1. Classification of rolls
Rolls are the main components of rolling cars. Rolls can be divided into active rolls and passive rolls. The active roller is directly driven by the transmission device, while the passive roller is driven by the friction of the active roller.
The roller surface of the active roller generally has a high hardness, and is usually made of hard rubber, cast iron, and is plated with copper or covered with stainless steel. In recent years, on dyeing machines, sub-bleaching machines and other machines, the active rollers of padding cars are made of soft rubber.
The roller surface of the passive roller must be elastic. Therefore, passive rollers are generally made of soft rubber, and there are also fiber rollers made of overlapping layers of cotton fiber, hemp fiber and paper and pressed under high pressure. The main purpose is to avoid damage to the fabric when it passes through the nip point and breakage of the seam head when it passes through the nip point.
The rollers can also be named according to the roller surface material, such as hard rubber rollers, stainless steel rollers, peron rollers (microporous rollers), etc. In order to prevent contamination, a layer of polytetrafluoroethylene material is evenly coated on the surface of some new rollers.
2. The structure of the roller
There are many structural forms of the roller, generally consisting of a shaft core, a shaft body, an outer cladding, a red ferrule, a corrugated pin, etc. Several commonly used ones are shown in Figure 3-1.
(1) Shaft core: The shaft core generally has There are two kinds of integral shaft and short shaft, which are made of 45 steel and made into ladder shape. The connection between the integral shaft and the roller body should be tightened with a corrugated pin, and the outer end should be tightened with a red ferrule to prevent the corrugated pin from loosening. In recent years, in order to save materials and simplify processing technology, the shaft core of most rolls uses short shafts with two ends, which are fastened into the shaft holes of the roll body with red ferrules.
The size of the shaft core depends on the rotation torque and pressure.
(2) Roll body: The roll body of the roll is generally made of HT15-33 or HT20-40 cast iron. However, cast iron rollers are not corrosion-resistant, so complete cast iron rollers are rarely used in wet processing and are mainly used in dry finishing machinery. . At present, the rolls of padding mills are mainly made of cast iron rolls covered with stainless steel or titanium plate coatings, and are also made of seamless steel pipes or steel plates ring-welded. In order to balance the operation of the roller, the hole in the roller body needs to be machined and statically balanced. The surface of the roller body should be free of defects such as pores and dust inclusions after processing. If the surface is no longer covered with rubber and is made of stainless steel rollers or chrome-plated rollers, the requirements will be higher. If there are no sesame points, the non-cylindrical degree and out-of-roundness should be less than 0.10mm. The wall thickness of the roller body should be determined according to the stress. The thickness of the cast iron roller body should not be less than 15mm. The minimum thickness of the roller body made of steel pipes and steel plates is as follows:
① Diameter ≤ 100mm, wall thickness not less than 5mm .
②The diameter is between 100~250mm, and the wall thickness is not less than 8mm.
③The diameter is between 250~500mm, and the wall thickness is not less than 12mm.
④Diameter﹥750mm, wall thickness not less than 15mm.
Stainless steel roll diameter: 150mm, 200mm, 225mm, 300mm, 350mm, 500mm.
Butadiene rubber roller diameter: 170mm, 190mm, 250mm, 280mm, 300mm, 350mm, 400mm, 500mm.
(3) The rubber-covered cast iron roller body must have air screw holes drilled at both ends to prevent internal pressure from being generated when the roller body is heated, and hot air can easily enter the roller body. The hole diameter should be no less than 20mm, and it should be blocked with bulkhead bolts after processing. If it is another metal roller body, if its diameter is less than 150mm and its length is less than 1200mm, no holes are required. The roller body made of steel pipe or steel plate does not need to have holes.
(4) Since rubber has unique elasticity, appropriate hardness, strength and certain corrosion resistance, except for some hard rolls that use metal rolls, the rest of the hard rolls and all soft rolls use hard rubber layers and Covered with soft rubber layer. Rubber hardness (Shore A type) is commonly used as Shore 70, 85, 100, etc. Generally, the active roller is higher than the passive roller.
For a long time, rubber rollers have been covered with natural rubber. However, with the rapid development of processes such as continuous steaming and bleaching, continuous pad dyeing, resin finishing, and high-temperature and high-pressure dyeing, natural rubber has poor oil resistance, heat resistance, acid resistance, and strong oxidant resistance, and its performance has been unable to adapt to Requirements for certain special processes. Therefore, in recent years, the natural rubber rollers used under certain process conditions in the printing and dyeing process have been replaced by various synthetic rubber rollers. In order to achieve the purpose of interchange, reduce reserves and reduce costs, the rolls are universal parts and are produced with unified specifications.
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