Analysis of Key Points for Selection, Installation and Maintenance of Bending Dies for Hydraulic Pipe Bending Machines

Bending dies are core components of hydraulic pipe bending machines, which directly affect the processing quality. I. Selection of Die TypesBending Die: Matched according to the outer diameter of the pipe; the commonly used bending radius R ranges from 1.5D to 4D (where D = pipe diameter), and the material is quenched Cr12MoV steel. Clamping Die: Prevents the pipe from sliding and needs to fit closely with the groove of the bending die. Anti-wrinkling Die: Essential for thin-walled pipes; it supports the inner side of the pipe to avoid wrinkling.   II. Specifications for Die Installation1.Clean the die mounting surface and remove iron filings and oil stains.2.Assemble in sequence: Bending Die → Clamping Die → Pressing Die, ensuring the alignment of the centerlines.3.After pre-tightening the bolts diagonally, perform secondary tightening with a torque of 150Nm.   III. Key Maintenance MeasuresRust Prevention: Apply anti-rust oil if the machine is out of service for more than 48 hours.Wear Detection: Measure the R-angle of the bending die with a caliper every month; if the wear amount exceeds 0.2mm, the die needs to be repaired.Storage: Place the dies vertically on a dedicated die rack to avoid collision. Case Study: A factory failed to replace the worn clamping die in a timely manner, resulting in batch pipe indentations and losses exceeding 10,000 yuan. Standardized maintenance extends the service life of the dies by 3 times.

Avoiding Pipe Bending Defects: Solutions for Pipe Wrinkling and Deformation in Hydraulic Pipe Bending Machine Processing

Pipe wrinkling and cross-sectional deformation are common defects, which can be resolved through process optimization:   Main Causes of Wrinkling and Countermeasures Excessively small bending radius: When R ＜ 1.5D, compulsorily adopt the combination of a mandrel and an anti-wrinkling die. Incorrect mandrel position: Set the advance amount to 10% of the pipe diameter (e.g., Φ40 pipe = 4mm). Excessively high speed: Adjust the hydraulic valve to reduce the bending speed to below 3mm/s.   Control of Elliptical DeformationFilling method: When bending copper pipes, fill the interior with fine sand (particle size ≤ 1mm) and seal both ends.Die compensation: Use a dedicated die blank with an elliptical correction groove.Pressure adjustment: Reduce the pressure of the clamping die to the minimum value that prevents pipe slippage (usually ＜ 10MPa).   Process Verification Process:Test bending → Sectioning and measuring ovality (standard: minor axis/major axis ≥ 0.85) → Adjust parameters → Mass production

Key Roles and Application Techniques of Mandrels in Precision Bending with Hydraulic Pipe Bending Machines

A mandrel is a core tool for ensuring the bending quality of thin-walled pipes (with wall thickness/pipe diameter ≤ 5%).   Mandrel Type Selection Cylindrical Mandrel: Used for simple bending with R ≥ 2D (lowest cost). Ball-Jointed Mandrel: Suitable for multi-angle bending with R = 1D ~ 2D, featuring higher degrees of freedom. Flexible Shaft Mandrel: Applied for sharp bending with R ＜ 1D; its flexible structure prevents pipe jamming.   Application Techniques Lubrication: Apply molybdenum disulfide paste on the mandrel surface, and reapply it every 10 bends. Positioning: The front end of the mandrel should be 3-5 mm away from the bending starting point (too close causes pipe cracking, while too far leads to pipe wrinkling). Maintenance: Disassemble and clean the ball-jointed mandrel weekly, and check for wear on its spherical surface.   Data: When bending Φ25×1mm stainless steel pipes using a ball-jointed mandrel, the ovality is improved from 0.72 to 0.92.