Punch forming process of rain cover

Abstract

The invention discloses a rain cover punch forming process which comprises the following steps: S1, blank preparation: selecting a pre-coated steel plate with a smooth surface, no scratch and a thickness of 0.8-1.2 mm, and uncoiling, flattening and shearing the pre-coated steel plate; s2, integrated composite stamping is conducted, specifically, a, pre-forming is conducted, specifically, a male die moves downwards to be matched with a female die, and one-time deep drawing of the main body part of the rain cover is completed; b, precise edge cutting is conducted, specifically, a negative gap edge cutting technology is adopted, so that the plate is stretched and thinned under the extremely small gap till separation is achieved; c, flanging; and S3, shaping. The procedures of deep drawing, trimming and flanging are continuously completed in the same die, the rain cover body is formed at a time, follow-up tailor welding is not needed, and the problem of multiple welding seams caused by traditional multi-procedure splicing is solved. The negative gap technology is adopted in the edge cutting procedure, so that the workpiece is pulled to be broken, thinned and separated under the action of extremely small reverse stretching, and the risk of installation damage or poor sealing caused by burrs is reduced.

Description

Technical Field

[0001] This invention relates to the field of rain cover technology, and in particular to a stamping process for a rain cover. Background Technology

[0002] Rain covers, as a common protective component, are widely used in automobiles, machinery, and electrical cabinets, primarily for dust and water protection. Rain covers are typically manufactured from sheet metal through stamping. Traditional stamping processes for rain covers usually involve multiple molds and procedures, generally including: blanking, deep drawing, trimming / cutting, flanging, and shaping.

[0003] However, the dispersed steps in the traditional stamping process for rain covers tend to increase the number of welds, which not only increases the welding workload during manufacturing but also creates potential leakage points. Welding defects or impacts during use can easily lead to leaks. Furthermore, the trimming stage in the stamping process often requires significant cutting forces. These forces can easily create burrs and corner collapses on the cut surface, severely affecting the appearance and dimensional accuracy of the rain cover, and can also cause localized deformation. Therefore, a new stamping process for rain covers has been invented to address these shortcomings. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a stamping process for a rain cover.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A stamping process for a rain cover includes the following steps:

[0007] S1. Blank preparation: Select pre-coated steel plates with a flat surface, no scratches, and a thickness of 0.8 to 1.2 mm, and perform uncoiling, leveling, and shearing.

[0008] S2, Integrated Composite Stamping: The sheet metal is fed into a composite mold, which is equipped with a drawing zone, a trimming zone, and a flanging zone.

[0009] a. Pre-forming: The punch moves downward and cooperates with the die to complete the first deep drawing of the main body of the rain cover, so that the main body of the rain cover is shaped to be close to the final outline;

[0010] b. Precise edge cutting: The negative clearance edge cutting process is adopted, and the cooperation of the punch and die is used to stretch, thin and separate the sheet material under negative clearance conditions.

[0011] c. Flanging: The flanging punch located inside the mold starts to move, folding the edge of the cut workpiece upward to form a vertical edge with a height of 8-12mm;

[0012] S3. Shaping: The workpiece is calibrated through the combined action of the punch, die, and flanging module.

[0013] In step S1, the pre-coated sheet is one of double-sided galvanized steel sheet, double-sided aluminum-zinc coated steel sheet, or double-sided zinc-iron alloy sheet.

[0014] The pre-coated sheet is a double-sided aluminum-zinc coated steel sheet, and the double-sided aluminum-zinc coated steel sheet is coated with epoxy resin, the thickness of which is 0.01mm to 0.03mm.

[0015] In step S2a, the drawing speed of the first drawing is 80-120 mm / s, and the blank holder force is set to 180-220 kN.

[0016] In step S2b, the gap value of the negative gap cutting edge is -0.02mm to -0.05mm, and the radius of curvature of the die edge is 0.02mm to 0.05mm.

[0017] The negative clearance cutting edge adopts a stepped cutting edge structure, which includes a shearing zone, a stretching zone, and a separation zone in sequence.

[0018] The cutting edge angle of the shearing zone is 20° to 25°, and the cutting edge rake angle is 0° to 2°; the cutting edge angle of the stretching zone is 8° to 12°, and the cutting edge rake angle is -2° to 0°; the cutting edge angle of the separation zone is 2° to 5°, and the cutting edge rake angle is -5° to -2°.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] By continuously completing the deep drawing, trimming, and flanging processes within the same mold, the rain cover body is formed in one step, eliminating the need for subsequent welding and fundamentally avoiding the multiple weld seams problem caused by traditional multi-process splicing. By employing a negative clearance process in the trimming process, the workpiece is "stretched, thinned, and separated" under minimal reverse tensile force, resulting in a smooth cut surface. This process controls burr height to below 10μm and cut roughness to below 1.6μm, effectively solving quality defects such as tearing and excessive burrs caused by ordinary punching. It not only significantly improves the edge quality of the workpiece but also reduces subsequent auxiliary processes such as grinding and deburring, thereby lowering the risk of installation damage or poor sealing caused by burrs and improving product reliability and production efficiency. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention;

[0022] Figure 2 A cross-sectional view of the mold of the present application is shown in FIG. 1.

[0023] Figure 3 A cross-sectional view of the mold of the present application is shown in FIG. 1. Figure 2 An enlarged view of area A in FIG. 1. DETAILED DESCRIPTION

[0024] The present application will be further described in conjunction with specific examples. It should be understood that the following examples are intended to illustrate the present application and are not intended to limit the scope of the present application.

[0025] The present embodiment discloses a stamping forming process for a rain cover, comprising the following steps:

[0026] S1, blank preparation: select a pre-coated steel plate with a smooth surface, no scratches and a thickness of 0.8-1.2 mm, and perform uncoiling, flattening and shearing on the pre-coated plate;

[0027] During the stamping forming process of the rain cover, the mold is tightly attached to the plate. If the plate surface has defects such as concave-convex and scratches, it will be further enlarged during the stamping forming process, resulting in obvious defects on the surface of the finished product. In addition, the appropriate thickness of the plate is crucial to the forming quality: too low thickness will easily cause wrinkles during stamping, affecting the stability of the component; too high thickness will exacerbate mold wear and increase production cost. Controlling the thickness of the plate within the range of 0.8-1.2 mm can effectively suppress the deformation of the rain cover during stamping, thereby reducing the occurrence of welding defects.

[0028] As an external protection product exposed to the natural environment for a long time, the rain cover needs to have good weather resistance and impermeability. The pre-coated steel plate has completed the coating treatment during the production process, and does not need to be coated again during stamping forming, which not only improves the production efficiency, but also avoids damage to the coating. The coating on such plate can effectively resist the erosion of environmental factors such as ultraviolet rays, rainwater and sand, and prevent water from penetrating into the substrate, thereby significantly prolonging the service life of the rain cover.

[0029] In addition, the pre-coated plate can be selected from one or more of double-sided galvanized steel plate, aluminum-zinc plated steel plate or zinc-iron alloy plate. These plates have good corrosion resistance and can meet the performance requirements of the rain cover during long-term use, among which the aluminum-zinc plated steel plate has the most significant effect on corrosion resistance.

[0030] Pre-coat 0.01mm-0.03mm thick epoxy resin on the galvanized aluminum plated steel sheet, although the galvanized aluminum plated steel sheet itself has excellent corrosion resistance, but in the process of stamping, the metal coating will be stretched, extruded and even micro-cracks, its corrosion resistance will be damaged to some extent, and the epoxy resin coating can form a continuous and dense protective layer to prevent water vapor, oxygen and other corrosive media from directly contacting the steel sheet, thereby reducing the damage to the original coating caused by stamping. In addition, the thickness of 0.01mm-0.03mm is the optimal choice that ensures effective corrosion prevention while taking into account the production cost and product precision requirements.

[0031] S2, integrated composite stamping: the sheet is sent into a composite die, which is provided with a drawing area, a trimming area and a flanging area, so that the drawing, trimming and flanging processes of the rain cover are completed in one set of die, reducing process transfer and greatly improving the precision and consistency of the rain cover during stamping.

[0032] a, preforming: the punch descends in the drawing area of the die and cooperates with the concave die to complete the first drawing of the main body of the rain cover, the drawing speed is 80-120mm / s, the blank holder force is set to 180-220kN, and the drawing coefficient is 0.52-0.55, so that the main body of the rain cover is formed close to the final profile.

[0033] Due to the complex shape of the rain cover, a whole main body profile is formed by one drawing to replace the structure formed by welding multiple small parts in the traditional stamping process, thereby greatly reducing the number of welds on the rain cover. Compared with multiple drawing, one drawing can avoid wrinkles, micro-cracks, uneven thickness and other defects on the surface of the rain cover, thereby significantly improving the overall quality and performance of the rain cover.

[0034] At a drawing speed of 80-120mm / s, the material flow can be relatively balanced during drawing, thereby reducing the flow resistance of the material in the die and improving the forming quality. The blank holder force is set to 180-220kN to apply sufficient pressure to the edge of the material to prevent wrinkles.

[0035] The drawing coefficient is an important parameter for measuring the deformation degree of the material during drawing. The drawing coefficient in the range of 0.52-0.55 can make the material obtain an ideal deformation degree during drawing, so that the main body of the rain cover is formed close to the final profile, while avoiding problems such as material rupture caused by excessive stretching.

[0036] b, precise trimming: negative clearance trimming process is adopted, the clearance value is-0.02mm--0.05mm, the R angle of the concave die blade edge is 0.02mm-0.05mm, and the cooperation of the punch and the concave die makes the sheet be stretched, thinned and separated under a very small gap.

[0037] Traditional trimming process between the male and female dies has a reasonable gap, and the cross section will have a collapse, bright band, fracture band and burr; while the negative gap trimming male die diameter is greater than the female die diameter, that is, the gap is negative, the male die goes down through the extruded plate, which is stretched and thinned at the female die port and finally separated, so as to ensure that the cross section has no fracture band and the burr is very small or even no burr.

[0038] Under the gap of-0.02mm to-0.05mm, the extrusion of the male die on the plate is more uniform, so that the material is uniformly stretched and thinned at the female die port, thereby realizing more uniform trimming effect; and the smaller R angle can effectively reduce the stress concentration in the trimming process, avoid material rupture or burr due to stress concentration, and thus help the edge of the part to be smoother, wherein the R angle of 0.02mm to 0.05mm can make the trimming process more stable, reduce the uneven trimming phenomenon caused by too sharp or too smooth blade edge, and ensure the consistency of the trimming quality of each part.

[0039] In addition, the negative gap trimming ensures that the profile edge of each stamped part is accurate and has less burr. When two parts to be welded are spliced together, their trimmed edges can fit together tightly with almost no gap. The very small burr means that a special deburring process may not be needed, simplifying the production process and reducing costs and part collisions.

[0040] The negative gap trimming adopts a stepped blade edge structure, which includes a shearing zone, a stretching zone and a separation zone in sequence. The shearing zone is the starting part of the blade edge and is mainly used for cutting into the plate. The blade edge angle of 20° to 25° provides a relatively sharp wedge angle, which can quickly break through the material surface at the initial stage with low stamping force, helping to reduce stamping noise and vibration, and the blade edge angle design of 0° to 2° can reduce the generation of burrs during shearing, making the trimming more smooth.

[0041] Further, the stretching zone is responsible for guiding the material to stretch and thin, and the blade edge angle is reduced to 8° to 12°, making the wedge more gentle, increasing the contact area with the material, and cooperating with the blade edge rake angle of-2° to 0°, making it like a "horn mouth", which produces an inward extrusion and gathering of the flowing material.

[0042] In addition, the separation zone is responsible for completing the final precise separation of the material. The very small blade edge angle (2° to 5°) makes it nearly parallel to the stamping direction, making its contact area with the material maximum, further optimizing the stress distribution, and the larger negative blade edge rake angle (-5° to -2°) produces the strongest extrusion effect, which applies a large compressive stress state to the material in the last moment before separation, resulting in a perfect cross section quality with very small or even no burr.

[0043] c. Flanging: the flanging punch inside the die starts to act, and the edge of the cut workpiece is folded upwards to form a standing edge with a height of 8-12 mm, which significantly increases the bending deformation resistance of the part, i.e. improves the overall rigidity and stability of the workpiece;

[0044] S3. Shaping: the workpiece is calibrated through the joint action of the punch, the die and the flanging module.

[0045] Comparative Example

[0046] The present comparative example discloses a conventional rain cover stamping forming process, which comprises the following steps:

[0047] S1. Blank preparation: select a common steel plate with a thickness of 0.8-1.2 mm, and perform pretreatments such as uncoiling, flattening and shearing on the steel plate.

[0048] S2. Main body forming:

[0049] a. First drawing

[0050] The plate is sent into the drawing die to perform the first drawing of the rain cover main body. In order to avoid cracking, a larger drawing coefficient (usually 0.58-0.62) is used, and the formed workpiece has a shallow depth and does not reach the final profile.

[0051] b. Second drawing: the semi-finished product after the first drawing is moved to another set of dies to perform the second drawing, so as to reach the required final depth and profile of the product.

[0052] c. Deburring and punching: the workpiece after drawing is transferred to a trimming machine, and a conventional positive clearance blanking method is used to trim the edge to obtain the final profile.

[0053] S3. Flanging and shaping: the workpiece after trimming is moved to the flanging die, and then flanging and shaping are performed to calibrate the shape of the workpiece.

[0054] S4. Welding and splicing: the parts after stamping and forming are moved to the welding station, and the parts are spliced by welding.

[0055] The application discloses application effects of an integrated stamping forming process and a traditional stamping forming process in production of a rain cover, and mainly analyzes significant influences of the two on a number of welds of the rain cover, process quality, and production efficiency. In the comparative example, the traditional stamping forming process adopts multiple sets of dies to perform multiple deep drawing operations, not only significantly increasing the number of welds of the rain cover, but also greatly reducing the overall production efficiency due to factors such as complex processes and frequent die replacement; and a trimming process of the traditional stamping forming process adopts a conventional positive clearance blanking mode, and defects such as more section burrs, easy occurrence of a collapse or deformation, and the like are prone to occur, seriously affecting appearance quality and sealing performance of the rain cover. Therefore, the importance of the stamping forming process adopting integration and cooperating with a negative clearance trimming process to reduce the number of welds of the rain cover to improve waterproofness and reduce section burrs and prevent deformation is highlighted.

[0056] II. Determination results

[0057] Table 1 Comparison results of various indexes of different stamping forming processes

[0058] Example Comparative Example Number of main processes 3 4 Number of mold changes 0 3 Weld length (mm) 0 150 Weld number (strip) 0 Multiple Burr height (pm) ≤10 ≥50 Burr occurrence rate (%) 5% 30% Cut roughness (pm) ＜1.6 3.2～6.3 Dimensional accuracy (mm) ±0.1 ±0.2 Single piece production time (sec) 15 25

[0059] The number of processes is an important index for measuring complexity and efficiency of a production process. The main process number of the embodiment is 3, and the process number of the comparative example is 4, which shows that the embodiment is more concise in the process. The reduction of the process in the stamping forming process is directly related to the improvement of the production efficiency, and each reduction of the process can reduce the corresponding equipment use, the operator demand and the time consumption. This shows that the embodiment significantly improves the production efficiency of the rain cover by integrating multiple processes through the integrated composite stamping forming technology.

[0060] The number of die changes is mainly affected by the number of processes. As shown in Table 1, the number of die changes of the embodiment is 0 times, and the number of die changes of the comparative example is 3 times. In the embodiment, since an integrated composite die is adopted, multiple processes can be completed in one die, and frequent die replacement is avoided, thereby further improving the production efficiency.

[0061] And the increase in the number of die changes is easy to cause the increase in the number of welds. In terms of the number and length of welds, the number of welds of the embodiment is 0, and the number of welds of the comparative example is multiple. The reduction of the number of welds is directly related to the improvement of the product quality, because the weld is a potential weak point, which may affect the strength and durability of the product. The embodiment reduces the welding process through the integrated forming technology, thereby reducing the number of welds and avoiding quality defects and additional processing costs caused by welding.

[0062] The large number of welds can easily lead to the increase of defects such as burrs, deformation and roughness. The burr height and occurrence rate refer to the protruding height of the processing edge residue and its frequency. In the embodiment, the burr height is ≤10 μm and the occurrence rate is 5%; while in the comparative example, the burr height is ≥50 μm and the occurrence rate is 30%, which indicates that the burr height and occurrence rate of the rain cover in the embodiment are lower, and the processing technology is more precise. The lower burr height means that the cross section after blanking is smoother, and since the negative clearance trimming process is used in the embodiment, trimming can be completed under a very small clearance, thereby effectively reducing the generation of burrs.

[0063] The burr height and occurrence rate greatly affect the roughness of the cut. In the embodiment, the cut roughness is <1.6 μm, while in the comparative example, the cut roughness is 3.2-6.3 μm, which indicates that the cut quality in the embodiment is higher and the secondary processing requirement is reduced. The lower roughness means that the cut is smoother, which helps to improve the appearance and functionality of the product, indicating that the embodiment achieves more precise cut processing through precise mold design and process control.

[0064] The roughness directly affects the dimensional accuracy, which refers to the allowable deviation range of the actual size of the part from the design size. In the embodiment, the dimensional accuracy is ±0.1 mm, while in the comparative example, the dimensional accuracy is ±0.2 mm, which indicates that the accuracy in the embodiment is higher, and the improvement of the dimensional accuracy is directly related to the accuracy and consistency of the product. Higher dimensional accuracy helps to reduce assembly problems caused by dimensional deviation, thereby improving the assembly quality and overall performance of the product.

[0065] The number of main processes and the number of mold changes directly affect the production efficiency of the rain cover, while the number and length of welds and the burr occurrence rate indirectly affect the production efficiency. As shown in the table, the single-piece production time in the embodiment is 15 seconds, while the single-piece production time in the comparative example is 25 seconds, which indicates that the efficiency in the embodiment is higher and the production capacity is increased by about 40%. The reduction of single-piece production time is directly related to the improvement of production efficiency, and shorter production time means that more products can be produced in the same time, indicating that the production efficiency in the embodiment is higher than that in the comparative example.

[0066] In summary, the embodiment significantly improves the production efficiency and product quality by simplifying the process, reducing the number of mold changes, reducing the number of welds, reducing burr generation, improving cut roughness and dimensional accuracy, and shortening the single-piece production time, while reducing potential problems in the production process. This not only improves the market competitiveness of the product, but also brings higher economic benefits to the manufacturer.

[0067] It is to be understood that the terminology "including", "comprising", or any other variation thereof, is intended to cover a non-exclusive inclusion such that process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises a... " does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0068] The preferred embodiments of the present application have been described above with the intent to enable those skilled in the art to make and use it. Various modifications to these embodiments will occur to those skilled in the art and are intended to be encompassed by the present application. The modifications are being considered as within the scope of this application as defined by the appended claims.

Claims

1. A stamping process for a rain cover, characterized in that, Includes the following steps: S1. Blank preparation: Select pre-coated steel plates with a flat surface, no scratches, and a thickness of 0.8 to 1.2 mm, and perform uncoiling, leveling, and shearing. S2, Integrated Composite Stamping: The sheet metal is fed into a composite mold, which is equipped with a drawing zone, a trimming zone, and a flanging zone. a. Pre-forming: The punch moves downward and cooperates with the die to complete the first deep drawing of the main body of the rain cover, so that the main body of the rain cover is shaped to be close to the final outline; b. Precise edge cutting: The negative clearance edge cutting process is adopted, and the cooperation of the punch and die is used to stretch, thin and separate the sheet material under negative clearance conditions. c. Flanging: The flanging punch located inside the mold starts to move, folding the edge of the cut workpiece upward to form a vertical edge with a height of 8-12mm; S3. Shaping: The workpiece is calibrated through the combined action of the punch, die, and flanging module.

2. The stamping process for a rain cover as described in claim 1, characterized in that, In step S1, the pre-coated sheet is one of double-sided galvanized steel sheet, double-sided aluminum-zinc coated steel sheet, or double-sided zinc-iron alloy sheet.

3. The stamping process for a rain cover as described in claim 2, characterized in that, The pre-coated sheet is a double-sided aluminum-zinc coated steel sheet, and the double-sided aluminum-zinc coated steel sheet is coated with epoxy resin, the thickness of which is 0.01mm to 0.03mm.

4. The stamping process for a rain cover as described in claim 1, characterized in that, In step S2a, the drawing speed of the first drawing is 80-120 mm / s, and the blank holder force is set to 180-220 kN.

5. The stamping process for a rain cover as described in claim 1, characterized in that, In step S2b, the gap value of the negative gap cutting edge is -0.02mm to -0.05mm, and the radius of the die cutting edge is 0.02mm to 0.05mm.

6. The stamping process for a rain cover as described in claim 1, characterized in that, The negative clearance cutting edge adopts a stepped cutting edge structure, which includes a shearing zone, a stretching zone, and a separation zone in sequence.

7. The stamping process for a rain cover as described in claim 6, characterized in that, The cutting edge angle of the shearing zone is 20° to 25°, and the cutting edge rake angle is 0° to 2°; the cutting edge angle of the stretching zone is 8° to 12°, and the cutting edge rake angle is -2° to 0°; the cutting edge angle of the separation zone is 2° to 5°, and the cutting edge rake angle is -5° to -2°.

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