Effect of Calibration Sleeve on Pipe Shrinkage

First of all, the shrinkage rate cannot be judged solely from the pipe diameter. Any pipe must consider its density, molecular weight, molecular weight distribution and additives. We should also consider the color quality. Generally, white calcium carbonate has more and smaller shrinkage rate. Shrinkage rate is also divided into radial shrinkage and horizontal shrinkage. The shrinkage rate of pipes with smaller diameters is generally smaller than that of pipes with larger diameters, but there are exceptions!

The structure, processing accuracy and cooling method of the pipe sizing sleeve are very important for the quality of PPR pipe processing. The water ring sizing sleeve (cooling water circulates and cools the sizing water jacket, but does not contact the pipe) can produce thin-walled (cold water) pipes in a short time. Because the temperature of the material entering the sizing sleeve is high and the viscosity is high, the use of water-free sizing sleeves will cause the surface of the pipe to gradually become rough or even break during long-term production.

Therefore, the PPR pipes currently widely used are water curtain copper sleeve sizing sleeves and water curtain disc sizing sleeves. The water curtain copper sleeve sizing sleeve has low price, simple structure, convenient maintenance, and good cooling effect, but the appearance of the pipe is slightly worse, the glossiness is low, and the resistance when the pipe passes is also large, which is not conducive to high-speed extrusion. Therefore, the water curtain disc sizing sleeve is currently more widely used. It has a higher price, complex structure, and difficult maintenance, but the cooling effect is good. The water ring is pre-cooled before the pipe billet enters the sizing sleeve. In addition, it also prevents the material from adhering to the entrance of the sizing sleeve and causing blockage. The pipe billet then enters the sizing sleeve and is fully in contact with the cooling water. The cooling effect is better, the glossiness is higher, and the actual contact area with the disc is small, the resistance is also small, and high-speed extrusion can be achieved.

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