How is the sanding belt made?

In the previous article, we mentioned some characteristics, advantages and application fields of our abrasive belts.

So how is a good abrasive belt made?

Today's article will show you how regular sanding belts are made.

The production of abrasive belts generally includes four processes: raw cloth processing, large roll manufacturing, large roll post-processing and conversion.

一. Raw fabric treatment

The substrates used in abrasive belts include cloth, paper and composite base. Paper generally does not need to be treated except water-resistant paper. Composite base is a composite of paper and cloth. Sometimes it is purchased directly from the sub-supplier, or in the abrasive belt manufacturer It is completed on the original cloth processing line or on the large roll manufacturing line. Here we explain the main processes of cloth base processing such as shaving, singeing, dewaxing, dyeing, dipping and squeegeeing, stretching, and calendering, which are selected according to different requirements. different processes.

1. Shaving and singeing

Shaving and singeing are to remove defects such as lint, neps, and impurities on the surface of the original cloth, scrape the surface of the gray cloth with a spiral scraper, and then burn off the plush on the surface of the gray cloth with a high-temperature flame to clean the surface of the gray cloth Smooth and smooth.

2. Desizing and degreasing

Desizing and degreasing is to remove the size on the cotton yarn and the wax in the cotton fiber. It is removed by soaking in lye. After desizing and degreasing, the cotton cloth is easy to absorb and penetrate the size.

3. Dyeing dipping and squeegeeing

Because abrasive belts have relatively low requirements on the color of the matrix, dyeing, dipping and squeegeeing are carried out together, that is, the dyes used for dyeing are directly dipped and added into the slurry to achieve the purpose of dyeing. The treatment of water-resistant products must be impregnated with resin materials, while the general non-water-resistant products are impregnated with animal glue.

4. Stretch

Stretching includes longitudinal and transverse stretching. Longitudinal stretching removes part of the elongation and reduces the elongation of the finished product. Transverse stretching has the effect of shaping and stretching, ensuring that the width of the processed cloth is controlled within a certain range.

5. Calendering

Calendering is the final process of raw cloth processing, the purpose is to make the cloth smooth and smooth, and it plays a role in ensuring the uniformity of glue application.

二. Large volume manufacturing

The production of jumbo rolls includes major processes such as trademark printing, gluing, sanding, gluing, and drying. These processes are all completed on one production line, which is a production line with linked operations.

1.Trademark printing: 

This process is to complete the printing of the factory trademark, abrasive grain size, model and relevant factory regulations on the back of the cloth base or paper base. The printing must be clear, clear, beautiful and easy for users to identify the relevant data of the product. When connecting, use the direction of the abrasive belt, etc.

2. Glue coating:

Including primer coating and recoating, such as the amount of top coating (primer glue and recoating) and sand planting amount, all of which are automatically scanned on modern production lines and their information is fed back to the automatic adjustment control device. In the past, many large enterprises used β-ray penetrating measurement, but its stability, safety and accuracy were poor. γ-ray online measurement has a measurement accuracy of 0.25mm and a measurement error of ±0.25%. The measurement accuracy, stability and safety are superior to those of the previous measurement system. It is equipped with touch monitor display and automatic feedback control. The online temperature is automatically controlled to form a complete quality control system for the measurement of abrasive paper, abrasive belt, and abrasive cloth rolls, which can ensure the stable quality of each batch of products.

The thickness of primer and compound glue is implemented by controlling the gap between two pairs of rollers in production.

3.Sand planting: 

There are two methods of sand planting, one is gravity sand planting, and the other is electrostatic sand planting. Gravity sand planting relies on the gravity of the abrasive itself to plant the sand on the rubber layer, so the arrangement of the abrasive on the rubber layer is rather messy and has no certain directionality. Electrostatic sand planting is the leading electrostatic magnetic field power to attract the abrasive to the adhesive layer after being polarized, so the arrangement of the abrasive is orderly, and the edges and corners of the abrasive and the tip are facing outward, which is very beneficial, because the axis direction of the abrasive must be in a certain relationship with the matrix. The orientation of the abrasive on the surface of the substrate forms a saw tooth-like structure, so the abrasive can fully achieve the best effect on the surface of the abrasive belt, and the grinding ability will inevitably be enhanced. Since electrostatic sand planting is not suitable for coarse-grained (40# and coarser), this part of the abrasive should be completed by gravity sand planting.

4.Drying:

Large rolls must be dried in the sand planting. The drying equipment has the characteristics of fully enclosed drying and closed drying with humidity control function. The fully enclosed drying should be dried at high temperature and long time. In order to reduce the diffusion heat and make full use of the heat cycle to improve the heat efficiency, the centralized treatment of harmful exhaust gas reduces environmental pollution. Pollution adopts the form of fully enclosed drying, which is beneficial to the production of abrasive belts, and generally has a capacity of more than one kilometer, which is beneficial to the characteristics of resin glue drying temperature and long time. The drying equipment with humidity control function is to make the emery cloth become brittle due to the physical moisture loss of the abrasive belt during high temperature and long-term baking. A humidifying device is added in the lead-out area of the emery cloth to keep the water content of the emery cloth at the same level as normal. Balance, so the emery cloth should have this function in the drying process.

三. Post-processing of large volumes

After the emery cloth is rolled out from the drying room, it must go through a series of treatments before entering the conversion process. Post-care of jumbo rolls includes post-curing, storage, humidification, flexing, etc. After these processing procedures, the performance and quality of the emery cloth (paper) can reach the predetermined goal.

1. Post curing. The large roll of emery cloth (paper) transferred out of the drying room, due to the low temperature and short time in the drying room, only completed the pre-curing stage and the abrasive reached the position, but from the curing reaction of the phenolic resin, it only reached the final position. Stage B, such as complete solidification, requires higher temperature and time to become insoluble and infusible stage C resin, and its quality can get the desired effect.

2. Storage. After the large roll is cured at high temperature for several hours, when the phenolic resin binder undergoes a curing reaction, due to the asymmetry of the cross-links formed on the polymer chains, an imbalance of internal stress occurs, forming a so-called "internal reaction force" that causes emery cloth Surface deformation is uneven or distorted. After a certain period of storage, this kind of defect will disappear slowly by itself, and the surface of the emery cloth will become flat and scratchy. It is best to store large rolls in a warehouse with constant temperature and humidity, and the storage effect will be better.

3.Humidify. 

Whether it is an abrasive cloth roll or a sandpaper roll, it must contain a certain amount of physical moisture under normal conditions. When this moisture is lost to a certain extent, the abrasive cloth or sandpaper will become brittle. When the large roll of emery cloth is baked at high temperature in the curing furnace, the loss of water is relatively serious, resulting in a certain degree of brittleness, so the moisture contained in the emery cloth is restored by humidification, and the flexibility and toughness of the emery cloth are improved.

4.Flex. 

Abrasive belts are also called flexible abrasives. In order to achieve flexibility, one is to choose a material with good flexibility for both the base material and the binder, so that the product itself is very soft, and this product does not need to be flexed, which is a relatively difficult thing. song. In order to deal with difficult-to-grind materials, large-scale grinding and heavy-duty grinding must use a substrate with a large thickness and weight, a thermosetting resin with high bonding strength and high heat resistance, so that its own flexibility will be improved, but overall The upper abrasive belt is soft but still microscopically hard, which is the task of mechanical flexing. The function of mechanical flexing, simply put, is to make tiny cracks on the surface of the abrasive belt, so as to obtain the softness of the entire abrasive belt.

四、 Conversion

The so-called conversion refers to the process of converting large rolls of abrasive cloth into abrasive belts or disc-shaped, sheet-shaped and other shaped products.