Why does the reinforcement cage require variable spiral pitch at the ends?

Q: Why does the reinforcement cage require variable spiral pitch at the ends?

Concrete pipes experience the highest shear and bending stresses at the joint interface (bell and spigot) during trench handling, backfill settlement, and hydrostatic joint pressure testing. The CNC roll welder is programmed to automatically reduce spiral pitch from 100–120 mm in the barrel to 40–50 mm at the joint zones, providing superior shear containment without manual wire tying.

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CNC Setup & Calibration13 min readASTM Compliant

Automatic Steel Reinforcement Cage Welding Machine: CNC Calibration, Rebar Pitch Control & Maintenance Manual

Zhang GuochengChief Engineer, Precast Equipment Engineering Division

2026-05-18Reviewed by Chief Engineer

Automatic Steel Reinforcement Cage Welding Machine: CNC Calibration, Rebar Pitch Control & Maintenance Manual

1. Machinery Scope & Operational Objective

The Automatic Concrete Pipe Steel Cage Roll Welding Machine (GHL Series) is engineered to fabricate circular and non-circular high-precision reinforcement cages for RCC pipes spanning diameters from 300 mm to 3,000 mm with lengths up to 4,000 mm.

2. Electrical & Pneumatic Resistance Welding Parameters

ParameterRecommended Operational SettingAcceptable RangeEngineering Significance

Primary Voltage380 V / 415 V $\pm 5\%$3-Phase, 50/60 HzVoltage instability triggers inconsistent weld penetration Welding Transformer Rating100 – 160 kVAWater-cooledIntegrated secondary thyristor phase-shift controller Secondary Welding Current18,000 – 32,000 AContinuous variableModulated based on wire diameter ($4 - 12\text{ mm}$) Pneumatic Clamping Pressure0.45 – 0.60 MPaAir regulator lockedEnsures zero-gap metal contact without spark spatter Welding Pulse Duration3 – 8 cycles(60 – 160 ms)Prevents thermal embrittlement in cold-drawn wire Electrode Cooling Water Flow$\ge 15\text{ Liters/min}$Pressure $> 0.25\text{ MPa}$Inlet water temp $< 25^\circ\text{C}$ to prevent electrode softening

Frequently Asked Engineering Questions

Concrete pipes experience the highest shear and bending stresses at the joint interface (bell and spigot) during trench handling, backfill settlement, and hydrostatic joint pressure testing. The CNC roll welder is programmed to automatically reduce spiral pitch from 100–120 mm in the barrel to 40–50 mm at the joint zones, providing superior shear containment without manual wire tying.

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2. Electrical & Pneumatic Resistance Welding Parameters