Due to the limitations of production methods and process requirements, a series of processing steps are required after the glassware is formed. Processing is an important process for the production of glassware. Processing is divided into two methods: hot processing and cold processing.
The processing that uses the characteristics of glass viscosity changing with temperature, surface tension and thermal conductivity is called hot processing. Kiln opening, sticking handles, patching, etc. are hot processing.
The process of changing the shape and surface state of glass and glass products by mechanical methods at room temperature is called cold processing. Grinding, polishing, cutting, sandblasting, engraving, sand carving and drilling are all cold processing.
1 Grinding is to remove surface defects of glass products or protruding parts remaining after molding, so that the products can obtain the required shape, size and flatness.
2 Polishing is to use polishing materials to eliminate the concave and convex layers and cracks that remain on the glass surface after grinding to obtain a smooth and flat surface.
3 Cutting is the process of scratching the glass surface with diamond or carbide tools and breaking it at the scratch. 4 Edge grinding is a method of grinding the edges and rough sections of glass.
5Sandblasting is a processing method that uses compressed air to spray abrasives onto the glass surface through a spray gun to form patterns or text.
6Drilling is the use of carbide drills, diamond drills or ultrasonic methods to make holes in glass products. 7Carving, also known as engraving, is a processing method that uses a grinding wheel to grind patterns on the surface of glass products.
Cold processing and hot processing are usually used in combination in product processing. General vessel glass is divided into two types: open products and burst products: open products have the characteristics of hand-blown products, the mouth treatment is completed before the product enters the kiln, there is a sticky material cake at the bottom of the product, and the bottom can be cold processed; burst products have a crown-shaped glass cap at the mouth when entering the kiln, which needs to be cut off at the cold processing location and the mouth is processed. The cold processing of open products and burst products is grinding and polishing, but the processing equipment is different. Usually, when a factory has both open and burst products, there will be two production lines for open cold processing and dry cold processing, which do not interfere with each other and improve processing efficiency. After the cold processing line for open products and the cold processing line for burst products, many products can be put into the warehouse after cleaning and packaging. However, according to different functions and design requirements, some products need to be drilled, carved, sanded, bonded and other deep processing links.
Explosion cold processing line
After the blown products are formed, they have a cap. Generally, scratches and local rapid cooling or rapid heating are used to break the edge (called burst or burst), and the broken edge is then smoothed by grinding and melting (called grinding and baking). Some remove the cap by melting the edge of the flame, but often leave a perceptible melt head on the edge.
The burst cold processing line has several processes, including burst, rough grinding, fine grinding (or baking), pouring, and polishing. 3.5.1.1 Explosion
Many glass products often have sharp edges, and flame cutting is often used to obtain products of suitable height. Applicable to cylindrical or tubular uniformly symmetrical glass products. First, use a glass cutter to make a mark at the place where the product needs to be cut. Place the glass product on a turntable that rotates at a constant speed. The flame point heats rapidly along the scratch line (Figure 3-35). When the product scratch is heated to a certain temperature or a slight glass popping sound is emitted, it is judged that the product has been broken along the scratch. Remove the product from the flame. If the product is not broken, gently tap a certain part of the product to make the scratch vibrate and break. You can also use a cold steel blade or dip a small amount of water to contact the heating point to make it cold and generate cracks. The flame is mostly gas-oxygen flame or liquefied gas-oxygen flame, which can be adjusted to a blue flame. Use a knife-shaped and oblique needle-shaped high-temperature flame, and try to concentrate the heating in a narrow area. Otherwise, it is very easy for the product to burst irregularly locally, resulting in unqualified products caused by improper processing.
When the glass of a vessel with a complex shape cannot be cut by a rotating disk flame due to its non-tubular symmetry, the cutting method or sawing method can be used. Common tools for cutting include glass cutters with diamonds embedded in the end of brass and carbide cutter wheels for cutting harder and thicker glass. Carbide such as tungsten-cobalt alloy. When cutting glass, water or kerosene and other liquids should be added for cooling, which is good for the incision and the life of the cutting tool. Sawing is to use the brittleness of glass for grinding. In the early days, the method of rotating a metal disc or pulling a metal wire with an additional grinding fluid was mostly used, but it was rarely used after the 1970s and 1980s. Now diamond saw blades or silicon carbide saw blades are mostly used for cutting. Diamond saw blades are made by embedding diamond particles in the serrated part of the edge of a circular saw blade, and bronze is used as a binder. Most coolants are water, and a few are kerosene. Its cutting rate is 4 to 5 times faster than that of a grinding wheel. Silicon carbide saw blades are made by combining various coarse and fine particles of silicon carbide with phenolic resin adhesives, and are formed, pressed, and hardened. Water should also be added for cooling during cutting.
In addition, electric heating cutting can also be used, that is, a resistance wire with low voltage power is used to cut the glass. This method is inefficient, but it is suitable for some products with larger sizes that are not suitable for slicing or sawing.
Grinding and polishing
Grinding and polishing are two different processes, which are collectively called polishing.
After the cracking, the product still has defects such as gaps and sharp edges, so grinding is often used for repair. According to the different abrasive grain sizes at different stages of grinding, it is divided into coarse grinding and fine grinding. Coarse grinding is to use coarse abrasives to grind away the rough and uneven parts of the glass surface or the surface of the product. It has a grinding effect and high efficiency, but the surface is rough, with depressions and crack layers. Fine grinding is a follow-up process between coarse grinding and polishing, which saves polishing time and reduces the difficulty of polishing.
Because abrasives are provided in addition to cooling water during the grinding process, the abrasive grain size and supply amount have a certain impact on the grinding efficiency and quality. Grinding requires the selection of appropriate abrasives and abrasive grain sizes. Coarse grinding uses coarser grain sizes to improve grinding efficiency, that is, through coarse grinding, the glass products can reach a suitable shape or surface flatness in a shorter time, →Fine abrasives are used to improve the grinding quality, that is, through fine grinding, the product can reach the surface quality required for polishing.
The hardness of the grinding disc material can improve the grinding efficiency. The grinding efficiency of cast iron material is 1, that of non-ferrous metal is 0.6, and that of plastic is only 0.2. However, the grinding disc with high hardness makes the depth of the concave surface of the grinding surface deeper. In addition, the rotation speed and pressure of the grinding disc are proportional to the grinding efficiency. Based on these two principles, a diamond grinding disc has been introduced in recent years to improve the rough grinding efficiency, save labor time, and reduce the labor intensity of workers. This grinding disc is a material with relatively high hardness-diamond particles cast on the grinding disc surface, and the thickness of the diamond particles is only a few millimeters. The hardness of diamond particles is greater than that of ordinary grinding disc cast iron materials. With extremely fast rotation speed (2100r/min, the rotation speed of ordinary grinding discs is usually 300r/min), there is no need to provide abrasives, only sufficient cooling water is needed to perform rapid grinding. The grinding disc has a fast rotation speed, a large cutting volume, and the rough grinding efficiency can be increased by 3~5 times, and the work site is clean and tidy. The flatness of the grinding disc is very high. It needs to be recast and leveled after about half a year of use. The grinding disc will be scrapped after two or three treatments. The cost of using the grinding disc is high.
In order to reduce the edges and corners on the inside of the mouth and increase the safety of the product, there is a process called chamfering after fine grinding. As shown in Figure 3-36, the grinding disc is used to process the sharp section of the mouth after the mouth bursts. It belongs to rough grinding or fine grinding, and can process the edges and corners on the outside of the mouth. As shown in Figure 3-37, it is a chamfering machine used after fine grinding, which mainly processes the edges and corners on the inside of the mouth.
Polishing can make the surface of the final product smooth and restore its original transparency and gloss. In addition to removing all the depression layer (3~4um) on the surface after grinding, polishing also needs to remove the crack layer under the depression layer (only 1/40~1/20 of the thickness removed during grinding). Although this thickness is much smaller than the thickness removed during grinding, the polishing efficiency is much lower than the grinding efficiency. The polishing process takes twice or even more time than the grinding process.
Generally, polishing discs are made of felt, and woolen cloth, amaranth roots, etc. can also be used. Coarse felt or semi-coarse felt has high polishing efficiency, while fine felt and woolen cloth have low polishing efficiency. The last level of polishing of glass enterprises' cracked products is mostly to glue the corresponding shape of felt on the cast iron disc with glue, and then use it to polish the product after the glue is dry.
In addition, cracked products have a processing method combined with drying products. Drying is a concentrated high-temperature flame that heats it locally, relying on the effect of surface tension to make the glass smooth when softened. Some products after mouth-blasting are ground and then dried, while some are directly dried after drying, which is called joint mouth-blasting. The three processes of mouth-blasting, mouth-grinding and mouth-drying can be completed at one time, but the mouth is obviously thickened, which is only suitable for low- and medium-end products. Since the mouth shape changes after mouth-drying, modern high-end glassware is no longer dried, but ground instead. Mouth-drying machines are mostly used for baking glass products such as beer cups, ashtrays and water cups. When baking the mouth of lead crystal glass products, a certain amount of oxygen must be added to assist combustion and the flame atmosphere must be adjusted to prevent the lead oxide in the glass from being reduced to metallic lead and causing the mouth of the product to turn black.