- 本站编辑:xghl发布日期：2019-11-27 20:06 浏览次数：
What is grinding? Grinding is a machining method to remove the redundant layer on the surface of the workpiece and make the surface quality of the workpiece reach the predetermined requirements by means of the cutting action of the abrasive tool.
Grinding is a widely used machining method in mechanical manufacturing. It USES abrasive tools as tools for cutting on the grinder. Its machining accuracy can reach IT6 ~ IT4, and the surface roughness Ra value is 1.25 ~ 0.01 m. It can also be used to finish other difficult materials, such as hardened steel, hard alloy, glass, ceramics and so on.
The grinding machine has a wide processing range, which can grind cylindrical surface, cone surface, plane, gear tooth profile surface, spiral surface and various forming surface, etc. With the continuous development of abrasives, the continuous improvement of machine structure and performance, as well as the adoption of high speed grinding, power grinding and other efficient grinding technology, grinding has been gradually expanded to the rough machining field.
The movement during grinding varies with the grinding tools used, the process and the shape of the workpiece surface. For a grinding machine processed with a grinding wheel, the main movement is the high-speed rotating movement of the grinding wheel. The form of feed movement depends on the shape of the surface of the workpiece and the grinding method adopted. It can be completed by the workpiece or the grinding wheel respectively, or both.
Type of grinder
There are many kinds of grinding machines, which can be used to process the workpiece with different surface and shape. The main types are: cylindrical grinder, surface grinder, tool grinder, cutting tool grinder and various specialized grinder, etc. There are also sand belt grinder with flexible belt as cutting tool, and fine grinding machine with whetstone and abrasive as cutting tool.
100 video screenshot of mounting operation on sinusoidal precision flat jaw pliers
M1432A universal cylindrical grinder
Universal cylindrical grinding machine has a wide range of technology, which can grind inner and outer cylindrical surface, inner and outer cone surface, end surface, etc. But its production efficiency is low, suitable for single small batch production.
Explosion diagram of 100 vell education M1432A universal cylindrical grinder
I. composition of M1432A grinder
(1) the bed
The bed 1 is the basic part of the grinder, which is used to support grinding wheel frame 5, table 3, head frame 2, tail frame 6 and other parts, and keep their accurate relative position and motion accuracy. Inside the bed is a hydraulic device and vertical, horizontal feed mechanism.
(2) the head
Head frame 2 is composed of shell, spindle parts, driving device, etc., used for mounting and clamping the workpiece, and driving the workpiece to rotate. Adjust the variable speed mechanism to change the rotating speed of the workpiece.
(3) working table
The working table is divided into two layers. The upper table can be rotated around the mandrel of the lower table at an Angle of ±10° in the horizontal plane for grinding the cone surface. The lower table is driven by mechanical or hydraulic, driving the head frame 2 and tail frame 6 to make longitudinal feeding movement along the bed body, and the travel is controlled by the collision block.
(4) internal round abrasives
Inner round grinding tool 4 is used for grinding the inner hole of the workpiece. The spindle end of the inner round grinding wheel can be installed to realize the grinding movement driven by a separate motor.
(5) grinding wheel rack
Grinding wheel rack 5 is used to support and drive the grinding wheel spindle with high speed rotation. The grinding wheel rack is mounted on the transverse guide rail and the operation of the transverse feeding hand wheel can realize the transverse feeding movement of the grinding wheel. When grinding the short cone surface, the grinding wheel holder and the head stand can rotate ±30° and +90° (counterclockwise) angles around the vertical axis, respectively.
(6) tail stock
The front center of tailstock 6 and headstock 2 is used to support the workpiece, and the spring at the rear end of tailstock sleeve can adjust the axial pressure of the center on the workpiece.
(7) pedal control board
It is used to control the hydraulic center of the tailstock for fast loading and unloading.
Ii. Other common grinder types:
1. Internal grinder
Internal grinder is mainly used for grinding various internal holes (including cylindrical through hole, blind hole, step hole, conical hole, ring groove, etc.) and shaft end face. Grinding is carried out on the periphery of the common grinding wheel and the end face of the grinding wheel.
2. Centerless cylindrical grinder
Grinding the cylindrical surface on the centerless cylindrical grinder, the workpiece does not need to make the center hole, so, not only to eliminate the error caused by the center hole eccentricity (that is, there is no positioning error), and can make loading and unloading simple and save time. As a result of the guide wheel and support plate along the full length of the supporting workpiece, some of the stiffness of the slender workpiece can also be used for grinding larger cutting parameters, so the productivity is higher.
But the machine adjustment time is longer, suitable for batch and mass production.
In addition, centerless external cylindrical grinders cannot grind a surface with a circumferential discontinuity (such as a keyway), nor can they guarantee the coaxiality of the external and internal holes being ground.
3. Tool grinder
Tool grinding machine is a general name for the grinding machine used in the grinding of various special and complex workpieces. It is mainly used for grinding the cutting edge of various cutting tools, such as turning tool, milling cutter, reamer, gear tool, thread tool, etc. Install the corresponding machine tool accessories, can be small size of the shaft class outer circle, rectangular plane, bevel, groove and hemisphere and other complicated shape of the machine, fixture, mold grinding. It includes tool curve grinder, bit groove grinder, broach grinder, hob grinder, spline shaft grinder, thread grinder, piston ring grinder, gear grinder and so on
4. CNC grinder
CNC grinder is a machine tool that grinds the surface of the workpiece. CNC grinder and CNC surface grinder, CNC centerless grinder, CNC internal and external cylindrical grinder, CNC vertical universal grinder, CNC coordinate grinder, CNC shape grinder and so on
The grinding process
In the process of grinding, the high-speed rotation of the grinding wheel is the main movement, and the low-speed rotation and linear movement of the workpiece are the feed movement. In mechanical parts processing and mechanical manufacturing is one of the most commonly used processing methods, the following for everyone to share the principle of grinding and related knowledge.
The grinding process is a process in which a large number of grinding grains distributed on the surface of the grinding wheel rotate on the surface of the workpiece at a high speed. Each grinding grain is like a small cutting edge.
In the grinding process of a single grinding particle, the role of cutting into the workpiece is divided into three stages:
(1) slip and rub phase. Friction and extrusion occur on the surface of the workpiece, resulting in elastic deformation of the workpiece. At this point, the abrasive particles do not play a cutting role, known as the sliding phase.
(2) marking stage. The grinding grains carve grooves on the surface of the workpiece. This stage is called the engraving stage.
(3) cutting stage. In front of the grain, the gold slippage along the shear surface to form the chip. This stage is called the cutting stage.
It can be seen that the grinding process of a grinding particle makes the grinding surface go through three steps: slip, scratch (uplift) and cutting
Segment. The common forms of debris are banding, node, tadpole and ash.
Grinding movement and amount
In grinding, there are generally four movements.
(1) main motion. The rotating motion of the grinding wheel is called main motion. Main movement speed nu c (m/s) is a cylindrical grinding wheel linear velocity, namely
Nu c = PI d0n0/1000. Where, d0 is the diameter of the grinding wheel (mm); N0 is the grinding wheel speed (r/s).
The ordinary grinding, main movement speed nu c for 3035 m/s; When nu c > 45 m/s, known as the high speed grinding.
(2) feed motion. There are three types of feed movements:
1) radial feed movement. Radial feed movement is the movement of the grinding wheel cutting into the workpiece. Radial feed fr refers to the radial movement distance of the workpiece relative to the grinding wheel within each double (single) stroke of the table, in mm/ double stroke. When the grinding wheel makes continuous feed, the unit is mm/s. In general, fr (or ap) =0.050.02mm/ double stroke.
2) axial feed movement. Axial feed motion is the axial motion of the workpiece relative to the grinding wheel. Axial feed refers to the axial movement distance of the workpiece relative to the grinding wheel in each turn or in each double stroke of the table, in mm/r or mm/ double stroke. In general, fa (or f) = (0.20.8) B, B is the width of the grinding wheel, the unit is mm.
3) circular (or linear) feed motion of the workpiece. Workpiece speed nu w is refers to the movement of the linear velocity, workpiece circular week or workbench (together with the workpiece) linear feed speed, the unit is m/s.
During grinding, due to the large backplane force Fp, the process system elastic deformation, so that the actual grinding depth and the value displayed on the grinder dial have a difference. So the actual grinding process of ordinary grinding is divided into three stages.
(1) initial grinding stage. When the grinding wheel just begins to touch the workpiece, due to the elastic deformation of the process system, the actual grinding depth is smaller than the radial feed shown on the grinder dial. The less rigid the process system, the longer the initial grinding stage.
(2) stabilization stage: in the stabilization stage, when the elastic deformation of the process system reaches a certain level and the radial feed continues, the actual grinding depth is basically equal to the radial feed.
(3) cleaning stage. After the main machining allowance is removed, the radial feed can be reduced or no feed at all for a further period of time. At this point, the actual grinding depth is larger than the radial feed due to the gradual recovery of the elastic deformation of the process system. As the workpiece is ground layer by layer, the actual grinding depth approaches zero and the grinding spark gradually disappears. The main purpose of the cleaning stage is to improve the grinding accuracy and surface quality.
About grinding fluid:
Grinding can achieve high dimensional accuracy and low surface roughness. Grinding, grinding speed, high calorific value of grinding temperature can be as high as 800 ~ 1000 ℃, is even higher, easy to cause the workpiece surface burns and surface cracks due to the effect of thermal stress and deformation of workpiece, the grinding wheel wear passivation, grinding grain fall off, and wear debris and the grinding powder easy splash, fall on the parts surface and affect the machining accuracy and surface roughness, machining toughness and plastic material, chip embedded plug in space or on the surface of the grinding wheel work wear debris and machining metal welded on the grinding wheel surface, deprive grinding wheel grinding ability, therefore, in order to decrease the temperature of grinding, rinse grindings and at the end of the grinding wheel, To improve the grinding ratio and surface quality of the workpiece, it is necessary to use a cutting fluid with good cooling and cleaning properties, and certain lubrication and rust resistance.