METHOD OF DETERMINING LAYER THICKNESSES OF 3D MODELS FOR ADDITIVE MANUFACTURING

Abstract

The present invention relates to a method of determining layer thicknesses (t) of a three-dimensional model (1) for generation with an additive manufacturing apparatus, the method comprising: a step of determining the layer thicknesses (t) according to an adaptive slicing algorithm in which the thickness of a layer (2) is calculated through a relation based on the inclination of the normal vectors (n) of the surface elements (s) of the 3D model (1) which at least partly enclose the layer (2) from a horizontal direction (x; y) the method being characterized by further comprising: a step of selectively imposing on at least one surface element (s) of the 3D model (1) a precision requirement out of one or more selectable different precision requirements which respectively differently alter in the determination step the relation with respect to the inclination of the normal vector (n) of the said at least one surface element (s) which allows, through the altered relation, the layer thickness (t) to obtain a value smaller or larger than the layer thickness (t) determined through the unaltered relation.

Claims

1. A method of determining layer thick messes (t) of a three-dimensional model for generation of a corresponding three-dimensional object with an additive manufacturing apparatus, the method comprising: a step of determining the layer thicknesses (t) according to an adaptive slicing algorithm in which the thickness of a layer is calculated through a relation which defines a reference precision requirement (R), and is based on the inclination of the normal vectors (n) of the surface elements (s) of the 3D model which at least partly enclose the layer from a horizontal direction (x; y), the method further comprising: a step of selectively imposing on at least one surface element (s) of the 3D model a precision requirement out of one or more selectable different precision requirements which respectively differently alter in the determination step the relation with respect to the inclination of the normal vector (n) of the said at least one surface element (s), wherein the one or more selectable different precision requirements comprise at least one of a high precision requirement which allows, through the altered relation, the layer thickness (t) to obtain a value smaller than the layer thickness u) determined through the unaltered relation: and a low precision requirement (L) which allows, through the altered relation, the layer thickness (t) to obtain a value larger than the layer thickness (t) determined through the unaltered relation, wherein the reference precision requirement (R) is between the low precision requirement (L) and the high precision requirement.

2. The method according to claim 1, wherein among the layer thicknesses (t) calculated for surface elements (s) corresponding to the same layer through the said relation and imposed through the one or more differently altered relations, the smallest value is determined as the layer thickness (t).

3. The method according to claim 1, further comprising: a step of selecting one or more surface elements (s) of the 3D model on which one or more precision requirements may be selectively imposed.

4. The method according to claim 1, further comprising: a step of selecting one or more surface elements (s) of the 3D model on which one or more precision requirements must not be imposed.

5. The method according to claim 1, further comprising: a step of displaying the 3D model to a user on a display; and a step of allowing the user to selectively mark on the display of the 3D model the surface elements (s) for which a precision requirement out of one or more selectable different precision requirements is to be imposed.

6. The method according to claim 1, wherein the determined layer thicknesses (t) are constrained by a maximum value and a minimum value.

7. The method according to claim 1, wherein the selective imposing step is further based on the characteristic features of the 3D model to be manufactured and/or the characteristics of the additive manufacturing process.

8. A three-dimensional object corresponding to a 3D model according to claim 1, wherein the 3D object is a single piece dental drilling template, wherein at the top of the drilling template, in contrast to those parts where the said template rests on the tooth or where the drill is guided, the precision requirement imposed is a low precision requirement (L), and at the parts where the said template rests on the tooth or where the drill is guided, the precision requirement imposed is a high precision requirement.

9. A computer-program comprising codes for causing a computer-based system to execute the method according to claim 1.

10. A computer-readable storage means comprising the computer-program according to claim 9.

11. A computer-based system which is adapted to execute the method steps. according to claim 1.

12. A computer-based system according to claim 11, further comprising: a display for displaying the 3D model to the user; and an input means for allowing the user to selectively mark on the display of the 3D model the surface elements (s).

13. The computer-based system according to claim 11, wherein the computer-based system further comprises an additive manufacturing apparatus for generating the three-dimensional object.

14. The computer-based system according to claim 13, wherein the computer-based system further comprises a post-processing apparatus for post processing the 3D object generated by the additive manufacturing apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the subsequent description, further aspects and advantageous effects of the present invention will be described in more detail by using exemplary embodiments and referring to the drawings, wherein

[0020] FIG. 1—is a three-dimensional spherical model having thin layers according to a comparative example;

[0021] FIG. 2—is another three-dimensional spherical model having thick layers according to another comparative example;

[0022] FIG. 3—is another three-dimensional spherical model having layers solely determined through the adaptive slicing algorithm known from the prior art;

[0023] FIG. 4—is another three-dimensional spherical model having layers determined through the modified adaptive slicing algorithm according to an embodiment of the present invention;

[0024] FIG. 5—is another three-dimensional spherical model having layers determined through the modified adaptive slicing algorithm according to another embodiment of the present invention.

[0025] The reference numbers shown in the drawings denote the elements as listed below and will be referred to in the subsequent description of the exemplary embodiments: [0026] 1. 3D model (Object) [0027] 2. Layer

[0028] t: Layer thickness

[0029] n: Normal vector

[0030] S: Surface element

[0031] x, y: Horizontal direction

[0032] L: Low precision requirement

[0033] R: Reference precision requirement

[0034] The present invention provides a method of determining layer thicknesses (t) of a three-dimensional model (1) for generation with an additive manufacturing apparatus. The method comprises: a step of determining the layer thicknesses (t) according to an adaptive slicing algorithm in which the thickness of a layer (2) is calculated through a relation based on the inclination of the normal vectors (n) of surface elements (s) of the 3D model (1) which at least partly enclose the layer (2) from a horizontal direction (x; y). FIG. 3 shows a sphere as a comparative example of a 3D model (1) whose layer thicknesses (t) have been determined according to the said adaptive slicing algorithm well known in the prior art.

[0035] The method of the present invention further comprises: a step of selectively imposing on at least one surface element (s) of the 3D model (1) a precision requirement out of one or more selectable different precision requirements which respectively differently alter in the determination step the said relation with respect to the inclination of the normal vector (n) of the said at least one surface element (s). FIG. 4 shows a sphere as an example of a 3D model (1) whose layer thicknesses (t) have been determined according to an embodiment of the present invention. In this embodiment, the one or more selectable different precision requirements comprises at least a low precision requirement (L) which allows, through the altered relation, the layer thickness (t) to obtain a value larger than the layer thickness (t) determined through the unaltered relation. As shown in FIG. 4, the low precision requirement (L) is selected and imposed on the entire upper hemisphere which is marked with a bold arc. In this simplest embodiment, in the determination of the layer thicknesses (t), the surface elements (s) with the low precision requirement (L) are treated as if their normal vectors (n) were all perpendicular to the z-axis, and thus alter, in the determination step, the said relation with respect to the inclinations of the normal vectors (n) of the said surface elements (s). Thereby, these surface elements (s) do not lead to the same layer thicknesses (t), as shown in FIG. 3, and calculated through the unaltered relation based on the real geometry according to the adaptive slicing algorithm. As shown in FIG. 4, in the upper hemisphere having the low precision requirement (L) as marked with the bold arc, all layer thicknesses (t) obtain a maximum value which is larger than those of the corresponding layers (2) in the comparative example of the 3D sphere in FIG. 3, while in the lower hemisphere the adaptive slicing algorithm is applied as usual, namely with a reference precision requirement (R).

[0036] FIG. 5 shows another sphere as an example of a 3D model (1) whose layer thicknesses (t) have been determined according to an embodiment of the present invention. As shown in FIG. 5, the low precision requirement (L) is selected and imposed only on the entire left upper half hemisphere as marked with the bold arc and is thus dominated by the right upper half hemisphere that doesn't have the low precision requirement (L) but the reference precision requirement (R) which is higher. In this embodiment, among the layer thicknesses (t) calculated for the surface elements (s) corresponding to the same layer (2) through the said relation and imposed through the one or more differently altered relations, the smallest value is determined as the layer thickness (t). Therefore, despite of the low precision requirement (L) imposed on the left upper half hemisphere, these surface elements (s) lead to the same layer thicknesses (t) as shown in FIG. 3. Thus, the adaptive slicing algorithm is applied as usual namely with the reference precision requirement (R).

[0037] The present invention is not limited to a low precision requirement (L). In another embodiment (not shown), the one or more selectable different precision requirements comprises at least a high precision requirement which allows, through the altered relation, the layer thickness (t) to obtain a value smaller than the layer thickness (t) determined through the unaltered relation that corresponds to the reference precision requirement (R).

[0038] The reference precision requirement (R) lies between the low precision requirement (L) and the high precision requirement.

[0039] In another embodiment, the method comprises a step of displaying the 3D model (1) to a user on a display; and a step of allowing the user to selectively mark on the display of the 3D model (1) the surface elements (s) for which a precision requirement out of one or more selectable different precision requirements is imposed.

[0040] In another embodiment, the method comprises a step of selecting one or more surface elements (s) of the 3D model (1) on which one or more precision requirements may be selectively imposed. In an alternative embodiment, the method comprises a step of selecting one or more surface elements (s) of the 3D model (1) on which one or more precision requirements must not be imposed. Through either of the alternative embodiments, the selective imposition of the precision requirements can be restricted.

[0041] In another embodiment, the determined layer thicknesses (t) are constrained by a maximum value and a minimum value which are preset or adjustable by the user.

[0042] The comparative examples of the 3D spheres respectively shown in FIG. 1 to FIG. 3 can be also obtained by the method of the present invention. For instance, the 3D sphere in FIG. 1 can be obtained through imposing a high precision requirement onto the entire surface i.e., onto all surface elements (s). Thereby all surface elements (s) with the high precision requirement are treated as if their normal vectors (n) were all parallel to the z-axis, and thus all layer thicknesses (t) obtain a minimum value which is equal to or smaller than those of the corresponding layers (2) in the comparative example of the 3D sphere in FIG. 3.

[0043] For instance, the 3D sphere in FIG. 2 can be obtained through imposing the low precision requirement (L) onto the entire surface i.e., onto all surface elements (s). Thereby all surface elements (s) with the low precision requirement (L) are treated as if their normal vectors (n) were all perpendicular to the z-axis, and thus all layer thicknesses (t) obtain a maximum value which is equal to or larger than those of the corresponding layers (2) in the comparative example of the 3D sphere in FIG. 3.

[0044] For instance, the 3D sphere in FIG. 3 can be obtained through imposing none of the different high/low precision requirements onto the entire surface. Thereby all surface elements (s) are treated according to the real geometry, and thus the adaptive slicing algorithm is applied as usual namely with the reference precision requirement (R).