What are the influences of mold structure on automobile stamping parts?

2023-07-11 08:37:01

Among the many factors that affect the quality of automotive stamping parts, the influence of mold structure is very large. The forming effect of the deep-drawing part is directly affected by factors such as the radius of the die, the geometry of the work piece of the die, the way the die is guided, the setting of the drawing rib (groove), and the size of the air hole in the die.

Determines the radius of the punch and die fillets. The radius of the punch and die plays an important role in obtaining the ideal deep-drawn part. The two main defects of cover drawn parts are wrinkling and stretch cracking. When the punch radius is too small: the bending deformation of the straight wall and the bottom of the billet increases, and the strength of the dangerous section is weakened;

When the die radius is too small, the tensile stress on the side wall of the blank will increase accordingly. Both of these situations will increase the draw factor and the deformation resistance of the sheet, resulting in an increase in the total drawing force and a decrease in die life.

If the punch or die radius is too large, the deformation resistance of the sheet is small and the fluidity of the metal is good, but it will reduce the effective area of blanking and make the parts easy to wrinkle. Therefore, when determining the radius of the punch and die, the deformation characteristics of the workpiece and the drawbead must be considered.

The geometry of the working part of the mold. The working parts of the mold with different shapes will also affect the quality of the drawn parts. The die is divided into flat die and conical die. The use of conical dies generally results in a greater resistance to instability in the deformation zone of the blank, allowing relative thickness (t/D) relative to flat-ended dies. Smaller blanks will not wrinkle.

Die-guided mode. The guidance of the drawing die includes two directions: the punch and the blank holder, and the blank holder and the blank holder. The rationality of the mold guide rail directly affects the reliability of drawing. A reasonable and stable guide rail can ensure the uniformity of the circumferential gap of the mold and the cooperation of the drawing surface, thereby ensuring the quality of the drawn part.

Ordinary drawing dies are mostly guided by guide plates or guide pillars, but for drawing dies with large lateral forces during the drawing process (referring to workpieces with asymmetrical structures), back block guide devices can be used for guidance. The convex ribs are generally arranged in the blank frame, corresponding to the groove on the surface of the die, that is, the concave ribs. The convex rod can also be arranged on the surface of the mold, and the concave rod can be arranged on the blank holder ring.

The role of drawbeads. 1. Strengthen the ability of materials to control the flow of materials. 2. Increase the feed resistance, make the blank bear enough tensile stress, improve the rigidity of the drawn part, and reduce the surface defects caused by springback. 3. Expand the adjustment range of blank holder force.

First of all, you need to know that the main function of "Spinnaker's Bar" is to increase the resistance of the material, so "Brim Holder" also plays the same role, these two are complementary and can reduce the hold down force to adjust the resistance of the Big Triangle Sail bars serve the same purpose.

Drawbead (groove) settings. The setting of the drawbead can increase the feed resistance of the corresponding part on the stamping surface and adjust the flow direction of the blank. However, if the position, number and shape of the drawbeads are not selected properly, a satisfactory cover cannot be drawn. In general, the number and location of drawbeads mainly depend on the shape of the cover layer, undulation characteristics and drawing depth.

For parts with large deep drawing, 1-3 deep-drawing beads are placed on the straight line part, and no deep-drawing bead is placed on the arc part. When the drawing of each part of the same part is quite different, the deep drawing part does not have deep draw ribs, and the deep draw ribs must be provided with shallow ribs. The direction of the drawbeads must be perpendicular to the flow direction of the blank.

Whether the drawbead is placed on the press cloth of the blanking ring or the press cloth of the die depends on whether the die is easy to adjust on the press. The drawbead is generally placed on the upper pressing surface, and the drawbead groove is placed on the lower pressing surface, which is convenient for material positioning. In order to ensure the reliability of the mold, it is often necessary to verify and adjust the drawbeads designed on the mold during the mold debugging process.