WO2020076276A9

WO2020076276A9 - An ultrasonically assisted die system for deep drawing process and its operating method

Info

Publication number: WO2020076276A9
Application number: PCT/TR2019/050852
Authority: WO
Inventors: Ali Tolga BOZDANA; Sadik OLGUNER
Original assignee: Gaziantep Universitesi
Current assignee: Gaziantep Universitesi
Priority date: 2018-10-11
Filing date: 2019-10-10
Publication date: 2020-06-25
Anticipated expiration: 2021-04-11
Also published as: TR201815097A2; WO2020076276A2; WO2020076276A3

Abstract

The invention relates to an ultrasonic vibration-assisted mold used in the deep drawing process for forming preferably a material such as a sheet metal (4) and to the method of operation of the mold. The mold according to the invention, in its general form, comprises a female mold (1), a male mold (2), an ultrasonic vibration unit, the ultrasonic horn (3) which is the equipment of the ultrasonic vibration unit being used as the pressure element.

Description

AN ULTRASONICALLY ASSISTED DIE SYSTEM FOR DEEP DRAWING PROCESS AND ITS OPERATING METHOD

Subject of the Invention

The invention relates to an ultrasonic vibration-assisted die used in the deep drawing process for forming sheet metal and to the method of operation of the die.

State of Art

Today, deep drawing die for forming sheet metal is widely used in many fields, especially in the automotive industry. The mentioned deep drawing die generally consists of three different parts: a female die, a punch, and a blank holder. During the deep drawing process, as the female die moves towards the punch, the punch enters into the female die cavity and the sheet metal in between is drawn into the female die. At this time, to prevent wrinkling of the portion (the flange region) of the material remaining on the die surface, a blank holder with a constant or variable force applied thereon is used. The punch must be fixed to the main frame of the press to be used in the forming process and disposed in the center cavity of the blank holder which will move with the movement of the female die.

The deep drawing die includes an ultrasonic vibration unit. The mentioned ultrasonic vibrations may be applied to the female die in the axial and/or in the radial direction, to the punch in the axial direction, and to the blank holder in the axial and/or radial direction. Among these applications, the most effective one is to apply ultrasonic vibrations to the blank holder in the axial direction in order to increase the limiting drawing ratios and to reduce the forming load of the sheet materials. However, it is difficult to apply ultrasonic vibrations to the blank holder in the axial direction, since the punch must be located in the center cavity of the blank holder and must be secured to the main frame. Thus, in the present dies, ultrasonic vibrations are generally applied to the female die and to the blank holder in the radial direction or to the male die in the axial direction .

Patent No . JPS6221427 (A) is exemplary document for the state of art. That invention relates to a die for deep drawing and a method of operation thereof. The invention relates to switching the ultrasonic vibration produced by a vibrator in the deep drawing process to radial directional vibration. In the invention developed, the vibration of the vibrator is transferred to a cone to carry out reciprocal movement in the combined axial direction. The die portion is vibrated in the axial direction. Then, on the die working surface, due to a restriction in the axial direction by a blank holder, the vibration in the axial direction is converted into a vibration in radial direction by a die attachment. Vibration in the radial direction is also carried out in the die disk part and the mentioned vibration is transferred to a blank holder. After an oscillation of the entire vibration system, deep drawing is carried out by the backflow of the pressure oil of a hydraulic pump. In the mentioned document, the ultrasonic vibrations produced in the die in the axial direction and transferred to the female die are converted into radial vibrations via the restriction applied in the axial direction by the blank holder and transferred to the blank holder. Therefore, no ultrasonic vibration is applied to the blank holder in the axial direction.

In the case of existing dies where ultrasonic vibrations are applied to the blank holder in the axial direction, the ultrasonic unit cannot be placed under the blank holder in the center, since a punch must be present in the center cavity of the blank holder. For this reason, more than one ultrasonic unit is used to apply vibrations in the axial direction and these units are disposed circumferentially under the blank holder so as not to interfere with the punch. This leads to an increase in costs. Furthermore, it becomes difficult to control mentioned plurality of ultrasonic units, and problems may occur such that the vibration amplitude is not homogeneously distributed on the blank holder.

The Patent No . CN103920786A of the known state of art can be given as another example. The mentioned invention relates to a vibration-based sheet-forming machine comprising a flexible punch and to the method of operation of the same. The mentioned machine is, in its most general form, consists of a lower die holder, a female die, a blank holder, granular medium, a unit that applies force to the blank holder, a vibration unit, a press die (punch) , an upper die holder, support columns and support arms. In the operating method of the mentioned machine, the metal sheet to be formed is placed between the blank holder and the female die. Then, deep drawing process is performed on the metal sheet with the help of flexible die. The vibration unit applies vibration to the press die, the blank holder and the female die separately or in combination. Described herein is that, with the developed method, the friction and deformation resistance between plates and dies can be reduced under the effect of vibration, the fluidity and force transfer properties of the granular medium can be increased and the plate forming limit can be increased. The mentioned method is suitable for processing and forming parts into complex shapes. In the mentioned document, the blank holder force is provided by using more than one spring. For a smooth blank holder movement, the geometric properties and the spring constants of the springs used must be the same (identical) . This brings along some risks, since a possible problem to arise in any spring (material degradation, unbalanced load distribution, etc.) will disrupt synchronization with other springs and thus result in a defective forming process. In addition, in the relevant document, the ultrasonic vibration unit is located freely on the blank holder. In this case, the ultrasonic vibrations are damped by the blank holder spring located on the blank holder. In addition, it will not be possible to preload the blank holder spring in the relevant document.

In order to eliminate the disadvantages in the art, there is a need to develop a die which improves the forming performance of the material, applies vibration in the axial direction to the blank holder by means of a single ultrasonic vibration unit in deep drawing operations.

Detailed Description of the Invention

The invention relates to an ultrasonic vibration-assisted die which allows the material to be formed by deep drawing.

It is aimed to increase the limiting drawing ratio of the material and to reduce the forming load during the forming process. To this end, the invention is based on increasing the forming performance of the material by applying vibration in the axial direction to the blank holder by means of a single ultrasonic vibration unit.

The die according to the invention, in its general form, comprises a female die (1), a punch (2), an ultrasonic vibration unit, the ultrasonic horn (3) which is the equipment of the ultrasonic vibration unit being used as the blank holder. In more detail, it comprises a female die (1) which is fixed to the press ram and moves together with the same; a horn (3) as a blank holder, disposed on the press main frame; a punch (2) located in the central cavity of the horn (3); an ultrasonic vibration unit comprising the horn (3) and moving with the horn (3) in axial direction by transferring the ultrasonic vibration to the horn (3); a die base plate (7) having a cavity in the center which suitable for placement of the horn (3); a plurality of supporting blocks (8) carrying the punch (2); a blank holder spring (9) providing blank holder force; spring tension adjusting screw (10) for adjusting the pre-tension of the blank holder spring (9); coupling flange (11); and an outer case (12) secured to the base plate (7), comprising inside thereof the coupling flange (11), the blank holder spring (9) and the spring tension adjusting screw (10) .

In an embodiment of the invention, the drawn material is sheet metal ( 4 ) .

In an embodiment of the invention, the horn (3) is used as the blank holder. The ultrasonic vibrations act in the axial direction to the horn (3) .

In an embodiment of the invention, the blank holder spring (9) is a coil spring. The mentioned coil spring maintains the equipment of the ultrasonic unit in its center cavity to provide the blank holder force. This makes the system more compact and rigid.

In an embodiment of the invention, the forming is carried out by the movement of the female die (1) .

In an embodiment of the invention, the ultrasonic vibration unit comprises an ultrasonic horn (3), an ultrasonic transducer (5) that produces ultrasonic vibrations, and an ultrasonic booster (6) that transfers the vibrations to the horn ( 3 ) .

One embodiment of the invention consists of two main parts, one to be fixed to the main frame of the forming press and the other to be fixed to the ram of the press which enables movement. The part which is fixed to the press ram and moves with the ram is the female die (1) . The punch (2) and the ultrasonic horn (3), used as the blank holder, that is the other equipment required for the deep drawing process, are disposed on the part placed on the press main frame. In addition, the base plate (7), supporting blocks (8) carrying the punch (2), coil spring providing the blank holder force, the spring tension adjusting screw (10) required to adjust the tension of the mentioned spring, ultrasonic transducer (5) producing ultrasonic vibrations, ultrasonic booster (6) transferring vibrations to the horn (3), coupling flange (11) and the outer case (12) housing all these equipment are provided in the part disposed on the press frame.

In an embodiment of the invention, there is a cavity in the center of the female die (1) . The female die (1) is connected to the ram of the forming press and moves as a result of the ram's movement towards the punch (2) which is fixed so that the sheet metal (4) is drawn into the female die (1) cavity. In order to prevent the drawn material from being trapped in the female die (1), there is a cup ejector (13) operating in the cavity of the female die (1) and ejection spring (14) which will push the material drawn on the mentioned cup ejector (13) . A female die case (15) is provided for fixing the female die (1) to the press ram and compressing the material ejection spring (14) with the movement of the ram. When the punch (2) enters the cavity of the female die (1), the cup ejector (13) compresses the ejection spring (14) located in the female die case (15) and the compressed spring produces the thrust force required to remove the material (sheet metal (4) ) from the female die (1) .

In one embodiment of the invention, centering and fixing in the portion disposed on the press frame is performed using the base plate (7) . In the center of the base plate (7) , there is a cavity in which the horn (3) used as the blank holder can be placed. The horn (3) moves in the axial direction in this cavity by the movement of the female die

(1) . The punch (2) in the central cavity of the horn (3) is the fixed element of the deep drawing system. In order to be positioned in the middle of the horn (3) and to carry the punch (2) which must be fixed to the base plate (7), 4 slots have been grooved on the peripheral surface of the horn (3) such that they will not affect the vibration performance. Between these slots, placed are two supporting blocks (8) which establish a connection between the punch (2) and the base plate (7) and which will carry the punch (2) . The punch

(2) is thus secured to the base plate (7) . Furthermore, the supporting blocks (8) disposed between the slots do not contact the horn (3) and do not interfere with the movement of the horn (3) . During the forming process, a coil spring is placed under the flange region of the ultrasonic booster (6) in order to provide the blank holder force. The coil spring will form the blank holder force by being compressed as a result of the female die (1) pushing the horn (3) . Since there is no vibration in the flange region of the ultrasonic booster (6), it is suitable to place the spring, particularly in this part. The flange on the ultrasonic booster (6) is enlarged using the coupling flange (11) so that the coil spring can be securely compressed. The ultrasonic transducer (5) and the ultrasonic booster (6) operate in the center cavity of the blank holder spring (9) . The equipment of the ultrasonic vibration unit and the blank holder spring (9) are located in an outer case (12) fixed to the base plate (7) . The pre-tension of the blank holder spring (9) can be adjusted by the spring tension adjusting screw (10) which is placed to the end portion of the outer case (12) by threading. In order to transfer power from the ultrasonic generator to the ultrasonic transducer (5), a hole is drilled in the center of the spring tension adjusting screw (10) and thus a cable connection between the generator and the ultrasonic transducer (5) is provided. With the movement of the horn (3) used as the blank holder, the blank holder spring (9) is being compressed and other ultrasonic equipment (ultrasonic transducer (5) and ultrasonic booster (6)) connected to the horn (3) moves on the blank holder spring (9) .

Ultrasonic vibration unit includes ultrasonic generator, ultrasonic transducer (5), ultrasonic booster (6) and horn (3) equipment. The ultrasonic generator generates high- frequency voltage signals. Piezoelectric crystals present in the structure of the ultrasonic transducer (5) convert these signals into mechanical oscillations (vibrations) . The ultrasonic booster (6) acts as an amplitude transformer, thereby increasing the amplitude of the vibrations. The specific characteristics and geometric form of the ultrasonic booster (6) allow amplification or reduction in the amplitude of the vibration. Horn (3) is the active component of the ultrasonic system which transfers ultrasonic vibrations to the apparatus used for forming.

In an embodiment of the invention, the amount of preload to be applied to the blank holder is adjusted. All the equipment of the ultrasonic unit and the coil spring which holds this equipment are placed in an outer case (12) fixed to the die base plate (7) . To adjust the tension of the spring, spring tension adjusting screw (10) is disposed on the end portion of the outer case (12) by threading. In this way, the desired preload amount can be adjusted.

In an embodiment of the invention, the blank holder spring (9) is positioned in the flange region of the ultrasonic booster (6) element. The flange region of the ultrasonic booster (6) is where no vibration occurs. Therefore, there is no case that ultrasonic vibrations are damped due to the effect of the blank holder spring (9) .

One embodiment of the invention comprises the female die (1) fixed to the ram of the press and the punch (2) fixed to the press frame and the ultrasonic horn (3) used as the blank holder. Since the ultrasonic horn (3) is also developed as a blank holder, there is no need to use a further blank holder. The geometry of the horn (3) is of great importance for transferring the ultrasonic vibrations produced by the ultrasonic transducer (5) to the sheet metal (4) such that they are not damped. Furthermore, in order to connect the punch (2) located in the center of the horn (3) to the base plate (7), 4 slots have been grooved on the circumferential surface of the ultrasonic horn (3) . These slots have been developed in the widest and highest possible dimensions based on the resonance frequency so as not to affect the vibration performance of the horn (3) .

The forming load to which the punch (2) will be subjected during operation will act on the supporting blocks (8) which will fix the punch (2) onto the base plate (7) . For this reason, the supporting blocks (8) passing through the slots of the horn (3) were designed such that they will not contact the horn (3) and taking into consideration the forming load. The horn (3) used as the blank holder and the supporting blocks (8) carrying the punch (2) are the first to get tested in this field. These components are therefore is of critical importance for the invention.

The ultrasonic horn (3) used in place of the blank holder in the system of the present invention provides axial vibrations during the process. Slots were grooved on the surface of the horn (3) for fixing the punch (2), which should be positioned in the center of the horn (3), to the base plate (7) and the punch (2) was placed on the supporting blocks (8) passing through these slots. In this way, the position of the punch (2) in the system does not interfere with the operation and movement of the horn (3) .

In addition, in order to secure the punch (2) located at the center of the horn (3) used as the blank holder to the main body, slots were grooved on the peripheral surface of the horn (3) and it was ensured that the supporting blocks (8) passing through these slots without contacting the horn (3) could carry the punch (2) . The number and geometric dimensions of the mentioned slots can be improved by considering the desired amplitude and frequency levels of the horn ( 3 ) .

The invention, in brief, is an ultrasonic vibration-assisted deep-drawing die comprising a female die (1), a punch (2) and a blank holder, characterized in that the female die (1) is fixed to the press ram so that it moves with the press ram, in that it comprises, to be disposed on the press main frame, a horn (3) used as a blank holder and having a punch (2) in its central cavity; an ultrasonic vibration unit applying vibration to the horn (3) in an axial direction and having an ultrasonic generator, an ultrasonic transducer (5), an ultrasonic booster (6), and horn (3) equipment; a die base plate (7) having a cavity in the center of which the horn (3) can be placed; the plurality of supporting blocks (8) carrying the punch (2); a blank holder spring (9) positioned in the flange region of the ultrasonic booster (6), providing blank holder force; spring tension adjusting screw (10) for adjusting the pre-tension of the blank holder spring (9); coupling flange (11) and an outer case (12) secured to the main body, comprising inside thereof the ultrasonic vibration unit equipment, the blank holder spring (9), the spring tension adjusting screw (10) and the coupling flange (11) . The method of operation of the deep drawing die according to the invention is also within the scope of the invention. The method essentially comprises the following steps: moving the female die (1) connected to the press ram towards the punch (2) that is positioned and fixed on the press main frame by moving the press ram; drawing the material into the cavity of the female die (1); applying vibration to the horn (3) in the axial direction in the cavity located in the center of the base plate (7) by means of ultrasonic vibration; moving the horn (3) axially in the base plate (7); transferring the applied vibration to the material by the horn (3); forming the blank holder force by compressing the blank holder spring (9) by the female die (1) pushing the horn (3) .

An embodiment of the invention comprises the steps of converting high frequency voltage signals generated by the ultrasonic generator into mechanical oscillations (vibrations) by piezoelectric crystals partaking in the ultrasonic transducer (5) structure, increasing the amplitude of these vibrations by ultrasonic booster (6) and transferring the ultrasonic vibrations to the material to be subjected to forming process.

The invention eliminates the need to use a plurality of ultrasonic vibration units for applying axial vibration in existing systems. By using only one ultrasonic vibration unit, the invention reduces the cost and makes it much easier to control the system. In addition, differences that may occur due to the frequency and amplitude levels of a plurality of ultrasonic vibration units may produce a non- uniform vibration distribution on the blank holder. A single ultrasonic vibration unit taking place in the present invention provides a more uniform vibration distribution on the surface. With the present invention, the limiting drawing ratio of sheet metal (4) to which deep drawing is applied are increased while forming loads are significantly reduced. Thus, it is ensured that the sheets can be drawn deeper under less forming loads. Furthermore, the press, die, and energy costs are reduced with the invention.

Descriptions of the Figures

Figure-1 Isometric View of Ultrasonically Assisted Deep Drawing Die of the Invention

Figure-2 Front View of Ultrasonically Assisted Deep Drawing Die of the Invention

Figure-3 Isometric Views of the Parts of the Ultrasonically Assisted Deep Drawing Die of the Invention

Disclosures of the Reference Numbers Partaking in Figures

1. Female die

2. Punch

3. Horn

4. Sheet metal

5. Ultrasonic transducer

6. Ultrasonic booster

7. Base plate

8. Supporting blocks

9. Blank holder spring

10. Spring tension adjusting screw

11. Coupling flange

12. Outer case

13. Cup ejector

14. Ejection spring

15. Female die case

Claims

1. An ultrasonic vibration-assisted deep-drawing die comprising a female die (1), a punch (2) and a blank holder characterized in that the female die (1) is fixed to the press ram so that it moves with the press ram, and it comprises,

- a horn (3), to be disposed on the press main frame and used as the blank holder and having the punch (2) in its central cavity,

- an ultrasonic vibration unit applying vibration to the horn (3) in an axial direction and having an ultrasonic generator, an ultrasonic transducer (5), an ultrasonic booster (6) and horn (3) equipment;

- a base plate (7) having a cavity in the center of which that is suitable for the horn (3) to be placed;

- the plurality of supporting blocks (8) carrying the punch ( 2 ) ;

- a blank holder spring (9) positioned in the flange region of the ultrasonic booster (6), providing blank holder force;

- spring tension adjusting screw (10) for adjusting the pre-tension of the blank holder spring (9);

- coupling flange (11);

- and an outer case (12) secured to the main body, comprising inside thereof the ultrasonic vibration unit equipment, the blank holder spring (9), the spring tension adjusting screw (10) and the coupling flange (11).

2 . The die according to claim 1, wherein the punch (2) comprises a plurality of conduits in which the base plate (7) is placed in the supporting blocks (8) so that the punch (2) is disposed in the center of the horn (3) and secured to the base plate (7) .

3 . The die according to claim 2, wherein the slot count of the die base plate (7) is four.

4 . The die according to claim 1, wherein the horn (3) comprises slots through which the supporting blocks (8) pass .

5 . The die according to claim 4, wherein the slot count of the horn (3) is four.

6. The die according to claim 3, wherein it comprises two supporting blocks (8) disposed between mentioned slots.

7 . The die according to claim 1, wherein the blank holder spring (9) is a coil spring.

8. The die according to claim 7, wherein the coil spring is disposed below the flange region of the ultrasonic booster ( 6 ) .

9 . The die according to claim 1, wherein the ultrasonic transducer (5) and the ultrasonic booster (6) are located in the center cavity of the blank holder spring (9) .

10 . The die according to claim 1, wherein it comprises a female die case (15) for the female die (1) to be secured to the press ram and the material ejection spring (14) to be compressed together with the movement of the ram.

11 . The die according to claim 10, wherein the female die case (15) comprises a cup ejector (13) and an ejection spring (14) which form the thrust force that achieves the discharge of the material in case the drawn material is compressed.

12 . A method of operation of a deep drawing die according to any one of the preceding claims, wherein the method comprises the steps of:

- moving the female die (1) connected to the press ram towards the punch (2) that is disposed and fixed on the press main frame by moving the press ram, - drawing the material into the cavity of the female die ( 1 ) ,

- applying vibration to the horn (3) by means of ultrasonic vibration, in the axial direction in the cavity located in the center of the base plate (7),

- moving the horn (3) axially inside the die base plate (7) ,

- transferring the vibration applied to the material by the horn ( 3 ) ,

- forming the blank holder force by compressing the blank holder spring (9) by the female die (1) pushing the horn (3) .

13 . The method according to claim 12, wherein the method comprises the steps, in the ultrasonic vibration unit,

- converting high-frequency voltage signals generated by the ultrasonic generator into mechanical oscillations (vibrations) by piezoelectric crystals found in the ultrasonic transducer (5) structure,

- increasing the amplitude of these vibrations by the ultrasonic booster (6) .

14 . The method according to claim 12, wherein the ejection spring (14) is compressed by the cup ejector (13) in case the drawn material is compressed in the cavity of the female die (1) and the compressed ejection spring

(14) forms the thrust force required to remove the material from the female die (1) .

15 . The method according to claim 12, further comprising adjusting the pre-tension (pre-load amount) of the blank holder spring (9) with the spring tension adjusting screw (10) which is disposed to the end portion of the outer case (12) by threading.

16 . The method according to claim 12, further comprising compressing the blank holder spring (9) with the movement of the horn (3) used as the blank holder and moving other ultrasonic equipment (ultrasonic transducer (5) and ultrasonic booster (6)) connected to the horn (3) on the blank holder spring (9) .