The principle of a suspended roller cement pipe making machine is as follows: The main shaft of the suspended roller cement pipe making machine rotates at a constant speed, driven by a motor. Simultaneously, the pipe mold, which is inserted into the main shaft, is driven by friction between the retaining ring and the main shaft. Concrete material fed into the pipe mold is evenly distributed along its inner wall due to centrifugal force. When the thickness of the concrete material exceeds the retaining ring of the pipe mold, it is subjected to roller pressure, gradually compacting the concrete. Furthermore, due to the uneven concrete surface, the rotation of the pipe mold generates vibration, which also contributes to the compaction of the concrete. Therefore, the suspended roller forming process achieves concrete compaction through the combined action of centrifugal force, roller pressure, and vibration.
This pipe-making technology was first used by the Australian Rockla Company in the 1940s. Since its introduction in the 1980s, this process has quickly gained popularity due to its simple equipment structure and ease of operation. It also uses dry, hard concrete, avoids laitance, and produces pipes with high compressive strength. Currently, approximately half of pipe manufacturers in my country have suspended roller production lines. However, after more than 20 years of practical experience, we have discovered that suspended roller cement pipe making also presents the following technical challenges:
1. Controlling feed thickness is difficult. Rolling requires excessively thick feedstock-concrete thickness exceeding the retaining ring of the pipe die-to achieve roller compaction. Typically, the finished pipe is required to be 2mm to 3mm thicker, which is difficult to achieve. Furthermore, wear on the retaining ring during use of the pipe die results in significant variations in pipe wall thickness. This large variation in pipe wall thickness has been a prominent issue in previous drainage pipe spot checks.
2. Strict requirements for the steel reinforcement framework. During pipe forming, the concrete is subjected to significant mechanical roller pressure, creating considerable torsional forces on the frame. Manually tying the frame can easily cause deformation and disintegration, compromising the structural strength of the pipe. Therefore, suspended roller forming utilizes a roll-welded frame.
3. The pipe socket is difficult to manufacture properly. The pipe body is primarily compacted by roller compaction. When an inner socket mold is installed, roller compaction is not possible. Direct roller forming, however, would result in a working surface dimension and flatness that would not meet the requirements for the rubber ring interface.