What are the three core issues that need to be paid attention to in the practical application of grinding wheel polishing machines?

1. Analysis of the core working principle and technical parameters of the abrasive polishing machine

As an indispensable surface treatment equipment in industrial production, the efficient operation of the abrasive polisher is based on a deep understanding of the core working principle and precise control of technical parameters. In essence, the abrasive polisher is a device that improves the surface quality of the workpiece based on the combined action of grinding and polishing, and its working process contains complex physical and mechanical principles.

The core working principle of the abrasive polisher is based on the abrasive cutting theory. The abrasive is made of a large number of tiny and extremely hard abrasive particles that are consolidated by a binder and rotate at high speed driven by a motor. When the rotating abrasive contacts the surface of the workpiece, the abrasive particles are like countless tiny tools that cut, scratch and squeeze the surface of the workpiece. During the cutting process, the abrasive particles cut into the surface of the workpiece to a certain depth and remove the workpiece material in the form of chips; scratching is the sliding of the abrasive particles on the surface of the workpiece, causing plastic deformation of the workpiece surface; under the action of extrusion, the surface material of the workpiece deforms and flows, thereby achieving surface flatness and smoothness. These three effects do not exist independently, but are intertwined to complete the processing of the workpiece surface.

From the perspective of equipment structure, the abrasive polishing machine is mainly composed of motor, spindle system, abrasive device, workbench, feed mechanism and control system. The motor provides power for the entire equipment, transmits power to the spindle through the transmission system, and drives the abrasive to rotate at high speed. The accuracy of the spindle system directly affects the rotation accuracy and stability of the abrasive. The high-precision spindle can ensure the smooth operation of the abrasive during polishing and reduce the impact of vibration on the processing quality. The abrasive device is responsible for installing and fixing the abrasive. Its design needs to consider the size, weight and installation method of the abrasive to ensure the safety and reliability of the abrasive when rotating at high speed. The workbench is used to carry the workpiece, and realize the relative movement between the workpiece and the abrasive under the drive of the feed mechanism to complete the polishing process. The control system is responsible for accurately controlling the operating parameters of the equipment, such as the abrasive speed, the workbench feed speed, the cooling system flow, etc., to meet the needs of different workpieces and processing techniques.

Technical parameters are important indicators for measuring the performance and processing capacity of abrasive polishers, and have a direct impact on processing quality and efficiency. Among them, the abrasive speed is one of the most critical parameters. A higher abrasive speed can increase the number of cutting times of abrasive grains per unit time, thereby improving processing efficiency. However, too high a speed will lead to increased abrasive wear and may even cause safety accidents such as abrasive breakage; too low a speed will reduce cutting capacity and affect processing efficiency and surface quality. Generally speaking, different types and specifications of abrasives have their appropriate speed ranges. In practical applications, they need to be reasonably selected based on factors such as the material, particle size and workpiece material of the abrasive.

The linear speed of the abrasive is also an important parameter. It refers to the linear speed of a point on the circumferential surface of the abrasive, which is related to the rotation speed and diameter of the abrasive. The appropriate linear speed can ensure that the abrasive particles can fully play the cutting role and obtain good processing results. Generally, for workpiece materials with higher hardness, a higher linear speed is required to enhance the cutting ability; for softer materials, the linear speed can be appropriately reduced to avoid over-cutting and surface burns.

The feed speed of the worktable should not be ignored either. If the feed speed is too fast, the cutting load of the abrasive will increase, resulting in increased surface roughness and even cutting vibration; if the feed speed is too slow, the processing efficiency will be reduced. In actual processing, it is necessary to reasonably adjust the feed speed according to factors such as the material, shape, size of the workpiece and the characteristics of the abrasive to achieve the best processing effect.

In addition, parameters such as the particle size, hardness and binder type of the abrasive will also have an important impact on the processing process. The particle size indicates the coarseness of the abrasive grains. The smaller the particle size number, the coarser the abrasive grains, which are suitable for rough processing; the larger the particle size number, the finer the abrasive grains, which are suitable for fine processing. The hardness of the abrasive reflects the difficulty of the abrasive grains falling off from the surface of the abrasive under the action of the grinding force. The abrasive grains of the abrasive with high hardness are not easy to fall off, which is suitable for processing materials with lower hardness; the abrasive grains of the abrasive with low hardness are easy to fall off, and can be used to process materials with higher hardness. The type of binder determines the strength, wear resistance and heat resistance of the abrasive. Different binders are suitable for different processing scenarios and materials.

Through in-depth analysis of the core working principles and technical parameters of the abrasive polisher, it can be seen that only by fully understanding the working mechanism of the equipment, accurately grasping various technical parameters, and making reasonable adjustments according to actual processing needs, can the performance advantages of the abrasive polisher be fully utilized to achieve efficient and high-quality surface processing.

2. Key requirements for abrasive selection for workpieces of different materials

In the actual application of abrasive polishing machines, accurate abrasive selection for workpieces of different materials is the key to ensuring processing quality and efficiency. Workpieces of different materials have their own unique physical, chemical and mechanical properties, which determine different requirements for the abrasive material, particle size, hardness and bonding agent of the abrasive during the polishing process.

• Metal materials are one of the most common workpiece materials in industrial production. Different types of metal materials have different requirements for the selection of abrasives. For ordinary metal materials such as carbon steel and alloy steel, due to their moderate hardness and good grinding performance, corundum abrasives can generally be selected. Brown corundum abrasives have high hardness and good toughness, and are suitable for rough grinding and semi-finishing grinding of carbon steel, alloy steel and other materials; white corundum abrasives have higher hardness and good self-sharpening properties, and are often used for fine grinding and grinding of hardened steel and other metal materials with higher hardness. In terms of particle size selection, 36#-60# abrasives can be selected in the rough grinding stage to improve grinding efficiency; 80#-120# abrasives are used in the fine grinding stage to obtain better surface finish. The selection of abrasive hardness needs to be determined according to the hardness of the workpiece material and the grinding allowance. Usually, for metal materials with lower hardness, a abrasive with higher hardness (such as medium hard grade) can be selected to ensure the durability of the abrasive; for metal materials with higher hardness, a abrasive with lower hardness (such as medium soft grade) should be selected so that the abrasive particles can fall off in time and maintain the sharpness of the abrasive. In terms of binders, ceramic bond abrasives have higher hardness and wear resistance, and are suitable for high-speed grinding of ordinary metal materials; resin bond abrasives have good elasticity and high grinding efficiency, and are often used for fine grinding and forming grinding.
• For difficult-to-process metal materials such as stainless steel, due to their high toughness and work hardening tendency, they are prone to problems such as sticking and clogging the abrasive during the grinding process, which puts higher requirements on the selection of abrasives. At this time, chrome corundum abrasives or single crystal corundum abrasives can be selected. These two types of abrasives have sharp abrasive grains and good cutting performance, which can effectively overcome the processing difficulties of stainless steel. In terms of particle size selection, it is similar to ordinary metal materials, but in terms of hardness, a abrasive with lower hardness (such as soft or medium-soft grade) should be selected to promote the timely shedding of abrasive grains and prevent abrasive clogging. Resin binders are preferably used as binders, and their good elasticity and self-sharpening properties help improve grinding efficiency and processing quality.
• Nonferrous metal materials such as aluminum and copper have low hardness and good plasticity. They are prone to sand sticking during grinding, which affects the surface quality. For this type of material, large-pore abrasives or rubber-bonded abrasives can be used. Large-pore abrasives have a larger porosity and can accommodate more chips and reduce sand sticking; rubber-bonded abrasives have good elasticity and polishing properties and can achieve a higher surface finish. In terms of abrasive material, white corundum or silicon carbide abrasives can be used, with a particle size generally between 60# and 100#, and medium-soft or soft hardness.
• There are many types of non-metallic materials with different properties, and their abrasive selection also has unique requirements. For materials with high hardness and high brittleness such as ceramics and glass, silicon carbide abrasives are a better choice. Black silicon carbide abrasives have high hardness and good sharpness, and are suitable for grinding ceramics and glass with lower hardness; green silicon carbide abrasives have higher hardness and good thermal conductivity, and are often used for grinding high-hardness materials such as cemented carbide and optical glass. In terms of particle size selection, 36# - 60# can be used for coarse grinding, and 80# - 120# can be used for fine grinding. The hardness of the abrasive is generally selected as medium hard or hard, and the binder is mostly a ceramic binder to ensure the strength and wear resistance of the abrasive.
• For soft non-metallic materials such as plastics and rubber, due to their low hardness and high elasticity, they are prone to deformation and heat during grinding, so it is necessary to use a abrasive with low hardness and loose structure. Super soft abrasives with resin bonds can be used, and the abrasive material can be white corundum or brown corundum, with a particle size between 80# and 120#. At the same time, in order to reduce heat generation and workpiece deformation, the abrasive speed and feed speed should be appropriately reduced, and sufficient cooling measures should be adopted.

Take the polishing of automobile engine cylinder (aluminum alloy) as an example. If an inappropriate abrasive is used, problems such as surface scratches and sand sticking may occur, affecting the sealing and service life of the cylinder. The correct selection should be: white corundum abrasive with rubber bond, 80# grain size, and soft hardness. Such a abrasive can effectively avoid sand sticking while ensuring polishing efficiency, and obtain good surface quality.

The characteristics of workpieces of different materials determine the key requirements for the selection of abrasives. Only by fully considering the physical, chemical and mechanical properties of the workpiece material and reasonably selecting the abrasive material, particle size, hardness and binder parameters of the abrasive can efficient and high-quality polishing be achieved to meet the processing needs of different workpieces.

3. Optimization of polishing process parameters (speed/feed rate/cooling)

In the processing of abrasive polishing machine, the optimization setting of polishing process parameters is very important to improve processing quality, improve processing efficiency and extend the service life of equipment and abrasive. The three key process parameters of speed, feed rate and cooling are interrelated and affect each other. It is necessary to comprehensively consider various factors such as workpiece material and abrasive characteristics to make reasonable adjustments to achieve the best processing effect.

• abrasive speed is one of the important parameters that affect the polishing effect. As mentioned above, a higher speed can increase the number of cutting times of abrasive grains per unit time, which can improve the processing efficiency to a certain extent. However, too high a speed will bring a series of problems. On the one hand, the friction between the abrasive grains and the workpiece surface intensifies, generating a lot of heat, which can easily cause the workpiece surface to burn and affect the surface quality; on the other hand, too high a speed will increase the centrifugal force of the abrasive. When the centrifugal force exceeds the strength limit of the abrasive, it may cause the abrasive to break, causing serious safety accidents. On the contrary, if the speed is too low, the cutting ability of the abrasive grains is insufficient, the processing efficiency is low, and it is difficult to obtain the ideal surface finish. Therefore, when setting the abrasive speed, it is necessary to comprehensively consider factors such as the hardness of the workpiece material, the material and particle size of the abrasive. Generally speaking, for workpiece materials with higher hardness, such as hardened steel, cemented carbide, etc., a higher speed is required to enhance the cutting ability of the abrasive grains; while for softer materials, such as aluminum alloy, copper alloy, etc., the speed can be appropriately reduced to avoid excessive cutting and surface deformation. For example, when using a vitrified bonded brown corundum abrasive (grit size 60#) to polish 45# steel, it is more appropriate to set the speed at 2800 - 3000r/min; while when polishing aluminum alloy workpieces, the speed can be adjusted to 2000 - 2200r/min.
• The feed rate also has a significant impact on the polishing process. If the feed rate is too large, the cutting thickness of a single abrasive grain will increase, resulting in increased cutting force, which is likely to cause workpiece vibration and surface roughness increase, and may even cause excessive wear and damage to the abrasive; if the feed rate is too small, the processing time will be extended and production efficiency will be reduced. The reasonable feed rate setting should be determined according to the shape, size, material hardness and characteristics of the workpiece. For workpieces with simple shapes and large sizes, the feed rate can be appropriately increased in the rough processing stage to improve processing efficiency; in the fine processing stage, the feed rate should be reduced to ensure surface quality. For example, when rough grinding a flat workpiece, the feed speed of the worktable can be set to 100-150mm/min; while in the fine grinding stage, the feed speed should be controlled at 30-50mm/min. For materials with higher hardness, the feed rate should be relatively small to reduce the impact of cutting force on the workpiece and abrasive; for softer materials, the feed rate can be appropriately increased. In addition, the feed rate should also match the abrasive speed. Generally speaking, when the speed is higher, the feed rate can be appropriately increased, but care should be taken to avoid a decrease in processing quality due to improper coordination between the two.
• The cooling system plays an indispensable role in the polishing process. Effective cooling can take away a lot of heat generated during the grinding process, reduce the temperature of the workpiece and the abrasive, prevent the workpiece surface from burning and deformation, and also help reduce the wear of the abrasive and extend its service life. There are two main cooling methods: liquid cooling and gas cooling, of which liquid cooling is the most widely used. When selecting the coolant, it is necessary to make a reasonable choice according to the requirements of the workpiece material and the processing technology. For the grinding of ordinary metal materials, water-soluble coolants have good cooling and lubrication properties, which can effectively reduce the cutting temperature and reduce the friction between the abrasive particles and the workpiece; for difficult-to-process metal materials, such as stainless steel, titanium alloy, etc., coolants containing special additives can be selected to improve their lubrication and anti-rust properties. The flow rate and pressure of the coolant also need to be optimized. Excessive flow may cause the coolant to splash, causing waste and environmental pollution; too small flow cannot fully play the cooling effect. Generally speaking, the flow rate of the coolant should be adjusted according to the size and speed of the abrasive. Usually, the coolant flow rate per square centimeter of the abrasive area is 5-10L/min. In terms of pressure, the coolant should be fully sprayed into the grinding area. Generally, the pressure is between 0.2 and 0.5 MPa. In addition, attention should be paid to the cleanliness of the coolant. The coolant should be replaced and filtered regularly to prevent impurities from entering the grinding area and affecting the processing quality.

In actual processing, the optimization setting of polishing process parameters needs to be explored and adjusted continuously through experiments and practice. For example, when polishing a new alloy material, due to lack of relevant experience, the initial setting of speed, feed rate and cooling parameters resulted in a large number of scratches and burns on the machined surface. By gradually adjusting the parameters, reducing the speed to the appropriate range, reducing the feed rate, and increasing the coolant flow and pressure, the ideal machined surface quality and processing efficiency were finally obtained.

The optimal setting of polishing process parameters (speed, feed rate, cooling) is a complex system engineering, which requires comprehensive consideration of multiple factors and reasonable adjustment through scientific methods and practical experience to achieve efficient and high-quality operation of the abrasive polisher and meet the processing requirements of different workpieces.

4. Key points of equipment maintenance and safe operation specifications

As a high-speed rotating mechanical equipment, the performance and accuracy of the abrasive polisher will gradually decline during long-term operation, and there are also certain safety risks. Therefore, strictly abiding by the equipment maintenance and safe operation specifications is an important measure to ensure the normal operation of the equipment, extend its service life, and ensure the safety of operators.

Equipment maintenance is a key link to ensure the performance and precision of the abrasive polisher, which mainly includes three aspects: daily maintenance, regular maintenance and fault repair.

• Daily maintenance is a simple inspection and maintenance work that operators perform on equipment before and after each shift or during work. Check the appearance of the equipment to ensure that there is no obvious oil, dust or damage on the surface of the equipment; check whether the connection of each component is firm and whether there is any looseness, especially whether the abrasive is firmly installed to prevent it from falling off during high-speed rotation. Check the lubrication system to observe whether the oil level of the lubricating oil is within the normal range and whether the oil circuit is unobstructed. Regularly add or replace the lubricating oil to ensure good lubrication of the moving parts of the equipment and reduce wear. Also check the cooling system to ensure that the coolant level is normal, there is no leakage in the pipeline, and the filter is not blocked, so as to ensure that the coolant can circulate normally and play a cooling and lubricating role. In addition, after each work, the chips and debris on the surface of the equipment and the workbench should be cleaned up in time to keep the equipment clean.
• Regular maintenance is a comprehensive inspection and maintenance of the equipment at a certain time interval, generally once every quarter or every six months. In addition to daily maintenance, regular maintenance also requires a more in-depth inspection and adjustment of the key components of the equipment. For example, check the accuracy of the spindle and the wear of the bearings, and adjust or replace them if necessary; check the belts and chains of the transmission system, adjust the tension or replace severely worn parts; check whether the line connection of the electrical system is firm and whether the electrical components are working properly, and repair or replace damaged components in time. At the same time, the accuracy of the abrasive polisher should be tested and calibrated, such as the flatness of the workbench and the verticality of the spindle, to ensure that the processing accuracy of the equipment meets the requirements.
• When equipment fails, it should be repaired in time. Fault repair requires professional maintenance personnel who have rich equipment maintenance knowledge and experience, and can accurately determine the cause of the failure and repair it. During the maintenance process, it is necessary to strictly follow the equipment maintenance manual, use appropriate tools and accessories, and ensure the quality of maintenance. After the maintenance is completed, the equipment should be tested to check whether the equipment has resumed normal operation and whether various performance indicators meet the requirements.

Safety operating regulations are important criteria for ensuring the personal safety of operators and the normal operation of equipment. Before operating a abrasive polisher, operators must undergo professional training, be familiar with the structure, performance, working principle and operation methods of the equipment, and master safe operating procedures and emergency response measures. Operators should wear appropriate labor protection equipment, such as protective glasses, protective gloves, work clothes, etc., to prevent injuries from chip splashing, abrasive fragments, etc. during processing.

When installing and replacing the abrasive, strictly follow the operating procedures. Check the appearance of the abrasive to ensure that the abrasive has no cracks, breakage or other defects; then, according to the size of the abrasive and the equipment requirements, select the appropriate flange and gasket, correctly install the abrasive on the spindle, and tighten the nut to ensure that the abrasive is firmly installed and has good concentricity. After installation, a no-load test run should be carried out to observe the rotation of the abrasive. If there is abnormal vibration or noise, the machine should be stopped immediately for inspection.

Before starting the equipment, check whether there are any obstacles around the equipment to ensure the safety of the working area. After starting the equipment, let the abrasive idle for 1-2 minutes to observe whether the equipment is running normally. After the equipment is running stably, place the workpiece on the workbench for processing. During the processing, the operator should pay close attention to the operating status and processing of the equipment. It is strictly forbidden to touch the rotating abrasive and workpiece with hands to avoid danger. At the same time, the operation must be carried out strictly in accordance with the process parameters, and the speed, feed rate and other parameters must not be changed at will to prevent equipment failure or safety accidents caused by improper parameter settings.

When the equipment has abnormal conditions, such as abnormal vibration, noise, smoke, etc., or a safety accident occurs, the operator should immediately press the emergency stop button to stop the equipment and report it to relevant personnel for processing. During equipment repair and maintenance, the power supply must be cut off and warning signs such as "Do not close the switch" must be hung to prevent others from misoperating and causing safety accidents.