Block pre‑outfitting is one of the core technologies of modern shipbuilding. Installing piping, cable trays, equipment foundations and other outfitting items at the block stage can significantly reduce work at height and cross‑operations in the dock. However, pre‑outfitting imposes extremely high demands on precision: if the positional deviations of outfitting items on blocks accumulate, serious problems such as flanges failing to align and foundation misalignment will occur during berth assembly. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. has established an “outfitting precision control network” to keep the positioning error of pre‑outfitting within millimetres. The core of outfitting precision control is datum transfer. For each block during its fabrication stage, Haizhongzhou first establishes the block’s own reference system on the cradle – including a longitudinal datum line, transverse datum line and height datum points. These datum points are projected from the block’s 3D model onto the actual workpiece using optical instruments. After the block structure is welded, a total station is used to re‑measure the actual coordinates of the datum points and calculate the deviation from theoretical values. The installation and positioning of all outfitting items are based on these verified datums, rather than directly measuring the relative positions between outfitting items, thereby avoiding error accumulation. For the positioning of pipe flanges and penetrations, Haizhongzhou uses a “simulated pipe” technique. Before actual pipe installation, adjustable‑length simulated pipes (with flanges at both ends) are pre‑routed on the block. The simulated pipe can quickly adjust its length and angle according to the reference system, determining the optimal pipe routing and flange interface positions. Once confirmed, the length and flange angle data of the simulated pipe are entered into the system as the basis for formal pipe fabrication. This method avoids the waste of repeatedly cutting and welding pipes on the block, while ensuring that...

Frames are an important part of the hull framework, and their bending quality directly affects the fairness of the hull shape. Traditional cold bending of frames relied on templates and manual experience, with operators repeatedly comparing and correcting, resulting in low efficiency and unstable accuracy. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. has introduced CNC frame bending machines, achieving digitalisation and automation of frame bending. The core of the CNC frame bending machine is the three‑point bending principle, where a concentrated load is applied to the profile through two fixed supports and one movable ram, causing plastic bending. Unlike traditional template bending, the CNC bending machine can automatically calculate the required ram stroke based on the input profile section parameters, material grade and bending radius. Haizhongzhou’s technicians first extract the theoretical shape of frames from the 3D design software, generating a bending data file for each frame, including chord length, camber, radius of curvature and twist angle, and then transfer the file to the bending machine’s control system via USB drive or network. During the bending process, the machine gradually bends the profile in set steps, and automatically compensates for spring‑back after each step. Spring‑back compensation is a key technology in CNC bending – because the profile undergoes elastic recovery after unloading, the actual bending angle is always smaller than the angle applied by the ram. Using a spring‑back prediction model developed in cooperation with a university, Haizhongzhou calculates the theoretical spring‑back amount based on the profile grade, sectional moment of inertia and bending radius, and adds an over‑bend amount to the program. After extensive validation, the prediction accuracy of the model exceeds ninety percent, and the first‑piece acceptance rate has increased from less than fifty percent with traditional methods to eighty‑five percent. For frames with twist (such as those in...

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...