PURPOSE: To perform lining of arbitrarily and partially different wall thickness to the metal-made bend, by doing three-dimensionally composite rotation in the range of centrifugal acceleration 0.001W0.1g of the biaxial rotation.

CONSTITUTION: The pouring bend is provided as a part of the circular bend 1 combination, the specified amount of the liquid polymer is poured from the pouring port of the pouring bend and the pouring port is closed by the lid having the air charging and discharging pipes. Then, three-dimensional composite rotation is done ca. 15min in the atmosphere of 120°C at the rotation number of the first rotational axis (a); 12W30rpm and the rotation number of the second rotational axis (b); 6W12rpm, and the poured resin is hardened. The wall thickness of the formed lining can be made uniform or partially thick by proper selection of the ratio of rotation numbers a:b in the range of 1.2W3.5:1, and polyurethane is preferable as liquid polymer.