CN108829971B - Automatic detection method for mold core electromachining missing-dismantling electrode - Google Patents
Automatic detection method for mold core electromachining missing-dismantling electrode Download PDFInfo
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- CN108829971B CN108829971B CN201810604109.4A CN201810604109A CN108829971B CN 108829971 B CN108829971 B CN 108829971B CN 201810604109 A CN201810604109 A CN 201810604109A CN 108829971 B CN108829971 B CN 108829971B
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Abstract
The automatic detection method for the missing electrode in the mold core electromachining process includes the steps of firstly, respectively carrying out thickness tolerance offset on a mold core model and an electrode model, then carrying out model difference reduction processing on the mold core model and the electrode model to obtain a residual model, then converting the residual model to obtain a residual solid model, and finally obtaining a corresponding model of a drain electrode by judging the drain electrode of the residual solid model. The invention fully considers the influence of electrode missing on the processing of the die core, overcomes the problem that the quality detection cannot be carried out in advance when the lower die is manufactured, and realizes the automatic detection of the missing electrode in the preparation stage of die core electric processing.
Description
Technical Field
The invention relates to a technology in the field of complex electrode discharge machining, in particular to an automatic detection method for a missing disassembled electrode in a mold core electric machining preparation stage.
Background
In the design process of the electrode, in order to process a mold core with a complex structure, the number of the disassembled electrodes is large, and the electrodes are easy to be disassembled in a leakage way. The missing removal of the electrode can cause the deviation of the mold core processing. If the mold cannot be predicted in advance, the mold processing quality and period can be seriously influenced, and the cost is also increased. Therefore, before the die is machined, the automatic detection of the electrode missing disassembly is particularly important, and the electrode missing disassembly is earlier found to help improve the benefit.
Disclosure of Invention
The invention provides an automatic detection method of a mold core electric machining missing-dismounting electrode, aiming at the defects that the mold manufacturing cost is increased, the delivery is delayed, the production period is prolonged and the like due to the fact that the existing electrode is unreasonable in design, the influence of electrode missing-dismounting on mold core machining is fully considered, the problem that quality detection cannot be carried out in advance when a lower mold is manufactured is solved, and automatic detection of the missing-dismounting electrode in a mold core electric machining preparation stage is realized.
The invention is realized by the following technical scheme:
the method comprises the steps of firstly, respectively carrying out thickness tolerance offset on a mold core model and an electrode model, then carrying out model subtraction processing on the mold core model and the electrode model to obtain a residual model, then converting the residual model to obtain a residual solid model, and finally obtaining a corresponding model of the drain electrode by judging the drain electrode of the residual solid model.
The thickness tolerance offset is to perform translation offset on three vertexes of a triangular patch in the model along the normal direction of the triangular patch.
The translational offset is e' ═ e · f (α), wherein:
e is the original bias value of the system, and alpha is the included angle between the normal vector of the triangular patch and the correction vector.
The system original bias value refers to: the thickness tolerance of the machined mold core is in millimeter, and the general value range is that e is more than 0 and less than or equal to 0.5.
The correction vector is as follows: and a vector from the center of the triangular patch to the center of a triangle formed by connecting the centers of three adjacent triangular patches of the triangular patch.
The center is the intersection point of the bisectors of the three inner angles of the triangle.
The model difference subtraction processing is as follows: mutually Boolean combining the mold core model with the electrode model after the thickness tolerance deviation to obtain a mold core electrode model, and performing Boolean subtraction treatment on the mold core electrode model and the blank model by taking the mold core electrode model as an intermediate model body to obtain a residual model, wherein the blank model is obtained by simulating the mold core model by a machining tool path; based on the model difference subtraction processing, the processing efficiency of boolean subtraction can be greatly improved.
The invention relates to a system for realizing the method, which comprises the following steps: tolerance offset module, boolean processing module, model to solid model module and drain electrode judgement module, wherein: the tolerance offset module is connected with the Boolean processing module and transmits geometric information in an STL format, the Boolean processing module is connected with the model-to-entity model module and transmits entity geometric information of a residual body, and the drain electrode judging module outputs missing disassembly information.
The tolerance offset module and the boolean processing module both support, but are not limited to, the STL model.
Technical effects
Compared with the prior art, the method can conveniently and quickly detect the condition that the electrode is likely to be missed to be disassembled, and meets the requirements of improving the processing quality, shortening the production period and reducing the cost in the manufacturing process of the die.
Drawings
FIG. 1 is a flow chart of automatic detection of electrode missing detachment;
FIG. 2 is a schematic diagram of the offset of triangular patches on the mold core STL model;
FIG. 3 is a schematic diagram of a triangle patch vertex biasing operation;
FIG. 4 is a schematic view of an embodiment of a mold insert;
FIG. 5 is a diagram illustrating the residual entities after automatic detection and result labeling in the embodiment;
FIG. 6 is a diagram illustrating the residual entity after the electrodes are repaired and removed and the results are labeled.
Detailed Description
Fig. 3 is a schematic view of a mold core to be processed according to the present embodiment. The purpose of this embodiment is to automatically detect the missing electrode during the preparation stage of the electrical machining of the mold insert, so how to remove the missing electrode is not described herein, and the machining tool path is known. For the electrical discharge machining of the mold insert, the number of the initially removed electrodes was 42. The automatic detection process of the missing-stripped electrode will be described in detail below by taking the mold as an example.
Step one, generating a blank STL model and an offset mold core STL model: performing machining tool path simulation on the mould kernel model to generate a blank STL model; converting the mold core solid model to generate a mold core STL model, and then offsetting the mold core STL model by a thickness tolerance e to generate an offset mold core STL model;
the bias operation is to increase the robustness of the detection method, so as to prevent the failure of automatic detection caused by errors of two attached surfaces during Boolean operation. The offset values at different positions are different, and the corresponding offset value of each vertex can be obtained by means of a calculation function of the offset coefficient.
As shown in fig. 2, a triangular patch on the mold core STL model is used as an object for performing the offset operation, wherein a is a triangular patch on the mold core STL model, and b, c, and d are triangular patches adjacent to a; p1, p2, p3 are the three vertices of a, p10 is the center of a; p1, p2, p4 are the three vertices of b, p7 is the center of b; p1, p3, p5 are the three vertices of c, p8 is the center of c; p2, p3, p6 are the three vertices of d, p9 is the center of d; p11 is the midpoint of the three points p7, p8 and p 9; v1 is the normal vector for a, V2 is the vector for p10 pointing to p 11; let alpha be the included angle between V1 and V2, and the value range is [0, pi ].
Bias coefficient of said bias operation
When the offset value of the whole patch is e, the corrected offset value e' is e · f (α); calculating the offset of each vertex of the triangular patch based on the corrected offset value, and offsetting the vertices in the manner shown in FIG. 3, i.e. the offset is calculated
Thereby completing the biasing operation.
The value range of the original bias value e of the system is 0< e < 0.5.
Step two, converting the disassembled 42 electrode entity models to generate electrode STL models, and then biasing each electrode STL model along the movement direction of the electrode in the electric machining process to generate biased electrode STL models;
thirdly, performing Boolean merging operation on the offset mold core STL model and the offset electrode STL model, taking the generated mold closing model as a Boolean subtraction tool body, and performing Boolean subtraction operation on the mold closing model and the blank STL model to generate a residual STL model;
step four, performing entity conversion on all triangular patches in the residual STL model to generate and label a residual entity, and obtaining the residual entity subjected to automatic detection and result labeling as shown in FIG. 5;
the entity conversion is as follows: traversing all triangular patches in the residual model and acquiring adjacent patches of each triangular patch, and deleting the triangular patches if the number of the adjacent patches of the current triangular patch is less than 3; and finally, carrying out convergence fitting on the triangular patches left after traversal through modeling software to obtain a residual entity.
And step five, judging the drain electrode of the residual entity to obtain the drain electrode shown in fig. 5, and repeating the steps one to four again to obtain the residual entity shown in fig. 6 after automatic detection and result marking. Comparing fig. 5 and 6, it can be seen that the electrode missing problem has been repaired.
The judgment of the drain electrode is as follows: and traversing all model individuals in the residual entity, and sequentially carrying out size screening and shape screening to finally obtain a corresponding model of the drain electrode.
The size screening is as follows: removing the residual solid with a thickness less than 0.01 mm and removing the residual solid with a volume less than 1 cubic mm.
The shape screening is as follows: and (3) obtaining surfaces on the residual entities, sequencing the surfaces according to the area from large to small, taking the surfaces of the first 25% in the sequence, taking the midpoints of the surfaces under respective U-V coordinate systems, and marking as sampling points, wherein when the characteristic section of more than 50% of the points is approximately triangular, the residual entities are marked as leaky scarfing roots, and the residual entities which are not marked are marked as drain electrodes.
The characteristic section of the points refers to that: by making a group of auxiliary planes at a point on the surface of the body, wherein the normal vector of each auxiliary plane is perpendicular to the normal vector of the point on the surface, a closed section with the distance of 0 from the point can be taken out from the body through each auxiliary plane, and the section with the smallest area is marked as the characteristic section of the point on the body.
The approximate triangle is as follows: and (3) in three straight line segments or curve segments on the same plane, sequentially connecting the three straight line segments or curve segments end to end, wherein the included angles of respective normal vectors of the two connected straight line segments or curve segments at the intersection point are not equal to 0 or 180 degrees, and obtaining the geometric figure.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (6)
1. The automatic detection method for the missing-removed electrode in the mold core electromachining is characterized in that a mold core model and an electrode model are subjected to thickness tolerance offset respectively, then model subtraction treatment is carried out on the mold core model and the electrode model to obtain a residual model, then the residual model is converted to obtain a residual solid model, and finally a corresponding model of a drain electrode is obtained by carrying out drain electrode judgment on the residual solid model;
the thickness tolerance offset is to perform translation offset on three vertexes of a triangular patch in the model along the normal direction of the triangular patch, and the offset is
Wherein:
，eis the original offset value of the system,
the included angle between the normal vector of the triangular patch and the correction vector is formed;
the correction vector is as follows: a vector from the center of the triangular patch to the center of a triangle formed by connecting the centers of three adjacent triangular patches of the triangular patch;
the judgment of the drain electrode is as follows: traversing all model individuals in the residual entity, and sequentially carrying out size screening and shape screening to finally obtain a corresponding model of the drain electrode;
the size screening is as follows: removing the solid bodies with the thickness less than 0.01 mm and the volume less than 1 cubic mm in the residual solid bodies;
the shape screening is as follows: and (3) obtaining surfaces on the residual entities, sequencing the surfaces according to the area from large to small, taking the surfaces of the first 25% in the sequence, taking the midpoints of the surfaces under respective U-V coordinate systems, and marking as sampling points, wherein when the characteristic section of more than 50% of the points is approximately triangular, the residual entities are marked as leaky scarfing roots, and the residual entities which are not marked are marked as drain electrodes.
2. The method of claim 1, wherein the mold core model is modeled by machining a tool path of the mold core solid model to form a blank STL model; then converting the mold core solid model to obtain a mold core STL model;
and the electrode model obtains an electrode STL model by converting the disassembled electrode entity model.
3. The method of claim 1, wherein the model difference subtraction process is: and mutually Boolean combining the mold core model with the electrode model after the thickness tolerance deviation to obtain a mold core electrode model, and performing Boolean subtraction treatment on the mold core electrode model and the blank model by taking the mold core electrode model as an intermediate model body to obtain a residual model, wherein the blank model is obtained by simulating the mold core model by a machining tool path.
4. The method of claim 1, wherein transforming the residual model into the residual solid model comprises: traversing all triangular patches in the residual model, acquiring adjacent patches of each triangular patch, and deleting the triangular patches when the number of the adjacent patches of the current triangular patch is less than 3; and finally, carrying out convergence fitting on the triangular patches left after traversal through modeling software to obtain a residual entity.
5. The method of claim 1, wherein the characteristic profile of the points is: making a group of auxiliary planes through a point on the surface of the body, wherein the normal vector of each auxiliary plane is perpendicular to the normal vector of the point on the surface, and a closed section with the distance of 0 from the point can be cut off on the body through each auxiliary plane, wherein the section with the smallest area is marked as a characteristic section of the point on the body;
the approximate triangle is as follows: and (3) in three straight line segments or curve segments on the same plane, sequentially connecting the three straight line segments or curve segments end to end, wherein the included angles of respective normal vectors of the two connected straight line segments or curve segments at the intersection point are not equal to 0 or 180 degrees, and obtaining the geometric figure.
6. A system for implementing the method of any of claims 1-5, comprising: tolerance offset module, boolean processing module, model to solid model module and drain electrode judgement module, wherein: the tolerance offset module is connected with the Boolean processing module and transmits geometric information in an STL format, the Boolean processing module is connected with the model-to-entity model module and transmits entity geometric information of a residual body, and the drain electrode judging module outputs missing disassembly information.
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