FR2679158A1 - METHOD AND PUNCHING PUNCH FOR MANUFACTURING REGULAR WALL CONTAINERS. - Google Patents

Abstract

The invention relates to a method for deep-drawing blanks of flat metal products having undergone a drawing or rolling operation, with a view to carrying out subsequent deep-redrawing or repeated-passing operations or with a view to manufacturing flanged containers, in particular cylindrical containers, characterised in that a punch is used whose tip has a variable transition (coupling) radius which is determined as a function of the anisotropic characteristics of the blank material. Advantageously the next step is an operation for grinding the bottom of the container by using a punch having a constant transition (coupling) radius. Application to the manufacture of metal tumblers.

Description

The present invention relates to a method of

  blanking of blanks for the manufacture of

  which may have a corresponding collar

to the non-stamped part of the flan.

  The blanks are generally made of a metal which has undergone a drawing or rolling operation, so that this metal has an anisotropy with regard to the resistance to thinning. Thus, when making collared containers of cylindrical section in circular blanks, for example steel having undergone extensive skin-pass operations, during the stamping, it creates different thinning and thickening on the body of the stamped objects and the collar obtained is irregular; it has a sinuous profile including

  "horns" and "hollow of horns".

  In the case of a stamping without collar, the irreversibility

  The uniformity is at the end of the wall.

  This irregularity creates significant obstacles during subsequent operations (the case of re-pressing or

ironing).

  The result is an irregular flange which, during an additional cutting operation, creates

  significant losses of base material.

  To decrease this effect of horn formation,

  a minimum hold is usually used under

  blank, that is to say that one works at the minimum pressure of greenhouse, at the limit of the appearance of folds on the flange In this solution, the stamping operation swallows in the matrix a

  greater quantity of metal and to obtain

  days the same dimension of collar, one is brought to

  increase the dimensions of the starting blank.

  The present invention therefore proposes to provide a method which makes it possible to reduce the formation effect

  without increasing the amount of material used.

See.

  The subject of the invention is a stamping process

  flat blanks of flat metal products which have undergone a drawing or rolling operation, with a view to carrying out subsequent operations of re-pressing or

  ironing or for the manufacture of glue

  particularly cylindrical containers, which are

  terized in that one uses a punch whose nose

  has a variable connection radius which is

  based on the anisotropic characteristics of the

blank material.

  The punch thus has a variable or evolving connection radius which is determined so as to

  to compensate for the anisotropic nature of the material used.

  The connection radius is determined according to the resistance to thinning of the material considered or LANDFORD coefficient. It is thus possible to determine for each base material and each container to manufacture the ideal profile of the punch nose which makes it possible to obtain

  a practically regular collar.

  Advantageously, it is then possible to carry out an additional operation of grinding the bottom of the container obtained by using a punch with a radius of

constant connection.

  This rectification operation makes it possible to render

  more regular the shape of the bottom of the container obtained.

  According to another characteristic of the invention, this grinding operation is carried out only in certain areas of the bottom of the container. This is done in particular in the case where the difference between the radii

  minimum and maximum connection of stamping punch

wise are important.

  This grinding operation can be used to create bosses in the bottom of the container; advantageously these bosses are four in number They serve as a support zone for the container

  whose background is not in contact with his

  This prevents damage, for example by scratching, an illustration carried by the outer wall

from the bottom of the container.

  The invention also relates to a punch

  stamping machine for carrying out the precise process

  té, characterized in that its nose has a variable radius of connection; advantageously, the nose of the punch comprises four zones distributed at right angles, having a maximum connection radius and separated

  by areas with a minimum connection radius.

  According to one embodiment of the invention, the maximum connection radius of the nose of the punch is equal

at five times its minimum radius.

  Other features and advantages of the

  will be apparent from the following description of a

  embodiment of the invention, with reference to the accompanying drawings, in which: FIGS. 1 to 3 show respectively the containers obtained in a stamping process of

  known type, in a stamping process according to the invention

  and in a stamping process according to the invention in which a grinding operation was then carried out;

  Figures 4 to 6 are corresponding curves

  respectively in Figures 1 to 3 and showing the thickness of the material at different points A, B, C, D and E of the side wall of the container obtained; FIGS. 7 to 9 are curves representing the thickness of the side wall of the container obtained in a known type of stamping process and in a stamping process according to the present invention,

  respectively for a transverse, longitudinal direction

  dinal and oblique with respect to the direction of stretching or rolling; and

  FIG. 10 is a partial perspective view

  tive stamping punch according to the invention.

  FIG. 1 is an exploded perspective view of the container obtained by a stamping process of known type using a punch whose nose has a

  constant connection radius; in the example shown

  As regards the manufacture of metal cups from 0.18 mm thick thin iron blanks which has undergone a major skin-pass operation, the radius of connection of the punch nose is 2 mm for a cup of which the diameter is 65 mm and the height is 45 mm. In this case, it can be seen that the flange 1 has an irregular shape and has horns 2 separated by horn cavities 3 The radius of connection of the punch nose is found at the bottom of the container and the connection radius of this bottom 4 with the wall 5, R1 or R2, is

constant and equal to 2 mm.

  The associated curve 4 represents the thickness of the vessel wall at different points A, B, C, D and E; the curve in solid line corresponds to a direction of formation of hollow of horns and the curve in broken line to a direction corresponding to the

horn formation.

  These horns and hollows correspond to different values of the coefficient of resistance to thinning of the material used or LANDFORD coefficient which is defined by the following formula: e 2 e 3 in which E 2 is the deformation in width and

  E 3 the deformation in thickness The directions of formation

  of horns correspond to a high LANDFORD coefficient and directions of horn formation

  at a low LANDFORD coefficient.

  FIGS. 2 and 5 correspond to FIGS. 1 and 4 and represent the product obtained in an embossing process with an evolutionary radius according to the invention. It can be seen that the flange 11 is very regular and that there is no longer any horn or Moreover, it appears from FIG. 5 that the distribution of the thickness of the wall is much more regular than in the known type of drawing process, the differences in thicknesses between the directions with a low coefficient of LANDFORD and LANDFORD high-coefficient directions

are smaller.

  The profile of the cup obtained corresponds to the profile of the punch used. The radius R11 of connection in an area normally corresponding to a formation of depressions is of small value, for example 1 mm, whereas the connecting radius R 12 corresponds to one direction.

  horn formation is higher, for example 5 mm.

  It can be seen that the modulation of the radius of connection of the nose of the punch as a function of the LANDFORD coefficient makes it possible to eliminate the formation of horns and troughs while using the same starting blank, ie the same amount of material In addition, one uses a pressure

normal blank holder.

  FIGS. 3 and 6 correspond to the case where the embossing method according to the invention was used by carrying out an additional operation of rectification of the bottom of the receptacle by using a punch with a regular profile. This treatment concerns practically only the bottom of the container. container, without stretching of the wall During this treatment, the shape of the flange 21 remains unchanged, but "catch up" important connecting radii

  corresponding to a high LANDFORD coefficient (forma-

  For example, the radius R 12 of FIG. 2 is reduced from 5 mm to a value R 22 of 2 mm, the radius R 21 corresponding to the low LANDFORD coefficient.

remaining unchanged.

  In FIG. 6, it can be seen that the dashed curve corresponding to the coefficient directions

  for which the operation is carried out

  rectification, is slightly modified in parti-

  in connection zone A.

  This rectification operation can not generally

  not be pushed to a regular profile.

  bind for the bottom of the box when using materials with significant anisotropy such as

  steels that have undergone an important skin-pass operation

  This grinding operation is performed so as to create slight bosses 26 protruding from the bottom of the container in the rectified areas; these bosses, which are four in number, are support surfaces of the container on its support, which allows to preserve the outer face of the bottom of the contact with its support In this way, we can avoid degradation, for example by stripe, a decorative pattern

  affixed or made on the outer face of the bottom 24.

  Figures 7 to 9 are representational curves

  the thickness of the wall of the container obtained according to a known type of process (solid curves) and

  according to a method according to the present invention (

  line) in a perpendicular direction

  in the rolling direction (FIG. 7), parallel to the direction of rolling (FIG. 8) and in a direction of 45.degree.

  compared to the first two (Figure 9).

  In Figure 7, the solid line curve corresponds to

  lays at a connection radius equal to 2 mm and the dashed line at a radius of 1 mm, ie in a direction where the LANDFORD coefficient is high; FIG. 8 corresponds to the same conditions and in these two cases, the connection radius for the known type of drawing process (solid lines) is 2 mm and the connection radius for the known type process (curves in FIG. broken line) is 1 mm. FIG. 9 corresponds to the oblique directions which form an angle of 45 with respect to the rolling direction and which are not privileged orientations such as the regions perpendicular or parallel to the rolling direction (FIGS. 6 and 7). In the case of FIG. 6 the connecting radius of the solid line curve is 2 mm and the radius of connection of the broken line curve corresponds to the radius Rll of Figure 2 and is

equal to 5 mm.

  From the examination of these FIGS. 7 to 9, it can be seen that the method according to the invention makes it possible to obtain a more even distribution of the thickness of the walls of the

  container in all directions.

  Indeed, the invention makes it possible to reduce the coefficient

  The value of this coefficient is for a known type of process and the method according to the invention, respectively, which is defined by: where O is the original thickness and the average thickness after stamping are 1.035 and 0.997 in the direction perpendicular to the rolling direction (Figure 7), 1.006 and 0.971 for the direction parallel to the rolling direction (Figure 8) and 0.969 and 0.972 for the direction

at 45 (Figure 9).

  It can be deduced that the process according to the invention

  tion makes it possible to obtain a better circu-

  the thickness of the thickness, the coefficient Ma passing from the value 0.025 for the known process to the value 0.006 for the process according to the invention, and a greater stretching on the height of the box, the passing coefficient of the value 0.995. at the value 0.978 for the process according to the invention. These two coefficients A "and to, which are well known in the art of stamping, are defined as follows: Aa a (L) + a (T) -2" (45) aa (L) + a ( T) + 2a (450) and Oa (L), a (T) and a (450) being the values of the coefficients of thinning a in the directions

  longitudinal, transverse and oblique at 45.

  Figure 10 shows partially in perspective

  A punch stamping machine for implementing the method just described This punch 41, which has been shown essentially the working face,

  has a connecting nose 42 with connection radius

  The zones 43 correspond to directions at an angle of 45 with the rolling axis 44 and the transverse axis 45; the zones corresponding to the axial direction 44 and the transverse direction 45 are areas where the connection radius is minimal As indicated above, the minimum radius is equal for example

  at 1 mm and the maximum radius at 5 mm.

  The Applicant has manufactured metal cups

  with the dimensions indicated above in blanks of 0.18 mm thick thin irons which have undergone a major skin-pass operation. It has been found that a 20% gain is obtained on the additional residual surface of the flange, a gain of 5% on the diameter of hollow horns which can result in a reduction of more than 3% of the initial blank surface Moreover, it was possible to reduce the forces of

retained under a 50% blank.

  The amplitude of the horns has been reduced by 42% on the collar This is particularly important in the case of making cups with patterns from preprinted blanks In fact, in this case,

  the illustration of the goblets is much more regular.

  In low LANDFORD coefficient directions, the connection radius was halved compared to the usual connection radius and doubled in high coefficient directions. This comparison was made with respect to stamping processes considered as the best performers

according to the prior art.

  It can be seen that the invention makes it possible both to obtain

  a gain in material and a better regularity of the thickness of the collar and the walls of the container

  obtained, which increases the mechanical strength of the latter.

  The field of stamping a material in terms

  of restraint force under blank is increased.

  This invention also applies to cups which require, for their obtaining, several sequences of stamping and redrawing In these cases where the horns and hollows of horns are an obstacle during resumption of re-pressing, the intermediate cups

  do not have a collar The regularity in thick-

  the wall of stampings is a factor of success

during subsequent operations.

he

Claims (6)

  1 Process for stamping blanks of flat metal products which have undergone a drawing operation or   rolling mill, in order to carry out subsequent operations   re-pressing or ironing machines or for producing flanged containers, in particular cylindrical containers, characterized in that a punch is used whose nose has a variable radius of connection which is determined according to   anisotropic characteristics of the blank material.   2 stamping method according to claim 1, characterized in that one proceeds then to an operation of rectification of the bottom of the container in   using a punch with constant connection radius.   3 stamping process according to claim 2, characterized in that the grinding operation of the bottom of the container is carried out only in certain areas of the last.   4 Pressing method according to claim 3, characterized in that the grinding operation is   as it creates bosses in the bottom of the recipe   tainer. Pressing method according to claim 4, characterized in that the grinding operation creates four bosses.   6 stamping method according to claim 1, characterized in that the maximum connection radius of the nose of the punch is equal to about five times its minimum radius. 7 Stamping punch for the implementation   method according to any one of claims 1 to   6, characterized in that its nose (41) has a radius variable connection.   8 stamping punch according to claim 7, characterized in that its nose (41) comprises four zones (43) distributed at right angles, having a maximum radius of connection and separated by zones (44, 45). with minimum connection radius.