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The Deep drawing forming process is a press working method of forming a flat blank into an open hollow part by using a mold. Drawing is one of the main stamping processes and is widely used. Through the Drawing process, cylindrical, rectangular, stepped, spherical, conical, parabolic and other irregularly shaped thin-walled parts can be made. If combined with other stamping processes, more complex shapes can be produced.

Drawing and forming of products using stamping equipment, including: drawing, re-Drawing, reverse Drawing, and thinning and drawing. Drawing: Using a platen device, a part or all of the flat material is pulled into the concave mold cavity by the punching force of the punch to form the bottomed container. The processing of the side wall of the container in parallel with the Drawing direction is a simple drawing process, and the drawing processing of a conical (or pyramidal) shaped container, a hemispherical container, a parabolic surface container, etc., further includes a Drawing process.

Re-Drawing: that is, a deep-drawing product which cannot be completed by one-time drawing processing, it is necessary to re-stretch the stretched formed product to increase the depth of the forming container.

Reverse drawing processing: The drawn workpiece in the previous step is reverse-stretched, and the inside of the workpiece becomes the outer side, and the outer diameter thereof is made smaller.

Thinning and drawing process: the formed container is extruded into a concave mold cavity which is slightly smaller than the outer diameter of the container by a punch, so that the outer diameter of the bottomed container is made smaller, and the wall thickness is thinned, thereby eliminating wall thickness deviation, and Make the surface of the container smooth.

When using stamping equipment for metal stamping and drawing, the following 16 types are included:

1.cylinder deep drawing processing

Drawing of flanged (flanged) cylinder products. The flange and the bottom are both planar shapes, the side walls of the cylinder are axisymmetric, and the deformation is evenly distributed on the same circumference, and the blank on the flange is subjected to deep drawing deformation.

2 elliptical deep drawing processing

The deformation of the blank on the flange is tensile deformation, but the deformation amount and the deformation ratio change correspondingly along the contour shape. The larger the curvature, the greater the amount of plastic deformation of the blank; conversely, the smaller the curvature, the smaller the plastic deformation of the blank.

elliptical deep drawing processing

3. rectangular deep drawing processing

A low profile piece that is stretched once. When Drawing, the tensile resistance at the rounded corner of the flange deformation zone is greater than the tensile resistance at the straight edge, and the degree of deformation at the rounded corner is greater than the degree of deformation at the straight edge.

rectangular deep drawing processing


4. mountain shape deep drawing processing

When the side wall of the stamping part is a beveled surface, the side wall is suspended during the stamping process, and is not pasted until the forming is completed. The deformation characteristics of different parts of the side wall during forming are not completely the same.

mountain shape deep drawing processing

5 hill shape deep drawing processing

The deformation of the blank of the dome-shaped cover member during the forming process is not a simple tensile deformation, but a composite formation in which both the Drawing and the bulging deformation are present. The deformation of the blank on the binder surface is tensile deformation (radial tensile stress, tangential direction is compressive stress), and the deformation of the blank inside the contour (especially the central region) is bulging deformation (radial and tangential deformation) For pulling stress).

hill shape deep drawing processing

6. flanged hemispherical Drawing

When the spherical member is stretched, the blank is in partial contact with the spherical top of the punch, and the rest is in an unconstrained free state in which it is suspended. Therefore, the main technical problem of Drawing of such spherical parts is the severe thinning of the partial contact portion, or the unstable wrinkling of the curved portion.

7. flange drawing processing

The flange portion of the drawn product is subjected to a shallow drawing process. Its stress-strain condition is similar to compression flanges. Due to the tangential compression stress, it is easy to wrinkle, so the forming limit is mainly limited by compression wrinkles.

8. edge drawing processing

The flange portion of the pre-processed stretched product is subjected to angular re-Drawing processing, which requires the material to have good plasticity.

9. deep drawing processing

A stretched product that exceeds the limit of the Drawing process can be completed after two or more Drawings. Products that have been stretched in the depth direction of the front station are re-stretched in the depth direction. The wide flange tensile member is stretched to the desired flange diameter upon first Drawing, and the flange diameter remains unchanged after subsequent Drawing.

10. tapered Drawing

For deep cones with h/d>0.8 and α=10°~30°, the depth of the blank is large due to the large depth. The local area of ​​the contact between the blank and the punch can transmit the forming force, which is easy to cause the blank. Excessive thinning and even rupture requires a gradual formation through multiple transitions. The step Drawing method firstly stretches the billet into a stepped transition piece whose stepped shape is tangent to the inner shape of the tapered portion and finally expands to form a taper. The number of times of Drawing, the process, and the like of the step transition member are the same as those of the stepped cylindrical member.

11. rectangular re-Drawing

The high rectangular member formed by Drawing a plurality of times has a deformation which is not only different from the Drawing of the deep cylindrical member, but also greatly different from the deformation of the low box member. Figure 1-46 shows the change in the shape and size of the part during the multiple Drawing process for the multi-station automatic transfer press for high rectangular box processing.

rectangular re-Drawing

12. surface forming processing

The curved surface is formed by drawing, and the outer flange portion of the metal flat plate blank is reduced, and the inner flange portion is elongated to form a stamping forming method for a hollow product having a non-straight wall non-flat bottom curved shape.

surface forming processing

13. step Drawing processing

The left initial stretched product is subjected to re-Drawing processing to form a stepped bottom portion on the right side. The deeper portion is deformed at the beginning of the stretch forming, and the shallower portion is deformed at the later stage of the Drawing. The side wall of the step change portion is liable to induce deformation of the shear stress.

step Drawing processing

14. reverse drawing processing

The workpiece stretched in the previous step is subjected to reverse Drawing and is a type of re-Drawing. The reverse Drawing method increases the radial tensile stress and provides better results for preventing wrinkles. It is also possible to increase the stretch factor of re-Drawing.

reverse drawing processing

15. thinning and Drawing

Unlike ordinary Drawing, thinning Drawing is mainly to change the thickness of the wall of the Drawing member during Drawing. The gap between the convex and concave molds is smaller than the blank thickness, and the straight wall portion of the blank is under a large uniform compressive stress when passing through the gap, and the wall thickness is thinned during the Drawing process, the wall thickness deviation of the container is eliminated, and the surface of the container is increased. Smoothness for improved accuracy and strength.

thinning and Drawing

16 panel drawing processing

The panel product is a stamped part of the sheet with a complex surface shape. In the Drawing process, the blank is complicated to deform, and the forming property is not simply stretch forming, but a composite forming in which the drawing and the bulging are simultaneously present.

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