Data processing: measuring – calibrating – or testing – Measurement system – Dimensional determination
Reexamination Certificate
2002-08-19
2004-10-26
Bui, Bryan (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Dimensional determination
C702S170000, C072S014800, C072S021100
Reexamination Certificate
active
06810352
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for aiding optimization of a die assembly shape for plasticity manufacturing, particularly, relates to the system for aiding optimization of the die assembly shape to calculate a die assembly shape for manufacturing a plastic workpiece. Moreover, the present invention relates to a method for aiding optimization of the die assembly shape, a computer program product for aiding optimization of the die assembly shape, and a storage medium storing the computer program product.
2. Brief Description of Related Art
Conventionally, in automobile-related manufacturing industries, for example, developing a body with a light weight and high rigidity is desired. For this purpose, it is necessary to widely use a high tensile strength steel sheet. Moreover, applying an aluminium sheet is increasingly needed. However, the following problem arises: a fault in dimensional accuracy, exemplified by a springback occurring after press working a plastic workpiece. Here, the springback is defined as that a press worked metal member recovers an original shape. Therefore, for example, the shape of the workpiece which press worked in accordance with the designed shape deforms after removed from a die assembly (die and punch).
FIG. 12
shows an example of the fault in dimensional accuracy caused by springback in various automobile components.
Here, a specific example of an occurrence of springback will be described with reference to FIG.
13
.
FIG. 13A
to
FIG. 13D
are figures showing processes of press working for the plastic workpiece. First, a blank member
101
is installed in the die assembly (FIG.
13
A.). Next, the blank member
101
is held by the die assembly with a draw bead
103
formed in the blank holder
102
(
FIG. 13B.
) Then, draw shaping of the blank member
101
is performed by press working which uses a die assembly
104
and a punch
105
(
FIG. 13C.
) Following this step, the plastic workpiece is finished by removal from the die assembly (FIG.
13
D). Where, the workpiece has not been plastically shaped corresponding to the die assembly completely, but is deformed in different shape from the die assembly shape cause of the springback., i.e., the workpiece is deformed to different shape from designed shape, thus the fault of dimensional accuracy is occurred.
Therefore, conventionally, occurrence of the fault of dimensional accuracy caused by the above described springback was generally subjected to a measure by an experience and guesswork of an expert technician. The example thereof will be described with reference to FIG.
14
and FIG.
15
.
FIG. 14
is a flow chart showing the steps for optimization of the die assembly shape conventionally.
FIG. 15
is a sectional diagrammatic figure showing the plastic workpiece.
First, according to the designed shape of the plastic workpiece (B
0
of FIG.
15
), namely, the designed shape supplied to step of manufacturing the product, the die assembly shape is designed (step S
101
.) Then, the shape of the plastic workpiece manufactured by using this die assembly is calculated by simulation (step S
102
.) In this step, various manufacturing conditions such as characteristics of a material of the workpiece and a press working condition are considered. Particularly, a springback characteristic of the workpiece is considered. Thus, the shape calculated becomes, as shown in
FIG. 15
, the shape subjected to springback from a reference point P of the workpiece to a position indicated by an arrow C (after-springback shape (B
1
of FIG.
15
). Evaluation of dimensional accuracy calculated for the plastic workpiece is carried out by comparing with the shape of a product by a human (step S
103
and step S
104
.) As a result, if NG decision is made, on the basis of the shape of the product and the result of simulation, the human analyzes fault of dimensional accuracy to express as an angle difference in a predetermined part of and the position difference in coordinate values on a 2-dimensional plane to calculate the new designed shape of the plastic workpiece (step S
106
.) In other words, the new designed shape is calculated considering deformation by the springback after the workpiece is removed from the die assembly (springback-considered shape (B
exp
—
1
of FIG.
15
). The die assembly shape is corrected according to such new designed shape of the workpiece (step S
107
), and new die assembly shape is calculated. On the other hand, if the shape of calculated workpiece satisfies a requirement of dimensional accuracy in the step S
104
, an actual die assembly is manufactured according to the shape of the workpiece (step S
105
.)
However, the above described approach requires a human decision for the dimensional accuracy for every calculation of the shape of the plastic workpiece. In addition, for a correction of die assembly shape, it is required a much cost of die assembly correction including labor cost and cost for repeating the simulation (about 8% of the cost of die assembly manufacture) and many steps for it. As the result, the following problems arise: rise of a cost of the product and bad influence such as an increase in a period for development on a time schedule of production preparation. Consequently, a manufacturing method capable of deciding an optimal die assembly shape considering the fault of dimensional accuracy is desired in a stage where no real die assembly can be used.
On the contrary, fault of dimensional accuracy in a certain degree is expected to be forecasted by simulation using finite element method (FEM). It is in progress that the fault of dimensional accuracy in a level of 2-dimensional plane of the component is considered for design of the die assembly. A technology and system for deciding mechanically the die assembly shape properly considering a fault of 3-dimensional accuracy on the basis of the result of simulation has not been realized.
As the system for deciding a certain variables on the basis of the result of press working simulation, Japanese Published Unexamined Patent Application No. 10-170253, Japanese Published Unexamined Patent Application No. 8-287294, Japanese Published Unexamined Patent Application No. 2000-172731, have been published. All these applications are not technology and system for deciding mechanically the die assembly shape properly considering the fault of 3-dimensional accuracy.
SUMMARY OF THE INVENTION
The present invention has an objective of solving a defect of the above described conventional example and particularly improving dimensional accuracy of the plastic workpiece and providing the system, method and computer program product, for aiding optimization of the die assembly shape in plasticity manufacturing, capable of reducing a product cost and shortening manufacturing time duration.
Therefore, the present invention is constituted as that the computer comprises: an initial die assembly shape calculating function to calculate a die assembly shape for the plastic workpiece according to a predetermined designed shape of said plastic workpiece; a workpiece shape calculating function to calculate the shape of the plastic workpiece to be manufactured with the initial die assembly shape considering a manufacturing condition of the plastic workpiece; a shape comparing function to compare the calculated shape of the plastic workpiece and the designed shape of the plastic workpiece; a workpiece-redesigning function to calculate a new designed shape of the plastic workpiece according to a result of the comparison; and a die assembly reshaping function to calculate a new die assembly shape according to the new designed shape of the plastic workpiece.
And, it is preferable that the shape comparing function calculates a predetermined comparison value by comparing the predetermined designed shape of said plastic workpiece with the shape calculated by said workpiece shape calculating function, and said workpiece redesigning function and said die assembly reshaping function work each in the case wher
Bui Bryan
Suzuki Motor Corporation
LandOfFree
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