(19)
(11)EP 3 159 148 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
26.04.2017 Bulletin 2017/17

(21)Application number: 16195931.7

(22)Date of filing:  19.04.2012
(51)International Patent Classification (IPC): 
B29C 67/00(2017.01)
B33Y 30/00(2015.01)
B33Y 10/00(2015.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 20.04.2011 IT VI20110099

(62)Application number of the earlier application in accordance with Art. 76 EPC:
12724706.2 / 2699408

(71)Applicant: DWS S.R.L.
36016 Thiene (VI) (IT)

(72)Inventor:
  • COSTABEBER, Ettore, Maurizio
    36010 ZANE' (VI) (IT)

(74)Representative: Marchioro, Paolo et al
Studio Bonini S.r.l. Corso Fogazzaro, 8
36100 Vicenza
36100 Vicenza (IT)

 
Remarks:
This application was filed on 27-10-2016 as a divisional application to the application mentioned under INID code 62.
 


(54)METHOD FOR PRODUCING A THREE-DIMENSIONAL OBJECT


(57) The invention is a method for producing a three-dimensional object (11) in layers by means of a stereolithography machine (1) comprising: a container (2) containing a fluid substance (3) suited to solidify through exposure to predefined radiation (4a); means (4) suited to emit the predefined radiation (4a) and to solidify a layer of the fluid substance (3) adjacent to the bottom (2a) of the container (2); a modelling plate (5) suited to support the solidified layer (6) and associated with actuator means (7) suited to move it perpendicular to the bottom (2a) of the container (2); levelling means (8) arranged in contact with the fluid substance (3), the levelling means (8) comprising a paddle (9) developed according to a longitudinal direction and having an edge facing the container's bottom (2a) and arranged inside the container (2). The method comprises the following operations: selectively irradiating the layer of fluid substance (3) to obtain the solidified layer (6); extracting the solidified layer (6) from the fluid substance (3); redistributing the fluid substance (3) in the container (2) by moving the levelling means (8) so that they are passed between the modelling plate (5) and the container (2).




Description


[0001] The present invention concerns a stereolithography method.

[0002] As is known, the stereolithography technique is used to produce three-dimensional objects through the successive deposition of several layers of a light-sensitive liquid resin capable of polymerizing through exposure to a light source.

[0003] In particular, each resin layer is superimposed to the preceding layer of the three-dimensional object to be produced and is allowed to selectively solidify in the points corresponding to the volume of the object itself.

[0004] A stereolithography machine according to a known embodiment comprises a container suited to contain said liquid resin and provided with a transparent bottom.

[0005] There is also a light source, generally a laser emitter or a projector, capable of selectively irradiating the layer of liquid resin arranged adjacent to the bottom of the container so that it solidifies.

[0006] The machine comprises also a modelling plate suited to support the solidified layers of the three-dimensional object, associated with actuator means suited to provide for moving the plate in a direction perpendicular to the bottom of the container.

[0007] According to a stereolithography method of the known type using the above mentioned machine, first of all the modelling plate is arranged at a distance from the bottom of the container that is equal to the thickness of the layer to be solidified.

[0008] Successively, the liquid resin layer adjacent to the bottom of the container is selectively irradiated by means of the light source in order to solidify it.

[0009] The modelling plate is configured so that the solidified layer adheres to it while, in the contrary, the bottom of the container is provided with a covering that reduces such adhesion.

[0010] The modelling plate is successively moved away from the bottom of the container, so as to make the solidified layer emerge from the liquid resin and thus make it possible to restore the thickness of the liquid resin that is necessary for processing a successive layer of the object.

[0011] In fact, lifting the modelling plate and the solidified layer means leaving a depression in the liquid resin, which is filled by the spontaneous flow of the resin itself.

[0012] Said levelling action restores the thickness of the liquid resin that is necessary to solidify a new layer of the object and furthermore prevents air bubbles from remaining trapped into the liquid resin during the successive lowering of the modelling plate, which may affect the integrity of the successive layer of the three-dimensional object.

[0013] Once said spontaneous levelling is completed, the modelling plate is immersed again in the liquid resin and a further layer of the object is solidified.

[0014] The method described above poses the drawback that the overall processing time of the three-dimensional object is considerably prolonged due to the waiting time needed after the solidification of each layer of the object for the liquid resin to level out.

[0015] Since the number of layers that form an object obtained through stereolithography can reach several hundreds, it can be understood that the waiting times mentioned above result in a considerable increase in the processing time.

[0016] Obviously, the waiting times are proportional to the viscosity of the liquid resin. Therefore, the drawback mentioned above is particularly important when resins of the so-called "hybrid" type are used, which comprise particles in ceramic or other materials mixed with the polymeric component.

[0017] Said hybrid resins are suitable for producing objects with high mechanical resistance but on the other hand their viscosity is much higher compared to the other resins commonly used in stereolithography.

[0018] A known embodiment, described in the Patent application WO 2010/045950, includes a movable tank and a fixed levelling paddle arranged in contact with the resin.

[0019] Before the solidification of each layer, the tank is moved so that the levelling paddle fills the depression left by the modelling plate when it is lifted.

[0020] This embodiment poses the drawback that it requires a certain amount of space for the movement of the tank that, consequently, involves an increase in the overall dimensions of the machine.

[0021] Document JP H07 1594 A discloses a method for producing a three-dimensional object according to the preamble of claim 1.

[0022] The present invention intends to overcome all the drawbacks of the known art as outlined above.

[0023] In particular, it is the object of the present invention to provide a stereolithography method that makes it possible to produce a three-dimensional object through the solidification of a fluid substance in layers, more rapidly than when employing the method of the known type described above.

[0024] It is a further object of the invention to limit the overall dimensions of the machine compared to the machines of the known type.

[0025] The above mentioned objects are achieved by a method for producing a three-dimensional object in layers according to claim 1.

[0026] Further characteristics and details of the invention are described in the corresponding dependent claims.

[0027] Advantageously, the method that is the subject of the invention makes it possible to produce a three-dimensional object in an overall time that is substantially independent of the viscosity of the fluid substance used.

[0028] Therefore, to advantage, the invention is particularly suited to be used with highly viscous liquid substances like, for example, the hybrid resins mentioned above, or with fluid pasty substances whose viscosity is even higher.

[0029] Still advantageously, the reduced overall dimensions make it easier to use the machine.

[0030] The said objects and advantages, together with others which will be highlighted below, are illustrated in the description of some preferred embodiments of the invention which are provided by way of non-limiting examples with reference to the attached drawings, wherein:
  • Figures from 1 to 6 show schematic side views of the stereolithography machine operating according to the method of the invention, in different operating configurations.


[0031] The method of the invention is described with reference to a stereolithography machine indicated as a whole by 1 in Figure 1, which comprises a container 2 containing a fluid substance 3 suited to be solidified through exposure to predefined radiation 4a.

[0032] It is specified since now that the term "fluid substance" means a substance suited to be distributed in the container 2 so that its surfaces assumes a substantially flat shape, for example like that of a liquid or pasty substance.

[0033] The fluid substance 3 is preferably but not necessarily a light-sensitive polymeric liquid resin and the predefined radiation is light radiation.

[0034] In particular, said resin is of the so-called "hybrid" type, comprising particles in ceramic or other materials that are capable of increasing the mechanical resistance of the resin once it has solidified.

[0035] However, the method of the invention may be used with a fluid substance of any type, provided that it is able to solidify following exposure to predefined radiation.

[0036] The machine 1 also comprises means 4 suited to emit the predefined radiation 4a, capable of selectively irradiating a layer of the fluid substance 3 having a predefined thickness and arranged adjacent to the bottom 2a of the container 2 so as to solidify it.

[0037] The emitter means 4 are preferably arranged under the container 2 and are configured so as to direct the predefined radiation 4a towards the bottom 2a of the container 2, which is transparent to radiation, as shown in Figure 2.

[0038] Preferably, if the fluid substance 3 is a light-sensitive resin, the emitter means 4 comprise a laser light emitter associated with means suited to direct the light beam towards any point of the above mentioned layer of the fluid substance 3.

[0039] According to an exemplary embodiment of the invention, not illustrated herein, the emitter means 4 comprise a projector suited to generate a luminous image corresponding to the surface area of the layer of fluid substance 3 to be solidified.

[0040] The stereolithography machine 1 also comprises a modelling plate 5 facing the bottom 2a of the container 2 and suited to support the three-dimensional object 11 being formed.

[0041] The modelling plate 5 is associated with actuator means 7 suited to move it with respect to the bottom 2a according to a modelling direction X that is perpendicular to the same bottom 2a.

[0042] In particular, the modelling plate 5 is configured in such a way that the fluid substance 3 adheres to it once it has solidified.

[0043] On the contrary, the bottom 2a of the container 2 is preferably made of a material that prevents said adhesion.

[0044] According to the method of the invention, the modelling plate 5 is immersed in the fluid substance 3 until arranging it at a distance from the bottom 2a that is equal to the thickness of the solidified layer to be obtained.

[0045] The layer of the fluid substance 3 is then selectively irradiated in order to obtain the solidified layer 6, which adheres to the modelling plate 5, as shown in Figures 2 and 3.

[0046] Successively, the modelling plate 5 is lifted in such a way as to move the solidified layer 6 away from the bottom 2a until it emerges from the fluid substance 3, as shown in Figure 4.

[0047] Following the above mentioned movement of the solidified layer 6 away from the bottom 2a, in the fluid substance 3 contained in the container 2 there still is a depressed area 3a at the level of the position previously occupied by the modelling plate 5 and/or by the three-dimensional object 11 being formed.

[0048] According to the method of the invention, to fill the above mentioned depression 3a, the fluid substance 3 is redistributed in the container 2 by pushing the fluid substance 3 towards the depression 3a through levelling means 8 arranged in contact with the fluid substance 3.

[0049] In particular, said levelling means 8 are associated with power means, not shown herein but known per se, configured so as to move them with respect to the bottom 2a of the container 2 in contact with the fluid substance 3 according to a direction of movement Y, so as to redistribute the fluid substance 3 as described above.

[0050] During said movement, the levelling means 8 are passed between the modelling plate 5 and the container 2, that is, under the modelling plate 5.

[0051] In this way, there is no need to move the container 2 to carry out the levelling operation and therefore it is possible to limit the overall dimensions of the machine 1.

[0052] Successively, the modelling plate 5 is lowered again and the operations described above are repeated in order to obtain the solidification of a further layer of the object 11.

[0053] It can be understood that the above mentioned levelling means 8 make it possible to fill the depression 3a in a much quicker way compared to the known method previously described, in which the filling action is due to the spontaneous redistribution of the fluid substance.

[0054] Therefore, the waiting time for the levelling of the fluid substance 3 after the solidification of each layer of the object is considerably reduced, thus reaching the aim to reduce the overall processing time compared to the time required by the methods of the known type.

[0055] In particular, the higher the viscosity of the fluid substance 3 used, the shorter the overall processing time.

[0056] Therefore, the method of the invention is particularly suited to be used when the fluid substance 3 is a hybrid resin with high viscosity, as previously explained.

[0057] Preferably, furthermore, to redistribute the fluid substance 3 during the interval between the solidification of two successive layers, the levelling means 8 are moved in one direction only, opposite the direction corresponding to the previous redistribution process, as can be seen in the figures.

[0058] In particular, once each layer has solidified, the levelling means 8 pass beyond the modelling plate 5 and come to be positioned beside the latter, on the opposite side with respect to the side where they were positioned after the solidification of the previous layer.

[0059] In this way, to advantage, each operation for the redistribution of the fluid substance 3 does not require the return of the levelling means 8 to the initial position and is therefore particularly rapid.

[0060] The levelling means 8 are placed in contact with the surface of the fluid substance 3 in an area where the level is higher than the level of the fluid substance 3 at the height of the depression 3a, so as to be able to push the fluid substance 3 towards the depression 3a.

[0061] Preferably, the levelling means 8 comprise a paddle 9 mainly developed according to a longitudinal direction and whose length preferably corresponds to the width of the container 2.

[0062] In the figures, the paddle 9 is shown in a side view and therefore the just mentioned longitudinal direction is perpendicular to the plane of the figures themselves.

[0063] To push the fluid substance 3, the above mentioned paddle 9, arranged in contact with the fluid substance 3, is moved according to a direction of movement Y that is perpendicular to the above mentioned longitudinal direction, as shown in Figure 5.

[0064] The movement of the paddle 9 makes it possible to level the fluid substance 3 in such a way as to obtain a substantially uniform thickness, as shown in Figure 6.

[0065] Obviously, the paddle 9 can have any shape, even different from that shown in the figures, provided that it is suited to come into contact with the surface of the fluid substance 3 contained in the container 2 in order to level it.

[0066] According to an exemplary embodiment of the invention not illustrated herein, the container 2 is movable with respect to the modelling plate 5 in a direction Y that is perpendicular to the longitudinal direction of the paddle 9.

[0067] In this case, the redistribution of the fluid substance 3 takes place through a combination of the movements of the paddle 9 and of the container 2.

[0068] The above clearly shows that the invention achieves all the set objects.

[0069] In particular, the use of levelling means to fill the depression present in the fluid substance after the solidification of each layer of the object makes it possible to reduce the waiting time before the solidification of the successive layer.

[0070] Consequently, the overall time necessary to make the three-dimensional object is considerably reduced compared to the time needed when using the stereolithography methods of the known type, and said time reduction becomes larger as the viscosity of the fluid substance used increases.

[0071] Furthermore, the fact that the levelling means are moved so that they pass between the modelling plate and the container makes it possible to limit the overall dimensions of the machine.

[0072] The method that is the subject of the invention may be subjected to further changes that, even though not described herein and not illustrated in the drawings, must all be considered protected by the present patent, provided that they fall within the scope of the following claims.

[0073] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the protection of each element identified by way of example by such reference signs.


Claims

1. Method for producing a three-dimensional object (11) in layers by means of a stereolithography machine (1) of the type comprising:

- a container (2) containing a fluid substance (3) in the liquid or paste state suited to be solidified through exposure to predefined radiation (4a);

- means (4) for emitting said predefined radiation (4a), suited to selectively irradiate a layer of said fluid substance (3) having a predefined thickness and arranged adjacent to the bottom (2a) of said container (2) in order to solidify it;

- a modelling plate (5) suited to support said solidified layer (6);

- actuator means (7) suited to move said modelling plate (5) with respect to said bottom (2a) at least according to a modelling direction (X) that is perpendicular to said bottom (2a);

- levelling means (8) arranged in contact with said fluid substance (3);

said method comprising the following operations:

- selectively irradiating said layer of fluid substance (3) in such a way as to obtain said solidified layer (6);

- moving said solidified layer (6) away from said bottom (2a) so as to make it emerge from said fluid substance (3);

- redistributing said fluid substance (3) in said container (2) so as to fill the depression (3a) caused by said movement of said solidified layer (6) away from said bottom (2a),

characterized in that said modelling plate (5) or respectively said modelling plate and the solidified layers is/are immersed in said fluid substance (3) until arranging said modelling plate (5) or respectively the last solidified layer at a distance from said bottom (2a) equal to said predefined thickness, and in that said redistribution process takes place by moving said levelling means (8) between said modelling plate (5) and said container (2) from a first area of said container (2), in which the level of said fluid substance (3) is higher than the level of said depression (3a), towards said depression (3a), wherein said levelling means (8) comprise a paddle (9) developed mainly according to a longitudinal direction, said paddle (9) having an edge facing said bottom (2a), wherein said edge is arranged inside said container (2).
 
2. Method according to claim 1, characterized in that said edge is immersed in said fluid substance (3).
 
3. Method according to any preceding claims, characterized in that the depth of said fluid substance (3) is smaller than the depth of said container (2).
 
4. Method according to any preceding claims, characterized in that said movement is performed through the displacement of said paddle (9) in a direction of movement (Y) perpendicular to said longitudinal direction.
 
5. Method according to any of the preceding claims, characterized in that during each redistribution process of said fluid substance (3) that takes place during the interval between the solidification of two successive layers said movement takes place in a single direction of movement (Y) so that said paddle (9) passes from one side of said modelling plate (5) to the other.
 
6. Method according to claim 5), characterized in that said movement of said paddle (9) during each of said redistribution operations takes place in the opposite direction with respect to the previous redistribution operation.
 
7. Method according to any claim from 1) to 6), characterized in that said fluid substance (3) is a mixture comprising a polymeric component and a particulate material, or is a pasty substance.
 
8. Method according to any preceding claims, characterized in that said movement of said paddle (9) is made by power means configured so as to move said paddle (9) perpendicular to said bottom (2a) and to immerse it in and extract it from said fluid substance (3).
 
9. Method according to claim 8), characterized in that said paddle (9) is configured such that said movement of said paddle (9) is capable of conferring a uniform thickness to said fluid substance (3).
 
10. Method according to claim 9), characterized in that said paddle (9) is arranged at a distance from said bottom (2a).
 




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Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description