MACHINE FOR MANUFACTURING GREEN PARTS FROM CERAMIC OR METALLIC MATERIAL

Abstract

This machine includes a horizontal receiving surface which is constituted by the bottom of a vat, the vat having a width and a length, and a device for supplying and spreading a suspension which includes a suspension applicator and an external tank, the applicator including a suspension reserve fed from the external tank, at least one vacuum-forming device in the reserve and at least one hole connected to the reserve and formed facing the surface the vacuum forming device being controlled to regulate the amount of suspension released from the hole, the applicator being arranged along the width of the vat and having at least the printing width and being configured to translate along the length of the vat to be able to apply suspension through the hole onto the surface.

Claims

1- A machine for manufacturing parts by the stereolithography technique, according to which layers of radiation-curable suspension are successively cured one on top of the other by irradiation according to a pattern defined for each layer, said machine comprising: a horizontal receiving surface, configured to receive the first layer and subsequent layers formed on top of each other from the first layer; a supply and spreading device configured to, at each layer formation, supply a quantity of suspension and spread the suspension on said horizontal receiving surface for the first layer, and on each previously cured patterned layer for each of the subsequent layers, the supply and spreading device and the horizontal receiving surface being movable relative to each other in the direction of layer stacking; and an irradiation device for irradiating each layer after said layer has been spread to cure said layer in the previously defined pattern, wherein the horizontal receiving surface is constituted by the bottom of a vat, said vat having a length and a width, and wherein said supply and spreading device comprises a suspension applicator and an external tank, the suspension applicator comprising a suspension reserve fed from the external tank, at least one vacuum forming device in the suspension reserve and at least one hole connected to the suspension reserve and formed facing the horizontal receiving surface, said at least one vacuum forming device being controlled to regulate the amount of suspension released from said at least one hole, the suspension applicator being disposed along the width of the vat and having at least the printing width and being configured to translate along the length of the vat to be able to apply suspension through said at least one hole onto the receiving surface.

2- The machine according to claim 1, wherein said at least one vacuum forming device is connected to a vacuum tapping to control the amount of suspension released from said at least one hole.

3- The machine according to claim 1, wherein the applicator is a rectangular parallelepiped, the active face facing the horizontal receiving surface being the release face of the applicator in which said at least one hole is formed.

4- The machine according to claim 3, wherein said at least one hole which is formed in the active face is constituted by a single slit formed over the entire width of the active face of the applicator or by a plurality of holes uniformly distributed over the entire width of the active face of the applicator.

5- The machine according to claim 3, wherein the suspension is supplied to the suspension reserve by several supplies from the external tank, uniformly distributed over the width of the applicator, internal suspension distribution tubes being able to be mounted dipping into the suspension reserve.

6- The machine according to claim 1, wherein the suspension reserve is divided into compartments each associated with a vacuum formation device by at least one vacuum tapping and with at least one supply of suspension from the external tank.

7- The machine according to claim 1, further comprising a device for controlling the supply of suspension to the suspension reserve cavity while the applicator is stationary or during the applicator's translational movement.

8- The machine according to claim 1, further comprising a sensor for the quantity of uncured suspension in the vat, and a controller regulating, for each layer, the supply of suspension by the applicator as a function of the level of uncured suspension detected in the vat by the suspension quantity sensor.

9- The machine according to claim 8, wherein the suspension quantity sensor is one of a level sensor and a volume sensor.

10- The machine according to claim 4, wherein the active face of the applicator carries at least one blade configured to allow scraping of the suspension deposited through the said at least one hole, the said blade being located set back from the said at least one hole in the direction of movement of the applicator.

11- The machine according to claim 4, wherein the front face of the applicator in the direction of movement has the form of a pushing shield.

12- The machine according to claim 8, wherein the vat is equipped with an overflow for discharging excess uncured suspension.

13- The machine according to claim 12, wherein the overflow is controlled as a function of the level of suspension detected by the sensor of the quantity of uncured suspension in the vat.

14. The machine according to claim 2, wherein the applicator is a rectangular parallelepiped, the active face facing the horizontal receiving surface being the release face of the applicator in which said at least one hole is formed.

15. The machine according to claim 4, wherein the suspension is supplied to the suspension reserve by several supplies from the external tank, uniformly distributed over the width of the applicator, internal suspension distribution tubes being able to be mounted dipping into the suspension reserve.

16. The machine according to claim 2, wherein the suspension reserve is divided into compartments each associated with a vacuum formation device by at least one vacuum tapping and with at least one supply of suspension from the external tank.

17. The machine according to claim 3, wherein the suspension reserve is divided into compartments each associated with a vacuum formation device by at least one vacuum tapping and with at least one supply of suspension from the external tank.

18. The machine according to claim 4, wherein the suspension reserve is divided into compartments each associated with a vacuum formation device by at least one vacuum tapping and with at least one supply of suspension from the external tank.

19. The machine according to claim 5, wherein the suspension reserve is divided into compartments each associated with a vacuum formation device by at least one vacuum tapping and with at least one supply of suspension from the external tank.

20. The machine according to claim 2, further comprising a device for controlling the supply of suspension to the suspension reserve cavity while the applicator is stationary or during the applicator's translational movement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] To better illustrate the object of the present invention, a particular embodiment is described below, by way of indication and not as a limitation, with reference to the attached drawing.

[0037] On this drawing:

[0038] FIG. 1 is a front elevation view of a suspension applicator of a machine according to the invention;

[0039] FIG. 2 is a top view of the device of FIG. 1;

[0040] FIG. 3 is a cross-sectional view according to III-III of FIG. 1;

[0041] FIG. 4 is a longitudinal sectional view according to IV-IV of FIG. 2;

[0042] FIG. 5 is a front view of the applicator of FIG. 1 in place in the machine according to the invention;

[0043] FIG. 6 is a schematic view illustrating the operation of the machine according to the invention;

[0044] FIG. 7a illustrates the formation of a layer as the suspension applicator advances;

[0045] FIG. 7b illustrates the formation of a layer seen in the vat of the machine;

[0046] FIG. 7c illustrates the formation of a layer with additional material;

[0047] FIG. 7d shows the formation of a layer with suction of excess material d); and

[0048] FIG. 8 is an exploded perspective view of a suspension applicator of a machine according to the invention, said applicator being in accordance with a variant of that shown in FIGS. 1 to 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Referring to FIGS. 1 to 5, it can be seen that a suspension applicator 1 is shown having the general shape of a rectangular parallelepiped formed by an elongated upper plate 2, horizontal in the position of use, bent downwards at each of its ends to form transverse plates 3 of greater thickness. On each side of these walls 2 and 3, a side plate 4 is fixed by screws 5.

[0050] A suspension reserve 6 (FIG. 4) is thus formed, which is delimited by the plates 2, 3 and 4, the lower face or release face (FL) being formed by the edges of the plates 3 and 4 and having a slit-shaped hole T (see FIG. 3).

[0051] The transverse plates 3 have holes 7 for the passage of fixing screws on an applicator holder 8. The applicator holder 8, with its applicator 1, is slidably mounted on rails 9 which frame a horizontal receiving surface 10 (see FIG. 5).

[0052] Recesses 11 are provided in the top plate 2, each of which is suitable for receiving an end fitting 12 of a hose 13. The hoses 13 are connected to an intermediate connection 14 from which a hose 15 extends, the two hoses 15 being joined to an intermediate connection (not shown) from which a hose for connection to an external suspension tank (R in FIG. 6) extends.

[0053] The recesses 11 are each connected to an internal suspension distribution tube 16 which dips into the reserve 6.

[0054] The supply of suspension to the reserve 6 is controlled by a device (not shown) which is programmed to open a dispensing valve or valves to supply suspension for example while the applicator 1 is stationary, in particular at a transverse edge of the receiving surface.

[0055] The plate 2 also has vacuum tappings 17 which are connected in pairs by hoses 18 to an intermediate connection 19 from which a connection to a vacuum forming device (not shown) is made.

[0056] Each of the plates 4 has a scraping blade L along its lower edge in the example shown, this having here the form of a pushing shield (FIG. 3). Details of this form can be found in the French patent application filed on 8 Jul. 2019 in the name of the present applicant and having the title “Device for applying layers of paste for a machine for manufacturing ceramic pieces by stereolithography”. Other shapes of scraping blades can be used, such as bevelled blades, for example with a high entry angle (e.g. 45°) or, if laminar flow is to be promoted, with a smaller entry angle.

[0057] In the example shown, the suspension applicator has two blades L, each of which is active in one of the two directions of movement.

The machine according to the invention works as follows: [0058] (a) formation of a first layer C of suspension in the bottom of a vat (B) (FIG. 6) by moving the applicator 1, the reserve 6 of which has been previously filled from the tank R; a vacuum is necessary in this operation to avoid any undesired deposition of suspension and to regulate this deposition; [0059] (b) hardening of the first layer according to the desired pattern; [0060] (c) lifting the applicator 1 by one layer height; [0061] (d) formation of the second layer C by moving the applicator 1 in the opposite direction; [0062] (e) hardening of the second layer C; [0063] with the repetition of steps (c) and (e) for the construction of the green part.

[0064] FIG. 6 shows a machine according to the invention in which the applicator 1 rises by one layer each time from the bottom of the vat B.

[0065] Alternatively, the working surface may be lowered as shown in FIG. 7b, 7c or 7d. In other words, it is the bottom of the vat that descends at each layer formation.

[0066] Referring now to FIG. 7a, it can be seen that as the applicator 1 deposits suspension on the previous layer from the suspension reserve 6, a wave V is formed at the front of the applicator which is scraped off by the front blade.

[0067] Referring to FIG. 7b, which shows the applicator 1 in its initial position (filling the reserve 6), in an intermediate position (during the actual deposit), and in its final position (after the deposit), it can be seen that an overflow TP has been provided on the edge of the tank opposite the starting position. The suspension that falls into the overflow TP can advantageously be returned to the external tank R.

[0068] Referring to FIG. 7c, it can be seen that a situation has been represented in which the level of a previous layer in an uncured location is too low compared to the rest of the layer. In this case, the supply of the missing suspension material is conducted.

[0069] Referring to FIG. 7d, it can be seen that a situation has been represented in which the level of a previous layer in an uncured location is too high compared to the rest of the layer. In this case, the suction of the excess slurry material is conducted.

[0070] Referring to FIG. 8, it can be seen that an applicator 1′ is shown which differs from applicator 1 in that the suspension reserve 6 is divided into compartments (four in the example shown) by three partitions 20 perpendicular to the top plate 2 and extending downwards to the vicinity of the suspension outlet slit T.

[0071] The components of applicator 1′ identical to those of applicator 1 are designated by the same reference numbers.

[0072] The compartments formed by the partitions 20 are of substantially the same volume and each is supplied with suspension by a hose similar to a hose 13 as shown in FIG. 5, and is connected to a vacuum forming device by a vacuum tapping 17.

[0073] In the example shown, the partitions 20 are bevelled at the bottom to facilitate the exit of suspension from each of the compartments.

[0074] Not shown in FIG. 8 are the internal distribution tubes 16 mounted internally in the recesses 11 receiving an end fitting 12 of a hose 13.

[0075] Thus each compartment has its own supply system and vacuum system, allowing the supply and vacuum to be controlled compartment by compartment.

[0076] Also shown in FIG. 8 are control windows 21 which can, if desired, be made into the front wall 4 to observe the behaviour of the suspension during its deposition.