How to correctly change the mold on a pipe bending machine?

Changing the molds on a pipe bending machine is a common operation in daily production. However, improper methods can affect bending accuracy, damage the molds, or even cause safety accidents. A standardized and orderly mold changing process is the foundation for ensuring equipment stability and product quality.

Preparation before mold change:

Confirm specifications: Check if the pipe diameter and bending radius of the new mold match the pipe to be processed.

Cleaning and maintenance: Clean oil stains and metal filings from the old mold and installation area. Check the working surface of the new mold for burrs or rust.

Tool preparation: Allen wrench, socket wrench, torque wrench, copper rod, special pipe bending oil, etc.

Safe operation: Turn off the equipment power and release the hydraulic system pressure (operate the return to origin or pressure relief action).

Removing the old mold:

Bending mold: Remove the fixing bolts of the bending mold and gently tap it with a copper rod to disengage it from the shaft. Keep the bolts and washers safe.

Clamping mold: Loosen the clamping mold seat bolts and remove the clamping mold. If the clamping force has caused adhesion due to prolonged use, use a pry bar to pry it evenly.

Anti-wrinkle mold: Loosen the fixing screws of the anti-wrinkle mold seat and pull out the anti-wrinkle mold along the slide rail direction.

Mandrel: Return the mandrel to the starting position, remove the connecting pin or lock nut at the end of the mandrel rod, and pull the mandrel out from the front or rear end (depending on the machine model).

Installing the New DieBending Die:

Insert the bending die onto the rotating shaft, ensuring the positioning key or positioning step is aligned. Apply a small amount of anti-rust oil to the contact surface. Pre-tighten the bolts diagonally, then tighten to the specified torque using a torque wrench.

Clamping Die: Install the clamping die, ensuring the opening direction of the die is aligned with the groove of the bending die. After gently clamping, use a dial indicator to check the parallelism and coaxiality of the clamping die and the bending die, adjusting with shims if necessary.

Anti-Wrinkle Die: Insert the anti-wrinkle die into the guide rail, adjusting its leading edge position so that it is precisely aligned with the tangent point of the bending die. Adjust the gap to fit snugly against the outer diameter of the pipe without jamming (approximately 0.1-0.2mm).

Mandrel: Insert the mandrel into the guide position of the pipe and connect the mandrel rod. Adjusting the mandrel extension: Generally, the center of the first ball socket of the ball-head mandrel should be 0.5-1.5mm before the bending die-cutting line (depending on the pipe wall thickness).

Post-die change inspection and trial run:

No-load test: Manually or at low speed run the bending arm without load to confirm no interference or abnormal noise.

First-piece trial bend: Take a section of pipe of the same specifications as the final product, apply bending oil, and perform a trial bend.

Quality inspection: Check the angle, cross-sectional ovality, and presence of wrinkles or scratches on the trial-bent piece. If it fails to meet the requirements, fine-tune the anti-wrinkle die clearance or mandrel position.

Parameter recording: Record the die specifications, mandrel position, and anti-wrinkle die position on the process card for easy quick die change next time.

Key Precautions

Tighten bolts diagonally to prevent uneven pressure from deforming the mold.

Excessive mandrel extension will scratch the inner wall of the tube; insufficient extension will not effectively prevent wrinkling.

A gap between the anti-wrinkle mold and the bending mold that is too large will cause wrinkling; a gap that is too small will cause scratches. Careful fine-tuning is required.

After changing molds, always clean the mold surface and apply a suitable amount of bending lubricant to avoid dry friction.

Regularly check the mold for wear; if wear exceeds tolerance, repair or replace it promptly.

A proper mold-changing procedure can not only ensure the accuracy of pipe bending, but also significantly extend the life of molds and equipment.