First, the original cloth processing
The base materials used in abrasive belt include cloth, paper and composite matrix. Paper generally needs no treatment except water-resistant paper. The composite matrix belongs to the composite of paper and cloth, and sometimes it is purchased directly from suppliers, or it is completed on the raw cloth processing line or large roll manufacturing line of abrasive belt factory. Here, the main processes of cloth base treatment such as scraping, singeing, dewaxing, dyeing, dip scraping, stretching and calendering are described, and different processes are selected according to different requirements.
1, shave, singe
Shaving and singeing are used to remove cotton wool, neps, impurities and other defects on the surface of the original cloth. Scrape the surface of the grey cloth with a spiral scraper, and then burn the plush on the surface of the grey cloth with a high-temperature flame to make the surface of the grey cloth smooth and flat.
2, desizing and degreasing
Desizing and degreasing is to remove the slurry from cotton yarn evenness and the wax from cotton fiber, and soak it in alkali solution to remove it. Desizing absorbent cotton cloth is easy to absorb and penetrate the slurry.
3. Dyeing, dipping and scraping
Because the abrasive belt has low requirements on the color of the matrix, dyeing, dipping and scraping are carried out together, that is, the dye for dyeing is directly dipped in the slurry to achieve the purpose of dyeing. Water-resistant products must be impregnated with resin, and water-resistant products are generally impregnated with animal glue.
Step 4 stretch
Stretching includes two directions: longitudinal stretching and transverse stretching. Longitudinal stretching takes away some elongation and reduces the elongation of finished products. Transverse stretching has the functions of setting and stretching, which ensures that the width of the fabric to be treated is controlled within a certain range.
5, calendering
Calendering is the last process of grey cloth treatment, which aims to make the cloth smooth and ensure the uniformity of gluing.
Second, mass production.
The manufacture of large rolls includes trademark printing, gluing, sand planting, re-gluing, drying and other main processes, all of which are completed in one production line, which is a joint production line.
1. trademark printing: this process is to print the factory trademark, abrasive particle size, model and related factory regulations on the back of cloth base or paper base. Printing must be clear, definite and beautiful, so that users can easily identify the relevant data of products, such as the direction of abrasive belt used when grinding.
2. Glue coating: including priming and repainting. For example, the above coating amount (primer coating and recoating coating) and sand planting amount are automatically scanned in modern production lines and the information is fed back to the automatic adjustment control device. In the past, many large enterprises used beta-ray transillumination, but its stability, safety and accuracy were poor. Recently, some well-known enterprises of sandpaper, abrasive belt and abrasive cloth roll have made major technical transformation, and successfully adopted γ -ray online measurement, with a measurement accuracy of 0.25mm and a measurement error of 0.25%. The measurement accuracy, stability and safety are better than the previous measurement system, plus touch monitoring display and automatic feedback control, plus automatic temperature control on the drying line.
The thickness of primer and compound adhesive is controlled by the gap between two pairs of rollers in production.
3. Planting sand: There are two methods to plant sand, one is gravity planting sand, and the other is electrostatic planting sand. Gravity sand planting relies on the gravity of abrasive to plant sand on the attachment layer, so the arrangement of abrasive on the attachment layer is messy and has no certain directionality. Electrostatic sand planting is to guide the electrostatic magnetic field to polarize the abrasive and attract it to the bonding layer, so that the abrasive is arranged in an orderly way, and the edge and tip of the abrasive are outward, which is very beneficial. Because the axial direction of the abrasive must form a certain angle with the matrix, the orientation of the abrasive on the surface of the matrix forms a sawtooth structure, so the abrasive can fully surface the abrasive belt, which is the best effect, and the grinding ability will inevitably be enhanced. Because electrostatic sand planting is not suitable for coarse grain size (40# is coarse), this part of abrasive depends on gravity sand planting.
4. Drying: The big roll of sand must be dried after planting. The drying equipment has the characteristics of closed drying and closed drying with humidity control function. The characteristics of fully enclosed drying should be high drying temperature and long drying time. In order to reduce diffusion heat, make full use of thermal cycle to improve thermal efficiency, centrally treat harmful waste gas, and reduce environmental pollution, fully enclosed drying is beneficial to the production of abrasive belt, and the general capacity is above 1000 m, which is beneficial to the drying temperature and time of resin adhesive. The disadvantage of drying equipment with humidity control function is that the abrasive belt will lose physical moisture when baking at high temperature for a long time, which will lead to brittle abrasive cloth. A humidifying device is added in the lead-out area of the emery cloth to keep the moisture content of the emery cloth in balance with the normal state, so the emery cloth should be equipped with this function in the drying process.
Third, the post-processing of large volumes.
After the emery cloth rolls out of the drying room, it must go through a series of treatments before entering the conversion process. The self-care of large rolls includes post-maintenance, storage, humidification and flexibility. Through these processes, the performance and quality of emery cloth (paper) can reach the predetermined goal.
1, post-curing. Due to the low temperature and short time in the drying room, the large roll of abrasive cloth (paper) transferred from the drying room only completed the pre-curing stage, and the abrasive reached the position. But judging from the curing reaction of phenolic resin, it only reached the B stage. If it is completely cured, it needs higher temperature and time to become an insoluble C-grade resin, and the quality will get the ideal effect.
2. storage. After several hours of high-temperature curing, when phenolic resin binder is curing, the so-called "internal reaction force" is formed due to the asymmetry of cross-linking in polymer chain and the imbalance of internal stress, which leads to uneven or distorted surface deformation of abrasive cloth. This kind of defect, after a certain period of storage, will slowly disappear by itself, and the surface of emery cloth will become flat and scratched. It is best to store large volumes in a warehouse with constant temperature and humidity, and the storage effect will be better.
3. Humidify. Both emery cloth rolls and sandpaper rolls must contain certain physical moisture under normal circumstances. When this moisture is lost to a certain extent, emery cloth or sandpaper will become brittle. When the large roll of emery cloth is baked at high temperature in the curing furnace, the water loss is also serious, resulting in certain brittleness. Therefore, the moisture contained in the emery cloth is recovered by humidification, and the flexibility and toughness of the emery cloth are improved.
4. Flexibility. Abrasive belt is also called flexible abrasive tool. In order to achieve flexibility, first of all, the substrate and the binder are both flexible materials, so the product itself is very flexible, and this product does not need flexibility, which is a very difficult thing, followed by flexibility. In order to deal with difficult-to-grind materials, it is necessary to select the matrix with large thickness and heavy weight and thermosetting resin with high bonding strength and high heat resistance for heavy grinding and heavy load grinding, so that the flexibility of the abrasive belt itself will be improved, but the abrasive belt is soft on the whole and still hard on the micro level, which is the task to be completed by mechanical bending. Simply put, the function of mechanical buckling is to create tiny cracks on the surface of the abrasive belt, so as to obtain the softness of the entire abrasive belt.
Fourth, transformation.
The so-called conversion refers to the process of converting a large roll of emery cloth into a product with the shape of an abrasive belt, a disk or a page.