Due to the different three components of the sand belt and various characteristic factors, the sanding belt can be divided into many varieties according to different grinding objects, grinding conditions and grinding requirements.
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The following is only a few of the most basic sand belt for some introduction.
1. Electrostatic sand and gravity sand
The electrostatic planting sand belt uses the principle of high voltage electrostatic adsorption to polarize the abrasive upward and embed it into the adhesive layer on the surface of the substrate in the direction of its own long axis, thus forming a neatly arranged and evenly distributed abrasive layer, as shown in Figure 1 (a). The grinding efficiency of electrostatic sand belt is more than 25% higher than that of general gravity sand belt. The surface roughness is uniform and good. The density of electrostatic sand is also easy to control.
Gravity sand planting (also known as mechanical sand planting) sand belt is the use of abrasive weight, free fall from a certain height and embedded in the rubber layer on the surface of the substrate to form an abrasive layer, with this method of sand planting, the direction of the abrasive arrangement is uncertain, mostly "lodging" state, as shown in Figure 1 (b). The sharpness of the abrasive cutting edge of this abrasive belt is poor, so the grinding efficiency and machining surface quality are not as good as the electrostatic planting sand belt. It is also more difficult to control the density of the sand.
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FIG. 1 Sand planting process has a significant impact on the shape of sand belt
Gravity sand planting is the main sand planting method in the early production process of sand belt and sandpaper. With the progress of technology, gravity sand planting has been basically replaced by electrostatic sand. In addition to the above methods, there are the following sand planting methods: standard sand, sparse sand and Combi sand, as shown in Figure 2. Different sand forms can optimize abrasive properties and grain spacing to improve chip capacity.
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Figure 2 Other sand planting methods
2. No joint sand belt, joint sand belt, and open sand belt
The jointless sand belt is made of special cylindrical cloth as the base material, after stretching, calendering and impregnating the original cloth on a special equipment, and then by gluing, sand planting and drying. The jointless belt is also an early product of the belt, which is no longer produced.
The joint sand belt is converted by cutting, edging, bonding and slitting the rolled sand belt in different sizes. The girth of the joint sand belt is not limited, and the production is very convenient, especially the development of the current joint method, joint adhesive and joint process equipment has made the sand belt joint, whether in thickness, strength, flexibility characteristics or even the overall consistency of the non-joint part has reached a very high level, which is the main form of the current sand belt.
Open sand belt is another kind of sand belt, which is a small rolled sand belt formed by directly dividing the rolled sand belt blank according to the size requirements. The open sanding belt is simple to make. It is also very convenient to use, and is often used in fine particle size precision machining, such as automotive engine camshaft, crankshaft, precision cylindrical parts and so on. It is characterized by high workpiece motion speed, slow sand belt speed, long service cycle, and there are always new abrasives involved in grinding in the grinding area, so the consistency of grinding surface quality is very good.
3. Dense planting sand belt and sparse planting sand belt
The densely planted sand belt is also called the closed coated sand belt, which is characterized by the fact that the abrasives are close to each other, the entire surface of the substrate is covered, and there is no obvious gap between the abrasives. Densely planted sand belts are mainly used for difficult grinding processes, including heavy duty grinding and heavy duty grinding.
The sparse planting sand belt is also called the open coated sand belt. The sand belt is arranged according to the preset distance between the abrasive particles, so there is a more obvious gap between the single abrasive particles. According to the use requirements, the abrasive particles should generally cover 50% to 70% of the substrate surface. The belt has good flexibility, and the space between abrasive particles can reduce the blockage of abrasive chips when grinding certain materials.
4. Dry and wet scrub belts
Dry film abrasive belt is widely used, because abrasive belt grinding is a "cold" grinding, often does not require coolant to burn the workpiece. Dry abrasive belt can not be used in wet grinding, because the adhesive used in it is easy to affinity with water or other media, loss of adhesion, resulting in abrasive drop, reduce the durability of the abrasive belt, and will seriously affect the processing quality.
Wet scrub strips are used for grinding with coolant, but also for dry grinding. It not only needs to use a water-resistant synthetic resin as the base glue and compound glue, but also the base material must be used water-resistant glue, so as to resist the erosion of the coolant. Wet-frosted belt grinding can reduce the heat of the workpiece, avoid thermal burn, reduce thermal stress and improve the surface quality of the workpiece.
