HK1191902B - Stereolithography machine for producing a three-dimensional object and stereolithography method applicable to said machine - Google Patents

Description

Stereolithography machine for producing three-dimensional objects and stereolithography method applicable to said machine

Description of the invention

The present invention relates to a stereolithography machine and a stereolithography method applicable to the same.

As is known, stereolithography techniques are used to manufacture three-dimensional objects by successively depositing several layers of photosensitive liquid resin that can be polymerized by exposure to a light source.

In particular, each resin layer is superimposed to the previous layer of the three-dimensional object to be manufactured and allows to selectively solidify in a position corresponding to the volume of the object itself.

A stereolithography machine according to a known embodiment comprises a container suitable for containing said liquid resin and provided with a transparent bottom.

The machine also has a light source, typically a laser emitter or projector, which is capable of selectively illuminating the layer of liquid resin disposed adjacent the bottom of the container, thereby curing it.

The machine further comprises a modelling plate suitable for supporting a solidified layer of the three-dimensional object, the modelling plate being associated with actuator means suitable for providing a movement of the plate in a direction perpendicular to the bottom of the container.

According to a stereolithography method of known type using the above-mentioned machine, first, the modelling plate is set at a distance from the bottom of the container equal to the thickness of the layer to be solidified.

Subsequently, the layer of liquid resin adjacent the bottom of the container is selectively irradiated by a light source to cure the resin layer.

The styling plate is constructed so that the cured layer adheres to it, while, conversely, the bottom of the container is provided with a covering that reduces this adhesion.

The modelling plate is then moved away from the bottom of the container in order to cause a solidified layer to emerge from the liquid resin and thus to be able to recover the thickness of the liquid resin, which is required for the treatment of the successive layers of the object.

In fact, lifting the modelling plate and the solidified layer means leaving a depression in the liquid resin, this depression being filled by the spontaneous flow of the resin itself.

The leveling action restores the thickness of the fluid resin that is required to cure a new layer of the object, and in addition, avoids air bubbles remaining trapped in the liquid resin during subsequent lowering of the moldboard, which could affect the integrity of successive layers of the three-dimensional object.

Once the spontaneous leveling is completed, the moldboard is again immersed in the liquid resin and the next layer of the object is cured.

The above-described method causes the drawback of considerably extending the total processing time of the three-dimensional object, due to the waiting time required for leveling the liquid resin after curing each layer of the object.

Since the number of layers forming the object obtained by stereolithography can reach hundreds of layers, it will be appreciated that the above-mentioned waiting times will lead to a substantial increase in processing time.

Clearly, the waiting time is proportional to the viscosity of the liquid resin.

The above disadvantages are therefore particularly important when using so-called "hybrid" resins, which comprise particles of ceramic or other material mixed with polymeric components.

The hybrid resins are suitable for the production of objects which have a high mechanical resistance but on the other hand have a much higher viscosity than other resins commonly used in stereolithography.

In a known embodiment described in patent application WO2010/045950, the stereolithography machine comprises a circular rotating tank and a fixed levelling paddle arranged in contact with the resin, which paddle extends radially with respect to the tank.

Before each layer is cured, the tank is rotated so that the levelling paddle fills the depression left by the modelling plate as it is lifted.

This embodiment entails the disadvantage that the diameter of the tank is at least twice the length of the paddle portion and therefore takes up significantly more space than the minimum surface required for shaping.

The present invention aims to overcome all the drawbacks of the known art as outlined above.

In particular, it is an object of the present invention to provide a stereolithography method and a stereolithography machine that enable the manufacture of three-dimensional objects by layerwise solidification of a fluid substance faster than when using the known types of methods described above.

Another object of the invention is to limit the overall dimensions of the machine compared to machines of known type.

The above object is achieved by a stereolithography machine for the layered production of three-dimensional objects according to claim 1.

The above object is also achieved by a stereolithography method according to claim 3 suitable for use in a stereolithography machine as described above.

Further features and details of the invention are described in the respective dependent claims.

Advantageously, the method and machine of the subject matter of the invention enable the manufacture of three-dimensional objects in a total time that is substantially independent of the viscosity of the fluid substance used.

The invention is therefore advantageously particularly suitable for use with high-viscosity liquid substances, such as the above-mentioned mixed resins, or with fluid pasty substances of even higher viscosity.

Still advantageously, the reduced overall dimensions enable the machine to be used in a smaller space.

Said objects and advantages, and others highlighted hereinafter, are illustrated in the description of some preferred embodiments of the invention provided as non-limiting examples with reference to the attached drawings, in which:

fig. 1 to 6 show schematic side views of a stereolithography machine according to the invention in different operating configurations.

The method of the invention is described with reference to a stereolithography machine, indicated as a whole with 1 in fig. 1, the stereolithography machine 1 comprising a container 2 containing a fluid substance 3, the fluid substance 3 being suitable for curing by exposure to a predetermined radiation 4 a.

It should be noted that by the term "fluid substance" it is meant a substance that is suitable to be distributed in the container 2 such that its surface assumes a substantially flat shape, like for example a fluid or pasty substance.

Preferably, but not necessarily, the fluid substance 3 is a photosensitive polymeric liquid resin and the predetermined radiation is light radiation.

In particular, the resin is a so-called "hybrid" type resin comprising particles in the form of ceramic or other material, which, once cured, can increase the mechanical resistance of the resin.

However, the method and machine of the present invention may be used with any type of fluid substance, provided that it is capable of curing after exposure to a predetermined radiation.

The machine 1 also comprises a device 4 suitable for emitting a predetermined radiation 4a, the device 4 being able to selectively irradiate a layer of fluid substance 3 having a predetermined thickness and disposed adjacent to the bottom 2a of the container 2 in order to solidify it.

The emitter device 4 is preferably arranged below the container 2 and is configured to direct a predetermined radiation 4a towards the radiation-transparent bottom 2a of the container 2, as shown in fig. 2.

Preferably, if the fluid substance 3 is a photosensitive resin, the emitter means 4 comprise a laser emitter associated with means suitable for directing a light beam towards any point of the above-mentioned layer of fluid substance 3.

According to an embodiment variant of the invention, not shown here, the emitter means 4 comprise a projector suitable for generating a luminous image corresponding to the surface area of the layer of fluid substance 3 to be solidified.

The stereolithography machine 1 further comprises a modelling plate 5, which modelling plate 5 faces the bottom 2a of the container 2 and is suitable for supporting the three-dimensional object 11 being formed.

The modelling plate 5 is associated with actuator means 7, which actuator means 7 are adapted to move the modelling plate 5 with respect to the base 2a according to a modelling direction X perpendicular to the same base 2.

In particular, the modelling plate 5 is constructed in such a way that, once the fluid substance 3 has solidified, this fluid substance 3 adheres to the modelling plate 5.

Conversely, the bottom 2a of the container 2 is preferably made of a material that avoids said adhesion.

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

Then, the layer of fluid substance 3 is selectively irradiated to obtain a solidified layer 6, which solidified layer 6 adheres to the modelling plate 5, as shown in fig. 2 and 3.

Subsequently, the modelling plate 5 is lifted in such a way as to move the solidified layer 6 away from the bottom 2a until the solidified layer 6 emerges from the fluid substance 3, as shown in fig. 4.

After the above-mentioned solidified layer 6 has moved away from the bottom 2a, there are still recessed areas 3a in the fluid substance 3 contained in the container 2, which recessed areas 3a are located at the level of the positions occupied by the modelling plate 5 and/or by the three-dimensional object 11 formed in front.

According to the method of the invention, in order to fill the aforementioned depression 3a, the fluid substance 3 is redistributed in the container 2 by means of pushing the fluid substance 3 towards the depression 3a by means of the levelling means 8 arranged in contact with the fluid substance 3.

In particular, said levelling means 8 are associated with power means, not illustrated here but known per se, configured to move the levelling means 8 in contact with the fluid substance 3 with respect to the bottom 2a of the container 2, so as to redistribute the fluid substance 3 as described above.

Subsequently, the modelling plate 5 is lowered again and the above operations are repeated to obtain the solidification of the next layer of the object 11.

It will be understood that the levelling means 8 described above makes it possible to fill the recesses 3a in a manner much faster than the known methods described previously, in which the filling action is due to the spontaneous redistribution of the fluid substance.

The waiting time for flattening the fluid substance 3 after curing each layer of the object is therefore greatly reduced, with the aim of reducing the overall processing time compared to that required by the known type of method.

In particular, the greater the viscosity of the fluid substance 3 used, the shorter the total treatment time.

Therefore, as explained earlier, the method of the present invention is particularly suitable to be used when the fluid substance 3 is a mixed resin having a high viscosity.

Preferably, the flattening device 8 is placed in contact with the surface of the fluid substance 3 in the region where the level of the fluid substance 3 is higher than the level of the fluid substance 3 at the level of the recess 3a, so as to be able to push the fluid substance 3 towards the recess 3 a.

Further, the container 2 is movable relative to the moldboard 5 in the moving direction Y.

The levelling means 8 comprise two paddle parts 9, 10, which paddle parts 9, 10 are arranged on opposite sides with respect to the modelling plate 5 and extend mainly in a longitudinal direction perpendicular to said direction of movement Y.

Preferably, the length of the paddle parts 9, 10 corresponds to the width of the container 2.

In the illustration, the paddles 9 and 10 are shown in side view, so that their longitudinal direction is perpendicular to the plane of the illustration itself.

Obviously, the paddles 9, 10 may have any shape, even different from the one shown in the figures, as long as these shapes are suitable for coming into contact with the surface of the fluid substance 3 contained in the container 2 to level it.

As shown in fig. 5 and 6, the redistribution of the fluid substance 3 is performed by keeping the paddles 9, 10 fixed and moving the container 2 along said movement direction Y.

In this way, as shown in fig. 6, the paddle portion disposed upstream of the recess 3a with respect to the moving direction pushes the fluid substance 3 into the recess, thereby filling the recess.

Advantageously, the presence of the two paddles 9 and 10 enables the redistribution of the fluid substance 3 in either of the two directions of movement of the container 2, thus avoiding the need to bring the container 2 back to its initial position before solidifying each layer.

More precisely, after curing the layer, the container 2 is moved so that the region visible in fig. 5 where the depression 3a is present is displaced with respect to the styling plate 5, thus aligning the styling plate 5 with a different region of the container 2 without being affected by the depression 3a, as shown in fig. 6.

Thus, the curing of successive layers can be carried out at the level of this new zone of the container 2.

At the same time, during the movement of the container 2, the recess 3a is filled so that the previous region can be used in the subsequent curing of another layer.

Obviously, the possibility of redistributing the fluid substance 3 while the container 2 is moved in each of the two opposite orientations makes it possible to use containers 2 having a smaller surface area compared to the surface area of the circular containers used in the known art.

In fact, the container 2 may have a rectangular shape with a length according to the direction of movement Y equal to about twice the minimum dimension required for the shaping, and a width equal to about said minimum dimension.

In contrast, in the machines of known type using circular tanks, the minimum diameter of the container must be equal to approximately twice said minimum dimension.

Preferably, the power means of the paddle parts 9 and 10 are configured such that each paddle part can be immersed in the fluid substance 3 and extracted from the fluid substance 3 independently of the other paddle part.

In this way, advantageously, the redistribution of the fluid substance 3 can be performed using only the paddle portion arranged downstream with respect to the modelling plate 5, or in other words upstream of the depression 3a, according to the direction of movement Y of the container 2.

In this way, the further paddle portion is avoided from pushing the fluid substance 3 away from the recess 3a and the redistribution process is facilitated.

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

In particular, the use of a flattening device to fill the recesses present in the fluid substance after the curing of each layer of the object makes it possible to reduce the waiting time before the curing of the successive layers.

Thus, the total time required for manufacturing the three-dimensional object is significantly reduced compared to the time required when using the stereolithography methods of the known type, and said time reduction will become greater as the viscosity of the fluid substance used increases.

Furthermore, the presence of two paddles provided on respective opposite sides of the modelling plate enables to level the fluid substance by means of an alternating movement of the container in two opposite directions, thus avoiding the need to use a rather bulky circular container.

Further modifications of the method and of the machine that are the subject of the invention, even if not described here and not shown in the drawings, must be considered as being fully protected by the present patent, provided they fall within the scope of the following claims.

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 afforded by the respective elements identified by such reference signs.

Claims (4)

1. A stereolithography machine (1) comprising:

-a container (2), said container (2) being intended to contain a fluid substance (3) in liquid or slurry state, said fluid substance (3) being suitable for curing by exposure to predetermined radiation (4 a);

-means (4) for emitting said predetermined radiation (4a), said means (4) being suitable for selectively irradiating a layer of said fluid substance (3) having a predetermined thickness and arranged adjacent to the bottom (2a) of said container (2) to obtain a solidified layer (6);

-a modelling plate (5), said modelling plate (5) being suitable for supporting said solidified layer (6);

-actuator means (7), said actuator means (7) being adapted to move said modelling plate (5) with respect to said base (2a) at least according to a modelling direction (X) perpendicular to said base (2 a);

-a flattening device (8), said flattening device (8) being associated with a power device configured so that said flattening device (8) moves in contact with said fluid substance (3) with respect to said bottom (2a) of said container (2), causing a redistribution of said fluid substance (3) in said container (2);

the power means being configured to move the container (2) in each of two opposite orientations of a movement direction (Y);

characterized in that said levelling means (8) comprises at least two paddle portions (9, 10), said two paddle portions (9, 10) extending mainly according to a longitudinal direction perpendicular to said movement direction (Y), said two paddle portions (9, 10) being arranged on two corresponding opposite sides with respect to said modelling plate (5), wherein said two paddle portions (9, 10) remain fixed during the movement of said container (2) along said movement direction (Y).

2. The stereolithography machine according to claim 1, wherein said power device is configured to: such that each of said paddle portions (9, 10) moves perpendicular to said bottom (2a) independently of the other of said paddle portions (9, 10), and such that each of said paddle portions (9, 10) is immersed in and extracted from said fluid substance (3) independently of the other of said paddle portions (9, 10).

3. Method for the layered production of three-dimensional objects (11) by means of a stereolithography machine (1) according to any one of the preceding claims, comprising the following operations:

-selectively illuminating a layer of fluid substance (3) having a predetermined thickness and arranged adjacent to the bottom (2a) of the container (2) in such a way that: so as to obtain said solidified layer (6);

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

-redistributing said fluid substance (3) in said container (2) by moving said levelling means (8) with respect to said container (2) and placing said levelling means (8) in contact with said fluid substance (3) so as to fill the recesses (3a) caused by lifting said solidified layer (6);

-repeating the operations described above on the fluid substance (3) to obtain the solidification of the next layer of the object (11);

characterized in that said redistribution process comprises two movements of said container (2) performed in mutually opposite orientations with respect to said movement direction (Y).

4. A method according to claim 3, characterized in that during each of said two movements, the paddle portion (9, 10) arranged downstream of the recess (3a) in a corresponding orientation of the direction of movement (Y) is kept higher than the fluid substance (3).