Design Considerations for Stamping and Drawing Die Structure

Problems that should be paid attention to in the design of automobile drawing dies.

Compared with general stamping parts, automobile coverings have the characteristics of thin material, complex shape, mostly space curved surface, large structure size and high surface quality requirements.

In the automobile covering parts, the covering parts with a simple shape and shallow depth are generally formed by a single-action press; a double-action press must form the covering parts with complex shapes and deep depth. This is because the pressing force of a single-action press is obtained by the oil cylinder or air cushion under the machine tool. The pressure and stroke of the oil cylinder (or air cushion) are much smaller than those of a double-action press, which can’t provide the forming force required for the complex deep drawing parts with large pressing force and stroke. Secondly, the drawing circle of the single-action press is relatively thin and rigid, and it cannot adapt to forming complex deep drawing parts.

The structure of the drawing die used in double-action press is relatively simple, mainly composed of three major parts (convex die, concave chess and press ring) or four major parts (convex die, convex die and press ring).

It is mainly composed of three major pieces (convex die, die holder, concave die and press ring) or four major pieces (convex die, die holder, concave die and press ring). This type of drawing die is in the form of a positive assembly, with the convex die and the press ring on top.

They are mounted on the inner and outer slider of the press, respectively, and the concave die is mounted on the bottom, directly on the lower table mat. The convex die, the press ring, the concave die, and the press ring are each equipped with an inner die.

The inner and outer guiding devices are installed between the convex die, the press ring, and the concave die and the press ring, respectively. The contour size and closing height of the die must be strictly adapted to the requirements of the press.

The design should be decided carefully.

Among the cover parts on the car (standard trim), there are 13 stamping parts, which are external surface parts.

Two surrounds: left/right side surround

Four wings: left / right front wing, left / right rear wing

Four doors: left/right front door outer panel, left/right rear door outer panel

Three covers: top cover, engine cover outer panel, luggage compartment cover outer panel.

In addition to the 13 kinds mentioned above of external surface parts, the car on the cover includes the front floor, rear floor, front fender, engine cover plate, luggage compartment cover plate, four doors inside the plate and so on.

The requirements of the covering parts are as follows.

(1) The size and shape should be by the inspection tool, and the sample parts matched by the welded fitment.

(2) Good surface quality. The surface of the outer covering part (especially the outer covering part of the car) is not allowed to have ripples, wrinkles, dents, scratches, scrapes, indentations and other defects; the prism should be clear, straight, the surface should be a smooth and uniform transition.

(3) Good rigidity. Covering parts in the forming process, the material should have enough plastic deformation to ensure that the parts have sufficient rigidity.

(4) Good processability. Covering parts should have good stamping and welding process performance to reduce the production cost of stamping and welding. Stamping processability mainly depends on whether each process, especially the drawing process, can be carried out smoothly and in stable production.

The movement process of drawing

Classification of drawing dies

Single-action drawing (outer-directed drawing, inner-directed drawing), double-action drawing, triple-action drawing, angle-cutting drawing, drawing with side shaping

Design convex die, concave die and crimp ring working part

Bar thickness requirements: 50MM for the type surface, 40MM for the force bar, and 30MM for other bars

Design of the working part of the concave die

Design of the working part of the crimped circle

(1) The shape of the working part of the crimped circle is cut out with the type surface and the parting line

(2) Determine the outline of the working part of the crimped circle with 10-20MM outside of the blank line (same as the concave die)

(3) Determine the height of the edge

The height of the press surface is generally 50MM when the surface is two-dimensional.

The press surface is three-dimensional and is generally 60MM in height.

(4) to make the stressing bar


Check the stroke of the drawing die and determine the number and position of the air top

Stroke of the crimped circle of the drawing die〉maximum drop after the drawing of part +20mm

The number of air roof = crimping force / single air roof force (3T-4T) + the number of safety (0-4)

Arrangement of air roof position

(1) Ensure that the air tops are evenly distributed on the outside of the parting line and as close to the parting line as possible

(2) Try to ensure that 300MM is evenly distributed

(3) Try to ensure the balance of forces

(4) Layout of adjusting pads and upsetting pads

Arrangement of a header block (lower die)

(1) Try to ensure 400MM is evenly distributed

(2) At least 4 pressure-adjusting pads and adjusting pads on to ensure balance

(3) In addition to maintaining the balance of the pad, try to make the adjusting pad close to the parting line

Determine the mold size, guide leg size and guide plate size position

Determine the mould size

(1) Transfer into the template, adjust the closing height, mold length and width

(2) Determine the operating mold height

(3) Determine the size and position of mold lugs, lifting bars, and flip sets

Determine the size of the guide leg

(1) The width of the guide leg should be at least 1/3 of the overall width, preferably about 2/5

(2) Determine the amount of edge of the guide leg

Size and position of the die guide plate

(1) For two guide plates in one direction, the installation position of the guide plate is about 1/6 of the length of the die.

(2) The width of the guiding surface of the guide plate is about 1/5-1/4 of the length of the die.

(3) The height of the guide plate is 〉60mm of the stroke of the crimped circle.

Determine the press core air top joint column and the second layer of the lower die plate

Determine the air top joint column

(1) the maximum height of the air top joint pillar = 2 x the diameter of the joint pillar

(2) the contact area of the air top joint pillar〉3/4 (the whole garden area of the joint pillar)

Determine the second layer of the lower mold plate

(1) careful consideration of the height of the guide plate on the crimping circle, the height of the air top joint column also confirms the height of the bottom plate of the press core, plus the installation space of the upsetting pad, then determine the height of the second layer of the plate

(2) Also consider the overall strength of the lower die and the space for lifting devices (lifting lugs, lifting rods, etc.)



Determine the press core limit range and blank feeding and positioning device

Determine the limit range of the press core

(1) Generally, the range is limited by the receding screw, and the outer guiding box type guiding mold uses the range limit plate.

(2) Limit range distance = press material core stroke + (10mm-20mm)

(3) generally choose 4 cloth in the four corners of the force balance

Determine the positioning of the feeding parts

(1) the left and right sides of the parts use more positioning guide plate positioning

(2) the front and rear of the parts are mostly positioned with positioning Jian, but the parts are too long to use the positioning plate positioning

(3) Manual line parts up and down more using the upper and lower material frame