CN103056214A - Numerical control incremental forming based die-less forming method for special-shaped pipe fittings - Google Patents

Abstract

A non-die forming method for special-shaped pipe fittings based on numerical control progressive forming, using a cylindrical rod-shaped tool head with a hemispherical or convex oblate spherical bottom end to press on the pipe blank, and extruding the pipe wall material to produce local plastic deformation. The upper end of the tool head is connected with the spindle of the CNC incremental forming machine tool and rotates around its own axis, while moving in space according to the preset trajectory of the program. There are two trajectory control methods of "layer cutting method" and "linkage method" for the feed movement of tool head and tube blank. The former tube blank is in a static fastening state, and the movement trajectory of the tool head is decomposed into multiple horizontal circular paths in the vertical direction, and the tool head walks through each horizontal circular path layer by layer until the forming is completed; the latter tube The billet is clamped in a horizontal state on the synchronous rotating mechanism fixed on the base of the machine tool. When forming, the tube billet rotates around its own axis at a certain angular speed. The method can form special-shaped pipe fittings that are difficult or even impossible to obtain in plastic processing such as traditional stamping, and does not need special molds.

Description

A Dieless Forming Method for Irregular Pipe Fittings Based on NC Progressive Forming

technical field

The invention belongs to the field of processing and manufacturing pipe parts, and relates to a numerically controlled progressive dieless forming method for special-shaped pipe parts.

Background technique

In the fields of vehicles, aerospace, light industry, petrochemical industry, etc., a large number of pipe parts obtained by processing thin-walled metal pipes are used as structural parts, fluid conduction, energy absorption or heat exchange elements. The application is very extensive. The use of stamping and other plastic forming methods to manufacture these pipe parts has great advantages in production efficiency, cost and quality, and is an important content and development direction of pipe fittings manufacturing. However, due to the hollow geometric characteristics of the pipe, its forming process and mold are very different from ordinary plate forming. In fact, the traditional stamping method is generally difficult to directly apply to the forming of pipe fittings. So far, forming processes such as blanking, bending, bulging, spinning, flaring and shrinking of pipes have been developed, but in practice, the existing processes still have problems such as low forming accuracy and low yield, especially some Special-shaped pipe fittings with complex structures or asymmetric shapes (such as the high-efficiency reinforced special-shaped grooved swirl heat transfer tube mentioned in Chinese patent 93213223.5) are difficult or even impossible to form by using the existing stamping forming process. This situation seriously restricts the design of pipe fittings and the improvement of product quality and performance. It is necessary to research and develop new pipe forming processes to meet the needs of practice.

Incremental forming is a digital flexible manufacturing technology developed in the late 20th century. It adopts the idea of "layered manufacturing" to transform the overall forming of complex three-dimensional sheet metal parts into CNC machine tools using general-purpose simple tool heads according to CAD digital models. Progressive layer-by-layer forming. Due to the multi-pass gradual forming, this method can make better use of the deformation ability of the material than the traditional stamping method, and can be used to form plate parts with large deformation and complex shapes, and does not require special molds or only simple molds, which is especially suitable It is suitable for the processing of small batches of sheet metal parts and new product development for aerospace, vehicles and some civilian products. But at present, incremental forming is mainly used in the manufacture of sheet metal parts, and its potential and advantages in plastic forming need to be further expanded.

Contents of the invention

The purpose of the present invention is to provide a non-die forming method for special-shaped pipe fittings based on numerical control progressive forming, so as to solve the problem that the existing plastic forming process cannot meet the practical pipe fitting production needs.

The solution of the present invention to solve the above-mentioned technical problems is: on the CNC incremental forming machine tool, the upper end of a cylindrical rod-shaped tool head is connected to the main shaft of the machine tool, and the bottom end of the tool head is pressed on the tube blank and has a hemispherical or outer shape. Convex and oblate spherical shape, extruding the tube blank through the bottom end of the tool head to cause local plastic deformation of the tube wall material. When forming, on the one hand, the tool head is continuously rotated around its own axis driven by the spindle of the machine tool; on the other hand, according to the shape of the pipe to be formed, the tool head moves in three-dimensional space according to the preset trajectory of the program, so that each part of the tube blank is gradually Plastic deformation occurs and the desired shape of the pipe is finally obtained.

According to the shape of the pipe fitting and its progressive forming requirements, the tube blank can be in a static fastening state during the forming process, or in a state of rotating at a certain angular speed around its own axis.

There are two trajectory control methods for the feed motion of the tool head and the tube blank:

(1) "layer cutting method". In this mode, the motion of the tool head is similar to the trajectory control method commonly used in sheet metal progressive forming, that is, according to the shape of the pipe wall to be formed, the motion trajectory of the tool head is decomposed into multiple horizontal circular paths in the vertical direction. The head walks through the horizontal circular path layer by layer, and gradually completes the forming of the part by replacing the profile surface of the mold with the envelope surface formed by the movement trajectory of the bottom end of the tool head. During the forming process, the tube blank is in a static fastening state;

(2) "Linkage method". In this way, a synchronous rotation mechanism is fixed on the base of the incremental forming machine tool. Before forming, the tube blank is clamped on the synchronous rotating mechanism in a horizontal state. During the forming process, the tool head moves in the three-dimensional space according to the trajectory preset by the program, and the tube blank is driven by the synchronous rotation mechanism to rotate around its own axis at a certain angular velocity.

The shapes of the special-shaped pipe fittings that can be formed by using the present invention include: along the axial direction of the tube blank, the pipe wall has grooves distributed in a straight line and a helical line; The shape of the combination of inner constriction, the pipe wall has a convex or concave annular groove, and the shape of the hole turned outward and inward is formed on the prefabricated hole of the pipe wall, and the shape obtained by combining the above shapes.

The method for forming pipe parts based on numerical control incremental forming proposed by the present invention can produce special-shaped pipe parts with complex shapes that are difficult or even impossible to obtain by traditional stamping and other plastic forming processes. At the same time, the invention belongs to a flexible moldless manufacturing method, which can complete the forming of pipe fittings without special molds and only needs to adjust the corresponding numerical control processing program, and is especially suitable for the production of some special-shaped pipe fittings with many varieties and small batches.

Description of drawings

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

Fig. 1 is a schematic view of the present invention utilizing a tool head with a hemispherical bottom to form a pipe fitting with helically distributed grooves on the pipe wall along the axial direction of the pipe blank;

Fig. 2 is a schematic diagram of a pipe fitting formed by the present invention with linearly distributed grooves on the pipe wall along the axis direction of the pipe blank;

Fig. 3, Fig. 4 and Fig. 5 are the pipe fitting schematic diagrams that the formed pipe end of the present invention has an outer flaring shape;

Fig. 6, Fig. 7 and Fig. 8 are the schematic diagrams of the pipe fittings formed by the present invention with the shape of the inner neck;

Fig. 9, Fig. 10 and Fig. 11 are schematic diagrams of pipe fittings formed by the present invention having a combined shape of an outer flare and an inner constriction;

Fig. 12 is a schematic diagram of the present invention utilizing a tool head with a protruding oblate spherical bottom end to form a pipe fitting with a protruding annular groove on the pipe wall;

Fig. 13 is a schematic diagram of a pipe fitting formed by the present invention with an outer convex annular groove and an outer flaring shape;

Fig. 14 is a schematic diagram of a pipe fitting with an outer convex annular groove and an inner neck shape formed on the pipe wall of the present invention;

Fig. 15 is a schematic diagram of a pipe fitting formed in the present invention with a combined shape of an outer convex and an inner concave annular groove;

Fig. 16 and Fig. 17 are the schematic diagrams of the pipe fittings formed in the prefabricated hole of the pipe wall according to the present invention to form the turned hole shape of turning outward and turning inside.

In Figures 1 to 17:

1. Tool head (the bottom is hemispherical) 2. Pipe fittings 3. Tool head (the bottom is convex and oblate).

Detailed ways

Next, the numerical control incremental forming method is used to realize the pipe fittings with linear and helical grooves on the pipe wall along the axis of the tube blank. The specific embodiment of the present invention will be described by taking the pipe fittings, the pipe fittings with convex and concave annular grooves on the pipe wall, and the pipe fittings with valgus and inverted hole-turning shapes formed on the prefabricated holes of the pipe wall as examples.

The outer diameter D of the pipe formed in this embodiment is between 5 mm and 500 mm, the wall thickness t is between 0.2 mm and 10 mm, and the relative wall thickness t/D is less than 0.2.

(1) Pipe fittings with straight and helical grooves on the pipe wall along the axis of the pipe blank

The tube blank is clamped on the synchronous rotating mechanism in a horizontal state before forming, and the synchronous rotating mechanism is fixed on the base of the CNC progressive forming machine tool. The upper end of the cylindrical rod-shaped tool head is connected to the main shaft of the progressive forming machine tool and rotates around its own axis driven by the main shaft of the machine tool, and at the same time moves according to the control track preset by the program. The bottom end of the tool head is hemispherical and pressed on the tube blank. By extruding the material of the pipe wall, it is plastically deformed sequentially.

The feed movement of the tool head and the tube blank adopts the trajectory control method of "linkage method". When forming pipe fittings with grooves distributed in a straight line on the pipe wall along the axial direction of the pipe blank, the pipe blank is horizontally clamped on the synchronous rotating mechanism and is in a static fastening state, and the bottom end of the tool head moves to the starting position of the pipe blank forming (such as the intersection of the groove and the end face of the tube blank), then the tool head moves along the axis of the tube blank and forms the first groove. After the groove is completed, the tool head exits along the top of the tube blank, and then the tube blank rotates around its own axis at a certain angle under the drive of the synchronous rotation mechanism and then stops and is in a static fastening state. The tool head moves down to the starting position and adopts The second groove is formed in the same way as the first groove is formed, and this is repeated until all grooves are formed.

When forming a pipe fitting with helically distributed grooves on the pipe wall along the axis of the pipe blank, the pipe blank is horizontally clamped on the synchronous rotation mechanism and is in a static state, and the bottom end of the tool head moves to the initial position of the pipe blank forming. Then the tool head moves along the axial direction of the tube blank, and the tube blank rotates around its own axis at a certain angular speed under the drive of the synchronous rotation mechanism, and the first groove is formed through the mutual cooperation of the tool head and the tube blank. After the groove is completed, the tool head exits along the top of the tube blank, and then the tube blank rotates around its own axis at a certain angle under the synchronous rotation mechanism and then stops. The tool head moves to the starting position and adopts the same method for forming the first groove Complete the forming of the second groove, and repeat until all grooves are formed.

(2) Pipe fittings with external flare, internal constriction, and the combination of external flare and internal constriction at the pipe end

Before forming, one end of the tube blank to be formed is vertically upward and is in a static fastening state. The upper end of the cylindrical rod-shaped tool head is connected with the spindle of the incremental forming machine tool, and driven by the machine tool, it rotates around itself on the one hand, and on the other hand moves in the three-dimensional space according to the path preset by the program; the bottom end of the tool head is hemispherical and pressed On the tube blank, local plastic deformation is produced by extruding the tube wall material.

When forming a pipe fitting with a flared shape at the pipe end, the bottom end of the tool head is pressed laterally on the pipe blank from the inside of the pipe blank; Press sideways on the tube blank. During the forming process, the movement of the tool head adopts the trajectory control method of "layer cutting method", that is, according to the shape of the pipe wall to be formed, the movement trajectory of the tool head is decomposed into multiple horizontal circular paths in the vertical direction, and the tool head Along the circumferential direction of the tube blank, each ring-shaped path is completed layer by layer, and the parts are formed successively with the envelope surface formed by the movement track of the bottom end of the tool head.

(3) Pipe fittings with convex and concave annular grooves on the pipe wall

Before forming, the end of the tube blank to be formed is vertically upward and in a static fastening state. The upper end of the cylindrical rod-shaped tool head is connected to the spindle of the incremental forming machine tool, and driven by the machine tool spindle, it rotates around itself on the one hand, and on the other hand moves in three-dimensional space according to the preset path of the program; the bottom end of the tool head is convex It is oblate and pressed on the tube blank, extruding the tube wall material to cause local plastic deformation. When forming a pipe fitting with a convex annular groove on the pipe wall, the bottom end of the tool head is pressed laterally on the pipe blank from inside the pipe blank; when forming a pipe fitting with a concave annular groove on the pipe wall, the bottom end of the tool head is pressed from the pipe blank The outside of the blank is pressed laterally against the tube blank.

The tool head movement adopts the trajectory control method of "layer cutting method", that is, the trajectory of the tool head is decomposed into multiple horizontal circular paths in the vertical direction, and the tool head completes each circular path in turn until the forming is completed.

(4) Form the pipe fittings in the shape of valgus and inversion on the prefabricated hole of the pipe wall

Before forming, the tube blank is in a stationary horizontal fastening state, and the prefabricated hole on the tube wall of the tube blank to be processed faces upward. The upper end of the cylindrical rod-shaped tool head is connected to the spindle of the progressive forming machine tool and rotates around its own axis continuously under the drive of the spindle, and at the same time moves in space according to the trajectory preset by the program; the bottom end of the tool head is hemispherical and pressed on the The pipe wall material at the prefabricated hole of the pipe blank is plastically deformed by extrusion. The movement of the tool head adopts the trajectory control method of "layer cutting method", that is, the movement trajectory of the tool head is decomposed into multiple horizontal circular paths in the vertical direction, and the tool head completes each circular path layer by layer in turn, and the bottom of the tool head The envelope surface formed by the end motion trajectory gradually completes the forming of the part.

The materials that can be processed by the present invention include ordinary carbon steel and alloy steel, non-ferrous metals such as copper, aluminum, titanium and their alloys, as well as some non-metallic materials such as plastics and "plastic-metal" composite materials.

Claims (4)

1. special piece mouldless shaping method based on Metal CNC Incremental Forming, it is characterized in that, on the Metal CNC Incremental Forming lathe, the upper end of the shaft-like tool heads of one cylinder is connected on the main shaft of lathe, the bottom of tool heads is pressed on the pipe and is shaped as hemispherical and the evagination oblate spheroid, makes pipe wall material produce local plastic deformation by tool heads bottom extrusion tube blank; During shaping, tool heads is constantly rotated around self axis under the drive of machine tool chief axis, simultaneously in three dimensions according to the predefined orbiting motion of program, make the pipe each several part produce gradually successively plastic deformation.

2. a kind of special piece mouldless shaping method based on Metal CNC Incremental Forming as claimed in claim 1 is characterized in that pipe is static tightening state in the forming process, and around self axis state with fixed angular speed rotation.

3. a kind of special piece mouldless shaping method based on Metal CNC Incremental Forming as claimed in claim 1, it is characterized in that, the feed motion of tool heads and pipe has " layer cutting method " and " interlock method " two kinds of TRAJECTORY CONTROL modes: the tube wall shape that the former is shaped as required is decomposed into stacked a plurality of horizontal cyclic path at vertical direction with the movement locus of tool heads, tool heads is successively covered described horizontal cyclic path successively, and pipe is in static tightening state in the forming process; The latter is fixed with a synchronous rotating mechanism at the base of progressive molding lathe, pipe is the level of state and is clamped on the described synchronous rotating mechanism before being shaped, in the forming process tool heads in the space according to the predefined orbiting motion of program, simultaneously pipe under synchronous rotating mechanism drives around self axis with certain angular speed rotation.

4. a kind of special piece mouldless shaping method based on Metal CNC Incremental Forming as claimed in claim 1, it is characterized in that, the shape of the special piece of formed thereby comprises: the groove that distributes with helix is arranged linearly along pipe axis direction tube wall, pipe end is the shape of the shape of outer enlarging, interior reducing and the shape that outer enlarging is combined with interior reducing, tube wall has the cannelure of evagination and indent, the tube wall pre-manufactured hole form turn up and in the hole flanging shape of turning over.

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