheel. However, chips and abrasive particles will still block the grinding wheel. Therefore, after grinding for a certain period of time, diamond turning tools are needed to repair the grinding wheel. When grinding, because the blade is many, so its cutting speed is high, machining accuracy is high. Grinding machine is a finishing machine, grinding accuracy up to IT6 - IT4, surface roughness Ra up to 1.25-0.01 muon, even up to 0.1-0.008 muon. Another characteristic of grinding is that it can be used to process hardened metal materials, which belongs to the scope of finishing, so it is often used as the final processing procedure. During grinding, heat is generated and sufficient cutting fluid is needed for cooling. According to different functions, grinding can be divided into outer circular grinding, inner hole grinding, flat grinding and so on.
Scope of application: external grinding, internal grinding, surface grinding, forming grinding, screw grinding, gear grinding
The process of machining various inner holes on the drilling machine is called drilling processing, which is the most commonly used method of hole processing. The precision of drilling is relatively low, generally ranging from IT12 to IT11, and the surface roughness is generally Ra5.0 to 6.3um. After drilling, reaming and reaming are often used for semi-finishing and finishing. The reaming hole is processed with reamer. The machining accuracy is generally IT9 -- IT6, and the surface roughness is Ra1.6 -- 0.4 microns. When reaming and reaming holes, the drill bit and reamer are generally along the axis of the original bottom hole, which cannot improve the position accuracy of the hole.
Application: drilling, reaming, tapping, strontium hole, scraping plane
Six, boring processing
Boring machining USES boring machine to enlarge aperture and improve quality of existing holes. Boring machining is based on rotary movement of boring tool. Boring pin processing can be compared to the position of the hole. The boring machining precision is generally IT9 -- IT7, the surface roughness is Ra6.3 -- 0.8mm, but the boring pin machining production efficiency is low.
Scope of application: machining high-precision hole, multiple hole finishing
Seven, tooth surface processing
The processing method of gear tooth surface can be divided into two categories: forming method and developing method. The machine tool used to process tooth surface by forming method is general milling machine, and the cutter is forming milling cutter. Shaping process tooth surface commonly used machine tools for gear hobbing machine, gear shaping machine, and so on.
Scope of application: gear, etc
Eight, complex surface processing
Three - dimensional surface machining, the main use of copying milling and CNC milling methods or special processing methods. Copy milling must have a prototype as a copy. In machining, the ball head contour head always contacts the prototype surface with a certain pressure. The motion of the copying head is transformed into the inductance, and the machining magnification controls the movement of the three axes of the milling machine to form the trajectory of the cutter head moving along the surface. Milling cutter and copy head radius of the ball head milling cutter. The appearance of numerical control technology provides a more effective method for surface machining. CNC milling machine or machining center processing, is through the ball head milling cutter point by point according to the coordinate value of processing. The advantage of machining complex surface with machining center is that there is a knife library on the machining center, equipped with dozens of knives. For rough and fine machining of surface, different tools can be used for different curvature radius of concave surface, and appropriate tools can be selected. At the same time, various auxiliary surfaces, such as holes, threads, grooves, etc. can be processed in one installation. In this way, the relative position accuracy of each surface is fully guaranteed.
Scope of application: parts with complex curved surface
Edm is realized by using high temperature corrosion of workpiece surface materials generated by instantaneous spark discharge between tool electrode and workpiece electrode. Edm machine tools are generally composed of pulse power supply, automatic feeding mechanism, machine body and working fluid circulation filtration system. The workpiece is fixed on the working platform of the machine tool. The pulse power supply provides the energy required for processing, and the two poles are connected to the tool electrode and the workpiece respectively. When the tool electrode and the workpiece are close to each other in the working fluid under the driving of the feeding mechanism, the voltage between the poles breaks down the gap and generates spark discharge, releasing a large amount of heat. The surface layer of the workpiece absorbs heat and reaches a very high temperature (above 10000℃), and its partial materials are eroded down due to melting or even gasification, forming a tiny pit. The working fluid circulation filtration system forces the clean working fluid to pass through the gap between the tool electrode and the workpiece at a certain pressure to timely eliminate the electrical corrosion products and filter them out of the working fluid. As a result of multiple discharges, a large number of pits are generated on the surface of the workpiece. As the tool electrode is driven down by the feed mechanism, its contour shape is "copied" to the workpiece (although the tool electrode material is also eroded)
Scope of application
(1) processing of hard, brittle, tough, soft and high melting point conductive materials;
(2) processing semiconductor materials and non-conductive materials;
(3) processing of various types of holes, curve holes and tiny holes;
(4) processing a variety of three-dimensional surface cavity, such as forging die, die casting die, plastic die chamber;
5 used for cutting, cutting and surface enhancement, engraving, printing nameplate and marking.
Ten, electrochemical machining
Electrochemical machining (ecm) is a method of forming workpiece by utilizing the electrochemical principle of anodic dissolution of metal in electrolyte. The workpiece is connected to the positive pole of the dc power supply, and the tool is connected to the negative pole, with a narrow gap (0.1mm ~ 0.8mm) between the two poles. The electrolyte with a certain pressure (0.5mpa ~ 2.5mpa) flows through the gap between the poles at a medium speed of 15m/s ~ 60m/s. When the tool cathode is continuously fed into the workpiece, on the workpiece surface facing the cathode, the metal material dissolves continuously according to the shape of the cathode surface, and the electrolytic products are taken away by the high-speed electrolyte, so the shape of the tool surface is "copied" on the workpiece accordingly.
Application: machining hole, cavity, complex surface, small diameter deep hole, riving, deburring, imprinting, etc.
Eleven, laser processing
The laser processing of workpiece is completed by the laser processing machine. Laser processing machine usually consists of laser, power supply, optical system and mechanical system. Lasers (solid and gas lasers are commonly used) convert electrical energy into light energy, producing the required laser beam, which is focused by the optical system and then shone on the workpiece for processing. The workpiece is fixed on the three-coordinate precision work table and controlled and driven by the numerical control system to complete the feed movement required for machining.
Scope of application: diamond wire drawing die, precious stone bearing for watch, porous skin for diffused air-cooled punching piece, small hole processing for engine nozzle, aero-engine blade, and cutting processing for various metal and non-metal materials.
Ultrasonic machining is a method to realize workpiece processing by using suspended abrasive in the working fluid of tool end face impact by ultrasonic frequency (16KHz ~ 25KHz) vibration. The ultrasonic generator converts the ac electric energy of power frequency into ultrasonic electrical oscillation with a certain power output, converts the ultrasonic electrical oscillation into ultrasonic mechanical vibration through the transducer, and amplifies the displacement amplitude of vibration from 0.005mm ~ 0.01mm to 0.01mm ~ 0.15mm with the help of amplitude expansion rod, driving the tool vibration. The end face of the tool strikes the suspended abrasive particles in the working fluid in vibration, making it constantly hit and polished the processed surface with a great speed, smashing the materials in the processing area into very fine particles and striking down. Although the material down each time is very small, but because of the high frequency of the strike, there is still a certain processing speed. Due to the circulating flow of the working fluid, the beaten material particles are carried away in time. As the tool moved in, its shape was copied onto the workpiece.
Application: hard cutting materials
With the development of science and technology, mechanical processing method are also gradually increase, when choosing machining methods will be in many respects, including machining surface shape, dimensional accuracy, position accuracy, surface roughness, etc., choose the appropriate machining method, can guarantee the quality of the workpiece under the minimum investment and the processing efficiency, can produce benefit maximization.