WO2018219446A1

WO2018219446A1 - Method for producing a grid model of a workpiece and storage medium

Info

Publication number: WO2018219446A1
Application number: PCT/EP2017/063142
Authority: WO
Inventors: Nicola Maria CERIANI
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-05-31
Filing date: 2017-05-31
Publication date: 2018-12-06

Abstract

The invention relates to a method for producing a grid model (3) of a workpiece (5) for a production machine for producing the workpiece (5). The aim of the invention is to improve the compromise betwen the accuracy of the representation of the digital model (2) by the grid model (3) and the storage requirement of the grid model (3). To this end, the grid model (3) is generated by means of a predetermined conversion specification on the basis of a digital model (2) of the workpiece (5), and, for the predetermined conversion specification, a maximum deviation (17) between the outer form of the grid model (3) and the outer form of the digital model (2) in a first partial region (30) is predefined by a first tolerance specification (37), and a maximum deviation (18) between the outer form of the grid model (3) and the outer form of the digital model (2) in a second partial region (32) is predefined by a second tolerance specification (35).

Description

description

A method of providing a mesh model of a workpiece and a storage medium

The invention relates to a method for providing a grid model of a workpiece, a production machine for producing the workpiece. The invention also relates to a storage medium with a program code.

For designing or designing a workpiece CAD programs are often used. In doing so, a digital model of the workpiece is made. CAD programs usually use a proprietary file format to store the digital model. This file format may not be used for other applications. To one

Production machine an image of the workpiece

Therefore, a grid model of the workpiece is often generated based on the digital model. The

Grid model is composed of primitives, such as triangles or squares. Since it is often impossible to obtain an exact representation of the digital model by the grid model based on the basic elements, a deviation in the external shape between the grid model and the digital model can occur.

To allow sufficient accuracy of the representation of the digital model through the grid model

have algorithms for generating the

Grid, also called meshing, often

Accuracy specifications. examples for this are

Angular specifications, limit specifications or arc tolerances:

Angle specifications can, for example, specify a minimum angle between two adjacent basic elements,

For example, limit specifications can specify a minimum distance between two surfaces, in particular basic elements, For example, arc tolerances may dictate a maximum distance between the grid model and the digital model.

One or more of the specified accuracy specifications may be fixed by a CAD program and / or adapted by a user. The more stringent the

Accuracy specifications are set, the smaller the basic elements of the grid model can be selected. This increases due to a larger number of basic elements of memory requirements. Therefore, there is always a conflict between good accuracy of the representation of the digital model through the grid model and low memory requirements for the grid model. In particular, the

Production machine have limited storage space. In this case, the storage requirements of the grid model must not exceed the limited storage space of the production machine.

It is an object of the present invention to provide an improved trade-off between the accuracy of the representation of the digital model by the grid model and

To allow storage requirements of the grid model.

This object is achieved by the

Objects of the independent claims. Advantageous embodiments with expedient developments are the subject of the dependent claims. Advantageous embodiments and expedient developments of the method according to the invention also apply analogously to the storage medium according to the invention or the program code stored thereon.

The invention is based on the recognition that for

different portions of the workpiece different manufacturing tolerances are to be observed. According to the invention, those partial areas of the workpiece for which high

Requirements for the manufacturing tolerance are to be met by the grid model with higher accuracy are represented, as such portions of the workpiece, for which lower requirements are to be adhered to the manufacturing tolerance.

To solve the problem of the invention is thus

provided that

- The grid model by means of a predetermined

Conversion rule is generated based on a digital model of the workpiece, wherein

for the predetermined conversion rule, a maximum deviation in the external shape between the mesh model and the digital model in a first partial region by a first tolerance indication and a maximum deviation in the external shape between the mesh model and the digital model in a second partial region by a second partial region

Specify tolerance.

The deviation in the outer shape between the

Grid model and the digital model may be, for example, by a distance between them

Be defined points on the surface of the grid model and the digital model. The corresponding points on the surface may, for example, lie on a straight line running perpendicular to the surface of the digital model.

The first tolerance specification is, in particular, a production tolerance for the workpiece in the first subarea. The second tolerance specification is in particular a production tolerance for the workpiece in the second partial area. Thus, the first

Tolerance indication and / or the second tolerance specification describe a permissible deviation from a nominal dimension of the component in the respective sub-range. The nominal size can be specified by the digital model. The permissible deviation from the nominal dimension can be specified as a percentage, by a factor or in absolute terms. For example, the first include

Tolerance indication and / or the second tolerance indication respective tolerance window within which the deviation of the workpiece from the nominal size is tolerable.

Possible predetermined conversion rules for generating the grid model are known in the art. An example of the predetermined conversion rule is the Delaunay triangulation. An accuracy specification of the predetermined conversion rule can be adapted on the basis of the first tolerance specification and / or the second tolerance specification such that the deviation of the external form between the mesh model and the digital model in the respective partial region the maximum deviation of the external shape between the mesh model and the digital model does not exceed in the respective sub-area.

The first tolerance indication and / or the second tolerance indication can be automatically predefined based on a technical function of the respective subrange. For example, it is provided that the workpiece in the first

Part area is in communication with another workpiece. In particular, the workpiece may be mounted in its first portion of another workpiece. This allows one, compared with other parts of the workpiece,

lower manufacturing tolerance for the workpiece in the first sub-area may be necessary. For example, it is provided that the workpiece in the second portion is not associated with any other workpiece. As a result, a greater manufacturing tolerance can be tolerated in the second subarea than in the first subarea. In each of the examples mentioned, the first tolerance specification may be smaller than the second tolerance specification.

Accordingly, the first tolerance indication and the second

Tolerance be different. In other words, by the first tolerance indication and the second

Tolerance specification different manufacturing tolerances

be specified. Thus, by the first

Tolerance indication and the second tolerance indication different Tolerable deviations from the nominal size of the component can be specified.

A further embodiment provides that the smaller the maximum deviation of the external shape between the grid model and the digital model is specified, the finer a respective resolution is selected for the grid. In other words, based on the maximum deviation of the outer shape between the grid model and the digital model in one of the subregions, the resolution for the

Grid in the appropriate sub-range can be specified. Thus, the resolution in the first partial area and / or the second partial area can be determined by the first partial area

Tolerance indication or the second tolerance indication can be specified indirectly.

A further development provides that it is determined how well the shape of the digital model in the first subarea and / or the second subarea can be represented by basic elements of the grid model. In particular, it is determined how well the shape of the digital model in the first subarea and / or in the second subarea match. A good representation or a good agreement between the basic elements of the

Grid model and the shape of the digital model is recognized, for example, when the shape of the primitives is triangular and the shape of the digital model is rectilinear or angular. Good representability is recognized in another example when the shape of the digital model can be accurately replicated by the primitives. A bad representation

or a bad match between the basic elements of the grid model and the shape of the digital model is recognized, for example, when the shape of the primitives is straight and the shape of the digital model is round or curved. In particular, the respective resolution for the grid can additionally be selected based on the representability of the digital model by the basic elements. In particular, the respective resolution is selected the finer the worse the representability and the smaller the maximum deviation of the outer shape is given.

The basic elements of the grid model are in particular triangular. Alternatively, the primitives may be quadrangular or n-sided. Triangular primitives have proven to be a good compromise for good representation of the digital model.

A further development provides that when pretending the

maximum deviation in the first partial area and / or in the second partial area through the first tolerance indication

or by the second tolerance indication a

Machining tolerance of the production machine is taken into account. The machine tolerance is in particular a tolerance, which is caused by the production machine. In other words, the crafted

Production machine the workpiece with a maximum

Deviation from the grid model in the amount of

Machine tolerance. For example, the maximum

Deviation in the outer shape between the grid model and the digital model in the first and / or the second sub-range by the first tolerance indication or the second tolerance indication, taking into account the

Machine tolerance specified.

When considering the machine tolerance, the maximum deviation in the first partial area and / or in the second

Subregion by subtracting the machine tolerance of the first tolerance indication or the second

Tolerance determined. This is based on the recognition that the machine tolerance and the deviation in the external shape can add up between the grid model and the digital model. For example, that gives way Grid model by the maximum deviation in the outer shape of the digital model. In addition, that can

Workpiece to deviate from the grid model by the machine tolerance after manufacture. Thus, the machined workpiece, added to the machine tolerance, may differ from the digital model with the deviation between the mesh model and the digital model. Alternatively, it can be assumed that machine tolerance and deviation of the

Grid model at least partially mutually

compensate.

A further development provides that for aligning

Basic elements in a boundary region between the first portion and the second portion of the grid model is refined in the boundary region of the coarser of the sub-areas. In particular, the grid model in the boundary region of the coarser of the subregions is refined such that no conflicts between basic elements of the first

Subarea and the second subarea occur.

For example, a conflict is referred to when corners and / or edges of adjacent basic elements of different subregions do not overlap one another. In this case, by refining the grid of the coarser of the

Subareas are achieved, that the corners and / or edges adjacent basic elements different subregions lie on each other. In particular, the resolution and / or the number of basic elements of the coarser of

Subareas in its border area increased.

A second aspect of the invention relates to a storage medium having a program code adapted to

Method according to one of the preceding claims

perform. The storage medium is

For example, to an optical disk, such as CD, DVD or BLU-Ray to a flash memory, such as a USB stick to a hard disk of a computer or

Memory of a computer. The program code is in particular by a computer program for the design of Workpieces includes. The program code is preferably part of a CAD software.

Further features and advantages will be apparent from the following description with reference to the accompanying figures. In the figures, like reference numerals denote like features and

Functions. The embodiments are merely illustrative of the invention and are not intended to limit this.

Show it:

1 shows a screenshot of a computer program, with a digital image of a workpiece;

2 shows a flow chart of an embodiment of the

inventive method;

3 shows another example of a digital model

a workpiece;

4 shows an exemplary grid model of the workpiece from FIG. 3.

1 shows a screenshot of a computer program. In the present case, the computer program is a CAD program for designing or designing a workpiece 1. The workpiece 1 is represented in the computer program as a digital model 2. By means of the

Computer program is an image of the workpiece 1 for a production machine for producing the workpiece. 1

provided. The image of the workpiece 1 is provided in the form of a grid model 3 for the production machine. For this purpose, the grid network model 3 is generated on the basis of the digital model 2.

The workpiece 1 has a plurality of different regions 20, 21, 22. The areas 20, 21, 22 have different functions. For example, areas 20 for Coupling be carried out by means of a splint. level

Areas 21 may be designed for storage and a warehouse. In summary, the areas 21 and the areas 20 are areas which are in a designated

Installation position of the workpiece 1 are in contact with other components. Finally, areas 22 as

Connection areas are understood. The areas 22 are in particular in the intended installation position of the workpiece 1 in no contact with other components. The intended installation position of the workpiece 1 designates in particular a position in which the workpiece 1 can be installed in a technical complex or device.

Due to their function or the different contact with other components in the installation position can for the different areas 20, 21, 22

Different manufacturing tolerances may be possible. The computer program includes several in this context

Adjustments for the different areas 20, 21, 22.

For example, a first import function 12

so-called PMI (Product and Manufacturing Information) are imported via the workpiece 1 from a database. In the database general tolerances for the workpiece 1 or groups of workpieces can be stored.

For example, the workpiece 1 by the first

Import function 12 assigned to a group of workpieces and loaded for the group tolerances from the database. On the basis of these tolerances from the database, respective tolerance indications 15 for the manufacturing tolerance of the workpiece 1 in each of the regions 20, 21, 22 can be specified for each of the regions 20, 21, 22. In particular, a function of the respective one of the regions 20, 21, 22 is taken into account. For example, for the

Areas 20, 21, which in the intended

Installation position in contact with other components, automatically a respective closer tolerance indication 35, 36 are given, as for the areas 22, which are in the intended installation position in no contact with other components. For the area 22 will be in

Compared to the areas 20, 21 a less close

Tolerance specified 37.

Alternatively or additionally, 13 user inputs of a user can be imported by means of a second import function. The second import function 13 can be activated on the basis of a user input. For example, tolerances 15 for individual regions 20, 21, 22 from further user inputs are generated by the second import function 13

imported. By way of example, the user first selects the second import function 13 and can then assign respective tolerance indications 15 to the regions 20, 21, 22. The

Tolerance information 15 can now be imported through selection menus 10, 11.

For example, the regions 20 are assigned a circular cylindrical tolerance of +/- 0.01 mm. For example, the areas 21 a planable tolerance of +/- 0.02 mm

assigned. For example, the areas 22 a

Assigned tolerance of +/- 0.1 mm. In other words, each of the regions 20, 21, 22 can be assigned a respective tolerance indication 15. Each tolerance indication 15 may have a value for a deviation from the nominal size and / or a type of

Tolerance (for example, planar or cylindrical) have.

The manufacturing tolerances for the workpiece 1, which are specified by the tolerance data 15, can be understood as the maximum deviation of the workpiece 1 after its production by the digital model 2. In other words, by means of the respective tolerance indications 15 for different regions of the workpiece 1 it can be specified to what extent deviations from the digital model 2 can be tolerated. According to the flowchart of FIG

Algorithm 4 for generating the grid based on the digital model 2 and on the basis of the tolerance information 15 generates the grid model 3. The grid model 3 may be an approximate representation of the digital

Model 2 act. In other words, the digital model 2 is not exactly imaged by the mesh model 3. The algorithm 4 is therefore given a value for a maximum deviation of the grid model 3 from the digital model 2. In other words, Algorithm 4 will do so

set that the grid model 3 at most by the value for the maximum deviation from the digital model 2 deviates. The algorithm 4 may be a

Algorithm for generating grids, as known in the art act. However, the value for the maximum deviation of the grid model 3 from the digital model 2 is predefined on the basis of the tolerance data 15.

For example, the algorithm 4 is based on the

Tolerance information 15 adapted so that the tolerance information 15 for the workpiece 1 are met. In other words, the grid mesh model 3 is considered in consideration of

Tolerance information 15 created so that the workpiece 1 after production by the production machine meets the tolerance specifications 15.

Since errors in the mapping of the digital model 2 by the grid model 3 and by production errors of the production machine can add up, a machine tolerance 16 is additionally considered here. The

Machine tolerance 16 can specify with which tolerance the production machine the workpiece 1 on the basis of

Grid model 3 can produce. In other words, by the machine tolerance 16, a maximum deviation between dimensions of the workpiece 1 and the

Grid model 3 be predetermined. By way of example, the maximum deviation of the grid model 3 from the digital model 2 is achieved

Subtracting the machine tolerance 16 predetermined by the tolerance 15. In other words, the

Machine tolerance 16 and the maximum deviation of the

Grid model 3 added the respective tolerance indication 15 for a range 20, 21, 22 correspond. Alternatively it can be assumed that deviations between grid model 3 and digital model 2 with

At least partially offset production errors by the production machine. In this case, the maximum deviation of the grid model 3 from the digital model 2 can be set greater than in the case of

Subtracting the machine tolerance 16 of the tolerance information 15. In this case, the maximum deviation of the grid model 3 of the digital model 2 is always smaller than that

Tolerance 15.

The generation of the grid model 3 will now be explained with reference to FIG 3 and FIG 4 in a concrete example. FIG. 3 shows a digital model 2 of a further workpiece 5. FIG. 4 shows the lattice network model 3 of the further workpiece 5. In this case, the workpiece 5 is only in the FIG case

presented in two dimensions to the explanation and the

Simplify drawing. The workpiece 5 has three

Areas 30, 31, 32 on. The areas 30, 32 are in

Essentially circular. The area 31 is substantially rectangular. For the two circular areas 30, 32 are

different tolerances 15 basis. Based on the tolerance information 15, a respective value for a maximum deviation 17, 18 between the grid network model 3 and the digital model 2 is specified for the two circular areas 30, 32. In the present case, the tolerance default 35 for the

Area 32 is narrower than the tolerance preset 37 for the area 30. Thus, the Tolervor vorgäbe 35 a smaller deviation between the digital model 2 and workpiece 1 Accordingly, a lower value for the maximum deviation 18 is specified for the region 32 than for the maximum

Deviation 17 in the range 30.

In the grid model 3, the digital model 2 is represented by the size, location and position of primitives 9. A density of basic elements 9 can be referred to as resolution. For example, the resolution is calculated as the number of primitives 9 per unit area or

Volume unit specified. The basic elements 9 are

preferably triangular, but may also be square or polygonal.

When generating the grid model 3 is first checked how the shape of the digital model 2 in the

Areas 30, 31, 32 can be represented by the basic elements 9. For example, angular or prismatic areas, such as rectangular area 31, may be angular

Basic elements 9 are well represented. For example, round or circular areas, such as

circular areas 30, 32 are represented poorly by angular basic elements 9. The less well the shape of the digital model 2 in the regions 30, 31, 32 can be represented by the primitives 9, the finer the resolution for the mesh model 3 in the respective regions 30, 31, 32 can be selected.

As already described above, based on the tolerance data 15 and optionally the machine tolerance 16, the maximum

Deviation 17, 18 between digital model 2 and

Grid model 3 are given. In the present case, the resolution of the grid network model 3 is also selected as a function of the respective value for maximum deviation 17, 18. In other words, the resolution of the grid mesh model 3 in the areas 30, 31, 32 depends both on the maximum deviation 17, 18 and on the representation of the shape by the basic elements 9. A lower value for the maximum Deviation 17, 18 is given, the finer the resolution in the underlying range 30, 32 can be selected. The rectangular area 31 may be through the triangular

Basic elements 9 are represented very well. Therefore, in this area 31, a low resolution is sufficient. Despite the low resolution, an exact representation of the digital model 2 can be achieved by the grid model 3 in the region 31.

The circular areas 30, 32 can through the

triangular basic elements 9 are poorly represented. A representation of the circular shape is only approximately possible by the triangular basic elements 9. Therefore, there is a deviation between the grid model 3 and the digital model 2. Depending on the respective value for the maximum deviation 17, 18 for the areas 30, 32, the resolution in the respective area 30, 32 is selected. The value for the maximum deviation 17 in the region 30 is greater than the value for the maximum deviation 18 in the region 32. For this reason, the resolution in the region 32 is selected to be finer than in the region 30 between two of the

Areas 30, 31, 32 conflicts due to the different resolutions, the grid model 3 in the coarser of the areas 30, 31, 32 can be refined. Refining means, in particular, that the resolution is increased. A conflict is in particular referred to when adjacent edges and / or corners of two basic elements 9 are not superimposed.

Due to the different resolutions in the areas 30 and 32 storage space for the grid model 3 can be saved. Nevertheless, sufficient representation accuracy for the respective area can be ensured in each of the areas 30, 31, 32. Because of that Manufacturing tolerance for the workpiece 1, 5 is already specified when creating the digital model 2, it is ensured that the workpiece 1, 5 meets qualitative requirements.

Claims

claims

1. A method for providing a grid model (3) of a workpiece (5) for a production machine for

Producing the workpiece (5), wherein

- The grid model (3) by means of a predetermined

Conversion rule based on a digital model (2) of the workpiece (5) is generated, and wherein

for the predetermined conversion rule, a maximum deviation (17) in the outer shape between the

Grid model (3) and the digital model (2) in a first portion (30) by a first tolerance (37) and a maximum deviation (18) in the outer shape between the mesh model (3) and the digital model (2) in a second portion (32) by a second tolerance indication (35) is given.

2. The method according to claim 1, characterized in that the first tolerance indication (37) and / or the second

Tolerance indication (35) by means of a technical function of the respective sub-range (30, 32) are automatically specified.

3. The method according to any one of the preceding claims, characterized in that the first tolerance indication (37) and the second tolerance indication (35) are different.

4. The method according to any one of the preceding claims, characterized in that the smaller the maximum deviation (17, 18) in the outer shape between the grid mesh model (3) and the digital model (2) in the first portion (30) and / or the second subregion (32) is predetermined, the finer a respective resolution is selected for the grating network model (3).

5. The method according to any one of the preceding claims, characterized in that it is determined how well the shape of the digital model (2) in the first portion (30) and / or the second subregion (32) can be represented by basic elements (9) of the grid model (3).

6. The method according to claim 5, characterized in that the basic elements (9) of the grid model (2) are triangular.

7. The method according to any one of the preceding claims, characterized in that when specifying the maximum deviation (17, 18) first portion (30) and / or in the second

Part area (32) through the first tolerance indication (37)

or by the second tolerance indication (35) a machine tolerance (16) of the production machine is taken into account.

8. The method according to claim 7, characterized in that when taking into account the machine tolerance (16), the maximum deviation in the first partial region (30) and / or in the second partial region (32) by subtracting the machine tolerance (16) from the first tolerance indication (37). or second tolerance indication (35) is determined.

9. The method according to any one of the preceding claims, characterized in that for aligning basic elements (9) in a boundary region between the first portion (30) and the second portion (32), the grid model (3) in the boundary region (33) of the coarser Subareas (30)

is refined.

10. Storage medium with a program code which is designed to carry out a method according to one of the preceding claims.