With the increasing number of mechanical industries, more mechanical products need to be processed. Typically, each product processing needs to be formed by cutting discs, followed by subsequent grinding and polishing, and through a series of processes to become a mature product. It is undeniable that the quality of the grinding wheel products on the market is uneven: “the grinding wheel is not durable”, “the cutting efficiency of the cutting wheel is very low”, “the grinding wheel has a safety accident”, etc. Therefore, by studying the factors affecting the service life of the grinding wheel Therefore, it is very important to find a way to prolong the service life of the grinding wheel.
Grinding wheel is a very common abrasive tool in the grinding process. It is usually made by adding a binder to the abrasive, and is made by compacting, drying and roasting. Its characteristic parameters mainly include abrasive, viscosity, shape, hardness, bonding. dosage, size, etc. Because of the differences in abrasives, bonding agents and manufacturing processes, the final grinding wheel discs are also quite different, so the abrasives, bonding agents and manufacturing processes have an extremely important impact on the processing quality and productivity of grinding.
Grinding wheels are divided according to abrasives. Grinding wheels can be divided into ordinary abrasives (corundum and silicon carbide, etc.) grinding wheels, natural abrasive superhard abrasives and (diamond and cubic grinding wheels, boron nitride, etc.) grinding wheels; According to the shape, the grinding wheel can be divided into It is divided into flat grinding wheel, cup grinding wheel, cylindrical grinding wheel, bevel grinding wheel, dish grinding wheel, etc.; according to the binder, grinding wheel can be divided into metal grinding wheel, rubber grinding wheel, resin grinding wheel, ceramic grinding wheel, etc.
Therefore, from the perspective of the characteristics of the grinding wheel, the factors affecting the grinding wheel are obvious.
(1) From the perspective of raw materials, the material of the grinding wheel is mainly composed of abrasives, binders and pores.
1. Abrasive. Abrasive refers to the abrasive material in the grinding wheel, which is the main component of the grinding wheel and the fundamental factor affecting the cutting effect of the grinding wheel.
2. Granularity. Particle size is a parameter that expresses the size of the abrasive grains. According to the basic particle size of the abrasive, there are 41 particle sizes, and the size of the particle size directly affects the quality and productivity of grinding.
3. Binder. The binder is to bond the dispersed abrasive particles into an abrasive tool with a certain shape and sufficient strength. The type and properties of the bond affect the hardness, strength, corrosion resistance, heat resistance and impact resistance of the grinding wheel.
(2) From the perspective of brand quality, choose high-quality grinding wheels, cutting wheels of well-known brands, and the performance of grinding wheels will be better. If you want to extend the service life of ultra-thin grinding wheels, you must understand the brand, production process, and use of cutting blades. raw material, cutting speed and power. Knowing everything, it’s easy to judge whether ultra-thin grinding wheels meet the needs of your business. If the quality of the cutting blade is up to standard, it can be used for a long time with a little protection during use. If quality problems are encountered during the operation, it will seriously affect the efficiency of the factory to cut workpieces, and sometimes even affect the production schedule of the factory.
(3) In addition, the dressing of the grinding wheel is crucial to the service life of the grinding wheel.
During the grinding process, the state of the working surface of the grinding wheel is constantly changed due to the wear of the grinding wheel itself. With the extension of the grinding time, the cutting ability of the grinding wheel decreases, and various grinding defects continue to appear, so that the grinding process cannot continue. At this time, the grinding wheel must be dressed to restore the normal grinding state. The actual grinding time of the grinding wheel between dressings is called the life of the grinding wheel. The life of the grinding wheel is an important factor affecting the grinding effect, especially for profile grinding.
To determine the life of the grinding wheel:
Generally, it is carried out through observation and testing according to various phenomena produced by the wear of the working surface of the grinding wheel. The grinding phenomena produced by the wear of the grinding wheel mainly include: self-excited vibration during the grinding process, and regeneration vibration lines on the surface of the workpiece; grinding Increased grinding noise; grinding burns on the surface of the workpiece; sharp increase or decrease in grinding force; decreased grinding accuracy; increased grinding surface roughness.
The wear of the grinding wheel and its dressing, that is, the influence of the effective contour of the grinding wheel circumferential surface on the machining, is a systematic error, especially in precision grinding, the grinding wheel should be finely dressed, and a special dressing program should be set so that the grinding wheel can be used for a long time. Contours maintained over time
Reasons for wheel wear:
A. Wear and tear
When the abrasive grains are severely worn, the surface of the grinding wheel is flat after the obvious wear plane appears on the top surface of the abrasive grains. At this time, the total wear area of the cutting disc increases, the friction intensifies, and it is difficult for the cutting edge to cut into the surface of the workpiece. However, the hardness of the grinding wheel is too high, so that the abrasive particles cannot be broken and fallen off in time. If you continue to use it, the grinding force and grinding heat will increase significantly, and there will be obvious vibration and noise, and the material cannot be removed effectively. At this time, the grinding wheel must be dressed. This wear generally occurs when the hardness of the abrasive grains is low, the hardness of the grinding wheel is high, the grain size of the abrasive grains is too fine, and the tensile strength of the workpiece material is high. This is the most common cause of the end of wheel life when machining normal steels under normal grinding conditions.
B. Oxidative wear
Common abrasives are oxides, carbides and nitrides. Oxide abrasives are stable in air, and the surface of other abrasives will be oxidized at high temperature, and the seventeenth will be gradually consumed.
C. Diffusion wear.
It refers to the wear caused by the weakening of the surface layer of the abrasive particles due to the mutual diffusion of the elements of the diamond grinding wheel when the abrasive particles and the material to be ground contact at high temperature. The interdiffusion of elements between the two materials is closely related to the chemical composition of the materials. Since the ability of the carbon element in the diamond abrasive to diffuse and dissolve in iron is greater than the ability of the element in the boron nitride abrasive to diffuse and dissolve in iron, the diamond grinding wheel is not suitable for grinding steel.
D. Thermal stress damage.
During the grinding process, the working surface of the abrasive grains instantly rises to a high temperature, and the grinding wheel is rapidly cooled under the action of the grinding fluid. Thermal stress cracks and shatters the surface of the abrasive grains. The thermal stress damage mainly depends on the thermal conductivity parameters of the abrasive, the coefficient of linear expansion and the properties of the grinding fluid. The smaller the thermal conductivity, the lower the coefficient of linear expansion. The larger the coefficient of linear expansion, the better the cooling performance of the grinding fluid, the greater the thermal stress, and the easier it is for the abrasive particles to be cracked and broken by thermal shock. The order of the thermal conductivity of various abrasives is diamond, cubic boron nitride, silicon carbide, corundum.
E. Plastic wear.
Under the action of high temperature grinding, the abrasive particles will wear due to plastic deformation. Plastic wear mainly depends on the hot hardness of the workpiece material. During grinding, if the thermal hardness of the chips of the grinding wheel on the rake face of the abrasive grains is greater than the thermal hardness of the contact area of the abrasive grains, the abrasive grains will undergo plastic wear.
The above reasons cause grinding wheel wear. Depending on the abrasive, workpiece material and grinding conditions, the main causes of wheel wear will vary. Therefore, the reasonable selection of the grinding wheel and the dressing accuracy of the grinding wheel will greatly affect the contour accuracy of the workpiece. Therefore, the grinding wheel needs to be dressed in time during grinding. In addition, the grinding wheel needs to be dressed after the initial installation. The essence of grinding wheel dressing is to shape and sharpen the grinding wheel. Shaping is to perform micro-cutting on the grinding wheel, so that the grinding wheel can meet the required geometric shape requirements, and the abrasive is finely broken to form a sharp grinding edge. Sharpening is to remove the bonding agent between the abrasive grains, so that there is a certain chip space between the abrasive grains, and the abrasive grain edge protrudes out of the bonding agent to form a cutting edge. The method is also different.
It can be seen that it is very important to choose the right grinding wheel first.
Secondly, the correct installation of the cutting disc also has a great impact on the use of the grinding wheel disc. When installing ultra-thin grinding wheels, many operators will install them in their own way. Sometimes there will be many detail problems during the installation process, which will cause the ultra-thin grinding wheel to vibrate a lot during operation, sparks will fly, and the cutting blade will greatly reduce the service life of the ultra-thin grinding wheel with the high temperature of the cutting workpiece. The correct installation procedure of the cutting blade is clearly marked on the packaging.
1. Before installing the fan, check whether the resin grinding wheel has cracks, and tap the grinding wheel with a wooden hammer to see if there is an abnormal silent sound. If it is, the cooling fan cannot be used for cutting to avoid damage or injury caused by the rupture of the grinding wheel.
2. The resin grinding wheel used on the next day or the next day should be idling for more than one minute before use. If everything is in order, it can be used in accordance with the relevant grinding machinery safety regulations.
3. Since the resin grinding wheel is fragile and brittle, please do not let it hit, collide or fall alone. When storing, it should be protected from freezing, moisture, cool and ventilated indoors, placed flat, stacked neatly, pay attention to dust, and keep unused grinding wheels clean and free from heavy pressure.
4. When installing the resin grinding wheel, you must find the center of the resin grinding wheel and fasten the flange at the same time. After installing the flange, check whether the outer ring of the grinding wheel is concentric with the spindle. At least one side of the resin grinding wheel is perpendicular to the centerline of the main shaft.
5. After installing the resin grinding wheel, for the sake of safety, do not install the unqualified protective cover. Then start the machine.
Finally, we all know that the grinding wheel is a consumable product, and the recession of the grinding wheel is what we need to pay attention to. The correct way of storing the grinding wheel can prolong the service life of the grinding wheel. After unpacking ultra-thin grinding wheels, many workers toss the cutting discs all over the place. This will not only be polluted by the acid and moisture in the air, but also affect the cutting effect of the ultra-thin grinding wheel during use. You can store them in the corresponding box or keep them neatly arranged. You can’t just place them anywhere. It’s easy to bump them when you put them anywhere. If you continue to use it, the consequences will be unimaginable.