Papers by Keyword: Negative Clearance

Abstract: The fine blanking with negative clearance is a process with characteristic of the high blanking precision and the better fracture quality, so the blanking fracture surface structure are intensity. This paper has carried on the contrast and analysis between common blanking and the fine-blanking with negative clearance fracture face and burrs zone cavity metallographic and further indicated the different process blanking work-piece fracture face characteristics, illuminated the anti-corrosion of blanking fracture surface between different blanking process by using corrupt principium. The anti-corrosion of blanking fracture face could enhance wear resistance of blanking work piece evidently. Therefore, it could improve fatigue strength and the working life of work piece greatly.

Abstract: The stainless steels are used more and more in blanking process. To further enhance the quality of blanking fracture surface, this paper made the related experiments of fine-blanking with negative clearance in stainless steel. Through the comparison analysis between the fine-blanking microstructure and common blanking one with stainless steel, the result points out that the fine-blanking with negative clearance inhibit the warping in common blanking, make the work-hardening of material fracture surface improves, and which can have a more positive effect for the fine-blanking with negative clearance. Meanwhile, the work-hardening capacity of two blanking methods was different, and it can enhance the punching section entire strength commendably by fine blanking with negative clearance.

Abstract: In order to improve the punching process, further enhance the blanking section quality. This paper studied the common blanking of 60Mn and the fine blanking with negative clearance of 60Mn blanking work piece metallographic structure by using scanning electron microscope. The results show that the fine blanking with negative clearance process can increase the work-hardening degree and further thin the punching surface tissue, inhibit the crack, and make the blanking surface smooth. The tensile and tear result in the generation of cracks and burrs, and the extrusion forming of fine blanking with negative clearance inhibit the generation of cracks, and eliminate the conditions of the burrs. As the extrusion process, the degree of work hardening in fine blanking with negative clearance is higher than the common blanking, the organizations are more closed.

Abstract: This paper has established geometry model of the rigid-plastic Finite Element Model (FEM) basing on the foundation of similarity theory. It has simulated and analyzed the material of ASTM-Gr.D used by finite element analysis software of metal plastic DEFORM with different negative clearance values blanking, which obtains the caver of the different negative clearance values with roll-over with sheared zone with punching load. According to the result of simulation, it has made an experiment on the ASTM-Gr.D of 2.0(mm) thickness with the different negative clearance, and obtained samples with sheared well and no burr, which summarized that it could achieve no burr in fine blanking when the values of negative clearances value took -0.1 ~ -0.3mm.

Abstract: Being an important blanking parameter, the blanking allowance of fine-blanking with negative clearance has a direct relationship with the quality of work piece and ejector force. The full process of fine-blanking with negative clearance for ASTM-1022 in different blanking allowances is simulated through the finite element analysis software DEFORM-2D, then the ejector force under different blanking allowances is measured through the experiment of fine-blanking with negative clearance. Based on the analysis of the ejector force, the proportion of burnish band and the work piece fracture, the following conclusions are summarized. The size of blanking allowance is not related with the blanking force with the sheet entering plastic state and the maximum blanking force, and is only related with the ejector force. When the value of the blanking allowance is between 0.1mm and 0.3mm, the friction force between the punch-die and the sheet affects ejector force, and the ejector force is not related with the mechanical properties of material. When the value of the blanking allowance is between 0.5mm and 0.8mm, with the blanking allowance increasing, the ejector force increases rapidly.

Abstract: Machining experiments of fine-blanking with negative clearance show that the blanking force is very different from ordinary blanking in different blanking stages. Studying on the blanking force size of fine-blanking with negative clearance in different blanking stages is a very important significance for studying die wear and analyzing the state of material stress-strain. Firstly, numerical simulation and stress state analysis of the fine-blanking with negative clearance are carried out, with DEFORM-metal forming finite element analysis software. Afterward the relationship curve of blanking force and stroke are measured, and the blanking force with different blanking stages of fine-blanking with negative clearance is analyzed by the simulation and the experiment. The analysis result shows that the simulation blanking force is bigger than the experimental result (error about 15%), but the blanking force variation tendency is accordant. while the punch pushes down within 0.1mm, the blanking force changes quickly. The metal sheet will enter into the state of plastic deformation after the blanking force reaching maximum value. Along with the punch continues to move down, the area of shear zone is decrescent so that the blanking force inches down, and the blanking force reaches a certain value in the place of blanking allowance value finally. With punch pushing the metal sheet to enter the plastic state and punch downward the place of the allowance value, the metal sheet sustained the big blanking force all the time as well as the deformation zone material keeps the plastic deformation. The research result provides theoretic reference and the experimental data for the practice application of fine-blanking with negative clearance, and has instructive significance and reference value to mould design.

Abstract: Fine-blanking with negative clearance is a kind of fine blanking processes. The punch size of fine-blanking with negative clearance is larger than the die size. The paper does lots of simulations for the changes of blanking force in fine-blanking with negative clearance and common blanking by DEFORM software, and the blanking force curves are gained by these experiments. The changing principle of blanking force and internal material is obtained through the simulation and experiments. The result shows that simulation blanking force of AISI-1045 is lager than the actual blanking force. According to the curves derived from experiments, we can see that the maximum blanking force of fine-blanking with negative clearance is higher than common blanking force. Compared with fine-blanking with negative clearance, the common blanking force reduces faster after the blanking force reaches maximum value. The experiment result shows that the force of fine-blanking with negative clearance under a smaller blanking clearance is a bit bigger than the force of common blanking force, and the blanking quality of fine-blanking with negative clearance is much better than that of common blanking. Cracks can be closed effectively by the special squeeze forming in fine blanking with negative clearance. Then, the crack can not expand continuously, and the bonding force is enhanced. The squeeze forming can restrain intergranular deformation and reduce the damage. However, the stretch forming easily leads to the inner crack and defect of materials. By means of the analysis on experimental curves, the paper further studies the changing law of fine-blanking with negative clearance blanking force.

Abstract: The plastic analysis software DEFORM was used to simulate the blanking process of metal plastic without burr. Based on theory of the rigid FEM, the geometry model used for blanking with a negative clearance was established. The facts of influence the quality of the blanking work pieces were analyzed and concluded, at the same time, the parameters were indicated to improve the quality of the blanking work pieces. Through the experiment, the blanking load was measured with different clearance, thickness and material in group. The reciprocity between these facts was analyzed and the clearance was optimized. After the blanking load was regress analysis, the coefficient of the load and these facts were researched. Using quality analysis of the work pieces in the experiment, the thickness and the material were obtained which were suitable for blanking of metal plastic without burr. The reactions which were used to separate the metal were studied, which offered thereunder for proper remaining based on the better quality and smaller blanking load.

Abstract: The workpieces of fine blanking with negative clearance were obtained through the fine-blanking with negative clearance processing experiment. The fractography photographs of workpieces shearing surface were scanned by scanning electron microscope (SEM), and the characterization parameters and quality standard of workpieces shearing surface with negative clearance were analyzed in the processing of blanking. According to the characterization parameters and quality standard of workpieces shearing surface with negative clearance, the workpiece with the length ratio of burnish band, deflection error, rollover error and blanking burr were analyzed qualitative. The findings have a certain reference value to the blanking related profession.

Abstract: The hardening layer of blanking boundary could enhance structure intensity and wear resistance of blanking work piece evidently. Therefore it could enhance fatigue strength and the working life of work piece greatly. This paper carried through fine-blanking with negative clearance processing experiment for the sheet with different hardening index and measured the blanking force and the punch stroke relations curves. The micro hardness of the blanking work pieces sheared surface were measured by Vickers Hardness instrument(MH-6), which obtained the relations curves of punch stroke and the micro hardness of the blanking work pieces. The level of working hardening were compared with different hardening index materials by fine-blanking with negative clearance, and the blanking work pieces working hardening were enhanced evidently by fine-blanking with negative clearance.