Today, the editor of Shenglida Technology Co., Ltd. will briefly talk about the use and principle of some mold parts when bending pipes. I hope it will be helpful to you.
When bending a pipe with a large diameter, a small bending radius and a thin pipe wall, an anti-wrinkle mold and a ball core rod should be used.
The use of an anti-wrinkle mold can increase the support in this area, so that the pipe wall thickens evenly after compression without wrinkles. However, due to improper adjustment, the anti-wrinkle mold cannot eliminate wrinkles after wrinkles have been generated.
The shape of the anti-wrinkle mold is very important. The groove through which the pipe slides should be slightly larger than the outer diameter of the pipe, and its value can be 10% of the wall thickness. It should also be carefully polished to prevent scratches on the pipe.
The front end of the anti-wrinkle mold should be made very thin so that it extends to the tangent point of the bending die to support the bending die and fix it to form a closed cavity. In order to reduce the resistance during bending, the anti-wrinkle mold should have a slight taper when installed. The pressure of the die should be adjusted appropriately. When installing and adjusting the anti-wrinkle die, it is best to use the “adjustment mandrel” and do it with the clamping die clamped.
During the bending process, an appropriate amount of oil should be applied to the anti-wrinkle die. However, too much or too thick oil will also cause wrinkles in this area.
When using the anti-wrinkle die, a ball mandrel is often used at the same time. The anti-wrinkle die is used to prevent the tube from wrinkling during bending; while the ball mandrel can keep the tube from collapsing after leaving the mandrel support point.
When bending thin-walled, large-diameter, and small-bending-radius tubes, in order to avoid wrinkles, the following points should be noted:
① Reduce the resistance between the mandrel and the inner wall of the tube during bending. Before the tube is bent, the inner cavity must be wet-sandblasted.
② The machine tool and spindle should have sufficient rigidity.
③ The mandrel rod should have sufficient rigidity to eliminate the trembling and stretching of the rod as much as possible.
④ The radial clearance between the mandrel and the inner diameter of the tube should not be greater than 10% of the wall thickness.
⑤ The clamping die, pressing die, mandrel and anti-wrinkle die should be properly adjusted, especially the pressing die pressure should be carefully selected and adjusted.
When bending large diameter pipes, the clamping of the clamping die is also a prominent problem. This requires that the straight section between the two bends of the pipe is longer and the clamping die is wider to increase the clamping force and ensure smooth bending. If the clamping die is too narrow and there is not enough clamping force during bending, the pipe will slip and not move forward, making the bending impossible.
⑥ Choose the right amount of lubricating oil.
⑦ The supply status of the material is also very important. For stainless steel pipes, the hardness is HB=180~220, and HB=180 is the most suitable.