Manufacturing Equipment & Production Lines

Every steel structure component begins as a steel plate or section arriving from the mill. The CNC cutting line is where mill material becomes engineered components — and where dimensional accuracy is either established or lost before any welding begins. Our cutting line integrates CNC plasma and oxy-fuel cutting machines with automatic nesting software that reads design data directly from the CAD/CAM pipeline.

Multi-torch configuration. Each cutting machine carries up to four cutting torches operating simultaneously, each following an independent CNC path. This means four identical plate components can be cut from the same nesting layout in a single pass, or four different components can be cut in parallel from the same plate. The nesting software optimizes plate utilization by arranging component geometries to minimize skeleton waste, typically achieving 82–92% material utilization depending on component geometry complexity.

Plate thickness capacity: 6mm to 120mm. The thinner range (6–12mm) is cut by plasma for speed and minimal heat-affected zone. The thicker range (25–120mm) is cut by oxy-fuel for straight-edge quality on thick plate. For plate above 40mm, the cutting line supports multi-pass bevel cutting, where the torch is angled to cut V, X, or K bevels in a single setup — preparing the weld groove directly on the cutting machine, eliminating a separate beveling operation and the dimensional error it introduces.

Cutting tolerance. The CNC controller maintains cutting path accuracy to ±0.5mm on straight cuts and ±1.0mm on complex curves, including circular and elliptical cutouts. This tolerance is verified by post-cut dimensional scanning before the plate enters the welding line.

Box columns carry the axial loads of super-tall buildings, long-span bridge piers, and heavy industrial structures. Unlike H-beams, box columns are closed sections with internal diaphragm plates — transverse stiffeners welded inside the column at each floor level or load-transfer point. The challenge: the internal diaphragm welds are physically inaccessible to conventional welding equipment because the column walls enclose them.

Multi-wire SAW for longitudinal seams. The four longitudinal corner seams of the box column are welded by multi-wire submerged-arc welding, where two or three welding wires feed into a single weld pool simultaneously. Multi-wire SAW increases deposition rate by 50–80% over single-wire, reducing heat-affected zone width and total heat input per unit length. The maximum box section is 1200 × 1200mm, with wall thicknesses from 8mm to 60mm. Maximum column length is 15 meters per section, with field splicing for taller columns.

Electroslag welding for internal diaphragms. Internal diaphragm plates are welded to the column walls using through-thickness electroslag welding (ESW). ESW deposits weld metal through the gap between the diaphragm edge and the column wall, filling the joint from bottom to top in a single pass. The process requires an access slot cut into the column wall (typically 25–35mm wide), which is plug-welded closed after the ESW pass. This technique achieves full-penetration welds on joints that no manual welder or conventional welding arm can reach — the engineering requirement for box columns carrying 5,000+ tons of axial load.

Pre-heat and interpass temperature control. For high-strength steel (Q355, Q390, Q420, Q460), pre-heat temperature (80–150°C depending on grade and thickness) and interpass temperature (200–230°C) are monitored by contact pyrometers at each weld pass, with temperature data logged against the column's QR code for traceability.

Pipe trusses are used in long-span roofs, stadium canopies, airport terminals, and bridge structures where the visual quality of exposed tubular members matters as much as their structural performance. The branch-to-chord intersection in a pipe truss — the "saddle" joint — is the most geometrically complex cut in steel structure fabrication. An imprecise saddle cut creates a root gap between branch and chord, and welding over a root gap produces a joint that is visually obvious and structurally inferior.

CNC tube cutting. Our CNC tube cutting machine rotates the pipe on its longitudinal axis while a plasma or oxy-fuel torch traces the saddle-cut profile in the pipe wall. The CNC controller reads the intersection geometry — branch diameter, chord diameter, intersection angle, and bevel angle — directly from the design model and computes the cutting path. Pipe diameter range is 60–400mm, with wall thickness from 4mm to 25mm. The saddle-cut profile includes the weld bevel, so the cut pipe arrives at the welding station ready for assembly with no secondary beveling or grinding.

Robot-assisted saddle welding. After the branch pipe is positioned on the chord, a six-axis welding robot traces the saddle joint profile, executing a multi-pass weld with parameter control for root, fill, and cap passes. The robot's advantage over manual welding is consistency: the saddle joint is a three-dimensional curve, and manual welding produces variable leg length, penetration, and surface profile along the curve. The robot welds the entire joint to the same parameter set, producing a uniform fillet weld that meets both structural and visual requirements for exposed pipe trusses.

The spray painting line applies the anti-corrosion coating system to blasted members. The standard system for atmospheric-exposure steel structures is a three-layer paint system, but the specific products and dry film thicknesses are configured per project specification, environment class (C1 through C5-M per ISO 12944), and client requirements.

Layer 1 — Zinc-rich primer. A zinc-rich epoxy primer is applied as the first coat, providing both barrier protection and cathodic protection (galvanic sacrifice) at any point where the coating is damaged. The zinc content is typically 70–80% by weight in the dry film, and the dry film thickness is 50–75µm. Zinc-rich primer is the critical layer for long-term corrosion resistance — it is what prevents rust creep from coating damage sites.

Layer 2 — Epoxy intermediate coat. A high-build epoxy intermediate coat is applied over the primer, adding barrier thickness and creating a smooth surface for the topcoat. Dry film thickness is 80–125µm. The epoxy intermediate provides the majority of the system's total barrier thickness and is resistant to water, salt, and chemical exposure.

Layer 3 — Polyurethane topcoat. The topcoat is a polyurethane finish that provides UV resistance (preventing the epoxy underneath from chalking), color retention, and the final aesthetic finish. Dry film thickness is 40–60µm. For projects in C5-M environments (marine, offshore, extreme industrial), the topcoat is upgraded to fluorocarbon (FEVE) for extended UV and chemical resistance, as was specified for the Antarctica Ross Sea Station.

Dry film thickness (DFT) verification. After each coat and after the full system, DFT is measured by electronic gauge at multiple points per member (typically 5 readings per square meter). Readings are logged against the member's QR code, creating a per-member coating record that can be submitted to the client or inspector. Total system DFT for standard atmospheric exposure is 170–260µm; for C5-M marine environments, 240–320µm.