Machine Grinding Principles of Sanding Belts

+ 查看更多

Coated abrasive belt grinding is a specialized form of abrasive machining that involves using an abrasive belt tensioned by a mechanism and driven at high speed by a wheel to grind the workpiece surface under controlled pressure. While both coated abrasive belt grinding and grinding with grinding wheels are high-speed"micro-cutting tools" based on the cumulative effect of micro-cutting by abrasive grains, they differ significantly due to the unique construction and usage of abrasive belts. In this article, we will explore the various types of coated abrasive base materials and their manufacturing treatment, which play a crucial role in the performance and overall efficiency of abrasive belts.

*1.Characteristics of Coated Abrasive Belt Grinding*

1)**Elastic Contact Grinding**:Unlike grinding wheels, which provide rigid contact grinding, coated abrasive belt grinding involves elastic contact grinding. The base material and bonding agents in the coated abrasive possess some level of elasticity. Even when steel contact wheels with low elasticity are used, the abrasive belt itself contributes to the elastic contact. This elasticity results in not only sliding, plowing, and cutting actions similar to grinding wheels but also the abrasive grains' extrusion effect on the workpiece surface. This extrusion leads to plastic deformation, cold work layer alteration, surface tearing, and the generation of heat-induced thermoplastic flow. The combination of these effects enables coated abrasive belts to perform multiple actions like grinding, honing, and polishing, leading to superior surface quality.

2)**Uniform Grain Distribution**:Coated abrasive belts have a uniform and regular distribution of abrasive grains on their surface compared to the random and irregular distribution seen on grinding wheels. The abrasive grains on the coated belts are typically shaped like elongated triangular prisms, created using advanced processes like electrostatic seeding. Their sharp orientation allows for better cutting conditions during grinding, reducing material deformation, increasing material removal rates, and minimizing grinding forces and resulting temperatures.

3)**Chip Space**:The space between abrasive grains on grinding wheels is typically limited due to the presence of bonding agents. In contrast, coated abrasive belts offer significantly larger chip space, generally at least ten times more than grinding wheels. This, combined with the uniformity and sharpness of the abrasive grains, provides a larger effective cutting area and higher cutting efficiency. Moreover, the chip space prevents the accumulation of debris on the abrasive belt surface, reducing the risk of clogging and excessive frictional heat generation, resulting in lower grinding zone temperatures.

4)**Longer Perimeter**:Coated abrasive belts can have much longer perimeters compared to grinding wheels. This feature allows for better heat dissipation during grinding and enables the oscillation of the unsupported portion of the belt, which naturally shakes off adhering debris. This further reduces the chance of abrasive grain blockage, minimizing frictional heat and contributing to the low-temperature characteristics of coated abrasive belt grinding.

*2.Single Grain Grinding Process*

Coated abrasive belt grinding relies on a multitude of abrasive grains vertically aligned on the belt surface to perform the cutting. Each abrasive grain can be likened to a micro-cutting tool, making the study of the single-grain grinding process fundamental to understanding the entire coated abrasive belt grinding process.

Looking at the abrasive grains on the belt surface from a microscopic perspective, they resemble micro-cutting tools with round-tip arcs and obtuse angles. The radius of these arcs can range from a few micrometers to several tens of micrometers, depending on the abrasive grain material and size. As the cutting depths are shallow(generally around 0.005 to 0.05 mm), most of the abrasive grains engage the workpiece in negative rake conditions during grinding. This induces significant extrusion and elastic deformation of the workpiece surface, with the material transitioning from elastic to plastic deformation under increasing pressure.

The grinding process with coated abrasive belts can be divided into four stages: extrusion, sliding, plowing, and cutting, due to the grain's geometric characteristics and elastic contact properties. As the cutting depth increases, the pressure applied to the workpiece by the abrasive grain intensifies, resulting in plowing and the formation of grooves on the workpiece surface. As the cutting depth continues to increase, the metal layer is pushed beyond its strength limits, leading to chip formation and separation from the workpiece surface. The cutting process varies in proportion at different stages of the grinding process, making coated abrasive belt grinding a complex operation.

In summary, coated abrasive belt grinding offers several advantages over grinding with conventional grinding wheels. The elastic contact grinding characteristic, uniform grain distribution, ample chip space, and longer perimeter contribute to superior cutting efficiency, improved surface quality, and lower grinding zone temperatures. Understanding the complex grinding process of single abrasive grains provides a theoretical basis for comprehending the overall coated abrasive belt grinding mechanism.