CN105583252A - Hydroforming method of axis continuous bending special-shaped pipe fitting - Google Patents

Abstract

A liquid-filling forming method for axial continuous bending special-shaped pipe fittings. Its main content is to use a bending section with a relatively large bending radius instead of a continuous bending section by adjusting the bending angle and bending radius without increasing the process, and use CNC (Computer? numerical? control) pipe bending machine to bend The tube blanks that are approximate to the axis of the final part are produced, and then these bent tubes are extruded into continuous bending sections by pre-forming, and finally the pre-formed tubes are shaped by the liquid-filled forming process. The liquid-filled forming method for axial continuous bending special-shaped pipe fittings provided by the present invention can reduce the thinning of the wall thickness of the continuous bending pipe fittings, reduce the cross-sectional distortion of the bending section of the pipe fittings, and have high forming precision. At the same time, the use of a single large-radius bending section instead of a continuous bending section in the CNC bending stage can greatly reduce the requirements on the capabilities of the bending mold and the CNC pipe bender, thereby reducing production costs and improving production efficiency.

Description

Liquid-filled forming method for axial continuous bending special-shaped pipe fittings

technical field

The invention belongs to the technical field of metal pressure processing, in particular to a liquid-filled forming method with continuous bending pipes in a plane.

Background technique

Axially bent special-shaped pipe fittings are widely used in automobiles, aviation, aerospace and other fields, and are often used in automobile air intake parts, car body structures and aerospace system piping. The liquid-filled forming process is the main method for forming such tubular parts. The generalized pipe liquid filling forming process usually includes bending, preforming, liquid filling forming, cutting and other processes. For the liquid-filled forming of curved axis heterosexual pipe fittings, the pipe is usually bent into the same or similar shape as the axis of the part through the bending process; if the cross-section of the part is complex or the diameter of the pipe is larger than the minimum width of the mold cavity, the pipe cannot be put into the mold The cavity also needs to be preformed. The preforming process has three main functions: First, for parts whose diameter is larger than the width of the mold cavity, the pipe is flattened by preforming so that the pipe can be smoothly placed in the liquid-filled forming mold to avoid the liquid-filled forming mold closing process The second is to pre-allocate the material to make the parts deform evenly during the liquid-filled forming process, and defects such as wrinkles and cracks appear on the instant surface. Equipment clamping force, improve production efficiency. The preformed pipe is pressed against the cavity of the liquid-filled mold under the action of high-pressure liquid to form parts of the desired shape. Finally, the excess process supplementary surface is cut off to form the final part.

The bending process of liquid filling forming mainly adopts CNC (Computernumerical control) bending. The heterosexual pipe parts used in the automobile chassis are mostly left-right symmetrical parts. In order to improve production efficiency and save mold costs, the usual practice is to use one mold to form two parts, so the number of pipe bends has doubled. CNC bending usually adopts a winding method with a mandrel, and the bent pipe fittings have high precision, small cross-sectional distortion, and high production efficiency. If the length of the straight section between the two curved sections is too small or the continuous curved section, the clamping section of the CNC bending mold needs to be realized by forming the clamping mold, which requires more complex multi-layer bending molds and multi-layer CNC bending. tube machine. The more layers of CNC pipe bending machine, the more expensive the price and the higher the cost. This also puts forward higher requirements for the bending of the pipe.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide an efficient and high-precision continuous axis bending special-shaped pipe fitting liquid-filled forming method without increasing the process and equipment capacity.

The technical scheme adopted in the liquid-filled forming method of continuous axis bending special-shaped pipe fittings provided by the present invention is:

1) Select a circular long tube as the blank, and determine the length of the tube blank according to the length of the centerline of the final part.

2) Bending process: The bending process is carried out on the CNC pipe bender. In order to avoid the requirements of the bending mold clamping die and multi-layer bending die, the two continuous bending segments (or the two straight segments whose length is less than 1.5 times the pipe diameter in the plane) A curved section) is replaced by a curved section with a relatively large bending radius, and the angle between the straight sections on both sides of the large curved section is guaranteed to be as close as possible to the angle between the straight sections on both sides of the continuous curved section. The same bending radius can be used for the bending process of multiple continuous bending segments in the same plane.

3) Preforming process: Put the bent pipe into the preforming mold to further bend the large bending section described in 2) and partially form other features to ensure that the preformed pipe can be placed smoothly Liquid-filled forming molds. The punching direction of the pre-forming is parallel to the plane in which the continuous curved segments lie.

4) Liquid-filled forming process: put the pre-formed pipe into the liquid-filled forming mold to perform high-pressure liquid-filled shaping on the bent section and other local features that are distorted or collapsed after bending.

5) Cutting process: cut off the supplementary surface of the process to form the final pipe fitting.

The beneficial effect of the present invention is that it can reduce the wall thickness thinning rate of the inner side of the continuous bending section of the pipe, and improve the forming quality; the number of layers and the complexity of the bending mold and the CNC pipe bending machine in the bending stage are reduced, and the production cost is reduced; the bending process Changing from the original two bending sections to one bending section saves process time and improves production efficiency.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a structural diagram of a left-right symmetrical part suitable for the liquid-filled forming method of the axial continuous bending special-shaped pipe provided by the present invention.

Fig. 2 is a schematic diagram of a forming scheme of two parts in one mold according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of the formed parts required in the typical part bending process of the liquid-filled forming method for axial continuous bending special-shaped pipe fittings provided by the present invention.

Fig. 4 is a schematic diagram of the pre-forming and mold-closing process of typical parts in the liquid-filled forming method for axial continuous bending special-shaped pipe fittings provided by the present invention.

Fig. 5 is a schematic diagram of the die-closing process of a typical part of the liquid-filled forming method for axial continuous bending special-shaped pipe fittings provided by the present invention.

Fig. 6 is a schematic diagram of typical cross-sectional changes during the liquid-filled forming process of a typical part of the liquid-filled forming method for axial continuous bending special-shaped pipe fittings provided by the present invention.

In the figure: 1, 4, 6, 8, 11 the straight line section in the typical parts to be formed; 2, 3, 5, 7, 9, 10 the bending sections in the typical parts to be formed; 12, 14, 16, 18 the bending process The straight section of the formed part; the curved section of the part formed by the bending process in 13, 15, and 17; 19 the upper mold of the preforming mold; 20 the pipe formed by the bending process; 21 the lower mold of the preforming mold; 22 the upper mold of the liquid-filled forming mold ; 23 The parts formed by the preforming process; 24 The lower mold of the liquid-filled forming mold.

detailed description

As shown in Figures 1 to 6, the liquid-filled forming method for axial continuous bending special-shaped pipes provided by the present invention includes the following steps in order:

1) According to the left-right symmetry of the parts, the forming method of one mold and two pieces is adopted.

2) Determine the specifications of the original tube blank according to the axis length of the part to be formed and the circumference of each section.

3) Bending process: Since the length of the straight section between bending sections 5 and 7 is less than 1.5 times the diameter of the tube blank, the design of the bending digital model uses bending section 15 to replace the middle straight section 6 and bending sections 5 and 7 of the target part. A segment 14 and a curved segment 13 replace the continuous curved segments 2, 3 of the target part, and a straight segment 16 and a curved segment 17 replace the continuous curved segments 9, 10. Guarantee simultaneously straight section 12,14 and straight section 1,4, straight section 14,16 and straight section 4,8, the included angle between straight section 16,18 and straight section 8,11 approximately its angular deviation is less than 10 °. The curved sections 13, 15, 17 have the same bending radius. The bending process can be completed on a single-layer CNC pipe bending machine using a single-layer bending mold.

4) Preforming process: the clamping direction of the preforming mold is parallel to the plane where the continuous curved sections 2, 3 and 9, 10 are located and perpendicular to the straight section 6. Put the pipe 20 formed in the bending process into the preforming mold, and due to the angle between the straight sections 14 and 16 in the bent pipe and the surface constraints of the lower mold 21 of the preforming mold, the pipe formed in the bending process The tube 20 can be positioned in the lower die 21 of the pre-forming mold.

5) Liquid-filled forming process: According to the geometric characteristics of the formed parts, the mold-closing direction of the liquid-filled process is perpendicular to the mold-closing direction of the pre-forming process. On the one hand, the pre-formed pipe can be smoothly placed into the cavity of the liquid-filled forming mold; on the other hand On the one hand, ensure that the side thrust cylinders at both ends of the mold cavity can be placed horizontally. The liquid-filled forming mold is closed and filled with high-pressure liquid, and finally the pipe fittings are completely attached to the mold and formed into the desired shape.

6) Cut off the redundant process supplementary surface to form a complete part as shown in Figure 1.

Claims (4)

1. an axis continuous bend special piece liquid-filling shaping method, is characterized in that: it comprise byThe following step in sequence:

1) axial length of the final part of basis and perimeter of section are determined the specification of original pipe;

2) bending pipes: replace in former part and coexist and put down with single bending section in bending pipes processContinuous two bending sections (or middle straight segment length is less than two bending sections of 1.5 times of calibers) in face,If there are multiple continuous bent sections that coexist in a plane, use single bending that multiple bending radius are identicalSection replaces. The straight section of each bending section both sides and between the former part continuous bent section of angle both sides straight sectionThe angular deviation of angle is less than 10 °;

3) preform: the tubing after bending is put into piece pre-forming die, wherein preformed matched moulds sideTo the plane that is parallel to continuous bent section place, utilize preform to suppress continuous bending section;

4) liquid-filling shaping: the part after preform is put into liquid-filling shaping mould, squeeze into highly pressurised liquidTo preform bend the cross section distortion that causes, subside and other features are carried out shaping;

5) excise the unnecessary process complementary surface complete part that is shaped.

2. axis continuous bend special piece liquid-filling shaping method according to claim 1, its spyLevy is that the described single bending section of bending pipes operation replaces in the plane that coexists in former part continuouslyTwo bending sections.

3. axis continuous bend special piece liquid-filling shaping method according to claim 1, its spyLevy is can use many for the continuous bending section of multiple planes that coexist in described bending pipes operationSingle bending section that individual bending radius is identical replaces.

4. axis continuous bend special piece liquid-filling shaping method according to claim 1, its spyLevy is that in described preform operation, preformed matched moulds direction is parallel to the flat of continuous bent section placeFace.