High-precision mandrel forming die

Abstract

The invention provides a high-precision mandrel forming die, and belongs to the technical field of die machining. The problem that an existing mandrel is low in machining precision is solved. The high-precision mandrel forming die comprises a die body with a die cavity and further comprises a machining unit connected with the die body and used for machining a workpiece. The lower die unit is arranged on the bottom plate and connected with the bottom plate, the limiting unit is arranged on the bottom plate and used for limiting the position of a workpiece, the upper die unit is connected with the limiting unit, matched with the lower die unit and used for stamping the workpiece, and the inner wall of the die cavity is of an annular boss structure. The method has the advantage of being high in machining precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of mold processing and relates to a high-precision mandrel forming mold. Background Art

[0002] Mandrel forming is a process of precisely pressing key teeth on the inner wall of a bearing sleeve through the collaborative action of a mold and a mandrel. The core lies in making the material flow directionally through plastic deformation to form a high-precision key structure, ensuring that the fit between the key and the shaft meets the requirements of torque transmission, positioning, and anti-shearing. Since the dimensional tolerance of the key usually needs to be controlled within the range of ±0.05 mm, the requirements for mold design, material properties, and process parameters are extremely high. However, the traditional mandrel forming process has the following defects. The first is uneven material flow: When the upper and lower molds are closed, the extrusion of the mandrel on the bearing sleeve is a single-point pressure application, resulting in uneven circumferential distribution of the material, which easily leads to inconsistent keyway width or depth (such as local bulging or depression).

[0003] After the bearing sleeve is formed, it rebounds due to the release of residual stress, resulting in the actual size of the key deviating from the design value (commonly seen in thin-walled kits); The second is the limitation of the mold structure: Rigid contact problem: The upper mold mandrel directly contacts the bearing sleeve, resulting in large friction during the pressure application process, exacerbating mold wear and affecting long-term stability; Lack of buffer design: There is a lack of dynamic regulation of material flow, and stress concentration is likely to occur at the root of the keyway, which may cause microcracks during subsequent use; thus, it does not meet the processing requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a forming mold that solves the above problems in view of the above problems existing in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions: A high-precision mandrel forming mold includes a mold body with a mold cavity. It is characterized in that it further includes a processing unit connected to the mold body and used for processing workpieces. The mold body includes a bottom plate, a lower mold unit arranged on the bottom plate and connected thereto, a limiting unit arranged on the bottom plate and used for restricting the position of the workpiece, and an upper mold unit connected to the limiting unit and cooperating with the lower mold unit for stamping the workpiece. The inner wall of the above mold cavity is arranged in a ring-shaped convex platform structure. When the upper mold unit presses down, a small amount of plastic deformation will occur at the end of the workpiece, thus forming a "material locking area" to prevent axial material loss during the subsequent forming stage.

[0006] In the above high-precision mandrel forming mold, the lower mold unit includes a lower mold main body connected to the bottom plate.

[0007] In the above-mentioned high-precision mandrel forming die, the limiting unit includes two positioning plates connected to the bottom plate, and the two positioning plates are the main positioning plate and the auxiliary positioning plate respectively.

[0008] In the above-mentioned high-precision mandrel forming die, the processing unit includes a driving cylinder, a mounting bracket, a connecting sleeve and a mandrel. The mounting bracket is arranged on the bottom plate and connected to it. The driving cylinder is arranged on the mounting bracket and connected to it. The connecting sleeve is connected to the output end of the driving cylinder. One end of the mandrel extends into the connecting sleeve and is limited by a clamping plate. A tooling hole is provided on the main positioning plate for the other end of the mandrel to extend into and facilitate the contact between the mandrel and the workpiece.

[0009] In the above-mentioned high-precision mandrel forming die, the upper die unit includes an upper plate, an upper backing plate, an upper die body, a nitrogen spring and a stripping screw. The upper backing plate is arranged on the lower end face of the upper plate and connected to it. The upper die body is arranged on the lower end face of the upper backing plate and connected to it. An installation hole axially recessed inward is provided on the upper end face of the upper backing plate, extends into the upper die body and is used for installing the nitrogen spring. An assembly hole axially recessed inward is provided on the upper end face of the upper plate for installing the stripping screw. The assembly hole extends axially downward, axially penetrates the upper backing plate and penetrates into the upper die body. The upper die body is connected to the auxiliary positioning plate through an inner guiding column.

[0010] The working principle of the main body of this die is as follows. It adopts the core process of the step-by-step progressive forming technology. The step-by-step progressive forming solves the problem of flow out-of-control caused by traditional single extrusion through multi-stage pressure distribution and dynamic material constraint. The key technical route is as follows: 1. Pre-pressing stage (material pre-constraint), Die structure: Adopt a split pre-pressing die (including an upper die body, an inner guiding column and a nitrogen spring). The upper die body applies an initial pre-pressure through a nitrogen spring (the adjustable pressure range is 0.5~5 MPa) to fix the bearing sleeve blank in the die cavity; Material wrapping control, The inner wall of the pre-pressing die is designed with an annular boss (height 0.1~0.3 mm). During pre-pressing, a small amount of plastic deformation is generated at the end of the bearing sleeve to form a "material locking area" to prevent axial material loss in the subsequent forming stage. The pre-pressure needs to be controlled within 30%~50% of the material yield strength to avoid premature plastic deformation; 2. Finishing stage (key tooth forming), Progressive extrusion of the mandrel: The hydraulic-driven mandrel (hardness HRC60 - 62) is pressed into the inner wall of the bearing sleeve at a low speed of 0.05 - 0.2 mm / s. The extrusion speed is matched with the strain rate of the material to reduce springback (too fast speed is likely to cause surface cracks). The surface of the mandrel is coated to reduce the friction coefficient (from 0.15 to 0.08) and improve the surface finish of the key tooth side wall (Ra ≤ 0.8 μm).

[0011] 3. Calibration stage (dimension stabilization), Pressure holding and shaping: After the mandrel is in place, maintain the maximum pressure (about 200 - 300 kN) for 5 - 10 seconds. Utilize the creep characteristics of the material to eliminate internal stress and reduce the elastic recovery after demolding (the springback amount can be reduced by 40% - 60%).

[0012] Compared with the prior art, this high-precision mandrel forming die improves the product qualification rate through the step-by-step progressive forming technology. Brief Description of the Drawings

[0013] Figure 1 It is a schematic side view structure diagram of this high-precision mandrel forming die.

[0014] Figure 2 It is a schematic structure diagram at the upper die unit of this high-precision mandrel forming die.

[0015] In the figure, 1. bottom plate; 2. lower die body; 3. main positioning plate; 4. auxiliary positioning plate; 5. driving cylinder; 6. mounting bracket; 7. connecting sleeve; 8. mandrel; 9. upper plate; 10. upper backing plate; 11. upper die body; 12. nitrogen spring; 13. unloading screw. Detailed Embodiment

[0016] The following are specific embodiments of the present invention and in combination with the drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0017] Such as Figure 1 、 Figure 2As shown, the high-precision mandrel forming mold includes a mold body with a mold cavity, and also includes a processing unit connected to the mold body and used to process the workpiece. The mold body includes a bottom plate 1, a lower mold unit arranged on and connected to the bottom plate 1, a limit unit arranged on and connected to the bottom plate 1 and used to limit the position of the workpiece, and an upper mold unit connected to the limit unit and matched with the lower mold unit and used to stamp the workpiece. The inner wall of the mold cavity is arranged in an annular boss structure. When the upper mold unit is pressed down, a slight plastic deformation will occur at the end of the workpiece, thereby forming The lower die unit comprises a lower die main body 2 connected to the bottom plate 1, and the limiting unit comprises two positioning plates connected to the bottom plate 1, the two positioning plates are respectively a main positioning plate 3 and an auxiliary positioning plate 4, and are respectively located outside the two sides of the lower die main body 2, and the processing unit comprises a driving cylinder 5, a mounting bracket 6, a connecting sleeve 7 and a mandrel 8, the mounting bracket 6 is arranged on the bottom plate 1 and connected thereto, the driving cylinder 5 is arranged on the mounting bracket 6 and connected thereto, and the connecting sleeve 7 is connected to the output of the driving cylinder 5. The outlet end is connected, one end of the mandrel 8 extends into the connecting sleeve 7, and is limited by the connecting sleeve 7 through the clamping plate. A tooling hole is provided on the main positioning plate 3 for the other end of the mandrel 8 to extend into and facilitate the mandrel 8 to contact the workpiece. Another tooling hole is also provided on the auxiliary positioning plate 4. An extension sleeve can be provided between the above-mentioned connecting sleeve 7 and the driving cylinder 5. A reversing valve structure connected to and matched with the driving cylinder 5 is provided outside the above-mentioned mold body. The upper mold unit includes an upper plate 9, an upper pad plate 10, an upper mold body 11, a nitrogen spring 12 and a discharge screw 13. The upper pad The plate 10 is arranged on the lower end surface of the upper plate 9 and connected thereto, the upper mold body 11 is arranged on the lower end surface of the upper pad 10 and connected thereto, the upper end surface of the upper pad 10 is provided with an axially inwardly recessed mounting hole extending into the upper mold body 11 for installing the nitrogen spring 12, the upper end surface of the upper plate 9 is provided with an axially inwardly recessed mounting hole for installing the unloading screw 13, the mounting hole extends axially downward, axially penetrates the upper pad 10, and penetrates into the upper mold body 11, the upper mold body 11 is connected to the auxiliary positioning plate 4 or the lower plate through an inner guide column.

[0018] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0019] Although the term "such as" is used more frequently in this article, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A high-precision mandrel forming die, comprising a die body with a die cavity, characterized in that, It further includes a processing unit connected to the mold body and used for processing workpieces. The mold body includes a bottom plate, a lower mold unit disposed on and connected to the bottom plate, a limiting unit disposed on the bottom plate and used for limiting the position of the workpiece, and an upper mold unit connected to the limiting unit, cooperating with the lower mold unit and used for stamping the workpiece. The inner wall of the above-mentioned mold cavity is provided with an annular boss structure. When the upper mold unit presses down, a small amount of plastic deformation will occur at the end of the workpiece, thereby forming a "material locking area" to prevent axial material loss during the subsequent forming stage.

2. The high-precision mandrel forming die according to claim 1, characterized in that, The lower mold unit includes a lower mold body connected to the bottom plate.

3. A high-precision mandrel forming die according to claim 1, characterized in that, The limiting unit includes two positioning plates connected to the bottom plate, and the two positioning plates are respectively a main positioning plate and an auxiliary positioning plate.

4. The high-precision mandrel forming die according to claim 3, characterized in that The processing unit includes a driving cylinder, a mounting bracket, a connecting sleeve and a mandrel. The mounting bracket is disposed on and connected to the bottom plate. The driving cylinder is disposed on and connected to the mounting bracket. The connecting sleeve is connected to the output end of the driving cylinder. One end of the mandrel extends into the connecting sleeve and is limited by a clamping plate. A tooling hole is provided on the main positioning plate for the other end of the mandrel to extend into and facilitate the contact between the mandrel and the workpiece.

5. A high-precision mandrel forming die according to claim 3, characterized in that, The upper mold unit includes an upper plate, an upper backing plate, an upper mold body, a nitrogen spring and a stripping screw. The upper backing plate is disposed on and connected to the lower end face of the upper plate. The upper mold body is disposed on and connected to the lower end face of the upper backing plate. An installation hole axially recessed inward, extending into the upper mold body and for installing the nitrogen spring is provided on the upper end face of the upper backing plate. An assembly hole axially recessed inward and for installing the stripping screw is provided on the upper end face of the upper plate. The assembly hole extends axially downward, axially penetrates the upper backing plate and penetrates into the upper mold body. The upper mold body is connected to the auxiliary positioning plate through an inner guide post.

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