Cross-Reference to Related Applications

This Patent Application claims priority from Italian Patent Application No . 102022000018051 filed on September 2 , 2022 , the entire disclosure of which is incorporated herein by reference .

Technical field

The present invention refers to a device for producing a three-dimensional layered obj ect and a method for producing a three-dimensional layered obj ect .

Background of the Invention

The European patent EP 2 285 552 by the same inventor describes a method for the manufacture of a three-dimensional obj ect formed by a plurality of superimposed layers of a liquid base photosensitive material at room temperature and capable of permanently solidi fying following the action of electromagnetic radiation . The method described in the patent comprises the steps of : depositing the base material in a modelling platform arranged in a cooled chamber such that said base material reversibly solidi fies forming a layer of solid material ; selectively exposing the solid layer to the electromagnetic radiation in one or more predefined areas defined based on the section of a three-dimensional model of the obj ect to be produced such that the base material irreversibly solidi fies ; and repeating the depos ition and selective exposure operations for all sections of the model of the three-dimensional obj ect .

At the end of these operations , an obj ect is formed comprising a plurality of irreversibly solidi fied superimposed layers surrounded by reversibly solidi fied layers . Following the increase in temperature , the reversibly solidi fied layers go back to the liquid form, hence freeing the three-dimensional obj ect . The present invention aims to :

A. Limit the consumption of material for the production of the three-dimensional obj ect ;

B . Expand the range of applications using materials , also of the non-photosensitive type ;

C . In the case of lost-wax micro-casting applications , use molten wax as the material of the three-dimensional ob ect ;

D . Use , for producing the three-dimensional obj ect , low- cost support material , easily available and guarantee total respect for the environment ;

E . Ensure maximum precision and printing quality;

F . Ensure maximum printing homogeneity;

G . Ensure the release of the three-dimensional obj ect without manual intervention of the operator ;

Ensure the release of the three-dimensional obj ect without the use of solvents ; and

H . Lower the operating costs .

Summary of the Invention

The above aim is achieved by the present invention in that it relates to a device of the type described in claim 1 and to a method described in claim 7 .

Brief Description of the Drawings

The invention will be shown with reference to the accompanying drawings which represent a preferred nonlimiting embodiment wherein :

• Figure 1 schematically shows a device reali zed according to the dictates of the present invention;

• Figure 2 shows a first step of the method according to the present invention;

• Figure 3 shows a second step of the method according to the present invention;

• Figure 4 shows a third of the method according to the present invention;

• Figure 5 shows a fourth step of the method according to the present invention;

• Figure 6 shows a fi fth step of the method according to the present invention;

• Figure 7 shows a sixth step of the method according to the present invention;

• Figure 8 shows a seventh step of the method according to the present invention;

• Figure 9 shows an eighth step of the method according to the present invention;

• Figures 10 and 11 show a step of repetition of the steps of Figures 2 - 9 ;

• Figures 12 , 13 and 14 show terminal steps of the method according to the present invention;

• Figure 15 shows a first variant to the method described in previous Figures 2- 14 ; and

• Figure 16 shows a second variant to the method described in previous Figures 2- 14 .

Description of the Embodiment Example

Figure 1 schematically shows a device 1 for producing a three-dimensional layered object T .

The device 1 comprises a modelling platform 2 ( schematically represented in the figures ) on which the three-dimensional obj ect T is formed; the modelling platform 2 is made with known technologies and comprises a support plane 3 movable along a direction Z with reversible linear motion due to the thrust of actuator means (not shown) in turn controlled by an electronic unit 4 ( schematically shown) .

Preferably, the direction Z is transverse , in particular orthogonal , to the support plane 3 .

In other words , the support plane 3 is preferably hori zontal , and the direction Z is preferably vertical .

The modelling platform is housed within a printing chamber 6 .

More in detail , the modelling platform 2 is preferably housed in a modelling chamber 5 which internally defines the printing chamber 6 , inside which the support plane 3 moves . The modelling chamber 5 is open at the top .

The device 1 further comprises at least one cooling device 7 ( schematically represented) designed to cool the printing chamber 6 bringing to a predetermined temperature , preferably a temperature lower than 0 ° C .

Preferably, the cooling device 7 is associated with the modelling chamber 5 .

Preferably, the electronic unit 4 is operatively connected to the cooling device 7 , so as to be able to control , in use , the operation thereof .

In particular, the electronic unit 4 is preferably configured to be able to activate , on command, the cooling device 7 in such a way as to be able to bring the temperature inside the printing chamber 6 to said predetermined temperature , i . e . preferably below 0 ° C .

In addition, the electronic unit 4 is preferably configured to be able to deactivate , on command, the cooling device 7 so that the temperature inside the printing chamber 6 can exceed said predetermined temperature , i . e . so that the temperature inside the printing chamber 6 can increase and be brought to about room temperature ( about in the neighbourhood of 20 ° C ) .

Cooling devices of di f ferent type can be used, for example using a cooling liquid that is circulated in cavities (not shown) of the modelling chamber 5 or using Peltier cells (not shown) .

The modelling platform 2 is also cooled as it is arranged inside the printing chamber 6 . Additional cooling devices of the support plane 3 can also be used, for example Peltier cells (not shown) .

In a position above the printing chamber 6 there are arranged : a first selective deposition device 8 for a first liquid 9 designed to produce a support layer of the three-dimensional ob j ect ;

• a second selective deposition device 10 for a second liquid 11 designed to produce a structural layer of the three- dimensional obj ect ; * a selective irradiation device 12 designed to generate a thermal radiation 13 ( e . g . a laser beam) ; and

• a levelling device 14 for the previously deposited layers designed to treat the deposited layers to produce a surface parallel to a hori zontal plane X-Y . Preferably, the plane X_Y is transverse to the direction Z . In particular, the plane X_Y is advantageously orthogonal to the direction Z .

The above-mentioned devices are schematically shown; the first selective deposition device 8 comprises a first noz zle 15 movable in the plane X_Y relative to the modelling platform 2 and designed to dispense the first liquid 9 preferably in the form of droplets .

The second selective deposition device 10 comprises a second noz zle 16 movable in the plane X_Y relative to the modelling platform 2 and designed to dispense the second liquid 11 preferably in the form of droplets .

The selective irradiation device 12 comprises an end 17 from which the thermal radiation exits which can be provided both in puncti form concentrated form and in di f fused form . Preferably, the end 17 is also movable in the plane X_Y relative to the modelling platform 2 .

Finally, the levelling device 17 comprises a movable milling cutter 18 which is also movable in the plane X_Y relative to the modelling platform 2 . The first liquid 9 has a melting temperature T1 such that it changes state passing from the liquid state to the solid state when it is dispensed onto the modelling platform by the noz zle 15 and the printing chamber 6 is cooled . Conveniently but not exclusively the first liquid i s formed by water which solidi fies at a melting temperature T1 lower than zero degrees centigrade ( ° C ) at the pressure of one atmosphere .

In other words , the melting temperature T1 is preferably higher than said predetermined temperature .

The second liquid 11 has a melting temperature T2 such that it changes state passing from the liquid state to the solid state when it is dispensed onto the modelling platform by the noz zle 15 . Suitably but not exclusively the second liquid is molten wax which solidi fies for a melting temperature lower than 60 ° C - 78 ° C . The melting temperature T2 is higher than the melting temperature T1 and is such that the second liquid remains solid at room temperature , i . e . at a temperature preferably ranging from 5 ° to 35 ° , and more advantageously around 20 ° C .

In other words , the melting temperature T2 is preferably higher than said predetermined temperature and is also preferably higher than the room temperature . Advantageously, the melting temperature T2 is higher than 20 ° C, and more in detail it is also higher than 35 ° C .

In use , the cooling devices 7 are activated by thermal conduction and bring the temperature of the printing chamber 6 and of the modelling platform 2 below the melting temperature T1 of the first liquid 9 .

The steps of the method according to the present invention controlled by the electronic unit 4 will now be shown . The electronic unit 4 is provided with an internal memory in which a three-dimensional model of the three-dimensional layered obj ect T to be produced is stored . Such a three- dimensional model comprises the coordinates of points defining the contours and the areas inside the contours of a plurality of successive sections of the three-dimensional ob ect .

The method preferably provides for the step of bringing the temperature inside the printing chamber 6 to said predetermined temperature , i . e . preferably below 0 ° C . More in detail , the method provides for the step of activating/operating the cooling device 7 , in such a way as to bring the temperature inside the printing chamber 6 to said predetermined temperature , i . e . preferably below 0 ° C . First step - selective deposition of the first liquid and formation of the layer Hl .

Figure 2 shows a first step of the method according to the invention reali zed by the device 1 .

The support plane 3 is arranged in an upper machining start position (Home position) .

The first selective deposition device 8 moving in the plane X_Y due to the control of the electronic unit 4 deposits the liquid 9 onto the hori zontal support plane 3 which immediately solidi fies in contact with the support plane 3 forming a first containing layer Hl . The first containing layer Hl defines an area which is greater than the area of the maximum section of the three-dimensional model defining the obj ect to be produced .

Second step - flattening of the first layer Hl .

Figure 3 shows a second step of the method according to the present invention .

The second step of the method according to the present invention preferably provides for the step of flattening, i . e . of shaping/ levelling/grinding, advantageously by means of a material removal process , the face 20 of the first containing layer Hl facing in the opposite direction relative to the support plane 3 , so that said face 20 is preferably flat and/or coplanar to the plane X_Y and/or parallel to the support plane 3 .

More in detail , the levelling device 14 by moving the milling cutter 18 on the plane X_Y preferably performs the f f attening/ levelling of the face 20 of the first containment state Hl facing in the opposite direction relative the support plane 3 , a first flat face 20 is thus created ensuring a constant thickness DI of the first containing layer Hl .

Third step - lowering the support plane .

Figure 4 shows a third step of the method according to the present invention .

The electronic unit 4 commands the modelling platform 2 so that the support plane 3 is moved along Z , i . e . preferably in a transverse direction and in particular orthogonal to the plane X_Y , and towards the bottom of the printing chamber 6 by a predetermined quantity, in particular a quantity equal to the thickness of the successive layer to be created . To optimi ze the printing time as a function of the surface quality of the final obj ect , use is often made of the "variable layer thickness" technique , in which each layer could have a thickness di f ferent from the previous one .

Fourth step - selective deposition of the second liquid and formation of the layer G2 .

Figure 5 shows a fourth step of the method according to the present invention .

The second selective deposition device 10 moving in the plane X_Y due to the control of the electronic unit 4 deposits , in particular selectively deposits , onto the first containing layer Hl , which was previously formed, the second l iquid 11 which immediately solidi fies in contact with the first layer Hl forming a first structural layer G2 of the three- dimensional obj ect having substantially constant thickness . The structural layer G2 is deposited in an area that has contours and area corresponding to the contours and to the area of a first section of the digital model of the three- dimensional obj ect . As mentioned above , the three- dimensional model of the obj ect to be produced is stored in the electronic unit 4 .

The first structural layer G1 defines an area that is smaller than the area of the first containing layer Hl and is preferably arranged over a central portion of the first containing layer Hl . Fifth step - melting of the edges of the layer G2 .

Figure 6 shows an optional fi fth step of the method according to the present invention .

The electronic unit 4 commands the movement of the selective irradiation device 12 so that the thermal radiation 13 leads to the melting of the side edges of the structural layer G2 . The side edges of the structural layer G2 are perpendicular to the plane X_Y . This operation is useful i f the second liquid 11 is made of molten wax . The wax, in fact , is emitted in tiny droplets which, when cooled, give an irregular wrinkled profile to the side edges of the structural layer G2 . The melting and the subsequent solidi fication of the edges of the structural layer G2 contributes to reducing the granular character of the edges and that is to " flatten" these edges . Preferably, the melting is carried out in the area within the edges of the structural layer, so as to ensure homogeneity reducing the granular character . This non-mandatory option is used to ensure the homogeneity of the material within the model to be produced .

Sixth step - selective deposition of the first liquid and formation of the layer H2 .

Figure 7 shows a sixth step of the method according to the invention reali zed by the device 1 .

The first selective deposition device 8 moving in the plane X_Y due to the control of the electronic unit 4 deposits , onto the containing layer Hl only in the zones that are not af fected by the structural layer G2 , the liquid 9 which immediately solidi fies in contact with the layer H forming a second containing layer H2 which completely surrounds the structural layer G2 in the directions X and Y, i . e . advantageously parallel to the plane X_Y , and which has a substantially constant thickness and/or substantially equal to the thickness of the structural layer G2 .

In other words , the directions X and Y are preferably transverse , in particular orthogonal , to the direction Z . Seventh step - flattening of the layers G2 and H2 .

Figure 8 shows a seventh step of the method according to the present invention .

The seventh step of the method according to the present invention preferably provides for the step of flattening, i . e . of shaping/ levelling/grinding, advantageously by means of a material removal process , the face 19a of the second containing layer H2 and the face 19b of the structural layer G2 facing in the opposite direction relative to the support plane 3 , so that said faces 19a and 19b are preferably flat and/or coplanar to the plane X_Y and/or parallel to the support plane 3 .

More in detail , the levelling device 14 preferably, by moving the milling cutter 18 on the plane X_Y , performs the f f attening/ levelling of the face 19a of the second containing layer H2 facing in the opposite direction relative to the support plane 3 and the flattening of the face 19b of the structural layer G2 facing in the opposite direction relative to the support plane 3 . These faces 19a and 19b are made coplanar and a constant thicknes s of the first structural layer G2 and of the second containing layer H2 is guaranteed . The deposited second layer may have a thickness di f ferent from that of the first layer .

Eighth step - lowering the support plane .

Figure 9 shows an eighth step of the method according to the present invention .

The electronic unit 4 commands the modelling platform 2 so that the support plane 3 is again moved along Z , i . e . preferably in a transverse direction and in particular orthogonal to the plane X_Y , and towards the bottom of the printing chamber 6 by a predetermined quantity, in particular a quantity equal to the thickness of the successive layer to be created .

Iterative repetition of the fourth step , the fifth step , the seventh step and the eighth step . The fourth step is repeated for the deposition of the second liquid 11 and the formation of a structural layer G3 on top of the structural layer G2 (Figure 10) . The structural layer G3 is deposited in an area that has contours corresponding to the contours and to the area of a second section of the digital model of the three-dimensional object.

Subsequently, after a possible melting operation of the edges of the structural layer G3 or a possible melting of the entire structural layer G3, the sixth step is repeated in which the liquid 9 (Figure 11) , which immediately solidifies in contact with the containing layer H2/the underlying structural layer G2, is deposited onto the containing layer H2 and/or onto the structural layer G2 in the zones that are not affected by the layer G3. In this way, analogously to what is shown for the sixth step, a third containing layer H3 is created which completely surrounds the structural layer G3 in the directions X and Y, i.e. advantageously parallel to the plane X_Y , and which has a thickness substantially constant to the thickness of the layer G3. Subsequently, the layers G3 and H3 are machined and flattened with milling cutter 18 and made coplanar. Finally, the horizontal plane 3 is lowered.

The repetition of these steps for all sections n of the three-dimensional model allows to produce an object formed by n superimposed structural layers G2, G3,...Gi, ... Gn which is incorporated at the bottom and on the sides (i.e. along X and Y) by n+1 containing layers Hl, H2, ...Hi,... Hn+1.

At the end of the completion of the iterations the cooling device 7 is deactivated (Figure 13) , so that the temperature of the chamber 6 increases and moves to that of the room (for example about 20 C°) exceeding the melting temperature Tl, so that the containing layers naturally go back to the liquid state, hence freeing the three-dimensional layered object thus formed. At room temperature (e.g. about 20 °C) the second liquid remains in the solid state since the room temperature is lower than the melting temperature T2 .

The formed three-dimensional obj ect T can thus be taken from the modelling platform 2 ( Figure 14 ) .

The following advantages are therefore achieved :

A. The deposition of the material of the obj ect takes place selectively, limiting its consumption and consequently lowering the operating costs ;

B . The material of the obj ect can be of the nonphotosensitive type , greatly expanding the range of the applications and lowering the operating costs ;

C . In the case of lost-wax micro-casting applications , the material that forms the three-dimensional obj ect can be molten wax, characteri zed by a lower melting temperature than a photosensitive resin, ensuring perfect compatibility with the heat treatment processes of these processes and consequently increasing the melting quality and lowering the operating costs ;

D . The support material can be composed of water, signi ficantly lowering the operating costs and ensuring total respect for the environment ;

E . The flattening step at the end of the deposition of each layer guarantees maximum precision and printing quality in the direction of the axis Z ;

F . The optional melting step of the edges of the layers Gn guarantees maximum precision and printing quality in the direction of the axes XY;

G . The optional melting step of the entire sections of the layers Gn guarantees maximum printing homogeneity in the direction of the axes XY;

H . The spontaneous melting of the support layers Hn by returning to room temperature guarantees the release of the three-dimensional obj ect without manual intervention of the operator, avoiding possible damages to the three-dimensional obj ect caused by the manipulation and by the detachment of the support structures ;

I . The spontaneous melting of the support layers Hn by going back to room temperature guarantees the release of the three-dimensional obj ect without the use of solvents , avoiding possible damages to the model caused by chemical action, consequently lowering its operating costs and guaranteeing total respect for the environment .

According to what is shown in the sixth step, the containing layer H2 is deposited only in the zones that are not af fected by the structural layer G2 .

Alternatively, the containing layer H2 may be deposited ( see Figure 15 ) both on top of the structural layer and on top of the zones that are not af fected by the structural layer . The subsequent flattening operation ( seventh step ) helps eliminate the first solidi fied liquid arranged on top of the structural layer .

According to the alternative variant of Figure 16 , following the deposition operations of the fourth step, an even thermal irradiation of the previously deposited structural layer G2 is operated by means of the irradiation device - alternatively to what is shown in Figure 6 - in order to guarantee the homogeneity of the layer itsel f .

Numerals

1 device for producing three-dimensional obj ects

2 modelling platform

3 hori zontal support plane

4 electronic unit

5 modelling chamber

6 printing chamber

7 cooling device

8 first selective deposition device

9 first liquid

10 second selective deposition device

11 second liquid 12 selective irradiation device

13 thermal radiation

14 levelling device

15 first noz zle 16 second noz zle

17 end

18 milling cutter

19a, 19b faces

20 face