Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
  • B21K21/00—Making hollow articles not covered by a single preceding sub-group
  • B21K21/04—Shaping thin-walled hollow articles, e.g. cartridges
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
  • B21D22/22—Deep-drawing with devices for holding the edge of the blanks
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
  • B21D22/28—Deep-drawing of cylindrical articles using consecutive dies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D51/00—Making hollow objects
  • B21D51/16—Making hollow objects characterised by the use of the objects
  • B21D51/54—Making hollow objects characterised by the use of the objects cartridge cases, e.g. for ammunition, for letter carriers in pneumatic-tube plants
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B33/00—Manufacture of ammunition; Dismantling of ammunition; Apparatus therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B5/00—Cartridge ammunition, e.g. separately-loaded propellant charges
  • F42B5/26—Cartridge cases
  • F42B5/28—Cartridge cases of metal, i.e. the cartridge-case tube is of metal
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F30/00—Computer-aided design [CAD]
  • G06F30/20—Design optimisation, verification or simulation
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F2113/00—Details relating to the application field
  • G06F2113/24—Sheet material

Definitions

• the present invention is directed to a method and system of forming from a metal sheet, preferably in the form of a disk to obtain an essentially cylindrical and essentially hollow final metal piece, with a bottom thickness essentially greater than the thickness of its walls.
• a metal sheet preferably in the form of a disk
• a bottom thickness essentially greater than the thickness of its walls.
• the invention is framed in the metalworking sector, and in a more concrete way to the manufacture of ammunition sheaths or caps.
• Deep drawing is a technique that allows an object whose shape is predetermined and essentially cylindrical and hollow to be obtained from a flat and essentially thin metal sheet with a specific thickness.
• the sheet is embedded in a drawing matrix by the mechanical action of a punch.
• Deep multi-stage drawing is characterized as a process that includes several consecutive drawing and re-drawing operations.
• Drawing is the action of mechanically deforming the flat metal sheet against the drawing matrix with the help of the punch.
• the re-drawing includes the repeated stages of drawing in which the piece is deformed iteratively until reaching the desired final shape.
• Stretching is characterized by being a process that allows reducing the thickness of the wall of the previously stuffed piece and consists of passing the previously stuffed piece through a stretching die.
• the manufacture of sheaths or shells for ammunition is carried out firstly by drawing operations to obtain the interior shape of the piece and subsequently reduce the thickness of the walls, and increase the length of the piece, by successive stretching operations.
• the stages of drawing, re-drawing and stretching are fundamentally defined by empirical-based design rules, without taking into account the plastic evolution of the material and without consideration as to the combination of stages or the optimization of the process.
• the present invention provides a different procedure that allows the manufacture of final parts with different design parameters and an optimized process that substantially improves the results obtained so far.
• This invention is based on the contributions made in the articles "The development of competencies in manufacturing engineering by means of a deep-drawing tool”, “Prediction of the limiting drawing ratio and the maximum drawing load in cup-drawing", “On multistage deep drawing of axisymmetric components "and” Energy of stretching in homogeneous deformation ".
• the definition of new methods based on assisted design, capable of improving some results has been the subject of patents, such as US Patent 7623939 B2 "Method of design a tool for deep drawing and tool for deep drawing of sheet metal", based on geometry parametrized and in the satisfaction of quality criteria. DESCRIPTION OF THE INVENTION
• the present invention provides a different procedure from the state of the art that allows the manufacture of final pieces with different design parameters resulting in a lower cost of the process and a lower energy consumption based on its dependence on forces, work and manufacturing time.
• the invention describes a process of forming a metal sheet to obtain an essentially cylindrical final metal part and essentially hollow according to claim 1 and a metal sheet forming system according to claim 6.
• forming refers to the forming of metal materials; that is, the technique of shaping a sheet or metal disk to obtain a piece of desired shape and volume.
• molded or “shaped.”
• a process of forming a metal sheet is presented to obtain an essentially cylindrical and essentially hollow final metal part in a system comprising at least the following elements:
• the process is carried out in a system comprising the described elements comprised in a machinery used for the process, each playing a role in the simultaneous drawing and drawing process of the invention.
• a drawing matrix is used per drawing step such that it contains the shape that in each step will be given to the metal piece to be obtained.
• each step is represented with an index i and n steps are completed.
• the punches are adapted to the internal dimensions of the internal diameters of the intermediate pieces in the intermediate stages to be obtained in the combined process.
• Each punch in each stage i is mechanically actuated on the sheet or disc (first stage) or metal part (following stages) by passing the piece first through the drawing matrix and then through the drawing matrix. So for each stage.
• the footsteps or fasteners of the part being stuffed (means for securing the part) of each stage i are used to prevent the appearance of wrinkles during the combined simultaneous drawing and drawing operation.
• processing means are used to program the operation of the machinery with parameters such as the working pressure of the machine and the travel speeds of the punches in approximation, operation and recovery.
• each element of the previously described is placed in a chain having, at each step of the chain, a drawing matrix, a punch, a fastening means, a stretching matrix, and it is operated consecutively completing the actions of a) to e) in each step of the chain.
• the metal sheet is provided, which in an exemplary embodiment has a disk shape, which is to be shaped.
• the operating parameters of the machinery in the first step of the chain are programmed by means of the processing means.
• the invention proposes the simultaneous combination of drawing and drawing processes in such a way that they are performed simultaneously, that is, drawing and drawing are no longer consecutive stages as in the state of the art but are performed in a single action, so that, in each step, the drawing matrix, the punch, the clamping means and the drawing matrix are actuated together causing all these elements to work at the same time.
• this invention allows obtaining parts with less total work developed and lower energy consumption during the process, by achieving more similar forces at each stage, to achieve the final piece, as well as in the intermediate stages, drawing coefficients , reduction coefficients of Wall thickness and length of the piece more uniform, producing minor deformations, all with a manufacturing cost and a shorter total process time, being therefore of the highest industrial interest.
• an essentially cylindrical and essentially hollow intermediate metal part is provided in the first stage, to be provided in the next stage of the chain.
• the intermediate metal parts are essentially cylindrical and essentially hollow, that is, in a tubular shape with variable section and hollow in the sense that the punch has been inserted in them so that a cavity inside of variable thickness, considerably different thickness remains. between the bottom of the piece and the walls, which characterizes the sheaths or ammunition shells.
• the final metal part sought Upon reaching the last stage n of the process, the final metal part sought is provided.
• the number of drawing and drawing stages combined depends on the relationship between the dimensions of the metal sheet to be formed and the dimensions of the final metal piece to be obtained, the ease of drawing the material and the thickness of the sheet. When more depth has to be given to the final metal piece to be obtained, more stages will be necessary for drawing and stretching and with it more tools and operations. Therefore it is necessary to provide for the way to always carry out operations with the least number of stages.
• the number of stages to be carried out is traditionally determined with data provided with the experience of the person skilled in the art, but they can be the result of simulations and optimizations to achieve less total work developed, lower energy consumption during the process, and achieve more similar forces at each stage.
• the stretching stages are mainly used to reduce the walls of parts such as automotive pipes, pipes, wires, etc.
• the system is the set of drawing dies, punches, drawing dies and fastening means and also the God of processing adapted to program all the machinery described.
• a computer program is presented, characterized in that it comprises means of program code for performing the simulation steps of a forming process.
• a support readable by a computer characterized in that it contains a computer program comprising program code means for performing the simulation steps of a forming process.
• an electronic signal is presented that contains information characterized in that it allows the reconstruction of a computer program according to the third inventive aspect.
• Figure 1 This figure shows a representation of the geometry of an artillery sheath, where the background thickness is substantially thicker than the walls.
• Figure 2 This figure represents a chain of production of metal parts by a process of forming a metal part like the one of the invention. In the figure the different elements are observed employees at every step of the chain.
• Figure 3a This figure represents a step i of the process of forming a metal sheet where the driven elements and the intermediate metal part with a certain shape are observed.
• Figure 3b This figure represents an intermediate step j of the forming process, j> i of the most shaped part of Figure 3a.
• Figure 4A This figure shows the evolution of the outer diameter of the piece that is obtained in each step in millimeters in an experimental example.
• FIG. 4Bn this figure shows the evolution of the wall thickness of the piece that is obtained in each step in millimeters in an experimental example.
• Figure 4CE This figure shows the evolution of the total length of the piece that is obtained in each step in millimeters in an experimental example.
• FIG. 5 This figure represents the evolution of the drawing ratio at each step of the process.
• FIG. 6 This figure represents a flow of actions performed in an optimized combined simulation process.
• the present invention relates to a process of forming a metal sheet (1) to obtain an essentially cylindrical and essentially hollow final metal part (2).
• the forming process is interesting in the manufacture of sheaths or ammunition shells whose particular geometry, represented in Figure 1, with the thicker background thickness than that of the walls allows drawing and drawing stages to be combined simultaneously for the manufacturing.
• the invention also relates to the system where the forming process is implemented.
• Sheet metal forming system The system, of which one of its embodiments is represented in Figure 2, comprises at least the elements:
• processing means • at least some processing means (4) adapted to provide all the previous elements with the full capacity to carry out the process (drawing and drawing force, working speed, etc.).
• step b) providing as a metal part, the essentially cylindrical and essentially hollow metal part (3) obtained in d),
• Figure 2 shows a production line with the tooling arranged in a chain so that in each step i is a position that is used to obtain an intermediate metal part (3).
• the metal sheet (1) is formed and from the last step n the final metal part (2) is obtained.
• the figure shows the processing means (4) as means adapted to accept input data through a numeric keypad and display means, such as a screen.
• a first stage drawing ratio, DR lt is applied which allows the thickness of the bottom to remain unchanged, since in one embodiment of the invention the application is the manufacture of ammunition sheaths, and it is It is essential to keep this background thickness constant throughout the multistage process.
• the forming parameters, work and number of stages, n are predetermined by a simulation process that allows to obtain a first combined solution.
• the simulation process can be executed by means of processing, for example a computer, or a microprocessor adapted to implement the stages of the optimized simulation.
• the combined simulation comprises two distinct parts: a simulation of drawing and drawing operations without combining simultaneously and a combination of the steps for combining drawing and drawing operations simultaneously.
• c) calculate and store simulation data, preferably data of the simulated intermediate metal part (1 1 w ) that has resulted as the diameter, length and thickness of the wall, and the parameters of the elements that have participated, such as the dimensions of the simulated elements: a simulated punch, a simulated clamping means and a simulated drawing matrix, the speeds of approach, operation and recovery of the punch, in step w,
• the drawing is simulated.
• the provision of the design data in the first stage is done by the user through data entry means, for example a computer keyboard.
• data entry means for example a computer keyboard.
• the data are used: inner diameter of the simulated metal part (10) to be obtained, length, depth of depth, wall thickness and type of material.
• the calculation, in the second stage, of the simulated metal sheet (9) necessary to obtain a simulated metal part (10) is performed by the processing means. This calculation is based on parameters such as the data entered by the user, and characteristics of the selected material, such as physical-chemical characteristics, in particular: density, tensile strength limit, creep resistance limit, behavior constant rigid-plastic, exponent of strain hardening and value of the normal anisotropy of the material. Considering the incompressible condition in the process of plastic deformation and constant the bottom thickness throughout the entire manufacturing process, the dimensions of the starting sheet (9) are obtained, which are the origin to develop the drawing steps, until the final dimensions of the simulated metal part (10) to be obtained are achieved.
• the initial dimension of elements used in a first simulation is calculated by the means of processing
• the design of this punch is calculated based on the limit drawing ratio and the final dimensions of the simulated metal part (10) to be obtained.
• the initial solution is determined based on the consideration of two deep drawing conditions.
• the first limit drawing condition is based on the fact that the maximum force made by the punch on the workpiece during the drawing process must be less than the breaking load of the material.
• the second drawing limit condition focuses on the limit drawing ratio and, considering the constant volume condition throughout the plastic deformation process, the value is determined limit of the drawing ratio for the conditions established by the input data, the normal anisotropy coefficient of the material considered, the efficiency factor of the drawing process and the strain hardening coefficient.
• an iterative process of simulation of drawing actions begins whose number of stages will be such that it is achieved, given the described characteristics of the selected material used, such as characteristics physicochemical, in particular: density, tensile strength limit, creep resistance limit, rigid-plastic behavior constant, strain hardening exponent and normal material anisotropy value, a simulated metal part (10 ) end whose inner diameter is the inside diameter of the simulated metal part (10) that is desired to be obtained.
• the walls of the piece are kept substantially constant throughout the steps successive drawing, maintaining the original thickness of the bottom of it, which coincides with the starting disc.
• the purpose of the successive drawing steps is to obtain certain dimensions of the piece in such a way that it is prepared for the subsequent drawing process, that is, to carry out drawing steps until the inside diameter of the piece (punch diameter) coincides with the inside diameter of the simulated metal part (10) that is desired to be obtained.
• the initial solution for the drawing step w ⁇ 1 is set based on the consideration of three drawing limit conditions.
• the first limit condition of re-drawing is fixed with the requirement that the maximum drawing force made by the punch on the simulated intermediate piece (1 1 w ) during the drawing process must be less than the breaking load of the material.
• the limit drawing ratio is applied in drawing operations, considering the effects of normal anisotropy of the material, the coefficient of friction, the coefficient of hardening by deformation and the radius of entry into the matrix.
• the limit drawing ratio is used in this model as a variable to determine the necessary number of drawing steps w and the corresponding tool dimensions. It is assumed that the material is rigid-plastic.
• the model determines the diameter of each step, giving a value to the diameter of the punch of a step w as a function of the relationship between the diameter of the previous step w - 1 and the limit of drawing limit.
• q as well as the parameters of the elements that They have participated, as the dimensions of the simulated elements: a simulated punch, a simulated clamping means, a simulated drawing matrix, the speed of the punch, in each step w, and the number q.
• stretching operations are simulated, that is, progressively reduce the wall thickness until the thickness of the final piece is achieved. New conditions are established for obtaining the diameters. The number of steps needed will depend on the dimensions of the final simulated metal part (10) to be obtained.
• the proposed model is based on the fulfillment of three stretching conditions in each of the drawing steps, and based on the data of the drawing process.
• the diameter of the intermediate metal parts (1 1 i-1 1 m ) is determined for each stretching limit condition and The largest diameter of the three is chosen since the model requires compliance with the three boundary conditions.
• the model stores the data obtained as that corresponding to an intermediate step j and again repeats the process. The process is recurring until the final thickness of the piece to be obtained is achieved.
• the first stretching limit condition is given by the fact that the average stretching tension must be less than the breaking stress of the material.
• This first stretching limit condition provides the diameter, depending on: the tensile strength limit of the material, a stretching coefficient that depends on the material, the diameter of the piece in the previous stage j - 1 and the stretching force in said step j-1.
• the second stretching limit condition it is expressed as the tension made in the material drawing process is less than the creep limit. Starting from annealed material and using an efficiency factor, the expression corresponding to the second stretching limit condition is determined, and the diameter, depending on the diameter of the previous stage j-1 and the increase in deformation.
• the forming parameters, work parameters and number of stages after having been predetermined by the simulation process without combining, are combined by a process that combines the number of stages for drawing and drawing so that the combined number n which depends on q and with which it is possible to operate the drawing and drawing simultaneously in the successive iterative steps instead of implementing them consecutively.
• the process that optimizes the number of stages for drawing and drawing so that the optimum number n is obtained is as described below.
• the simulation combines the drawing operations with the drawing operations, in such a way that the total number of stages is reduced, in addition to reducing the manufacturing time, the cost of the process, the total work performed and the energy consumption. In this way you get the optimal number n that depends on q and m, and includes the steps:
• the thickness of the final piece to be obtained is taken as the background thickness of the n combined stages, and remains unchanged throughout the combined process,
• K t stage thickness il,. ⁇ ,,. ,. ⁇ ,. ⁇
• the drafting rates DR ⁇ and the diameters of the intermediate stages of the combined process are obtained by calculating the parameters: diameter, thickness and the length of the intermediate stages that complete the process resolution, d ⁇ , Si, Z ⁇ , obtaining d ⁇ , s ⁇ iteratively taking the mentioned parameters and Z ⁇ as follows: K d ⁇ s n 2
• the thickness of the final piece to be obtained is taken as the background thickness of the n combined stages, and remains unchanged throughout the combined process
• the stretching ratios K ⁇ and the diameters of the intermediate stages of the combined process are obtained by calculating the parameters: diameter, thickness and the length of the intermediate stages that complete the process resolution, d ⁇ , Si, Z ⁇ , Obtaining d ⁇ , s ⁇ iteratively taking the mentioned parameters and Z ⁇ as follows:
• C E cost of electricity used to drive the machines used for drawing and drawing
• Wi total work in the simulation step /.
• the method of forming a metal sheet is implemented by previously carrying out the simulation and optimization processes.
• the manufacture of an ammunition socket made of brass UNS C26000 has been simulated.
• Table 1 shows the final dimensions of the piece to be obtained as well as the characteristics of the material used in the experiment. The friction coefficients that have been used are also included.
• Table 1 Final dimensions and material of the experiment
• the system consists of three parts: tooling, hydraulic system and control panel.
• the tooling consists of a support that houses the dies and fasteners.
• the punch is integral with the moving head of the press.
• control panel (12) the operation of the machinery is performed as well as the regulation of pressure, speed regulation and recording of pressures along the stroke of the punch.
• Figure 4A shows the evolution of the outer diameter of the piece that is obtained in each step in millimeters
• Figure 4B shows the evolution of the wall thickness of the piece that it is obtained in each step in millimeters
• figure 4C shows the evolution of the total length of the piece that is obtained in each step in millimeters.
• the new designed process (15) shows a much more compensated process than the traditional one
• table 2 shows the results represented in the graphs of Figures 4A, 4B and 4C.
• step 0 1 2 3 4 5 6 7 solution without combining 128, 1 122, 1 17, 1 14.2 1 12.0 1 10.6 1 10,
• the drawing ratio (DR) has similar values for the five stages designed, which shows a much more balanced process compared to the initial solution.
• the higher drawing ratios (DR) obtained in the first phases of the initial design (14) are reduced in the combined process (15).
• Simulation without simultaneously combining drawing and drawing stages Simulation stage of drawing steps.
• Simulation without simultaneously combining drawing and drawing stages Simulation stage of drawing steps.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Evolutionary Computation (AREA)
• Geometry (AREA)
• General Physics & Mathematics (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Forging (AREA)
• Metal Extraction Processes (AREA)
• Extrusion Of Metal (AREA)
• Heat Treatment Of Steel (AREA)

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• 2012
  • 2012-04-19 ES ES201230585A patent/ES2426319B1/es not_active Expired - Fee Related
• 2013
  • 2013-04-18 CA CA2870815A patent/CA2870815A1/en not_active Abandoned
  • 2013-04-18 WO PCT/ES2013/070249 patent/WO2013156656A1/es not_active Ceased
  • 2013-04-18 US US14/395,098 patent/US9908164B2/en not_active Expired - Fee Related
  • 2013-04-18 CN CN201380027649.6A patent/CN104364028B/zh not_active Expired - Fee Related
  • 2013-04-18 ES ES13731351.6T patent/ES2611338T3/es active Active
  • 2013-04-18 EP EP13731351.6A patent/EP2842650B1/en active Active
• 2014
  • 2014-11-18 IN IN9711DEN2014 patent/IN2014DN09711A/en unknown

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