Causes and Countermeasures of the most popular iro

2022-08-24
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Causes and Countermeasures of iron printing bracket injury

after printing, during the heating process in the tunnel oven, the defects of scratching the coating film due to various reasons of the iron frame are called bracket injury in the iron printing industry. There are serious injuries and disadvantages of stents. If it is light, a faint white mist like drying frame mark will be formed on the dried coating film; It is important to cut the coating film to expose the iron sheet; Generally, the coating film is scratched, but the iron sheet is not exposed. The injury of the bracket poses great harm to the quality of the iron printing, which cannot be taken lightly. Stent injury is caused by many reasons, especially in the processing of food coating iron with high temperature (200 ~ 210 ℃), it is more likely to produce stent injury, which is a big headache for operators. In order to understand the disadvantages of the iron frame in operation, we first understand the structural characteristics of the iron frame. There are various specifications of iron shelves, usually 3.5mm × 10mm and 3mm × 6mm flat steel bar is formed by bending welding and riveting. The iron frame is inserted into the square hole of the conveying chain bearing plate and fixed with a cotter pin. Stent injury is one of the common ills in the iron printing industry, and the causes are no more than three points:

① the trend of stent is unstable

② poor quality of the support itself

③ other relevant factors

I. The trend of the support is unstable

the tunnel oven for iron printing is composed of a frame, a transmission part, a heat source, a circulating air system, a synchronous device, a remote temperature control system, etc. The heating system of iron printing oven is divided into direct heating and indirect heating. Generally, indirect heating is adopted for oil heating, which is mainly to prevent the pollution of oven gas by oil combustion and affect the drying quality of iron printing. Gas or electric heating can be directly heated. At present, the fuel gases used mainly include city gas, natural gas (methane), propane gas, butane gas and mixed gas. The design of heating device is very important. Generally, a mixing burner is equipped in the combustion chamber, and gas and combustion air are introduced respectively. The combustion air is fed by the blower, and the burner is equipped with an ignition device and an ultraviolet flame flameout alarm device. The latter is used to monitor the main flame. When the main flame goes out, the gas is cut off and the red signal light is displayed at the same time. The iron printing oven is equipped with an automatic temperature control system, which adopts pneumatic temperature control to realize stepless regulation. The brand competition of cars is becoming increasingly fierce, and the temperature is controlled within the minimum fluctuation range

II. Poor quality of the support itself

for the support used for iron printing oven, from the perspective of quality, there are the following requirements:

1 The steel used for the support is required to be hard and not deformed under the high temperature of 220 ℃

2. In the manufacturing of the support, it is required that the support should be straight without unevenness. When the large chain is installed and operated, it should not be deformed, distorted and kept straight

3. The surface shall be bright and clean without roughness

in practical use, the support of German LTG oven is ideal, which can generally meet the above quality requirements. Therefore, in the normal production process, as long as the operation and adjustment are reasonable, the injury and disadvantage of the support can be avoided. The experimental software of Nantong drying room equipment as the universal tensile testing machine (auto parts testing machine) is upgraded for free. The first domestic support, regardless of material or processing and manufacturing quality, has a certain gap with the advanced German LTG support. The main problems are poor material, easy to deform under high temperature, poor flatness of the support in processing and manufacturing, and easy to deform when installed on the large chain. In addition, there is a big gap between the surface finish and LTG oven. It can be seen that the low quality of the stent itself is another important reason for the injury of the stent. III. other relevant factors

1 The influence of circulating air system should be properly adjusted. Improper adjustment, too large air volume and too fast wind speed will cause vibration of the support with tinplate print, resulting in damage to the support. Especially in the constant temperature area of the oven, the air volume of the air nozzle and the return air outlet is too large, which is easy to cause the support shaking and lead to the damage of the support. When the thickness of the tinplate print is 0.15 ~ 0.20mm, the heating area requires to reduce the hot air circulation. If it cannot be reduced, the oven manufacturer is required to specially design it to avoid scratches and other ills. 

2. Influence of tinplate

tinplate is composed of steel base, tin coating, tin iron alloy, oxide film, oil film, etc. Generally, tin melting will not occur below 230 ℃. However, in the actual construction, due to uneven drying temperature, surface temperature and furnace temperature, it is also easy to produce support injury. In production practice, it is also found that for tinplate of the same specification, due to different places of origin, the occurrence of bracket damage is also different, which may be caused by different materials and processing technology of steel-based tin layer. 

3. Influence of coating

non toxic, tasteless and low water absorption. Its products can be painted into various colors

iron printing coating can be divided into external coating and internal coating according to different uses. External coating is the coating process before and after color printing, including non color printing external wall coating. It mainly includes primer, white paint, ink gloss paint, transparent paint, etc. the inner paint is the inner wall paint after the product is formed, which has the anti-corrosion effect on the contents, as well as the rust prevention and protection effect. The above coating is mainly composed of vinyl resin, polyester resin, acrylic resin, epoxy phenolic resin, etc. Due to different paint manufacturers, the quality is also mixed. Take epoxy phenolic resin as an example. There are hundreds of manufacturers in China. When selecting, we must do a lot of experiments to select products with excellent quality. In general, the better the adhesion is, the higher the surface hardness of the cured film is, and the less the possibility of stent injury is, on the contrary, the greater. 

4. Other

many iron printing manufacturers may still use old-fashioned ovens, which use long shaft transmission. There are more than 20 bearings on the long shaft. The wear of the bearings leads to the unstable rotation of the long shaft and affects the stability of the support. Therefore, it is very important to maintain and lubricate the bearings regularly. Many manufacturers' ovens have been changed to frequency conversion synchronous drive, which is conducive to the stability of the support. In addition, various manufacturers have taken many effective measures to reduce or avoid the injury of the support, including:

① wrap heat-resistant and wear-resistant rubber rings on the support to reduce the contact point between the support and the tinplate

② when the experimental force exceeds the set maximum force by 2~10%, it will stop automatically. Try to choose epoxy phenolic paint with high hardness and good wear resistance (the quality of paint produced by different manufacturers varies greatly)

③ when purchasing the support, use high-quality steel or stainless steel materials to ensure that the support will not deform under high temperature. In addition, in terms of reasonable arrangement of construction technology, installation of guide rails and large chains, and selection of graphite rollers, many ideas were also used

source: China tinplate printing

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