Method of optimising the joints between layers in modelling or prototyping involving layer decomposition, and parts thus obtained

Translation of description of equivalent WO 2004079463 A1

Method 1 'Opit imisat ion j anointed strata in june modélisat ion or prototyping by decomposing into strata and parts obtained.

The present invention relates to a method for optimizing joints strata in their portion flush with the surface of a part obtained by modeling or prototyping of the type decomposition assisted strata

5 computer.

The invention also relates to the primary strata thus obtained, and that parts resulting from their assembly.

In a rapid prototyping process known type, eg subject of European Patent EP 0585502 -B1, we realize a prototype piece by putting

10 implements a software decomposition of the part to be produced into elementary strata, said strata being assembled together and the final assembly can be externally taken in particular to remove any asperities or assembly imperfections.

There is shown in Figures 3 and 4 schematically a detail

15 strata assembly with illustration of the problem.

In an assembly of two layers (1,2) a portion of the gasket (3) comes outside flush according to (4). It is understood that the region (5) of the layer (1) has at this place little material, which by machining, polishing, may result in removal of material precisely as this seal

20 schematically shown in Figure 4 (6).

This results in an imperfect part, non-uniform surface and therefore unsatisfactory for certain applications.

This design classic seal also has other drawbacks:

25 - low resistance;

- Poor resistance to machining;

- Poor resistance to mechanical stress during use (particularly stresses the pressure, whether mechanical or fluidic origin);

30 - poor resistance to all assembly operations: gluing, welding, grouting;

- Possible deformations during machining, manipulation and during assembly.

The invention aims to remedy these drawbacks. According to the invention a method for optimizing strata boundaries in their portion flush with the surface of a part obtained by modeling or prototyping of the type decomposition computer assisted strata is proposed in effect, characterized in that the profile connecting two successive strata is mathematically and numerically defined by implementing an algorithm in which the surface of the seal at the end region near the portion coming flush is always substantially normal to the plane tangent to the surface at the point outcrop.

The invention will be better understood using the description below of a number of implementation variants with reference to the accompanying drawings in which:

• 1A and a CAD representation of a complex part to be made, with some possible position variants,

• Figure 1 B illustrates a CAD layer obtained with the method of the invention, showing it in three dimensions,

• Figures 2A and 2B representing a layer obtained according to the invention, seen from above (Fig. 2A), and cutting (Fig. 2B),

• Figures 3.4 illustrate problems potentially with the layers of the prior art, where Figures 5 and 6 schematically illustrate the basic principle of the method according to the invention,

• Figures 7, 8A, 8B, 8C illustrate s simple variants implementation, • 9 illustrates an application of the undercut profiles and / or against undercut,

• Figure 10 shows a detail on stratum of an assembly according to Figure 9,

• Figure 11 shows a detail on a stratum assembly undercut according to Figure 9, with two variants,

• Figures 12A-F illustrate the application to a wall. firstly refers to Figure 5.

It was indicated in FIG essential parameters of a seal obtained according to the method of the invention: - Angle α between the tangent and the strata plan

- A: length of the joint

- B: offset stratum plane, n: normal at the junction. According to the invention, the seal (7) is normal to the tangent plane (T) of a length a.

Note that:

- If a is constant, b is f (α);

- If α = π / 2, b = 0. We thus solves the problem of the seal, as explained above, but the resulting strata requiring this type of calculation will be of varying thickness. In addition, the profile of the stratum is variable throughout the periphery. Furthermore, the joint line is not necessarily in the same plane.

For angles α close to π / 2, it will also provide for relative positioning means the plies together, as explained below. Reference is made to Figure 6.

All things being equal with respect to the embodiment of Figure 5, are carried out: a mastery of the material at the joint (goal) - a mastery of positioning (X, Y) by a centering insert (8 )

- A mastery of precision (Z) by the positioning profile (8 '),

- Control and strengthening the assembly and its mechanical strength. Various remarks may be made in this regard:

- The positioning profile is calculated with respect to the outer contour of the layer, the angle α being variable along the contour;

- The profile can be obtained in micromilling, milling or profile with a shape cutter. In the latter case, it is of course well established on the periphery;

- The socket is indeterminate; it is possible to provide games are in favor certain contacts.

Different variants are described briefly below: - In Figure 7, the socket is made dismountable by the presence of a against undercut (β) on the positioning profile (9), the arrangement being possible due to the elasticity of the materials;

- As shown in Figures 8A, 8B and 8C, it is also possible to arrange the joint to the outside depending on the desired degree of sealing, namely: o for supplying the additional material resulting in a bead outside by deformation: 8B and 8C, o to arrange a reserve seal, 8A. Is shown in Figures 9, 10 and 11 sample applications with the spoils and cons undercuts.

Details of the layers 8 and 9 show that the breakdowns are possible remains and cons undercut, always with the same principle of joint, the choice is also possible on the side of the socket (upper or lower stratum) or their combination in the space.

Finally, there is shown in Figures 12A to 12E of the walls application variants:

- Without socket: 12A;

- With outer socket and only map: 12B; - With indoor and outdoor socket and map: 12C; with indoor and outdoor socket on the same plane: 12D;

- With single normal decomposition: Figure 12 E;

- Socket with double setback: Figure 12 F. It will be seen from the above that it is scanning the profile that provides a binding profile and nesting mathematically defined functionally set.

There is no limit, the profile can be left, the joint surfaces can be complex and calculated. It will be understood that the major innovation lies in the principle of fitting the shapes are completely parameterized and dependent on the sectional area in which performs interleaving; it can be a planar surface but also a curved surface, as shown in Figures 1B; 2A and 2B. For the implementation of a geometric algorithm, the shape of interlocking joints is obtained by systematically computing.

Accordingly, the shape of the joint depends on the bedding plane, and it can not be known in advance. It may, in sockets, provide the functional parts of the functions induced in the final part, by non-limiting example, control channels (cooling, heating, etc ..) and / or supply of goods and assembly / or fluid circulation.

This process is used in all areas of design pieces by strata prototyping and rapid tooling already mentioned, with all conceivable possible extensions by the skilled person to the existing part of decomposition or designing new rooms.