CN110705050A - Design method of die surface and die for deep drawing process of inner plate of car door - Google Patents
Design method of die surface and die for deep drawing process of inner plate of car door Download PDFInfo
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Abstract
The invention belongs to the technical field of dies, and particularly relates to a design method of a die surface and a die for a deep drawing process of an inner plate of a car door. The surface size of the inner panel of the car door is very large and the forming is difficult. The inner plate of the car door is composed of a plurality of curved surfaces, mainly free curved surfaces, and different structures of the inner plate of the car door of different cars are different, so that a drawing model which completely meets the standard is often not found from the existing mould. In the whole process of designing the die surface and the die, the invention not only considers the characteristics of the curved surface of the car body, but also considers the characteristics of the prototype of the car door, is an inventive process, can design corresponding deep drawing dies aiming at different types of car door inner plates, automatically completes the processes of positioning, discharging and the like, uses the stepped blank holder which is divided into blocks to reduce the wrinkling phenomenon of the sheet material at the thin side, ensures that the blank holder and a pushing pin play a discharging role simultaneously, prevents the blank from being clamped in the die, has simple structure, convenient manufacture and low cost, and can be popularized and applied to the stamping forming of other large covering parts such as car door outer plates, front walls, side walls and the like.
Description
Technical Field
The invention belongs to the technical field of dies, and particularly relates to a design method of a die surface and a die for a deep drawing process of an inner plate of a car door.
Background
The vehicle body has a function of providing a safe operating environment for the driver. Therefore, the vehicle body parts adopt a load-bearing vehicle body structure, and part of the parts are used as a framework structure of the vehicle body while the arrangement of a transmission system is met. The inner plate of the car door is composed of a plurality of curved surfaces, mainly free curved surfaces, and different structures of the inner plate of the car door of different cars are different, so that a drawing model which completely meets the standard is often not found from the existing mould.
The car industry in China is in a high-speed development stage, and the automobile covering parts have the characteristics of high surface quality and high precision requirements. The inner panel of the door, which is the most important outer cover constituting the cab, has a relatively large surface area and is difficult to form. The inner plate of the car door is not uniform, the variety of the inner plate is more and more diversified, and a plurality of problems to be solved urgently exist in the aspects of mold design and manufacture. The existing deep drawing die is complex in structure, the connection mode of the upper die base and the lower die base with the male die and the female die is too complex, so that the disassembly, the assembly and the cleaning are very inconvenient, waste materials are easily accumulated, and the number of parts is too large. Meanwhile, most of the discharging devices of the existing dies are designed independently, and occupy a large amount of space, so that the assembly is difficult. In actual production, the edge pressing ring is a whole, so that the deep drawing wrinkling phenomenon of the large-scale covering part is serious.
Disclosure of Invention
The invention provides a simple design method of a deep drawing process die surface and a die for an inner plate of a car door, which considers the characteristics of a curved surface of a car body and the characteristics of a prototype of the car door, designs the corresponding deep drawing process die surface and the die for different types of inner plates of the car door, and solves the defects of the deep drawing process die surface and the die for the existing inner plate of the car door.
The technical scheme of the invention is described as follows by combining the attached drawings:
a design method of a die surface and a die in a deep drawing process of an inner plate of a car door comprises the following steps:
step one, carrying out process analysis on a given vehicle door inner plate: the inner plate of the vehicle door is in an asymmetric pattern, so that laser tailor-welded steel plates are selected for stamping and drawing in pairs;
step two, internal process supplement: the method comprises the following steps that a creative curved surface design module of CATIA software is used for carrying out process supplement on an inner plate of the vehicle door, if a hole which cannot be directly filled exists in the process of the process supplement, a new curved surface needs to be established, and then the new curved surface is bridged with a boundary;
step three, adding the pressed noodles: in order to adapt to the shape of a wheel, a part of the boundary of the inner plate of the vehicle door is concave, when a material pressing surface is supplemented to the boundary of the curve, a method of offsetting the curve is adopted, and then the process supplementation is carried out to the part between the two curves;
step four, improving the form of the pressed noodles: after the addition of the material pressing surface is finished, the shape of the boundary is irregular, and the shape of the blank is difficult to determine, so the shape of the blank needs to be normalized;
step five, carrying out simulation analysis on the generated die surface of the female die: if the severe tension cracking or wrinkling phenomenon occurs, improving the form of the pressing surface;
and step six, designing a die for the generated die surface of the drawing process of the inner plate of the vehicle door.
The concrete method of the sixth step is as follows:
step 61) calculating the blank holder force and the drawing force of the die:
the formula of the blank holder force for drawing workpieces in any shapes is as follows: fPress and press＝Ap，p＝48(z-1.1)D/tσbx10-5，z＝1/m，m＝d/D；
In the formula, A is the area of the blank holder; p is unit blank holder force; z is the reciprocal of drawing coefficient m of each procedure; sigmabIs hairTensile strength of the blank material in MPa; t is the material thickness in mm; d is the diameter of the blank in mm; d is the diameter after drawing;
the drawing force is given by the formula: fPulling device＝Ltσbk；
In the formula, L is the peripheral length of the male die and the unit is mm; t is the material thickness in mm; sigmabResistance of the stock material
Tensile strength in MPa; k is a coefficient;
step 62), selecting the tonnage of a press machine; looking up a stamping manual, and selecting the type of the press according to the drawing force and the blank holder force calculated in the step 61);
step 63) calculating the edge pressing force and the drawing force obtained in the step 61) to determine the die filling height; for a single action press: nominal force F of press>FPulling device+FPress and press；
According to the nominal force, looking up a stamping manual and determining the die filling height;
step 64) selection of the spring: because the edge pressing force is large, the requirement cannot be met by a common spring, and a nitrogen spring special for the die is selected; the number n of the needed springs is equal to blank holder force/nominal pressure, and n is an integer;
step 65) the positioning device is used for ensuring that the blank is positioned at a proper position to ensure that a qualified workpiece is obtained, and 6 positioning pins for the medium-sized hole are selected because the workpiece is large;
and step 66) adopting the partitioned stepped blank holder, and regarding the researched laser tailor-welded blank part, the part is formed by tailor-welding the plates with two thicknesses, so that the blank holder is partitioned into two blocks, and the partitioning of the blank holder is shown in figure 8. Three schemes are adopted for partitioning the blank holder, namely scheme 1: the blank holder is not a stepped blank holder, the two sides adopt unequal blank holding forces, the blank holding force of the thin side plate is 750KN, and the blank holding force of the thick side plate is 350 KN; scheme 2: the two sides of the stepped blank holder adopt equal blank holding force, and the blank holding force of the two sides is 525KN respectively; scheme 3: the step type blank holder adopts unequal blank holding forces on two sides, and the blank holding forces on the two sides are respectively 750KN for the thin side material and 350KN for the thick side material. According to the forming simulation result, the following results are obtained: scheme 1 does not adopt a step type blank holder, and the two sides adopt unequal blank holding force, so that the forming effect cannot be improved; scheme 2 and scheme 3 of adopting the step type blank holder both make the formability of the blank holder region of the thin side improved, the wrinkle phenomenon is reduced, scheme 2 adopts equal blank holder force, the thin side thickness reduction rate is increased, scheme 3 adopts unequal constant blank holder force on the thin and thick both sides, the thin side blank holder force is big and the thick side blank holder force is little, although the thickness reduction rate is slightly reduced than the original scheme, the integral formability is better, and the wrinkle phenomenon of the thin side blank holder region is greatly reduced. A blocked stepped blankholder is selected. The numerical value pairs of the molding results of the schemes 1 to 3 are shown in FIG. 9.
Step 67) is combined with step 61), step 62), step 63), step 64), step 65) and step 66) according to specific requirements to carry out mechanical structure design.
The process supplement in the second step is the part supplemented by the user except the large-scale covering part of the automobile body, and the user removes the part of the material after all stamping work is finished; the added process supplement part is mainly used for drawing a stamped part meeting the use requirement; holes and gaps can not be formed in the parts, and the holes and the gaps can cause the parts to deform in the drawing process, so that the holes need to be filled, namely the inner process supplement process;
during the design process, care should be taken to prevent defects from occurring on the surface of the part; the specific operation steps are as follows:
step 21) the original part contains a plurality of repeated curves and curved surfaces, the curves, the curved surfaces and the part are not integrated, so the curves, the curved surfaces and the part need to be deleted, then the original part is integrally jointed, small protrusions and bolt holes are deleted for the following process, if the protrusions exist, a stamping die is not convenient to design, the cost is increased, and the cracks are easy to occur in the stamping process; selecting the projection and directly deleting the part;
step 22) deleting or hiding redundant sidelines and curved surfaces in the vehicle door inner plate part; after the completion of the part, the vehicle door inner plate part is integrally jointed by using a sewing command, and at the moment, the combined distance CATIA system gives 0.001mm by default, but the distance between some curved surfaces in the vehicle door inner plate part is more than 0.001mm, so that the vehicle door inner plate part cannot be operated if the sewing is directly carried out; if the situation occurs, the merging distance is changed from 0.001mm to 0.1mm, and then the vehicle door inner plate part is integrally jointed;
step 23), after the integral joint, designing an inner process supplement part for the vehicle door inner plate part; before adding the inner process supplement part, firstly establishing a CATIA subdirectory, so that the subsequent steps are all stored in the subdirectory, and if a certain process supplement of the vehicle door inner plate part needs to be modified later, the subsequent steps can be directly carried out under the subdirectory;
step 24), a plurality of holes for positioning are formed in the vehicle door inner plate part, internal process supplement is carried out, holes are mainly supplemented in the part, and then all the process supplement is sewn with the integral vehicle door inner plate part;
step 25), a hole is formed in the middle of the vehicle door inner plate part and is mainly used for mounting accessories such as a glass lifter, the boundary line of the hole is not on a plane, and the surface is uneven if the hole is directly filled; in this case, the filling is carried out directly, the surface quality of the filled part is checked, if no convex hull exists, the operation can be continued, if a convex hull exists, a space curved surface is built by itself, and then the space curved surface is connected with the periphery of the hole through bridging;
step 26) some parts in the inner plate of the vehicle door cannot be directly bridged, in this case, a new curve can be established to be respectively bridged with the parts or cut and then bridged again; firstly, selecting a proper plane, drawing a regular pattern with a larger area, then drawing the regular pattern to enable the regular pattern to be completely intersected with a part, cutting off redundant parts by using a CATIA (computer-graphics aided three-dimensional interactive application) segmentation command, and then chamfering to enable the regular pattern to be in smooth transition.
The concrete method of the third step is as follows:
step 31) adopting an extrapolation extension instruction in a generative curved surface design module in CATIA software curved surface modeling to extend the asymmetric boundary of the part by 300mm and the symmetric boundary by 50mm, wherein in order to make the pressing surface smooth, adjacent extension parts can be connected through a filling command or a bridging command; the more distant extensions may have black lines after filling due to the discontinuity of the curved surface; by adopting a method of connecting sample lines during internal process supplement and then filling, the curved surface continuity of the material pressing surface part can be improved, so that black lines are greatly reduced, and simultaneously, the curved surface boundary which is not easy to draw is extracted and translated, and then the vacant part is completely filled, and the occurrence of the black lines is avoided by repeatedly modifying, changing curvature, changing tangent lines and other operations; the processing process of the material pressing surface is very important because the whole part is ensured to have no black line during simulation; the round corner part can not be formed by direct deep drawing, and only the bridge connection line meeting the requirement can be drawn by self, attention is paid to guarantee the smoothness of connection, and then filling is carried out;
step 32) integrally sewing the filled part and the original part, if the distance between the two curved surfaces is larger than 1mm, filling can be carried out according to the method in the step 31), and after the operation is finished, checking by using the operation of extracting the boundary until the whole part has no black line;
step 33) entering a sketch editing mode of the part, selecting a proper position to draw a plane, wherein the shape of the drawn plane is consistent with the edge of the part, then exiting from the sketch editing interface, drawing the boundary of the drawn plane through a drawing command, wherein the drawing direction should select the direction of the part, and the drawing depth is greater than the depth of the part, so that the whole part can be placed in the rectangle; trimming the redundant parts except the drawing part to remove; then, hiding the drawn rectangular frame; finally, hiding redundant lines and surfaces in the draft to ensure that a black line on the part does not exist;
and step 34) in order to adapt to the shape of the wheel, a part of the boundary of the inner plate of the vehicle door is concave, when the material pressing surface is supplemented to the boundary of the curve, a method of shifting the curve is adopted, and then the process supplementation is carried out to the part between the two curves.
The invention has the beneficial effects that:
1) and the die surfaces of the deep drawing process adopt paired deep drawing, so that the production efficiency is greatly improved.
2) The rough shape of the deep drawing blank designed by the method is consistent with that of a deep drawing process piece, and raw materials are saved, so that the production cost is greatly reduced.
3) The method is suitable for the die surface design of various covering parts and has strong popularization.
Drawings
FIG. 1 is a design flow diagram of the present invention;
FIG. 2 is a diagram showing simulation results of step five of the present invention;
FIG. 3 is a front view of a mold designed according to the present method;
FIG. 4 is a left side view of a mold designed according to the present method;
FIG. 5 is a top plan view of a mold assembly constructed in accordance with the present method, with the upper mold removed in the left half and the lower mold removed in the right half;
fig. 6 is a schematic illustration of a shot pin configuration of a mold designed according to the present method.
FIG. 7 is a cross-sectional view taken at A-A of FIG. 6;
FIG. 8 is a schematic view of a blank holder block;
FIG. 9 is a numerical comparison of the forming results for several binder schemes;
FIG. 10 is a front view of a car door inner panel drawing process piece;
FIG. 11 is a left side view of a car door inner panel drawing process piece;
FIG. 12 is a top view of a car door inner panel drawing process piece.
In the figure: 1. an upper die holder; 2. a female die; 3. the upper die base is connected with the female die through a screw; 4. a male die; 5. a blank holder; 6. positioning pins; 7. a guide sleeve; 8. a guide post; 9. a nitrogen spring; 10. a lower die holder; 11. a discharge screw; 12. the male die is connected with the lower die base through a screw; 13. a limiting block; 14. and (6) promotion.
Detailed Description
Examples
Referring to fig. 1, step one, a process analysis is performed on a given door inner panel: the inner plate of the vehicle door is in an asymmetric pattern, so that the ST06Z steel plate with the thickness of 0.7mm is adopted for pair stamping and drawing, the production rate can be greatly improved, and the method is more suitable for industrial requirements.
Step two, internal process supplement: the method comprises the following steps that a creative curved surface design module of CATIA software is used for carrying out process supplement on an inner plate of the vehicle door, a new curved surface needs to be established when a hole which cannot be directly filled is met in the process of the process supplement, and then the new curved surface is bridged with a boundary;
the process supplement in the second step is the part supplemented by the user except the large-scale covering part of the automobile body, and the user removes the part of the material after all stamping work is finished; the added process supplement part is mainly used for drawing a stamped part meeting the use requirement; holes and gaps can not be formed in the parts, and the holes and the gaps can cause the parts to deform in the drawing process, so that the holes need to be filled, namely the inner process supplement process;
during the design process, attention should be paid to the process replenishment problem of preventing surface defects of parts; the specific operation steps are as follows:
step 21) the original part contains a plurality of repeated curves and curved surfaces, the curves, the curved surfaces and the part are not integrated, so the curves, the curved surfaces and the part need to be deleted, then the original part is integrally jointed, small protrusions and bolt holes are deleted for the following process, if the protrusions exist, a stamping die is not convenient to design, the cost is increased, and the cracks are easy to occur in the stamping process; selecting the projection and directly deleting the part;
step 22) deleting or hiding redundant sidelines and curved surfaces in the vehicle door inner plate part; after the completion of the part, the vehicle door inner plate part is integrally jointed by using a sewing command, and at the moment, the combined distance CATIA system gives 0.001mm by default, but the distance between some curved surfaces in the vehicle door inner plate part is more than 0.001mm, so that the vehicle door inner plate part cannot be operated if the sewing is directly carried out; if the situation occurs, the merging distance is changed from 0.001mm to 0.1mm, and then the vehicle door inner plate part is integrally jointed;
step 23), after the integral joint, designing an inner process supplement part for the vehicle door inner plate part; before adding the inner process supplement part, firstly establishing a CATIA subdirectory, so that the subsequent steps are all stored in the subdirectory, and if a certain process supplement of the vehicle door inner plate part needs to be modified later, the subsequent steps can be directly carried out under the subdirectory;
step 24), a plurality of holes for positioning are formed in the vehicle door inner plate part, internal process supplement is adopted, holes are mainly supplemented in the part, and all process supplement is sewn with the integral vehicle door inner plate part;
step 25), a hole with the diameter of about 730mm is formed in the middle of the vehicle door inner plate part and is mainly used for mounting accessories such as a glass lifter, the boundary line of the hole is not on a plane, and the surface is uneven if the hole is directly filled; in this case, the filling is carried out directly, the surface quality of the filled part is checked, if no convex hull exists, the operation can be continued, if a convex hull exists, a space curved surface is built by itself, and then the space curved surface is connected with the periphery of the hole through bridging;
step 26) some parts in the inner plate of the vehicle door cannot be directly bridged, in this case, a new curve can be established to be respectively bridged with the parts or cut and then bridged again; firstly, selecting a proper plane, drawing a regular pattern with a larger area, then drawing the regular pattern to enable the regular pattern to be completely intersected with the part, then cutting off redundant parts by using a cutting command, and then chamfering to enable the regular pattern to be in smooth transition.
Step three, adding the pressed noodles: in order to adapt to the shape of a wheel, a part of the boundary of the inner plate of the vehicle door is concave, when a material pressing surface is supplemented to the boundary of the curve, a method of offsetting the curve is adopted, and then the process supplementation is carried out to the part between the two curves;
the concrete method of the third step is as follows:
step 31) adopting an extrapolation extension instruction in a generative curved surface design module in CATIA software curved surface modeling to extend the asymmetric boundary of the part by 300mm and the symmetric boundary by 50mm, wherein in order to make the pressing surface smooth, adjacent extension parts can be connected through a filling command or a bridging command; the more distant extensions may have black lines after filling due to the discontinuity of the curved surface; by adopting a method of connecting sample lines during internal process supplement and then filling, the curved surface continuity of the material pressing surface part can be improved, so that black lines are greatly reduced, and simultaneously, the curved surface boundary which is not easy to draw is extracted and translated, and then the vacant part is completely filled, and the occurrence of the black lines is avoided by repeatedly modifying, changing curvature, changing tangent lines and other operations; the processing process of the material pressing surface is very important because the whole part is ensured to have no black line during simulation; the round corner part can not be formed by direct deep drawing, and only the bridge connection line meeting the requirement can be drawn by self, attention is paid to guarantee the smoothness of connection, and then filling is carried out;
step 32) integrally sewing the filled part and the original part, if the distance between the two curved surfaces is larger, filling can be carried out only according to the first method, and after the operation is finished, checking is carried out by using the operation of extracting the boundary until the whole part has no black line;
step 33) entering a sketch editing mode of the part, selecting a proper position to draw a plane, wherein the shape of the drawn plane is consistent with the edge of the part, then exiting from the sketch editing interface, drawing the boundary of the drawn plane through a drawing command, wherein the drawing direction should select the direction of the part, and the drawing depth is greater than the depth of the part, so that the whole part can be placed in the rectangle; trimming the redundant parts except the drawing part to remove; then, hiding the drawn rectangular frame; finally, hiding redundant lines and surfaces in the draft to ensure that a black line on the part does not exist;
and step 34) in order to adapt to the shape of the wheel, a part of the boundary of the inner plate of the vehicle door is concave, when the material pressing surface is supplemented to the boundary of the curve, a method of shifting the curve is adopted, and then the process supplementation is carried out to the part between the two curves.
Step four, improving the form of the pressed noodles: after the addition of the material pressing surface is finished, the shape of the boundary is irregular, and the shape of the blank is difficult to determine, so the shape of the blank needs to be normalized;
step five, carrying out simulation analysis on the generated die surface of the female die: if the severe tension cracking or wrinkling phenomenon occurs, improving the form of the pressing surface; the simulation results participate in fig. 5. The simulation result output graph is a color level graph which is processed to show the effect of the graph 5. As can be seen from the figure, the parts required for forming the parts are all in the safe area, and the material pressing surface part tends to wrinkle, but the influence can be removed by means of cutting, shaping and the like at the later stage, so that the addition of the material pressing surface and the internal process supplement are acceptable, and the design of the die in the drawing process can be continued.
And step six, designing a die for the generated die surface of the drawing process of the inner plate of the vehicle door.
The concrete method of the sixth step is as follows:
step 61) calculating the blank holder force and the drawing force of the blank holder:
the formula of the blank holder force for drawing workpieces in any shapes is as follows: fPress and press＝Ap，p＝48(z-1.1)D/tσbx10-5，z＝1/m，m＝d/D；
In the formula, A is the area of the blank holder; p is unit blank holder force; z is the reciprocal of drawing coefficient m of each procedure; sigmabThe tensile strength of the blank material is MPa; t is the material thickness in mm; d is the diameter of the blank in mm; d is the diameter after drawing.
In the embodiment, a is 1218350mm2, wherein a is 2000x1655-2x1/2x1020x1020-725x725-2x1/2x725 x;
m＝d/D＝2000/2420＝0.83，Z＝1/m＝1/0.83＝1.21；
σb＝318.2Mpa；
t＝0.7mm；
D＝2420mm；
P＝4.5Mpa；
Fpress and press＝1218350x4.5＝5482.58kN；
The drawing force is given by the formula: fPulling device＝Ltσbk；
In the formula, L is the peripheral length of the male die and the unit is mm; t is the material thickness in mm; sigmabThe tensile strength of the blank material is MPa; k is a coefficient;
in this example, L ═ (945+725x1.21) x2 ═ 3644.5 mm;
T＝0.7mm；
σb＝318.2MPa；
kσ＝0.8；
F＝3644.5x0.7x318.2x0.8＝649.42kN；
taking the drawing force F as 650 kN;
step 62), selecting the tonnage of a press machine; referring to the press manual, based on the drawing force and the blank-holding force calculated in step 61),
the inner plate of the vehicle door belongs to a large stamping part with a complex structure, and the nominal force is 6100kN, so a closed type press is selected instead of an open type mechanical press, and the open type mechanical press can only meet the nominal force below 2500kN generally. The maximum die filling height of the invention is 950 mm. Closed single point presses generally can only meet the die requirements of die height less than 750 mm. In conclusion, JH36-800 closed double-point press is selected. The press has the advantages of good rigidity and high precision.
Step 63) calculating the edge pressing force and the drawing force obtained in the step 61) to determine the die filling height; for a single action press: nominal force F of press>FPulling device+FPress and press5450+650 ═ 6100 kN; the maximum die filling height can be 950mm by consulting the stamping manual.
Step 64) selection of the spring: because the edge pressing force is large, the requirement cannot be met by a common spring, and a nitrogen spring special for the die is selected; the number of springs n is 27.25 for the clamping force/nominal pressure 5450/200 and 28 for the clamping ring bottom 120mm from the upper part of the lower die holder. Therefore, MQC 200.0-125-.
Step 65) the positioning device is used for ensuring that the blank is positioned at a proper position to ensure that a qualified workpiece is obtained, and 6 positioning pins for the medium-sized hole are selected because the workpiece is large;
and step 66) adopting the partitioned stepped blank holder, and regarding the researched laser tailor-welded blank part, the part is formed by tailor-welding the plates with two thicknesses, so that the blank holder is partitioned into two blocks, and the partitioning of the blank holder is shown in figure 8. Three schemes are adopted for partitioning the blank holder, namely scheme 1: the blank holder is not a stepped blank holder, the two sides adopt unequal blank holding forces, the blank holding force of the thin side plate is 750KN, and the blank holding force of the thick side plate is 350 KN; scheme 2: the two sides of the stepped blank holder adopt equal blank holding force, and the blank holding force of the two sides is 525KN respectively; scheme 3: the step type blank holder adopts unequal blank holding forces on two sides, and the blank holding forces on the two sides are respectively 750KN for the thin side material and 350KN for the thick side material. According to the forming simulation result, the following results are obtained: scheme 1 does not adopt a step type blank holder, and the two sides adopt unequal blank holding force, so that the forming effect cannot be improved; scheme 2 and scheme 3 of adopting the step type blank holder both make the formability of the blank holder region of the thin side improved, the wrinkle phenomenon is reduced, scheme 2 adopts equal blank holder force, the thin side thickness reduction rate is increased, scheme 3 adopts unequal constant blank holder force on the thin and thick both sides, the thin side blank holder force is big and the thick side blank holder force is little, although the thickness reduction rate is slightly reduced than the original scheme, the integral formability is better, and the wrinkle phenomenon of the thin side blank holder region is greatly reduced. A blocked stepped blankholder is selected. The numerical value pairs of the molding results of the schemes 1 to 3 are shown in FIG. 9.
Step 67) is combined with step 61), step 62), step 63), step 64), step 65) and step 66) according to specific requirements to carry out mechanical structure design.
Referring to fig. 3 to 8, the specific structure of the mold designed according to the above method is: the die comprises an upper die base 1, a female die 2, an upper die base and female die connecting screw 3, a male die 4, a blank holder 5, a positioning pin 6, a guide sleeve 7, a guide pillar 8, a nitrogen spring 9, a lower die base 10, a discharging screw 11, a male die and lower die base connecting screw 12, a limiting block 13 and a push pin 14.
The female die 2 is connected with the upper die base 1 through an upper die base and female die connecting screw 3; four upper die seats and four female die connecting screws 3 are arranged; the male die 4 is connected with the lower die holder 10 through male die and lower die holder connecting screws 12, and the number of the male die and lower die holder connecting screws 12 is four; the upper die holder 1 is connected with the lower die holder 10 through a guide pillar 8; the female die 2 and the male die 4 can be directly connected with the male die through the connecting screws, so that the problems that the connecting mode of the upper die base and the lower die base with the male die and the female die is too complicated, and the disassembly, the assembly and the cleaning are inconvenient are solved. The guide sleeve 7 is sleeved on the guide post 8; the nitrogen spring 9 is fixed in the lower die holder 10; the blank holder 5 is connected with the lower die holder 10 through a discharging screw 11; the positioning pin 6 is in interference fit with the blank holder 5; the blank holder can play a role in unloading, so that the blank is prevented from being clamped on the male die 4; the number of the limiting blocks 13 is four, and the limiting blocks are all cylindrical. The limiting block 13 is fixed on the lower die holder 10; said push pins 14 are fixed in the female die 2. Grooves are formed in the two sides of the upper die holder 1 and the lower die holder 10. The blank holder 5 is a sectional blank holder.
The car door inner panel adopts laser tailor-welded steel sheet to carry out the punching press deep-drawing, through calculating, gets the pressure side force F5450 kN, and the deep-drawing force is F650 kN, and the press of this embodiment selection is the double-point press of closed type. For a single action press: f > F pull + F press 5450kN +650kN 6100kN, and 950mm is taken as the maximum die height H2. The number N of the nitrogen springs 9 is 27.25, 5450/200, 28, and may be model MQC 200.0-125-. The limiting blocks 13 are 4 cylindrical No. 45 steel parts, so that stability in die assembly can be guaranteed, and the strength and rigidity of the lower die holder cannot be damaged. The push pins are four in total and consist of a fixed cover plate, a spring, a push rod and four connecting screws. The cover plate is fixed in the female die by a screw, and the push rod can move up and down under the action of the spring. The connecting screw is M5 and GB60-76 is adopted; the distance between the bottom of the blank holder 5 and the upper part of the lower die holder 10 is 120 mm. The push pin 14 can prevent the blank from being blocked in the female die 2, and solves the problems that waste materials are easy to accumulate, the number of parts is too large, and the occupied space is large; the blank holder 5 adopts a sectional blank holder, so that the integral formability is better, the wrinkling phenomenon of a thin side blank holder area is greatly reduced, and the problem of serious wrinkling phenomenon of the existing production mold is solved.
The working principle of the die is as follows:
(1): the blank is placed in the limited range of the positioning pin 6, the upper die holder 1 drives the female die 2 to move downwards, in the process, the nitrogen spring 9 is compressed, the discharging screw 11 moves downwards, the push rod in the push pin 14 moves upwards, and the spring in the push pin is compressed.
(2): when the blank holder 5 moves downwards to contact the limiting block 13, the die assembly is completed.
(3): after the die assembly is completed, the upper die base 1 moves upwards, the nitrogen spring 9 drives the blank holder 5 to rebound, so that the blank is prevented from being clamped on the male die 4, meanwhile, the spring in the push pin 14 is reset, a push rod in the push pin is pushed out downwards, and the blank is prevented from being clamped in the female die 2. At this point, the drawing process is complete. The drawing process of the inner plate of the vehicle door is shown in the attached figures 10-12.
Claims (4)
1. A design method of a die surface and a die in a deep drawing process of an inner plate of a car door is characterized by comprising the following steps:
step one, carrying out process analysis on a given vehicle door inner plate: the inner plate of the vehicle door is in an asymmetric pattern, so that laser tailor-welded steel plates are selected for stamping and drawing in pairs;
step two, internal process supplement: the method comprises the following steps that a creative curved surface design module of CATIA software is used for carrying out process supplement on an inner plate of the vehicle door, if a hole which cannot be directly filled exists in the process of the process supplement, a new curved surface needs to be established, and then the new curved surface is bridged with a boundary;
step three, adding the pressed noodles: in order to adapt to the shape of a wheel, a part of the boundary of the inner plate of the vehicle door is concave, when a material pressing surface is supplemented to the boundary of the curve, a method of offsetting the curve is adopted, and then the process supplementation is carried out to the part between the two curves;
step four, improving the form of the pressed noodles: after the addition of the material pressing surface is finished, the shape of the boundary is irregular, and the shape of the blank is difficult to determine, so the shape of the blank needs to be normalized;
step five, carrying out simulation analysis on the generated die surface of the female die: if the severe tension cracking or wrinkling phenomenon occurs, improving the form of the pressing surface;
and step six, designing a die for the generated die surface of the drawing process of the inner plate of the vehicle door.
2. The design method of the die surface and the die in the deep drawing process of the inner plate of the car door as claimed in claim 1, characterized in that the concrete method of the sixth step is as follows:
step 61) calculating the blank holder force and the drawing force of the die:
the formula of the blank holder force for drawing workpieces in any shapes is as follows: fPress and press＝Ap，p＝48(z-1.1)D/tσbx10-5，z＝1/m，m＝d/D；
In the formula, A is the area of the blank holder; p is unit blank holder force; z is the reciprocal of drawing coefficient m of each procedure; sigmabThe tensile strength of the blank material is MPa; t is the material thickness in mm; d is the diameter of the blank in mm; d is the diameter after drawing;
the drawing force is given by the formula: fPulling device＝Ltσbk；
In the formula, L is the peripheral length of the male die and the unit is mm; t is the material thickness in mm; sigmabThe tensile strength of the blank material is MPa; k is a coefficient;
step 62), selecting the tonnage of a press machine; looking up a stamping manual, and selecting the type of the press according to the drawing force and the blank holder force calculated in the step 61);
step 63) calculating the edge pressing force and the drawing force obtained in the step 61) to determine the die filling height; for a single action press: nominal force F of press>FPulling device+FPress and press；
According to the nominal force, looking up a stamping manual and determining the die filling height;
step 64) selection of the spring: because the edge pressing force is large, the requirement cannot be met by a common spring, and a nitrogen spring special for the die is selected; the number n of the needed springs is equal to blank holder force/nominal pressure, and n is an integer;
step 65) the positioning device is used for ensuring that the blank is positioned at a proper position to ensure that a qualified workpiece is obtained, and 6 positioning pins for the medium-sized hole are selected because the workpiece is large;
and step 66) adopting the partitioned stepped blank holder, and for the researched laser tailor-welded blank part, the part is formed by tailor-welding the plate materials with two thicknesses, so that the blank holder is partitioned into two parts. Three schemes are adopted for partitioning the blank holder, namely scheme 1: the blank holder is not a stepped blank holder, the two sides adopt unequal blank holding forces, the blank holding force of the thin side plate is 750KN, and the blank holding force of the thick side plate is 350 KN; scheme 2: the two sides of the stepped blank holder adopt equal blank holding force, and the blank holding force of the two sides is 525KN respectively; scheme 3: the step type blank holder adopts unequal blank holding forces on two sides, and the blank holding forces on the two sides are respectively 750KN for the thin side material and 350KN for the thick side material. According to the forming simulation result, the following results are obtained: scheme 1 does not adopt a step type blank holder, and the two sides adopt unequal blank holding force, so that the forming effect cannot be improved; scheme 2 and scheme 3 of adopting the step type blank holder both make the formability of the blank holder region of the thin side improved, the wrinkle phenomenon is reduced, scheme 2 adopts equal blank holder force, the thin side thickness reduction rate is increased, scheme 3 adopts unequal constant blank holder force on the thin and thick both sides, the thin side blank holder force is big and the thick side blank holder force is little, although the thickness reduction rate is slightly reduced than the original scheme, the integral formability is better, and the wrinkle phenomenon of the thin side blank holder region is greatly reduced. A blocked stepped blankholder is selected.
Step 67) is combined with step 61), step 62), step 63), step 64), step 65) and step 66) according to specific requirements to carry out mechanical structure design.
3. The design method of the die surface and the die in the deep drawing process of the inner panel of the car door as claimed in claim 1, wherein the process supplement in the second step is the part supplemented by the user except the large covering part of the car body, and the user removes the material after all punching work is finished; the added process supplement part is mainly used for drawing a stamped part meeting the use requirement; holes and gaps can not be formed in the parts, and the holes and the gaps can cause the parts to deform in the drawing process, so that the holes need to be filled, namely the inner process supplement process;
during the design process, care should be taken to prevent defects from occurring on the surface of the part; the specific operation steps are as follows:
step 21) the original part contains a plurality of repeated curves and curved surfaces, the curves, the curved surfaces and the part are not integrated, so the curves, the curved surfaces and the part need to be deleted, then the original part is integrally jointed, small protrusions and bolt holes are deleted for the following process, if the protrusions exist, a stamping die is not convenient to design, the cost is increased, and the cracks are easy to occur in the stamping process; selecting the projection and directly deleting the part;
step 22) deleting or hiding redundant sidelines and curved surfaces in the vehicle door inner plate part; after the completion of the part, the vehicle door inner plate part is integrally jointed by using a sewing command, and at the moment, the combined distance CATIA system gives 0.001mm by default, but the distance between some curved surfaces in the vehicle door inner plate part is more than 0.001mm, so that the vehicle door inner plate part cannot be operated if the sewing is directly carried out; if the situation occurs, the merging distance is changed from 0.001mm to 0.1mm, and then the vehicle door inner plate part is integrally jointed;
step 23), after the integral joint, designing an inner process supplement part for the vehicle door inner plate part; before adding the inner process supplement part, firstly establishing a CATIA subdirectory, so that the subsequent steps are all stored in the subdirectory, and if a certain process supplement of the vehicle door inner plate part needs to be modified later, the subsequent steps can be directly carried out under the subdirectory;
step 24), a plurality of holes for positioning are formed in the vehicle door inner plate part, internal process supplement is carried out, holes are mainly supplemented in the part, and then all process supplement parts are sewn with the whole vehicle door inner plate part;
step 25), a hole is formed in the middle of the vehicle door inner plate part and is mainly used for mounting accessories such as a glass lifter, the boundary line of the hole is not on a plane, and the surface is uneven if the hole is directly filled; in this case, the filling is carried out directly, the surface quality of the filled part is checked, if no convex hull exists, the operation can be continued, if a convex hull exists, a space curved surface is built by itself, and then the space curved surface is connected with the periphery of the hole through bridging;
step 26) some parts in the inner plate of the vehicle door cannot be directly bridged, in this case, a new curved surface can be established to be respectively bridged with the parts or cut to be normalized and then bridged again; firstly, selecting a proper plane, drawing a regular pattern with a larger area, then drawing the regular pattern to enable the regular pattern to be completely intersected with a part, cutting off redundant parts by using a CATIA (computer-graphics aided three-dimensional interactive application) segmentation command, and then chamfering to enable the regular pattern to be in smooth transition.
4. The design method of the die surface and the die in the deep drawing process of the inner plate of the car door as claimed in claim 1, characterized in that the concrete method of the third step is as follows:
step 31) adopting an extrapolation extension instruction in a generative curved surface design module in CATIA software curved surface modeling to extend the asymmetric boundary of the part by 300mm and the symmetric boundary by 50mm, wherein in order to make the pressing surface smooth, adjacent extension parts can be connected through a filling command or a bridging command; the more distant extensions may have black lines after filling due to the discontinuity of the curved surface; by adopting a method of connecting sample lines during internal process supplement and then filling, the curved surface continuity of the material pressing surface part can be improved, so that black lines are greatly reduced, and simultaneously, the curved surface boundary which is not easy to draw is extracted and translated, and then the vacant part is completely filled, and the occurrence of the black lines is avoided by repeatedly modifying, changing curvature, changing tangent lines and other operations; the processing process of the material pressing surface is very important because the whole part is ensured to have no black line during simulation; the round corner part can not be formed by direct deep drawing, and only the bridge connection line meeting the requirement can be drawn by self, attention is paid to guarantee the smoothness of connection, and then filling is carried out;
step 32) integrally sewing the filled part and the original part, if the distance between the two curved surfaces is larger than 1mm, filling can be carried out according to the method in the step 31), and after the operation is finished, checking by using the operation of extracting the boundary until the whole part has no black line;
step 33) entering a sketch editing mode of the part, selecting a proper position to draw a plane, wherein the shape of the drawn plane is consistent with the edge of the part, then exiting from the sketch editing interface, drawing the boundary of the drawn plane through a drawing command, wherein the drawing direction should select the direction of the part, and the drawing depth is greater than the depth of the part, so that the whole part can be placed in the rectangle; trimming the redundant parts except the drawing part to remove; then, hiding the drawn rectangular frame; finally, hiding redundant lines and surfaces in the draft to ensure that a black line on the part does not exist;
and step 34) in order to adapt to the shape of the wheel, a part of the boundary of the inner plate of the vehicle door is concave, when the material pressing surface is supplemented to the boundary of the curve, a method of shifting the curve is adopted, and then the process supplementation is carried out to the part between the two curves.
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