Block fabrication cannot be separated from cradles. The cradle is a temporary structure that supports the weight of the block, and its accuracy and stiffness directly determine the ability to control distortion during welding. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. treats the cradle as the first “mould” for the block, establishing strict control standards throughout the design, fabrication and use process.
Haizhongzhou uses adjustable articulated cradles instead of traditional fixed cradles for blocks with curved shapes. The height of each support post in an articulated cradle can be independently adjusted to match the theoretical bottom shape of the block, achieving millimetre‑level adjustment using screw jacks or hydraulic devices. Before use, technicians measure the three‑dimensional coordinates of the top points of all support posts using a total station, creating a cradle profile table for comparison with the theoretical block shape. Support posts with deviations exceeding two millimetres must be readjusted. This adjustable articulated cradle not only improves the reuse rate of cradles but also significantly reduces sagging distortion of the block under its own weight during welding.
For bow and stern blocks with complex curvature and for superstructures, Haizhongzhou uses a combination of template‑type cradles and auxiliary supports. The template is precisely cut according to the theoretical shape of the block and serves as a rigid former, against which the shell plating is fitted. Auxiliary supports are added at critical load‑bearing points inside the block to prevent panel instability caused by welding heat input. Rubber pads or wooden shims are placed at the contact points between the cradle and the block to avoid coating damage or local indentation from hard contact.
The stiffness of the cradle is equally important. Haizhongzhou performs finite element analysis on the cradle structure to ensure that, under the most unfavourable conditions (such as shrinkage stress during welding), the deformation of the cradle does not exceed one millimetre per metre. The cradle base is fixed to the ground with anchor bolts to prevent displacement during block lifting or welding.
After use, Haizhongzhou does not arbitrarily dismantle or discard the cradles. Each cradle has a numbered record file documenting its applicable block type, fabrication date and cumulative number of uses. After inspection and verification, adjustable cradles can be reconfigured for other similar blocks, greatly reducing the cost of fixture fabrication. It is these invisible cradles that provide solid and precise support for every block, becoming the invisible cornerstone of high‑quality block construction.
