Internal necking stamping part machining process and necking forming die

Abstract

The invention discloses a machining process for an inner necking stamping part. The machining process comprises the following steps that S1, an intermediate part with a side wall with the expected thickness is prepared; s2, side cutting is conducted on the intermediate part, and a back extrusion material with a preset sectional area is reserved in a target area; s3, the intermediate part obtained after side cutting is machined into a semi-finished product in the shape close to an inner necking through a pre-necking die; and S4, the semi-finished product is machined through a necking forming mold, and final necking forming is completed. Wherein the necking forming die adopts an interference type design, and a ribbing structure is arranged at an inner bending part of an inner slide of the necking forming die. According to the machining technology for the internal necking stamping part, the back extrusion material is reserved in the side cutting procedure, necking forming is carried out in cooperation with the interference type necking forming die with the ribbing structure, the comprehensive input cost is effectively saved, and it is guaranteed that the product quality is controllable.

Description

Technical Field

[0001] This invention relates to the field of stamping parts processing, and in particular to a process for processing stamping parts with an inwardly narrowed opening and a narrowing forming mold. Background Technology

[0002] In the production of metal stamping parts for consumer electronics products such as tablets, 5252 H32 grade aluminum is commonly used as the base material. This type of aluminum has good stamping plastic deformation capabilities and is suitable for conventional sidewall upsetting and thickening processes. In existing technology, the conventional sidewall upsetting and thickening ratio of 5252H32 aluminum stamping parts is usually 30% to 40%, with specific upper limits for thickness: for products with an initial sidewall thickness T of 0.8mm, the maximum sidewall thickness after upsetting does not exceed 1.15mm; for products with an initial sidewall thickness T of 1.0mm, the maximum sidewall thickness after upsetting does not exceed 1.40mm. In recent years, to adapt to the trend of ultra-thin PADs in the consumer market, a recessed opening structure design has emerged in metal stamping parts. This design places higher demands on the sidewall thickness of the stamped parts, explicitly requiring a minimum thickness of ≥1.45mm. Comparing the thickness upper limit of conventional processes with the thickness requirement of the recessed opening design, it is clear that the core bottleneck of existing technology lies in the fact that conventional upsetting and thickening processes cannot achieve the ≥1.45mm sidewall thickness requirement for the recessed opening design in 5252 H32 aluminum stamped parts. To overcome the aforementioned technical bottlenecks, two improvement schemes have been proposed in the industry, but both have significant drawbacks: Option 1 involves replacing the aluminum material with a new material. The initial sidewall thickness of 1.0mm is changed to 1.2mm. This option directly increases the cost of raw material procurement. On the other hand, due to the increased thickness of the base material, it is necessary to add or adjust the CNC machining process to meet the overall size requirements of the product, which further increases the cost of subsequent processing. Option 2 involves using a two-stage upsetting process for 1.0mm aluminum material. First, the sidewall is upset to 1.30mm, and then it is upset again to 1.50mm. This option not only requires the development of a second upsetting die, increasing the cost of die development and manufacturing, but also has a lower maturity level in the two-stage upsetting process. This can easily lead to defects such as three types of damage to the product's appearance (scratches, bumps, and pressure marks) and large-area upsetting marks, resulting in a 5-8% reduction in product yield and hindering mass production.

[0003] Based on this, the present invention proposes a processing technology for internally narrowed stamping parts and a narrowing forming mold to solve the problems mentioned above. Summary of the Invention

[0004] The purpose of this invention is to provide a processing technology and a die for internally tapered stamping parts, which enables the workpiece to exceed the thickness limit achievable by conventional processes without increasing the thickness of the raw material or adding a secondary upsetting process.

[0005] To solve the above technical problems, the present invention provides a processing method for internally tapered stamped parts, comprising the following steps: S1. Prepare an intermediate part with sidewalls of the desired thickness; S2. Side-cut the intermediate part and leave a pre-defined cross-sectional area of ​​re-extruded material in the target area; S3. The side-cut intermediate part is processed into a semi-finished product with an inwardly narrowed shape using a pre-shrinking mold. S4. The semi-finished product is processed through a necking forming mold to complete the final necking forming; The narrowing forming mold adopts an interference fit design and has a pressure rib structure at the inner bending part; the interference fit between the narrowing forming mold and the semi-finished product, the size of the pressure rib structure, and the reserved back extrusion material cross-sectional area are coordinated and matched.

[0006] Furthermore, in step S4, the specific steps by which the necking forming mold simultaneously completes the final necking forming and local thickening are as follows: The semi-finished product is positioned and clamped by the inner slide of the upper and lower molds; Drive the forming punch to move until the remaining inner slides of the lower die are pressed together without gaps.

[0007] Furthermore, the forming punch is driven by a nitrogen spring block.

[0008] Furthermore, in step S1, the specific steps for preparing the intermediate include: The substrate is gradually processed into an intermediate part with a preset sidewall thickness through a series of processes including blanking, gradient preforming, and initial back-extrusion and thickening.

[0009] Furthermore, the gradient preforming process is implemented in a step-by-step stamping manner, and the forming deformation amount of each step is adapted to the plastic deformation characteristics of the substrate.

[0010] Furthermore, each step of the gradient preforming stamping process uses a unified positioning reference.

[0011] Furthermore, in step S2, by controlling the range and depth of the side cut, redundant material in the non-critical areas of the intermediate body is cut off, leaving only the re-extrusion material of the preset cross-sectional area in the inner diameter target thickening area.

[0012] Furthermore, the processing technology for internally tapered stamped parts also includes the following steps: According to the product construction requirements, the crater forming process is carried out after step S2 and before step S3.

[0013] Furthermore, the processing technology for internally tapered stamped parts also includes the following steps: According to the product's shape accuracy requirements, after step S4, the side-pushing shaping and flatness-leveling processes are performed in sequence.

[0014] The present invention also provides a necking forming mold, including an upper mold, a lower mold inner slide, a forming punch, and a nitrogen spring block; The inner bend of the lower mold inner slide is provided with a pressure rib structure; The upper mold, forming punch and lower mold are fitted together to form an interference-fit cavity; The nitrogen spring block is connected to the forming punch and is used to drive the forming punch to move until it is pressed tightly against the inner slide of the lower die without gap.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: The internal necking stamping process provided by this invention, by retaining the back extrusion material in the side cutting process and using the interference fit and necking forming die with pressure rib structure for necking forming, can achieve local additional thicknessing of the workpiece while necking forming. This allows the workpiece to break through the thickness limit that conventional processes can achieve without increasing the thickness of the raw material or adding a secondary upsetting process, effectively saving the overall investment cost and ensuring controllable product quality. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the processing technology for the internally tapered stamped part in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the necking forming mold in an embodiment of the present invention; Figure 3 This is a schematic diagram showing the overall structure and core dimension distribution of the internally tapered metal stamping part processed in Example 1 and Comparative Example 1 of the present invention; Figure 4 This is a schematic diagram of the interference cavity structure of the necking forming mold in Example 1 of the present invention; Figure 5 This is a partial dimensional schematic diagram of the pressure rib structure of the necking forming mold in Example 1 of the present invention; Figure 6 This is a schematic diagram of the theoretical thickening dimension at the inner corner of the necking after necking in Example 1 of the present invention; Figure 7 This is a schematic diagram comparing the wall thickness at the corner of the constricted opening in Example 1 of the present invention. Figure 8 This is a schematic diagram illustrating the actual slice thickness detection of the product after necking and forming in Example 1 of the present invention; Figure 9 This is a schematic diagram of the structure of the traditional open-type necking mold used in Comparative Example 1 of the present invention; Figure 10 This is a schematic diagram comparing the wall thickness at the corner of the constricted opening in Comparative Example 1 of the present invention. Detailed Implementation

[0017] The processing technology of the internally recessed stamped part of the present invention will be described in more detail below with reference to the schematic diagrams, which illustrate preferred embodiments of the present invention. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the present invention.

[0018] The invention is described more specifically by way of example in the following paragraphs with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description and claims. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0019] like Figure 1 As shown, an embodiment of the present invention provides a processing technology for a punched part with an inwardly narrowed opening, comprising the following steps: S1. Prepare an intermediate part with sidewalls of the desired thickness; Specifically, the steps for preparing the intermediate include: sequentially processing the substrate into an intermediate part with a preset sidewall thickness through blanking, gradient preforming, and first back-extrusion and thickening processes.

[0020] The gradient preforming process is implemented in a step-by-step stamping manner, and the forming deformation amount of each step is adapted to the plastic deformation characteristics of the substrate. The step-by-step stamping station of the gradient preforming adopts a unified positioning reference.

[0021] By using step-by-step stamping to adapt to the plastic deformation characteristics of the substrate, it is possible to ensure that the sidewalls of the intermediate parts are free from cracks and wrinkles, and that the sidewall thickness uniformity tolerance is controlled within a low range. This provides a stable and dimensionally accurate processing foundation for subsequent processes such as side cutting to retain re-extrusion material and necking to thicken the parts. At the same time, the design with a unified positioning reference ensures the positional accuracy of each stamping step and avoids dimensional deviations of the intermediate parts caused by step-by-step stamping.

[0022] S2. Side-cut the intermediate part and leave a pre-defined cross-sectional area of ​​re-extruded material in the target area; Specifically, by controlling the range and depth of the side cut, redundant material in the non-critical areas of the intermediate component is cut off, leaving only the re-extruded material of the preset cross-sectional area in the target thickening area of ​​the inner neck.

[0023] S3. The side-cut intermediate part is processed into a semi-finished product with an inwardly narrowed shape using a pre-shrinking mold. S4. The semi-finished product is processed through a necking forming mold to complete the final necking forming; The necking mold adopts an interference fit design.

[0024] Specifically, refer to Figure 2 The necking forming mold includes an upper mold 01, a lower mold inner slide 02, a forming punch 03, and a nitrogen spring block (not shown in the figure). The upper mold 01, the lower mold inner slide 02, and the forming punch 03 together form an interference-fit chamber. The inner bend of the lower mold inner slide 02 is provided with a pressure rib structure 04. The nitrogen spring block is connected to the forming punch 03 to drive the forming punch 03 to move. The interference between the necking forming mold and the semi-finished product a, the size of the pressure rib structure, and the reserved back extrusion cross-sectional area are matched in a coordinated manner.

[0025] The specific steps for the necking forming mold to simultaneously complete the final necking forming and local thickening are as follows: S41. The semi-finished product is positioned and clamped by the inner sliding position of the upper and lower molds to ensure that the inner shrinkage target thickening area of ​​the semi-finished product is precisely aligned with the mold pressing rib structure, laying the foundation for the subsequent directional flow of materials. S42. The forming punch is driven by a nitrogen spring block until the remaining inner slides of the lower die are pressed together without gaps. At this time, the inner slides of the upper and lower dies and the forming punch form a closed interference cavity. On the one hand, the final shrinking and shaping is completed by the cavity extrusion. On the other hand, the closed cavity restricts the overflow of the back extrusion material. With the help of the pressure rib structure, the back extrusion material is guided to flow in a direction to the target area to achieve thickening.

[0026] In an optional embodiment, the process for processing the internally tapered stamped part further includes the following steps: Based on product structural requirements, the crater forming process is performed after step S2 and before step S3. The core purpose of crater forming is to machine a "crater-shaped" recess / step structure in the non-recessed area of ​​the workpiece to match the snap-fit, positioning post, or assembly guide requirements of subsequent components, ensuring assembly compatibility between the product and other parts. This process is positioned after the side-cutting process and before the pre-recessing process for the following reasons: After side cutting, the workpiece has completed the back extrusion material reservation and has not undergone necking deformation. The overall shape is regular and can be accurately positioned based on the unified positioning hole reference of the whole process, avoiding touching or damaging the reserved back extrusion material in the inner necking target area during processing. If it is delayed until after the pre-necking, the workpiece has formed the inner necking prototype and the shape is irregular. Not only does the positioning difficulty increase, but the stamping pressure of volcano forming may also cause deformation of the pre-necking structure, affecting the subsequent core necking thickening effect.

[0027] Another process for processing internally tapered stamped parts includes the following steps: according to the product's shape accuracy requirements, after step S4, side-pushing shaping and flatness-leveling processes are performed in sequence.

[0028] Side-pushing shaping and flatness finishing are both precision post-processing steps, added only for products with high dimensional accuracy requirements. The purpose of side-pushing shaping is to precisely correct dimensional deviations around the inner neck after necking (such as slight sidewall tilting, localized protrusions / recesses on the outer contour), ensuring the workpiece's outer contour dimensions meet design requirements and providing a precise dimensional reference for subsequent assembly. The purpose of flatness finishing is to correct large-area flatness deviations caused by the entire process (especially multiple stamping and necking), improving surface flatness and preventing uneven machining depth due to insufficient flatness during subsequent CNC machining. It also ensures a tight fit (no gaps, no wobble) when the product is assembled with other components.

[0029] The internal necking stamping process provided by this invention, by retaining the back extrusion material in the side cutting process and using the interference fit and necking forming die with pressure rib structure for necking forming, can achieve local additional thicknessing of the workpiece while necking forming. This allows the workpiece to break through the thickness limit that conventional processes can achieve without increasing the thickness of the raw material or adding a secondary upsetting process, effectively saving the overall investment cost and ensuring controllable product quality.

[0030] The following provides an example and a comparative example to further explain the embodiments of this product.

[0031] Example 1 The product processed in this example is a metal stamping part with an inwardly tapered opening for PAD consumer electronics products. Its overall structure and core dimension distribution are as follows: Figure 3 As shown, the core technical requirement is that the minimum thickness of the sidewall of the inner shrinkage target thickening area (corner) after metal upsetting and extrusion is ≥1.45mm, so as to reserve a CNC machining allowance of not less than 0.25mm and ensure that the subsequent CNC machining is 100% visible (without machining blind spots caused by insufficient wall thickness).

[0032] This example uses the process disclosed in the embodiments of the present invention for processing, and the specific process flow is as follows: M1: Material feeding; Precision cutting equipment is used to cut 5252H32 aluminum plates with a thickness of 1.0mm into blanks of a preset size, with the cutting tolerance controlled within ±0.05mm.

[0033] M2: 70° preform; Using the positioning holes on the edge of the blank as a unified reference (the positioning reference that runs through the entire process), the flat blank is pre-formed into a 70° inclined transition shape by a stamping die.

[0034] M3: 90mm molding; Based on a unified positioning benchmark, the 70° preform blank is further stamped to process into a 90° vertical structure. During the forming process, the deformation amount per step is controlled to be ≤20% (to match the plasticity characteristics of 5252H32 aluminum).

[0035] M4: Thick sidewall of the back extrusion block; The sidewall thickness of the workpiece after 90° forming is increased by using a special back extrusion die, which increases the sidewall thickness from the original base material T1.0mm to 1.40mm, providing a stable wall thickness base for subsequent re-extrusion material.

[0036] M5: Side cut; The side-cutting station precisely cuts away excess material in the non-inward-recessed target area of ​​the workpiece, leaving only a preset cross-sectional area S=1.12mm in the target thickened area at the inward-recessed corner. 2 The re-extrusion material (the re-extrusion material size is 0.8mm × 1.4mm, where 0.8mm can be adapted and adjusted according to the interference design of the subsequent necking molding die).

[0037] M6: Crater formation.

[0038] M7: 60° pre-shrinking molding; The workpiece is machined into a 60° inward-reduced shape using a pre-reduced die.

[0039] M8: 92° necking molding.

[0040] The necking forming mold described in the embodiment is used, and the necking forming mold adopts an interference fit design (e.g. Figure 4 As shown), the interference fit is approximately 0.8mm, and the rib structure size is designed to be 0.1×0.4mm (as shown). Figure 5 (As shown).

[0041] When the mold is closed, the workpiece is first positioned and clamped by the inner slides of the upper and lower molds. Then, the forming punch is driven by the nitrogen gas spring block to press against the inner slide of the lower mold without gap, forming a closed interference cavity. While the cavity extrusion achieves the final 92° necking and shaping, the pressure rib structure guides the remaining 1.12mm. 2 The re-extruded material flows directionally towards the inward-curving corner, completing a secondary local re-extruded thickening, in conjunction with reference. Figure 6 and Figure 7 Theoretically, there will be a 0.18mm increase in thickness from M4 to M8, meaning that the corner dimension can be increased from 1.4mm to 1.48mm after the M8 process, which meets the technical requirement of greater than 1.45mm.

[0042] The final product's measured wall thickness at the corners was greater than 1.45mm, verifying the feasibility of the theory. Figure 8For a product that has undergone the M8 process, the thickness at the corner can reach up to 1.781mm.

[0043] M9: Lateral push shaping.

[0044] M10: Flatness.

[0045] Comparative Example 1 This comparative example product is processed using the same traditional process as Example 1, and the process flow includes M1-M10 of Example 1. The difference is that: in M5, there is no re-extrusion material reservation; and in M8, the necking mold is a traditional design: an open design (a 2mm gap is reserved between the pre-necked product and the necking mold) and there is no introduction of nitrogen gas springs or pressure rib structures (such as...). Figure 9 (As shown).

[0046] The final product's sidewall thickness remains consistent with the dimensions after re-extrusion, and the necking process does not increase the thickness (e.g., Figure 10 As shown in the figure, the thickness remains at 1.4mm, which cannot meet the design requirements.

[0047] As can be seen from the above, the metal stamping parts produced by adopting the solution of the present invention can not only break through the thickening barrier of traditional processes, but also form a comprehensive advantage in terms of quality, cost and stability, and are more suitable for the high requirements of PAD and other consumer electronic products for precision metal parts.

[0048] In summary, compared with the prior art, the present invention has at least the following advantages: The internal necking stamping process provided by this invention, by retaining the back extrusion material in the side cutting process and using the interference fit and necking forming die with pressure rib structure for necking forming, can achieve local additional thicknessing of the workpiece while necking forming. This allows the workpiece to break through the thickness limit that conventional processes can achieve without increasing the thickness of the raw material or adding a secondary upsetting process, effectively saving the overall investment cost and ensuring controllable product quality.

[0049] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A processing method for internally tapered stamped parts, characterized in that, Includes the following steps: S1. Prepare an intermediate part with sidewalls of the desired thickness; S2. Side-cut the intermediate part and leave a pre-defined cross-sectional area of ​​re-extruded material in the target area; S3. The side-cut intermediate part is processed into a semi-finished product with an inwardly narrowed shape using a pre-shrinking mold. S4. The semi-finished product is processed through a necking forming mold to complete the final necking forming; The narrowing forming mold adopts an interference fit design and has a pressure rib structure at the inner bending part; the interference fit between the narrowing forming mold and the semi-finished product, the size of the pressure rib structure, and the reserved back extrusion material cross-sectional area are coordinated and matched.

2. The processing technology for internally tapered stamped parts as described in claim 1, characterized in that, In step S4, the specific steps by which the necking forming mold simultaneously completes the final necking forming and local thickening are as follows: S41. The semi-finished product is positioned and clamped by the inner slide of the upper and lower molds; S42, drive the forming punch to move until the remaining lower die inner slides are pressed together without gaps.

3. The processing technology for internally tapered stamped parts as described in claim 2, characterized in that, The forming punch is driven by a nitrogen spring block.

4. The processing technology for internally tapered stamped parts as described in claim 1, characterized in that, In step S1, the specific steps for preparing the intermediate include: The substrate is gradually processed into an intermediate part with a preset sidewall thickness through a series of processes including blanking, gradient preforming, and initial back-extrusion and thickening.

5. The processing technology for internally tapered stamped parts as described in claim 4, characterized in that, The gradient preforming process is implemented in a step-by-step stamping manner, and the forming deformation amount of each step is adapted to the plastic deformation characteristics of the substrate.

6. The processing technology for internally tapered stamped parts as described in claim 5, characterized in that, The step-by-step stamping stations of the gradient preforming process adopt a unified positioning reference.

7. The processing technology for internally tapered stamped parts as described in claim 1, characterized in that, In step S2, by controlling the range and depth of the side cut, the redundant material in the non-critical areas of the intermediate body is cut off, and the re-extrusion material of the preset cross-sectional area is left only in the target thickening area of ​​the inner neck.

8. The processing technology for internally tapered stamped parts as described in claim 1, characterized in that, It also includes the following steps: According to the product construction requirements, the crater forming process is carried out after step S2 and before step S3.

9. The processing technology for internally tapered stamped parts as described in claim 1, characterized in that, It also includes the following steps: According to the product's shape accuracy requirements, after step S4, the side-pushing shaping and flatness-leveling processes are performed in sequence.

10. The necking forming die in the internal necking stamping process according to any one of claims 1-9, characterized in that, This includes the upper mold, the inner slide of the lower mold, the forming punch, and the nitrogen spring block; The inner bend of the lower mold inner slide is provided with a pressure rib structure; The upper mold, forming punch and lower mold are fitted together to form an interference-fit cavity; The nitrogen spring block is connected to the forming punch and is used to drive the forming punch to move until it is pressed tightly against the inner slide of the lower die without gap.

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