WO2016063198A1

WO2016063198A1 - Apparatus and method for additive manufacturing of three-dimensional objects

Info

Publication number: WO2016063198A1
Application number: PCT/IB2015/058033
Authority: WO
Inventors: Tommaso BECCUTI
Original assignee: Industrie Additive S.R.L.
Priority date: 2014-10-20
Filing date: 2015-10-19
Publication date: 2016-04-28

Abstract

An apparatus (10) and a method for additive manufacturing of three-dimensional objects by means of fused deposition modeling comprises a board (16), an extrusion head (12) arranged to dispense construction material in fused state and to deposit it on the board (16), driving means (18a, 18b, 18c, 20a, 20b, 20c, 22a, 22b, 22c) arranged to suitably position the extrusion head (12) and the board (16) in the space relative to each other by moving the extrusion head (12) and/or the board (16), radiant heating devices (24', 24", 24"', 24a, 24b, 24c) arranged to heat the exposed surface of the object, both during the manufacturing process and once the manufacturing process has been completed, and manually- or automatically-operated orientation adjustment means for adjusting the spatial orientation of the radiation emitted by each of said radiant heating devices (24', 24", 24"', 24a, 24b, 24c

Description

Apparatus and method for additive manufacturing of three-dimensional objects

The present invention relates to an apparatus and a method for manufacturing three- dimensional objects by the so-called additive manufacturing technology, and more specifi- cally to an apparatus and a method for additive manufacturing of three-dimensional objects by fused deposition modeling.

The fused deposition modeling technique, typically referred to with the acronym FDM, consists in producing the three-dimensional object by deposition of construction material (typically thermoplastic material or metal) which is conveyed at the solid state to an extrusion head, heated at least up to the melting point and then deposited onto a board by virtue of the coordinated movement of the extrusion head and/or of the board in the space. Apparatuses and methods for manufacturing three-dimensional objects by means of the fused deposition modeling technique are known for example from US 4,749,347 and US 5,340,433. This technique is traditionally associated to polymeric materials, which are still the most important ones in the market of the additive manufacturing apparatuses, but has recently been used also for producing metal parts.

One of the drawbacks of this additive manufacturing technique is represented by the physi- cal phenomena resulting from the thermal shock to which the object under construction is subject in the cooling phase, during which solidification of the material of the object takes place. The cooling phase produces, in fact, to a larger or smaller extent depending on the cooling time and on other factors such as the temperature of the surrounding air or gas, the pressure and the type of construction material used, not negligible physical phenomena, in particular surface tensions which may result in dimensional distortion of the object. These phenomena may even lead to an early detachment of the object from the board and/or definitively jeopardize the shape, the mechanical properties and/or the surface finish of the object. The greater the thermal shock to which the object under construction is subject, and hence the higher the melting point of the material of the object, the more significant these phenomena are.

In order to overcome this drawback the use of apparatuses provided with a closed working chamber at a controlled temperature, where the temperature is kept at a value higher than the temperature of solidification of the construction material, has been proposed (see US 5,866,058 and US 6,722,872). It has been realized, in fact, that producing the object in a chamber heated up to a temperature higher than that of solidification of the construction material allows to reduce the above-mentioned stress phenomena. The use of closed working chambers at a controlled temperature has however some limits in terms of yield and efficiency of the manufacturing process, which are due to the fact that heat transmission to the air (or other gas) filling the working chamber, and from the air (or gas) to the object being manufactured, takes place in an indirect way, namely by conduction. Such a way of heat transmission is in fact not very efficient, and therefore this solution is in practice not usable on large-sized apparatuses. Moreover, since heat is transmitted to the object by means of the convective motions of the air (or gas) surrounding the same object, it is not possible to heat separately from each other one or more specific areas of the object being manufactured.

WO 92/08566 discloses an apparatus for additive manufacturing of three-dimensional objects by means of the selective laser sintering technique (usually referred to with the acronym SLS), in which a radiant heater of annular shape is arranged to heat only the upper surface of the object being manufactured in a substantially homogeneous manner, i.e. with a substantially uniform density of radiant energy per surface unit. Such a known solution, therefore, relates to an additive manufacturing technique different from that of the present invention and, furthermore, as will be clear from the following description, heats the object being manufactured in a substantially different way with respect to the present invention and hence requires an arrangement of the radiant heater (or heaters) different from the one provided for by the present invention. Another example of an apparatus for additive manufacturing of three-dimensional objects by means of the selective laser sintering technique is known from EP 2 340 925.

An apparatus for additive manufacturing of three-dimensional objects by fused deposition modeling according to the preamble of the enclosed independent claim 1 is known from DE 44 22 146. The apparatus known from this prior art document comprises a plurality of radiant heating devices which are mounted in a fixed position on the structure of the appa- ratus and are adapted to heat the whole exposed surface of the object. This prior art document does neither mention nor suggest the possibility of changing the orientation, and hence the position of the radiating source, represented in this case by the radiant heating devices. An apparatus such as the one disclosed in document DE 44 22 146 is not for ex- ample suitable for heating objects extending over a wide surface, given the impossibility to control the temperature of the whole exposed surface of the object without the use of a plurality of radiating sources - with clear negative consequences on the efficiency of the process. It is an object of the present invention to provide an apparatus and a method for additive manufacturing of three-dimensional objects by means of the fused deposition modeling technique which are not affected by the above-discussed drawbacks of the prior art, which allow in particular to keep the temperature of the object at a controlled level both during and after the manufacturing of the object, without the need of direct contact between the object and the heat source used to heat the object, even with large-sized objects, in particu- lar objects extending over a wide surface.

This and other objects are fully achieved according to the invention by virtue of an apparatus having the features set forth in the enclosed independent claim 1 , as well as by virtue of a method as defined in the enclosed independent claim 10.

Advantageous embodiments of the invention are specified in the dependent claims, the subject-matter of which is to be intended as forming an integral and integrating part of the following description.

In short, the invention is based on the idea of providing orientation adjusting means for adjusting the spatial orientation, and hence the position, of the radiation generated by the radiant heating devices. This allows to heat the object in a dynamic, targeted and differentiated manner, in particular - if necessary - with different heating levels in the various areas of the exposed surface of the object. Moreover, thanks for example to the possibility of moving the radiant heating devices in the three directions, in particular in the horizontal plane, the apparatus according to the invention is able to work also with large-sized objects acting dynamically on the heating cycle, heating in a targeted manner the entire exposed surface of the object, or part thereof, depending on the specific requirements.

Further features and advantages of the present invention will become more apparent from the following detailed description, given purely by way of non-limiting example with reference to the appended drawings, where:

Figure 1 is a perspective view of an apparatus for additive manufacturing of three- dimensional objects by means of the fused deposition modeling technique according to an embodiment of the present invention;

Figure 2 is a perspective view from below of the extrusion head of the apparatus of

Figure 1 ;

Figure 3 is a perspective view of a radiant heating device provided with deflectors that can be used in an apparatus according to the invention;

Figure 4 shows further examples of radiant heating devices, differing from one an- other in their shape, which can be used in an apparatus according to the invention; and

Figure 5 shows an example of a guide system for moving the radiant heating devices in an apparatus according to the invention.

With reference first to Figure 1, an apparatus for additive manufacturing of three- dimensional objects by fused deposition modeling according to an embodiment of the present invention is generally indicated 10. In per-se-known manner, the apparatus 10 comprises an extrusion head 12 arranged to dispense the construction material in fused state through a nozzle 14 (which can be seen in Figure 2) and a board 16 on which the fused material (which may be for example polymeric material or metal) dispensed by the nozzle 14 is deposited and on which the three-dimensional object (not shown) is thus formed layer by layer.

The extrusion head 12 and the board 16 are movable in the space relative to one another to allow deposition of the material along a given three-dimensional path that is programmed depending on the geometry of the object to be manufactured. To this end, the apparatus 10 comprises driving means arranged to move the extrusion head 12 and/or the board 16. Known examples of driving means used on apparatuses for additive manufacturing of three-dimensional objects are robotic arms, Cartesian kinematics driving systems and inverse kinematics driving systems. In the embodiment shown in the drawings, only the extrusion head 12 is movable in the three directions, and more specifically is driven by an inverse kinematics driving system comprising - in per-se-known manner - three pairs of rods 18a, 18b, 18c, wherein each pair of rods 18a, 18b, 18c is hinged at one end to the extrusion head 12 and at the other end to a respective carriage 20a, 20b, 20c slidably mounted along a respective vertical guide 22a, 22b, 22c. As can be clearly understood, the inverse kinematics driving system illustrated herein is only one of the various examples of driving systems that can be used in an apparatus according to the invention and does not therefore constitute an essential feature of the invention.

In order to heat the object during and/or after the manufacturing process, the apparatus 10 according to the invention is provided with radiant heating devices which are arranged to emit a radiation with a variable spatial orientation so as to enable to heat any exposed sur- face of the object without requiring direct contact with the same.

Preferably, the radiant heating devices are infrared radiant heaters that emit an infrared radiation (with a wavelength smaller than 100 μπι) to generate heat in the object hit by the radiation. In this case, the radiant heating devices are preferably arranged to emit radiations with a wavelength smaller than 10 μπι. More specifically, infrared radiant heaters with so- called "long" wavelengths (4 to 10 μηι) are used to heat materials having melting points lower than 750°C approximately (such as, for example, thermoplastic materials, low- melting metal alloys and aluminium alloys), while infrared radiant heaters with so-called "short" (1 to 2 μηι) or "medium" (2 to 4 μηι) wavelengths are used to heat metals. In the case of metal, which may have low absorption and high reflection with respect to infrared radiations, it is preferable to apply on the object being manufactured, by means of a special deposition system, a suitable absorbing varnish which absorbs, thus becoming hotter, the infrared radiation emitted with a given wavelength by the radiant heating devices and then transmits by conduction the heat thus generated to the object being manufactured.

The radiant heating devices may be positioned in different points of the apparatus. The apparatus shown in Figure 1 , for example, comprises a first set of radiant heating devices, in- dicated 24', which are positioned inside the working area of the apparatus (that is to say, approximately inside the volume delimited by the vertical guides 22a, 22b and 22c), a second set of radiant heating devices, indicated 24", which are positioned outside the working area of the apparatus, a third set of radiant heating devices, indicated 24"', which are posi- tioned on the extrusion head 12, and/or a fourth set of radiant heating devices, indicated 24a, 24b and 24c, which are positioned on the vertical guides 22a, 22b and 22c. It is preferable to use many radiant heating devices positioned in different points of the apparatus, as in this way a homogeneous irradiation on all of the exposed surfaces of the object is obtained. It is however clear that both the number and the arrangement of the radiant heating devices may be varied 'depending on the specific requirements, the principle of using these radiant heating devices as heating means to heat the object during and/or after the manufacturing process remaining unchanged.

As is shown in Figure 4, the radiant heating devices to be used on the apparatus 10 may have different geometries, and hence lead to different diffusions of the radiation. For ex- ' ample, the radiant heating devices may be convex (if a non-focussed heating is to be obtained), concave (if, on the other hand, a focussed heating is to be obtained), flat, etc.

The apparatus 10 is arranged to allow to adjust one by one, in manual or automatic mode, the spatial orientation of each radiant heating device. To this end, the radiant heating devices may be mounted for example so as to be orientable by means of special joints and be adjusted manually, in servo-assisted mode by means of special actuators operated on the basis of commands imparted by the user via special control members or, furthermore, in automatic mode under control of automatic adjusting means. In order to change the orien- tation, as well as the intensity, of the radiation emitted by the radiant heating devices, it is also conceivable to use deflectors 26, which may be made as heat-absorbing or heat- reflecting deflectors, such deflectors being mounted on the radiant heating devices (see Figures 2 and 3) so as to be orientable and being also movable manually, in servo-assisted mode or in automatic mode. As is shown in Figure 5, in order to allow to adjust the spatial orientation of the radiation emitted by the radiant heating devices, the apparatus 10 may be provided with a guide system comprising for example horizontal guide bars 28, along which the radiant heating devices (in this case, the radiant heating devices 24") are slidably guided, and vertical guide bars 30, along which the horizontal guide bars 28 are slidably guided. In this way, the radiant heating devices 24" can be moved both in the horizontal plane and in the vertical direction. Preferably, the apparatus 10 is also arranged to allow to adjust individually, in manual or automatic mode, the intensity of the radiation produced by each radiant heating device, in order to improve the control of the temperature of the object and, if necessary, to keep different temperature levels on the various exposed surfaces of the same. To this end, the apparatus may be provided with switches, potentiometers or other manual adjusting mem- bers, of per-se-known type, to adjust manually the intensity of the radiation of each single radiant heating device and/or set of radiant heating devices. Alternatively, the apparatus may be provided with automatic adjusting means to adjust automatically the intensity of the radiation of each single radiant heating device and/or set of radiant heating devices, for example with temperature-feedback control.

The radiant heating devices may be used before, during and/or after the manufacturing process. Before the manufacturing process they may be used to heat the board 16. During the manufacturing process they have the function of keeping the temperature of the object being manufactured under control. Finally, once the manufacturing process has been com- pleted, they may remain in operation and then be progressively switched off, so as to control the cooling of the object that has just been produced to prevent the physical phenomena described in the introductory part of the description from occurring.

Preferably, the apparatus 10 is also provided with temperature measuring means, of per-se- known type, for measuring the temperature in various areas of the surface of the object exposed to the radiation. These temperature measuring means may be for example infrared thermometers, thermocouples, etc. The measures of the temperature provided by the temperature measuring means may be read by the user (for example on a display on board of the apparatus or by software) to enable him to suitably adjust the radiation (intensity and orientation of the radiation emitted by the radiant heating devices). In case where the apparatus is provided with an automatic radiation control system, the measures of the temperature provided by the temperature measuring means will be used by control system to con- trol the radiant heating devices in order to reach and keep a given desired temperature, which may also change depending on the area of the surface of the object exposed to the radiation. Finally, the apparatus 10 is preferably provided with shielding means (not shown, as they are of per-se-known type) for shielding all those components of the apparatus that would be otherwise exposed to, and might be damaged by, the radiation. In particular, the extrusion head 12 and the relating driving system (rods 18a, 18b, 18c, carriages 20a, 20b, 20c and guide 22a, 22b, 22c) will advantageously be shielded. Special absorbing, shielding and/or reflecting materials may be used for example as shielding means.

The operation of the above-described apparatus provides therefore for the radiant heating devices to be suitably controlled (in terms of direction of the radiation, as well as of intensity, if necessary) to emit a radiation over the whole exposed surface, or at least part thereof, of the object being manufactured so as to keep its temperature under control during the manufacturing process and, once the manufacturing process has been completed, to control cooling of the object just produced. As already stated above, the radiant heating devices may also be used, if necessary, to heat the board 16 on which the construction material will be deposited, even before the manufacturing process has been started.

As will be clear from the above description, the apparatus and method for additive manufacturing of three-dimensional objects by fused deposition modeling according to the invention allow to generate heat in the object, both during and after the manufacturing process, without the need to use air or gas as heat transmission means and therefore without the need to close the working area, with evident advantages in terms of lower cost and complexity of the apparatus and higher efficiency of the method. Moreover, an apparatus according to the invention makes it possible to heat in a differentiated and dynamic manner the various areas of the exposed surface of the object, even in case of large-sized objects, in particular objects extending over a wide surface, and hence to control the process more effectively, which clearly results in improved quality of the final product and increased efficiency of the process. Furthermore, especially in case of large-sized apparatuses it is no more necessary to provide many radiation sources, which is clearly advantageous in terms of costs.

Naturally, the principle of the invention remaining unchanged, the embodiments and the constructional details may vary widely from those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention as defined in the appended claims.

Claims

1. Apparatus (10) for additive manufacturing of three-dimensional objects by fused deposition modeling, comprising a board (16), an extrusion head (12) arranged to dispense construction material in fused state and to deposit it oh the board (16), driving means (18a, 18b, 18c, 20a, 20b, 20c, 22a, 22b, 22c) arranged to suitably position the extrusion head (12) and the board (16) in the space relative to each other by moving the extrusion head (12) and/or the board (16), and radiant heating devices (24', 24", 24"', 24a, 24b, 24c) ar- ranged to heat the exposed surface of the object, both during the manufacturing process and once the manufacturing process has been completed,

characterized

in that said radiant heating devices (24', 24", 24"', 24a, 24b, 24c) are arranged to emit a radiation with a variable spatial orientation, and

in that the apparatus further comprises manually- or automatically-operated orientation adjustment means for adjusting the spatial orientation of the radiation emitted by each of said radiant heating devices (24', 24", 24"', 24a, 24b, 24c).

2. Apparatus according to claim 1, wherein said radiant heating devices (24', 24", 24"', 24a, 24b, 24c) are movable along at least one of the three spatial directions (x, y, z).

3. Apparatus according to claim 2, wherein said radiant heating devices (24', 24", 24"', 24a, 24b, 24c) are movable both vertically (z) and in the horizontal plane (x, y).

4. Apparatus according to any of the preceding claims, further comprising deflectors (26) which are mounted on said radiant heating devices (24', 24", 24"', 24a, 24b, 24c) so as to be orientable to change the orientation and/or the intensity of the radiation emitted by said devices.

5. Apparatus according to any of the preceding claims, wherein said radiant heating devices (24', 24", 24"', 24a, 24b, 24c) are infrared radiant heaters.

6. Apparatus according to any of the preceding claims, wherein said radiant heating devices (24', 24", 24"', 24a, 24b, 24c) are positioned in different points of the apparatus to emit a radiation on all of the exposed surfaces of the object.

7. Apparatus according to any of the preceding claims, further comprising manually- or automatically-operated intensity adjustment means for adjusting the intensity of the radiation generated by each radiant heating device (24', 24", 24"', 24a, 24b, 24c).

8. Apparatus according to any of the preceding claims, further comprising temperature measuring means for measuring the temperature in various areas of the surface of the ob- ject exposed to the radiation.

9. Apparatus according to claims 7 and 8, further comprising an automatic radiation control system arranged to receive the measures of the temperature provided by said temperature measuring means and to control said intensity adjustment means and said orienta- tion adjustment means to feedback control the temperature of the object.

10. Method for additive manufacturing of three-dimensional objects by fused deposition modeling, wherein during the manufacturing process and/or once the manufacturing process has been completed the temperature of the object is adjusted in a controlled man- ner by emitting a radiation over all of the exposed surfaces of the object by means of radiant heating devices (24', 24", 24"', 24a, 24b, 24c) and by adjusting the spatial orientation of the radiation emitted by each of said radiant heating devices (24', 24", 24"', 24a, 24b, 24c).