The Heidelberg four-color offset press was in operation when an issue arose with the automatic suction system, causing unstable paper feeding. Due to urgent production demands at the time, the machine wasn't disassembled for inspection and maintenance promptly. After a period of continued use, the gas distribution valve failed, and the suction nozzles could no longer function properly.
To address the problem on-site, we first removed the check valve. Upon inspection, the valve body (made of cast copper, 42mm in diameter, about 30mm long) had severe surface damage, showing signs of grinding and "burning" marks, along with groove-like wear. This kind of damage required either replacing the entire body or repairing the worn area to ensure proper mating with the sleeve. Since spare parts were unavailable, we opted for repair welding as a temporary solution.
We considered using brazing filler metal, but during the heating process, there was a risk of warping the workpiece. Welding, on the other hand, would not cause deformation and was easier to handle, though it wouldn’t match the original copper hardness. However, since this was an emergency, we decided to proceed with soldering. We used rosin flux (which performed better than solder paste) and a 150W soldering iron. Once the temperature was reached, we applied the solder, ensuring the layer was slightly higher than the original cylindrical size.
After welding, the valve body was mounted on a lathe, and the excess solder was ground down to restore the original dimensions. For the valve sleeve, we simply placed it on the lathe and used 0# abrasive cloth to smooth out the damaged areas. The entire repair was completed quickly, and after reinstallation, the machine ran smoothly, meeting all operational requirements. This confirmed that the method was effective.
In addition to welding, adhesive repair is also a viable option for such wear conditions. Adhesive coating technology is known for its ease of use, broad applicability, strong adhesion to the base material, fast repair speed, and cost-effectiveness. The adhesives typically come in two components (A and B), similar to a thick paste. Before application, the surface should be cleaned with acetone, then the two components are mixed in the correct ratio and evenly applied. After curing, the part can be restored to its original shape.
The cured adhesive has a hardness close to that of copper, making it suitable for functional repairs. Popular options include imported products like Belzona from the U.S., or domestic alternatives such as TS111, both offering good quality. These adhesives are ideal for quick and effective on-site repairs and can be a great choice for similar situations.
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Ningbo Yinzhou Weinuo Machinery Manufacturing Co., Ltd. , https://www.gftopoven.com