The metal stamping process of the middle face shield bracket is: blanking punching - punching incision - flanging forming - incision - flanging. There are various forms of tearing and skewing during the forming process of the middle armor bracket, and the tearing parts are mainly distributed in the hole shape of the part, the junction of the R arc at the corner of the side wall and the wall neck, etc., due to stamping and production Due to the difference in process conditions, the proportion of each fracture site is different. The tear can be a one-time forming tear, or it can be caused by the development of a fatigue crack, that is, an invisible crack. Analysis of the cause of the tear:

    According to the actual situation on site, by checking the tearing part, fracture shape and degree of crushing of the part, it is considered that the tearing and skewing of the part are mainly reflected in the flanging forming process. The reasons for this phenomenon are as follows:

    1. Insufficient implementation of forming process parameters

     During the forming process of the part, the process requires that the die, the pressing core and the parts of the two must be closely bonded together, and the plastic deformation of the sheet is pressed when the machine tool slides down to realize the forming. But now, due to the shortcomings of the pressed parts such as unstable quality, it means that the pressure of the machine tool is in a state of unbalanced pressure jump during the production process. The main reason is that the processing technicians did not adjust the machine tool pressure in time according to the process specification requirements at this stage, or did not communicate the machine tool pressure stability information with each other during the handover of each shift, resulting in poor product quality. Stablize.

    2. Design defects of flanging forming die

    This mold is common for left and right pieces with one mold and two cavities. In addition to flanging, the content of this process also includes shape forming content. In addition, the parts are special and complicated, and the bending surface is narrow. The forming requires that the pressing core of the die should match the forming surface As a result, the structural conditions of the mold have a large forming stroke and a small pressing area. In the initial mold design, the designer only considered the small binder surface, but ignored the following design defects in the guide slide stroke of the binder core forming:

(1) The guide length of the binder core is designed to be 125mm, and the actual guide length is 115mm. Although it is within the design range, there is a 115mm movement of the lifting part that exceeds the effective guide length by 10mm. standard disadvantages.

(2) For a forming height of up to 115mm, a special guide plate needs to be designed, which cannot be guided by the sliding gap between the processing surface and the side wall of the die. If it is not effectively eliminated, the guide gap will increase due to long-term wear after mass production, and the normal guide effect of the mold will be lost in advance, resulting in vicious quality accidents.

   3. There are errors between mold processing parts and drawing design

    For example, clearly mark the area that needs to be processed. However, since the pressing core is a complex surface, the guide surface is machined after the casting is formed, resulting in a gap error after the machining surface and the guide surface of the die are slippery, and the left/right side of the pressing core appears during the normal operation of the mold. Swing right.

    Before the part is formed, the positioning is carried out by the positioning pins and holes on the upper plane of the pressing core, which requires that the pressing core must ensure stable, reliable and correct sliding during the forming of the part, otherwise the part will fail during forming. Stable, so that the pressing core and the die wall collide and squeeze, causing the workpiece to generate tensile stress. When the strength limit of the material is exceeded, the workpiece will be torn and skewed. In addition, if other factors are considered in the mold structure, and the use of special guide slides is ignored, there is a danger that the guide gap will be destroyed instantly after the two parts are extruded strongly and the guide gap cannot be correctly guided.

    Since the guide gap of this structure is a debugging slip fit gap, once damaged, there will be no more effective adjustment means, which will affect the forming quality of the part for a long time and bring safety hazards. Moreover, instead of using a special guide slide plate at the guide part, a mutual guiding structure of the processed profiles is used. There is a defect that it cannot be adjusted after the gap is too large, resulting in tearing and skewing of the workpiece.