What is mandrel?

The mandrel is a part of a mold used to form a contour surface in the compact or sintered body in the pressing direction.

The core rod mainly plays the role of supporting the inner wall of the bending radius of the catheter to prevent its deformation during the bending process.

The shape of the mandrel is diverse. For pipe fittings with different relative bending radii or relative wall thicknesses, and different processing requirements, different shapes of mandrels should be selected. Under normal circumstances, mandrels can be divided into two categories: one is a rigid mandrel:

One is a soft mandrel:

The basic shape of the mandrel
(a) Cylindrical mandrel (b) Cylindrical ball-end mandrel (c) Claw mandrel (d) Chain mandrel (e) Flexible shaft mandrel (f) Ball and socket mandrel

When using hard mandrel, due to the simple shape and convenient manufacture of cylindrical mandrel (or cylindrical ball-head mandrel), they are more commonly used than claw-shaped core rods; while soft mandrel are selected, due to the ball and socket joints The core rod can bend by tube bender in multiple directions, and the ball joints are hinged on the spherical surface, which can adapt to various deformations. Therefore, it is often used when pipe bender bending thin-walled or relatively small pipe fittings. At the same time, the ball joint core rod is also used. The number of ball joints should be selected according to different relative bending radii, relative tube wall thickness and bending angle. If the number of ball joints is small, the expected effect will not be achieved; if the number of ball joints is large, it is difficult to manufacture and it is inconvenient for the pipe to penetrate.

After the shape of the mandrel is selected, high-quality pipes cannot be guaranteed to be bent. The gap between the mandrel and the inner diameter of the pipe is also an important factor affecting the quality of the bend. If the diameter of the ball joint of the mandrel is too small, wavy wrinkles may occur on the inside of the arc when the tube is bent, and it may not be able to prevent the outside of the arc from flattening; when the diameter is too large or the outside diameter of the ball joint is not smooth enough , It will strain the pipe wall, and the outside of the arc of the pipe may bulge or even break. Choosing a reasonable mandrel diameter and fully lubricating it are indispensable elements to ensure the quality of the elbow.

After the shape and size of the mandrel are determined, the size of the position where the mandrel is inserted into the tube to bend is also a factor that cannot be ignored that affects the quality of the bend. If it protrudes forward, it may crack the outer wall of the pipe; if it is insufficiently inserted, it will not have the corresponding anti-flattening effect, and the inside of the arc may also wrinkle.