Pressed component manufacturing method, die designing method, die shape designing device, and die

A die designing method, the die being used in press forming a metal sheet into a final component shape through a plurality of press steps, the die designing method comprising:

• selecting one step from the plurality of press steps and setting the one step as a selection step, a component shape obtained in the selection step being set as a selected component shape;
• selecting one press step from the plurality of press steps to be carried out before the selection step and setting the one press step as a reference step, a shape of the metal sheet before press forming in the reference step being set as a reference shape, wherein the press steps from the reference step to the selection step include a press step having drawing,
• a cross section setting step of setting a line orthogonal to, in plan view, a direction in which a material flows when the metal sheet of the reference shape is drawn into the selected component shape by a single step, and setting a plurality of cross sections individually cut by each of planes orthogonal to the line in plan view and extending in a direction along a sheet thickness direction of the metal sheet before forming;
• an inflow amount calculation step of individually determining the inflow amount of the material required for forming the reference shape into the selected component shape based on a cross-sectional line length of the selected component shape cut by the cross section, a cross-sectional line length in the reference shape cut by a same cross section as the cross section, and a uniform elongation of the material of the metal sheet for each cross section;
• an inflow amount distribution step of distributing the determined inflow amount to each step from the reference step to the selection step for each cross section;
• a cross-sectional line length calculation step of individually calculating the cross-sectional line length for each cross section in each step from the reference step to a step one before the selection step based on the distributed inflow amount;
• and
• a shape determination step of determining a die shape used in each step from the reference step to the step one before the selection step based on the calculated cross-sectional line length,
• a manufacturing step of manufacturing a die having the determined die shape in a step from the reference step to the step one before the selection step.

A die shape designing device for, in press forming a metal sheet into a final component shape through a plurality of press steps, determining a die shape of a die used in each step excluding a final press step, wherein

• when one step is selected from the plurality of press steps and set as a selection step, a component shape obtained in the selection step is set as a selected component shape, one press step selected from the plurality of press steps and carried out before the selection step is set as a reference step, and a shape of the metal sheet before press forming in the reference step is set as a reference shape,
• the press steps from the reference step to the selection step include a press step having drawing,
• the die shape designing device comprising:
• a cross section setting unit configured to set a line orthogonal to, in plan view, a direction in which a material flows when the metal sheet of the reference shape is drawn into the selected component shape by a single step, and set a plurality of cross sections individually cut by each of planes orthogonal to the line in plan view and extending in a direction along a sheet thickness direction of the metal sheet before forming;
• an inflow amount calculation unit configured to individually determine the inflow amount of the material required for forming the reference shape into the selected component shape based on a cross-sectional line length of the selected component shape cut by the cross section, a cross-sectional line length in the reference shape cut by a same cross section as the cross section, and a uniform elongation of the material of the metal sheet for each cross section;
• an inflow amount distribution unit configured to distribute the determined inflow amount to each step from the reference step to the selection step for each cross section;
• a cross-sectional line length calculation unit configured to individually calculate the cross-sectional line length for each cross section in each step from the reference step to a step one before the selection step based on the distributed inflow amount;
• and
• a shape determination unit configured to determine the die shape in each step from the reference step to the step one before the selection step based on the calculated cross-sectional line length, wherein
• a die is manufactured having a determined die shape in a step from the reference step to the step one before the selection step.

A die used in each step when a pressed component is manufactured by press forming a metal sheet into a final component shape through a plurality of press steps, wherein

• when one step is selected from the plurality of press steps and set as a selection step, a component shape obtained in the selection step is set as a selected component shape, one press step selected from the plurality of press steps and carried out before the selection step is set as a reference step, a shape of the metal sheet before press forming in the reference step is set as a reference shape, and the press steps from the reference step to the selection step include a press step having drawing,
• for a forming surface of a die used in each step from the reference step to the selection step,
• the forming surface of the die in the selection step has a shape following the selected component shape,
• a line is set, the line being orthogonal to, in plan view, a direction in which a material flows when the metal sheet of the reference shape is drawn into the selected component shape by a single step using the die in the selection step, and a plurality of cross sections is set, the cross sections being individually cut by each of planes orthogonal to the line in plan view and extending in a direction along a sheet thickness direction of the metal sheet before forming,
• for each cross section arranged along an extending direction of the set line, each of the cross-sectional shapes cut by the plurality of cross sections in the forming surface of the die in each step is set from an inflow amount of the material set based on a cross-sectional line length of the selected component shape cut by the cross section, a cross-sectional line length in the reference shape cut by a same cross section as the cross section, and a uniform elongation of the material of the metal sheet, and
• a number of the plurality of cross sections is defined as n, a subscript identifying each cross section is defined as i (1≤i≤n), a line length in the selected component shape is defined as Li1 and a line length in the reference shape is defined as Li2, which are cut by the same cross section for each cross section, the uniform elongation of the material is defined as El, a number of the press steps from the reference step to the selection step is defined as m, and a subscript identifying the press step is defined as j (1≤j≤m),
• for the set inflow amount of the material, an inflow amount (Li3) of the cross section i is set by Expression (1) below,
• a cross-sectional line length (Li4) of the cross section i in the forming surface of a die used in a j-th step is represented by Expression (2) below, and
• a coefficient bk (1≤k≤m) satisfies Σj=1m(bk)=1,
• Li3=Li1−Li2−a·El (1),
• wherein, 0<a<1 is established,
• Li4=Li2+Σk=1j(bk·Li3) (2),
• wherein 0≤bk≤1 is established.