A purlin roll forming machine is a continuous production line that uses multiple passes of rollers to gradually press metal strips from a cold state into profiles with specific cross-sections. Its working principle is based on the synergistic effect of metal plastic deformation and roller geometry. Relying on precise speed matching and force transmission, the strip passes through leveling, pre-forming, shaping, and cutting stages during its journey, ultimately producing purlins that meet the design dimensions. Understanding this principle helps achieve stable production and quality control during operation.
The machine's workflow begins with uncoiling and leveling. The metal coil is placed on the uncoiling device, drawn out by the feed rollers, and fed into the leveling unit. The leveling roller group applies reverse bending to the strip through staggered rollers, eliminating the original curl and internal stress, making it flat in the width direction. The purpose of this stage is to provide a uniform load-bearing base for subsequent forming, avoiding roll forming instability or cross-sectional distortion caused by strip undulations.
The flattened strip then enters the roll forming section. This section consists of several forming roller groups arranged sequentially along the production line. Each roller group is designed with a specific profile based on the purlin cross-sectional characteristics. The strip is subjected to continuous radial compression and longitudinal traction between the rollers, resulting in plastic bending and localized stretching, gradually forming the initial shape of the target cross-section. Since large deformation in a single pass can easily lead to springback and cracking, the forming process is typically divided into multiple passes. Each pass only changes a portion of the cross-sectional shape, allowing for gradual stress release and uniform metal flow, thereby improving forming accuracy and surface quality.
During the rolling process, the coordination of speed and tension is crucial. The traction device pulls the strip forward at a constant rate, keeping the linear speed of each forming roller group synchronized, preventing strip accumulation, stretching, or slippage due to speed differences. The radial pressure required for forming is provided by the roller bearings and drive system. The pressure is adjusted according to the material thickness and yield strength to minimize over-processing of the metal while ensuring proper forming.
After forming, the strip enters the sizing and cutting stage. The sizing rollers further refine the cross-sectional details, stabilizing dimensions and counteracting springback effects. The cutting device slits the continuously formed purlins to a set length. The smoothness of the cut depends on the matching of the tool gap and the cutting speed. The impact generated at the moment of cutting is transmitted through the machine structure; therefore, the equipment must have sufficient rigidity to suppress the impact of vibration on the formed profile.
The electrical and control system runs throughout the entire working process. Sensors monitor the strip position, speed, tension, and roll gap status in real time, feeding the data back to the controller. The controller then performs closed-loop adjustment of each drive unit to ensure consistent forming rhythm and stable parameters. In case of abnormalities such as material breakage, overload, or dimensional deviation, the system can automatically alarm and take shutdown or deceleration protection measures to reduce the risk of scrap and equipment damage.
Overall, the working principle of the purlin roll forming machine is to use multiple rollers to perform controllable plastic deformation of the metal strip. Through the organic connection of leveling, progressive forming, shaping, and cutting, the planar coil is transformed into a purlin with a fixed cross-section and length. The key lies in the rationality of the roller profile design, the precise matching of speed and tension, and the real-time adjustment of the control system. Mastering this principle allows for more scientific setting of process parameters and diagnosis of operational anomalies during production, thereby ensuring efficient and stable equipment operation and continuous compliance with purlin quality standards.
