CN100443211C - Drawing Die Based on Variable Blank Holder Force Control - Google Patents

Abstract

The invention discloses a drawing die based on variable blank-holding force control. The lower end of the upper template is equipped with a punch, and the punch is installed in the hole of the middle plate and the binder ring. There are more than three through holes on the upper template, and the through holes are equipped with stripping screws, which are exposed on the lower end of the upper template. The feeding screw is installed in the hole of the upper spring, the middle plate and the lower spring in turn, and the end of the feeding screw is threaded with the binder ring; the center of the upper end surface of the lower template is equipped with a top spring and a "∏" shaped die, and the center of the die is Die pad is installed, the spring of the top part is on the end surface of the die pad, and there are more than three holes on the upper end of the die, and the variable blank holder rod is installed in the hole, and the variable blank holder rod is in the cavity of the die. One end is installed in the hole of the moving spring, and the variable blank holder force cams are pushed against the endpoints of the respective variable blank holder force rods respectively, and the stretching arms of the variable blank holder force cams are connected with the die pads with movable pins. Adding several mold parts can achieve variable blank-holding force control. On a general-purpose press, deep-drawing parts with simple and arbitrary changes and complex shapes can be deep-drawn.

Description

Drawing Die Based on Variable Blank Holder Force Control

technical field

The invention relates to equipment for forming sheet metal, in particular to a drawing die based on variable blank-holding force control.

Background technique

Wrinkling and cracking are the main failure modes of sheet drawing, and the blank-holder force (blank-holder force, BHF) size (or blank-holder force control curve) and loading method are one of the important factors affecting wrinkling and cracking. The traditional The blank holder force control method generally adopts the steady loading or increasing loading mode, that is, the blank holder force remains constant or increases linearly with the stroke of the punch, and the variable blank holder force (Variable bkankholder force, VBHF) control is in the sheet drawing. During the forming process, the blank holder force that changes with time is applied at different moments when the flange of the stamping part (such as a cylindrical part) shrinks, or at different positions of the flange of the stamping part (such as a box-shaped part), different pressure is applied The time-varying blankholder force can change the frictional resistance between the blank and the mold contact surface by adjusting the positive pressure of each point, increase the tensile stress in the sheet, thereby reducing the tangential compressive stress of the blank, so as to control the metal flow and avoid or Effectively suppress wrinkling and cracking in sheet forming, improve the dimensional accuracy of stamping parts, the stability of the stamping process, and the forming limit of the sheet. Which blank-holding force control curve is optimal in sheet metal deep drawing has always been a research hotspot of variable blank-holding force control at home and abroad. Judging from the research results at home and abroad, the blank holder force control curves are mainly concentrated in the following types: (1) The theoretical control curve of the blank holder force must first rise and then fall following the change of the rupture curve; The minimum blank-holding force curve when the force reaches the maximum, that is, the blank-holding force curve is a type that first decreases and then rises; (3) gradually increasing blank-holding force; (4) constant blank-holding force; (5) V-shaped blank-holding force ; (6) Decreasing blank holder force (respectively shown in Figure 1 as a, b, c, d, e, f).

According to the research results of the blank-holding force control curve, the variable blank-holding force press has been developed to control the flow of metal, avoid or effectively suppress wrinkling and cracking in sheet metal forming, and improve the dimensional accuracy of stamping parts and the stability of the stamping process. And the forming limit of the plate has a better effect. But its shortcomings are as follows:

The variable blank-holding force press can only control the variable blank-holding force for specific deep-drawing parts, such as box-shaped deep-drawing, 10 control points (as shown in Figure 2), and 10 control points for box-shaped parts The position of the blank holder cylinder is predetermined,

If this kind of press draws other shapes of deep-drawn parts (such as car doors, front wall, etc. in automobile panels), then this kind of variable blank-holder force press for deep-drawing box-shaped parts cannot be used. That is to say, the blank holder cylinder of the variable blank holder force press cannot be arranged arbitrarily with the shape change of the drawn part. At present, only according to a certain type of deep-drawing parts, a variable blank-holder force press suitable for the deep-drawing of this kind of deep-drawing parts can be developed.

The results of transforming the existing ordinary single-acting and double-acting blank-holding force presses into variable blank-holding force presses are similar to the development of variable blank-holding force presses.

From the point of view of the developed variable blank-holding force mold, the effect is not ideal. It is only suitable for small-sized deep-drawing parts such as cylindrical parts, and has a small-tonnage blank-holding machine with leakage holes on the lower table. It cannot solve the problem of arranging different variable blank-holding force mechanisms on different flange positions of large and complex deep-drawn parts such as automobile panels. For all the reasons above, no matter it is a variable blank-holding force press or a variable blank-holding force mold, it cannot be popularized in actual production.

Contents of the invention

The purpose of the present invention is to provide a drawing die based on variable blank-holding force control, which solves the problem of applying time-varying blank-holding force at different moments of stamping shrinkage, or applying different time-varying blank-holding forces at different positions of the stamping part. The variable blank holder force can realize different types of blank holder force control curves to control the drawing process.

The technical solution adopted by the present invention to solve its technical problems is to include an upper mold assembly and a lower mold assembly, wherein:

1) Upper die assembly: including middle plate, upper spring, ejection screw, lower spring, binder ring, punch, guide sleeve and upper die. The center of the lower end surface of the upper template is equipped with a punch with air holes. The punch is set in the hole of the middle plate and the hole of the binder ring in sequence from top to bottom, and forms a sliding fit with the hole of the middle plate and the hole of the binder ring. There are more than three through holes on the upper template, and each through hole is equipped with a stripping screw, and the stripping screws exposed on the lower surface of the upper template are sequentially set in the holes of the upper spring, the middle plate and the lower spring. The end of the feeding screw is threaded with the binder ring, and there are more than three through holes on the binder ring outside the retracting screw, and the lower end of the upper template outside the middle plate and the binder ring is equipped with a guide sleeve;

2) Lower mold assembly: including die, variable blank holder force rod, moving spring, pin shaft, variable blank holder force cam, die pad, top piece spring, limit ring, movable pin, positioning pin, lower template and guide post. The top piece spring is installed in the limit ring at the center of the upper end surface of the lower formwork, and the "∏" shaped die is installed on the upper end face of the lower formwork outside the limit ring. The small end of the die pad and the "Π"-shaped die form a sliding fit, the spring of the top piece is on the large end surface of the die pad, the center line of the die pad coincides with the center line of the punch, and the " There are more than three through holes on the upper end of the Π"-shaped die, and each through hole is equipped with an upper variable blank holder rod, and the small end of the variable blank holder rod extends out of the "Π" shaped die. One-to-one correspondence with the holes on the binder ring, respectively forming a sliding fit, the small end of the variable blank holder force rod in the "∏" shaped die is set in the hole of the moving spring, and more than three variable blank holder force cams are pressed against each other. At the end points of the big ends of the respective variable blank holder force rods, the variable blank holder force cam rotates around the pin shaft, and the extension arm of the variable blank holder force cam is connected with the big end of the die pad with a movable pin, and the "∏" shaped die outer The lower formwork is equipped with a number of guide posts corresponding to the guide sleeves of the upper formwork. When working, the guide posts can be inserted into the respective guide sleeve holes to form a sliding fit. At the same time, the positioning pins on the "∏"-shaped die are inserted into the pressing material. Position the ring in the positioning hole.

During the deep drawing process, the upper plane of the variable blank holder force rod just collides with the middle plate, and when the pad block of the die die moves down, the movable pin pulls down the extension arm of the variable blank holder force cam, so that the variable blank holder force cam can rotate When the pin shaft rotates, the variable blank holder force cam passes through the end point of the large end of the top variable blank holder force rod, and the variable blank holder force rod passes through the hole of the binder ring and pushes up the middle plate, so that the height of the lower spring increases or decreases, thereby Reduce or increase the pressure of the blankholder to press the sheet. The variable blank-holding force control is adopted in the drawing process.

The variable blank-holding force cam described above, when drawing a regular flange-shaped deep-drawn part, that is, a flange-shaped deep-drawn part represented by a parameter, the shape curve of the variable blank-holder force cam is the same and centered on the mold pressure Symmetrical arrangement or symmetrical arrangement of mold geometric center.

When the variable blank-holding force cam is used to draw irregular flange-shaped deep-drawn parts, that is, the flange-shaped deep-drawn parts that cannot be represented by one parameter, the shape curves of the variable blank-holding force cams are different. Variable blank-holding force cams with different shape curves arranged at different flange shape positions.

The beneficial effects of the present invention are: by designing and adding several mold parts such as the intermediate plate, the variable blank-holding force rod and the variable blank-holding force cam, the variable blank-holding force control in the drawing process is achieved and realized, and the size of the stamping parts is increased. The precision and stability of the stamping process as well as the ability to form the limit of the sheet. The present invention does not need to install a special press, has low cost and wide applicability. It can draw simple deep-drawn parts such as cylindrical parts, and can also deep-draw deep-drawn parts with arbitrary changes and complex shapes such as automobile panels. The blank-holding force that changes with time is applied at different moments when the flange of the stamping part (such as a cylindrical part) shrinks. It is also possible to apply different blank-holding forces that vary with time at different positions on the flange of the stamping part (such as a box-shaped part). Force, different types of blank holder force control curves can be realized to control the drawing process.

Description of drawings

Figure 1 shows several main types of blank holder force control curves.

Figure 2 Control points of the box-shaped piece.

Fig. 3 is a top view of the lower mold assembly in the state of non-working state.

Figure 4 is a state diagram of the drawing die based on variable blank holder force control when it is not working.

Figure 5 is the initial state diagram of the drawing die based on variable blank holder force control.

Figure 6 is a diagram of the working state of the drawing die after pressing based on variable blank holder force control.

In the figure: 1. Middle plate, 2. Upper spring, 3. Return screw, 4. Lower spring, 5. Binder ring, 6. Punch die, 7. "∏" shaped die, 8. Variable blank holder force Rod, 9, moving spring, 10, bearing pin, 11, variable blank holder force cam, 12, die spacer, 13, top piece spring, 14, limit ring, 15, movable pin, 16, sheet material, 17, Locating pin, 18, lower template, 19, guide post, 20, guide sleeve, 21, upper template.

Detailed ways

As shown in Fig. 3 and Fig. 4, the present invention includes an upper mold assembly and a lower mold assembly, wherein:

1) Upper die assembly: including middle plate 1, upper spring 2, ejection screw 3, lower spring 4, binder ring 5, punch 6, guide sleeve 20 and upper die plate 21. The center of the lower end surface of the upper template 21 is equipped with a punch 6 with air holes. The punch 6 is sequentially set in the middle plate 1 hole and the binder ring 5 holes from top to bottom, and is connected with the middle plate 1 hole and the binder ring 5 holes. To form a sliding fit, there are more than three through holes on the upper template 21 outside the punch 6, each through hole is equipped with a stripping screw 3, and the stripping screws 3 exposed on the lower end surface of the upper template 21 are sequentially set on the In the holes of the upper spring 2, the middle plate 1 and the lower spring 4, the end of the stripping screw 3 is threadedly connected with the pressure ring 5, and the pressure ring 5 outside the stripping screw 3 has more than three through holes, and the middle plate 1 And the lower end of the upper template 21 outside the binder ring 5 is equipped with a guide sleeve 20;

2) Lower mold assembly: including die 7, variable blank holder force rod 8, motion spring 9, pin shaft 10, variable blank holder force cam 11, die pad 12, top piece spring 13, limit ring 14, Moving pin 15, positioning pin 17, lower template 18 and guide post 19. The limit ring 14 in the center of the upper end face of the lower template 18 is equipped with a top piece spring 13, and the upper end face of the lower template 18 outside the limit ring 14 is equipped with a "∏" shaped die 7, and the center of the upper end face of the "∏" shaped die 7 is installed. There is a die cushion block 12, the small end of the die cushion block 12 forms a sliding fit with the "∏" shaped die 7, the top piece spring 13 is pushed against the large end surface of the die cushion block 12, and the center line of the die cushion block 12 is in line with the The center line of the punch 6 coincides, and the upper end surface of the "∏" shaped die 7 outside the die pad 12 has more than three through holes, and each through hole is equipped with an upper variable blank holder force rod 8, and a variable blank holder. The small end of the force bar 8 extends out of the "Π"-shaped die 7, and the end can correspond to the holes on the binder ring 5 one by one, forming a sliding fit respectively. The inner small end is sleeved in the 9 holes of the moving spring, and more than three variable blankholder force cams 11 are respectively supported on the endpoints of the respective variable blankholder force rods 8 big ends, and the variable blankholder force cams 11 rotate around the pin shaft 10 to change The extended arm of the blank holder force cam 11 is connected with the large end of the die pad 12 with a movable pin 15, and the lower template 18 outside the "∏" shaped die 7 is equipped with guide sleeves 20 corresponding to the number of guide sleeves 20 of the upper template 21. Post 19, during work, guide post 19 can be inserted in the respective guide sleeve hole and form sliding fit, meanwhile, the positioning pin 17 on the "∏" shape die 7 is inserted in the positioning hole of binder ring 5 for positioning.

The variable blank-holding force cam 11, when drawing a regular flange-shaped deep-drawn piece, that is, a flange-shaped deep-drawn piece represented by a geometric parameter, has the same shape curve of the variable blank-holding force cam 11 and is represented by The symmetrical arrangement of the mold pressure center or the symmetrical arrangement of the geometric center of the mold. For example, when drawing a cylindrical part, its flange shape can be expressed by a diameter parameter. On the initial flange of the cylindrical part, four variable pressure transformers with the same shape curve are arranged symmetrically with the mold pressure center (die geometric center). Edge force cam11. Or on the initial flange circumference of the cylindrical part, 3 variable blank-holding force cams 11 with the same shape and curve are set at 120° uniformly distributed at the center of the mold pressure center (die geometry).

The variable blank-holding force cam 11, when drawing a deep-drawn piece with an irregular flange shape, that is, a flange-shaped deep-drawn piece that cannot be represented by a single geometric parameter, the shape curves of the variable blank-holding force cam 11 are each Not the same, the variable blankholder force cams 11 with different shape curves are arranged at different flange shape positions. For example, when drawing a box-shaped piece, the box-shaped piece is composed of rounded corners (arc) and straight sides, and the blank shape of the box-shaped piece cannot be expanded. It is expressed by a geometric parameter, but the shape of the blank flange is basically connected by a smooth transition between a circular arc and a straight edge, and variable blank-holding force cams with different shapes and curves are respectively arranged at the circular arc and the straight edge.

The working principle of the present invention is as follows:

When the upper mold assembly has not yet descended, there is a certain difference between the lower plane of the punch 6 and the lower plane of the binder ring 5 . At this time, the upper spring 2 and the lower spring 4 have respectively reached the initial preloaded state, as shown in FIG. 3 . The upper mold assembly continues to descend until the lower plane of the binder ring 5 contacts the upper plane of the sheet 16 placed on the "∏"-shaped die 7, and then the binder ring 5 remains still, when the punch 6 goes down to When contacting the upper plane of the blank 16, the compression of the upper spring 2 and the lower spring 4 increases, and then the pressure increases and is transmitted to the blank 16, which is the initial blank-holding force of the variable blank-holding force control curve. And the upper plane of the time-varying blankholder force rod 8 just collides with the middle plate 1, as shown in Figure 5 . At the beginning of deep drawing, the force of the punch 6 pressing the plate is transmitted to the die pad 12, and the die pad 12 moves downward. There is a movable pin 15 on the large end surface of the die pad 12, which is inserted into the variable blank holder force In the chute of the extension arm of the cam 11. When the die cushion block 12 moves downward, the movable pin 15 pulls down the extending arm of the variable blank-holding force cam 11, so that the variable blank-holding force cam 11 can rotate around the pin shaft 10, and the variable blank-holding force cam 11 passes through the top variable blank-holding force cam. The end point of the large end of the force bar 8, the variable blank holder force bar 8 passes through the 5 holes of the binder ring and pushes up the middle plate 1, so that the height of the lower spring 4 increases or decreases, so that the pressure of the blank holder ring to press the sheet material 16 Decrease or increase. The variable blank-holding force control is adopted in the drawing process. Changing the shape curve of the variable blank holder force cam can complete the drawing process controlled by any blank holder force curve, as shown in Figure 6.

Cam brief design description:

(1) According to theoretical calculation or finite element simulation, the blank holder force-time curve required for the drawn part is obtained, where the time is obtained from the working speed of the press and the drawing height of the drawn part;

(2) Select a suitable spring, convert the blank holder force-time curve to calculate the spring force-time curve, and convert it into a height-time curve after the spring is compressed according to the spring force-time curve;

(3) According to the designed structure, the turning angle of the variable blank-holding force cam from the beginning of deep drawing to the end of deep-drawing is obtained, and the time for changing the blank-holding force is equal to the turning time of the variable blank-holding force cam;

(4) According to the height-time curve after the spring is compressed, the time is divided into several equal parts, and each small section of time unit has a corresponding spring height after being compressed;

(5) On the circumference of the base circle of the variable blank holder force cam, divide a number of equal parts according to the rotation direction of the variable blank holder force cam, and the number of equal parts is equal to the number of equal parts divided by the drawing time. According to the design method of the cam, according to the spatial position of the mold and the relationship between each part, when designing, ensure that the pressure generated by the compression height of the lower spring is just equal to the required pressure when the variable blank holder force cam rotates through a small angle. Corresponding blank-holding force, in this way, a continuously changing variable blank-holding force cam shape curve can be obtained.

In the specific implementation, the following problems should be solved:

1. According to theoretical calculation or finite element simulation, obtain the blank holder force-time curve required for the deep-drawing part, select the spring, determine the initial pressure, calculate the spring force-time curve according to the conversion of the blank holder force-time curve, and calculate the spring force-time curve according to the spring force- The time curve is converted into the spring height-time curve, and the angle of the variable blank-holding force cam is calculated within this time, and the equal part of the rotation angle and time is taken to obtain the curve of the shape change of the variable blank-holding force cam and design the variable blank-holding force The length of the force bar and the length of the chute and the variable blank holder force bar determine the position of the movable pin.

2. When drawing cylindrical parts, when only three variable blank holder rods are arranged, the variable blank holder rods can also be used as positioning parts for deep drawing parts.

3. Deep drawing Simple deep drawing parts such as cylindrical parts are as described above.

4. For drawn parts with arbitrary changes in depth and complex shapes, such as automobile panels, at different positions on the flange of the stamping part, with the variable blank holder as the center, uniformly distribute the compression elements, or use the variable blank holder under the The peak is the center, and the upward ejection rod adopts the shape of 4, and then the compression elements are evenly distributed. In this way, variable blank-holding force cams, variable blank-holding force rods and other mechanisms are installed on different flange positions of the deep-drawing parts, so that different blank-holding force can be applied over time, and different types of blank-holding force control curves can be realized. deep drawing process,

The above specific embodiments are used to explain the present invention, rather than to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention.

Claims (3)

1, based on the cupping tool of pressure variable edge force control, it is characterized in that comprising mould assembly and lower mould assembly, wherein:

1) goes up mould assembly: comprise intermediate plate (1), upper spring (2), material returned screw (3), lower spring (4), holding pad (5), punch (6), guide pin bushing (20) and cope match-plate pattern (21); The punch (6) of leaving pore is equipped with at cope match-plate pattern (21) center, lower surface, punch (6) is sleeved in intermediate plate (1) hole and holding pad (5) hole from top to bottom successively, and form with intermediate plate (1) hole and holding pad (5) hole and to be slidingly matched, have the through hole more than three on the cope match-plate pattern (21) of punch (6) outside, material returned screw (3) all is housed in each through hole, expose on the material returned screw (3) of cope match-plate pattern (21) lower surface and be sleeved on upper spring (2) successively, in intermediate plate (1) and lower spring (4) hole, material returned screw (3) end is threaded with holding pad (5), have the through hole more than three on the holding pad (5) outside the material returned screw (3), guide pin bushing (20) is equipped with in cope match-plate pattern (21) lower end of intermediate plate (1) and holding pad (5) outside;

2) lower mould assembly: comprise die (7), pressure variable edge force bar (8), motion spring (9), bearing pin (10), pressure variable edge force cam (11), die cushion block (12), head part spring (13), spacing collar (14), untie-sell (15), alignment pin (17), lower bolster (18) and guide pillar (19); In the spacing collar (14) at lower bolster (18) center, upper surface head part spring (13) is housed, on lower bolster (18) upper surface of spacing collar (14) outside " П " shape die (7) is housed, die cushion block (12) is equipped with at " П " shape die (7) center, upper surface, the small end of die cushion block (12) forms with " П " shape die (7) and is slidingly matched, head part spring (13) withstands on die cushion block (12) large end face, die cushion block (12) center line and punch (6) central lines, " П " shape die (7) upper surface of die cushion block (12) outside has the through hole more than three, pressure variable edge force bar (8) is housed respectively in each through hole, the small end of pressure variable edge force bar (8) stretches out the outer end of " П " shape die (7) can be corresponding one by one with the hole on the holding pad (5), form respectively and be slidingly matched, the small end of pressure variable edge force bar (8) in " П " shape die (7) is sleeved in motion spring (9) hole, pressure variable edge force cam (11) more than three withstands on the end points of the big end of pressure variable edge force bar (8) separately respectively, pressure variable edge force cam (11) rotates around bearing pin (10), the cantilever arm of pressure variable edge force cam (11) is connected with untie-sell (15) with the big end of die cushion block (12), " П " shape die (7)) guide pillar (19) with guide pin bushing (20) corresponding number of cope match-plate pattern (21) is housed on the Wai lower bolster (18), during work, guide pillar (19) can insert to form in separately the dowel hole and be slidingly matched, simultaneously, the alignment pin (17) on " П " shape die (7) inserts in holding pad (5) locating hole and locatees;

In drawing process, pressure variable edge force bar (8) is gone up the plane and intermediate plate (1) just collides, die cushion block (12) untie-sell when down moving (15) is toward the cantilever arm of drop-down pressure variable edge force cam (11), thereby pressure variable edge force cam (11) is rotated around bearing pin (10), pressure variable edge force cam (11) is by the end points of the big end of top pressure variable edge force bar (8), pressure variable edge force bar (8) passes just top intermediate plate (1) up of holding pad (5) hole, the height of lower spring (4) is increased or reduce, thereby the pressure that makes blank holder pressing plate material (16) reduces or increases, and has reached to adopt pressure variable edge force control in the drawing process.

2, the cupping tool based on pressure variable edge force control according to claim 1, it is characterized in that: described pressure variable edge force cam (11), when the drawing part of pull and stretch rule flange shape, the i.e. drawing part of the flange shape of representing with a parameter, the pattern curve of pressure variable edge force cam (11) is identical and with Mould's Pressure Center symmetric arrangement or mould geometric center symmetric arrangement.

3, the cupping tool based on pressure variable edge force control according to claim 1, it is characterized in that: described pressure variable edge force cam (11), during the drawing part of the irregular flange shape of pull and stretch, the i.e. drawing part of the flange shape that can not represent with a parameter, the pattern curve of pressure variable edge force cam (11) has nothing in common with each other, and different flange shaped positions place arranges the pressure variable edge force cam (11) of difformity curve.

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