Pipe Bending Machine

Pipe breakage (cracks, wrinkles, scratches) is the main cause of finished product scrap. To avoid damage, systematic control is needed in three aspects: materials, molds, and processes.

1. Prevent bending cracks (external tensile cracks)

Ensure bending radius R/D ≥ 3 (larger value for thin-walled pipes)

Use pipes with elongation ≥ 20%; high-strength steel can be bent after annealing.

Avoid the tension zone for welded pipes (place in the neutral layer or on the inner side).

Accurate mandrel extension (0.5-1.5mm before the tangent point).

2. Prevent internal wrinkling

The gap between the anti-wrinkle die and the bending die should be such that an A4 sheet of paper can slide between them.

Ball-head mandrels must be used for thin-walled pipes or small R bends.

Reduce bending speed to avoid material buildup.

Appropriately increase pipe wall thickness or use a harder material.

3. Prevent surface scratches

Keep the die grooves clean and polish and remove rust regularly.

Apply special bending oil (to the bending die, mandrel, and anti-wrinkle die).

Clamping force should be such that the pipe does not slip; avoid excessive tightening and indentation.

Remove burrs and metal filings from the pipe blank before bending.

4. Prevent cross-sectional distortion (flattening)

Check if the mandrel specifications match the pipe diameter

Avoid excessively small bending radius (R/D < 2.5, high risk)

The bending die groove depth should match the pipe's outer diameter by more than 85%.

5. Process Validation and First-Piece Control

A first-piece bending test must be performed after each mold or material change.

Use an angle gauge, calipers, and R-gauge for full inspection.

Record successful parameters (pressure, speed, mandrel position) and solidify the process.

Damage stems from stress concentration and lack of support – selecting the right mold, using the right mandrel, ensuring adequate lubrication, and conducting first-piece verification can improve the yield rate to over 99%.