WO1992017329A1

WO1992017329A1 - Process and device for producing a three-dimensional object

Info

Publication number: WO1992017329A1
Application number: PCT/EP1992/000689
Authority: WO
Inventors: Hans J. Langer; Dave Retallick; Johannes Reichle
Original assignee: Eos Gmbh Electro Optical Systems
Priority date: 1991-04-04
Filing date: 1992-03-27
Publication date: 1992-10-15
Also published as: DE4110903A1; DE4110903C2

Abstract

In a device or process for producing an object by the successive securing of superimposed layers in a bath of fluid or powdered material by the action of electromagnetic radiation, there arises the problem of how to adjust the layer thickness of the material quickly and accurately before securing. To solve this problem it is proposed to adjust the distance between a base plate or the layer already secured and the top of the bath in such a way that it is greater than the thickness of the layer to be secured, to form a region at the point of action of the radiation in the bath with a surface reduced in suitable proportion to the thickness of the layer to be secured and to shift the region together with the position of the effect of the radiation to secure the object along the surface of the bath.

Description

Method and device for producing a three-dimensional object

The invention relates to a method and a device for producing a three-dimensional object according to the preamble of claim 1 and claim 10.

An example of such a method is known under the term "stereography" or "stereolithography" and in the article by Hideo Koda a, "Automatic method for fabricating a three-dimensional plastic model with photo-hardening polymer", Rev. Sci.Instrum. 52 (11), Nov. 1981, pages 1770 to 1773. In this method, the object is lowered after a layer has solidified, so that a liquid layer of the plastic can form on the solidified layer. The problem arises here that the thickness of this plastic layer, which represents the layer thickness of the next layer and thus decisively influences the manufacturing accuracy, cannot be set exactly or depends on how quickly the liquid plastic drops onto the solidified layer can flow and any excess amount can flow out again. The layer thickness is therefore not precisely defined in this method and, depending on the viscosity of the plastic, a considerable time is required to set a desired thickness.

It is therefore an object of the invention to accelerate the manufacture of the object. Furthermore, the accuracy in the manufacture of the object is also to be improved.

This object is achieved by the method characterized in claim 1 and the device characterized in claim 10. Developments of the invention are characterized in the subclaims.

Further features and advantages of the invention result from the description of exemplary embodiments with reference to the figures. From the figures show:

Fig.l is a schematic side view of an embodiment of the device according to the invention;

2 shows a plan view of the embodiment according to Fig.l;

3 shows an enlarged sectional illustration of an embodiment of the body used in the device of FIGS. 1 and 2; and

4 shows an enlarged sectional illustration of a further embodiment of a body which can be used in the device of FIGS. 1 and 2.

A container 1, which is open on its upper side, is filled to a level or a surface 2 with a light-curable, liquid plastic 3. In the container in the area of the plastic 3 there is a carrier 4 with an essentially flat and horizontal carrier plate 5 which is arranged parallel to the surface 2 and by means of a schematically indicated displacement or height adjustment device 6 perpendicular to the surface 2 or to the support plate 5 can be moved up and down and positioned.

On the support plate 5 is the object 7, which is constructed from a plurality of layers 7a, 7b, 7c and 7d, each extending parallel to the surface 2 and to the support plate 5, in the manner described later.

A translucent body 8 in the form of a channel 9 which is open at the top is provided on the open top of the container 1. As can be seen in particular from Figure 3, the channel 9 consists of a translucent bottom area 10 and lateral edge regions 11, 12 projecting obliquely outwards and upwards therefrom. The bottom area is essentially flat and is formed from a material that does not adhere to the plastic 3. PTFE is preferably selected for this purpose, but polyethylene or quartz glass or a similar material which is permeable to light or UV radiation can also be used. The edge regions 11, 12 can likewise either be formed from such a non-adhesive material or be coated with such a non-adhesive material.

As can be seen in particular from FIGS. 1 and 2, the channel 9 extends over the open upper region of the container 1 at such a height above the container base that the base region 10 is at a height below the surface 2 and the upper edges of the container Edge regions 11, 12 are arranged above the surface 2, that is to say the channel 9 is immersed in the plastic 3 from above. End plates 13, 14 are also provided at both ends of the channel, which prevent the plastic from penetrating into the cavity of the channel 9 from the sides.

The gutter ^" 9 is mounted in the manner indicated in FIGS. 1 and 2 on a support device 15 such that the gutter 9 in a plane parallel to the support plate 5 and to the surface 2 in a direction parallel to the longitudinal direction of the gutter 9 over the open top the container may ^{^} be erschoben. for this purpose, for example, each end of the channel to be slidably mounted on a guide extending parallel to or along the an¬ adjacent container wall guide rail 16,17. 9 the displacement takes place via a shifter 18 with a drive 19, which can be designed, for example, in the form of a spindle, cable or chain device known per se for stepless parallel displacement of the channel 9.

There is also a solidification device 20 for radiography the channel 9 provided with light. The solidification device 20 has an illumination device 21 with a light source 22, which generates a bundled light beam 24 via an optical system 23. Depending on the type of plastic used, a UV light source, a laser or other light sources which can cause the plastic 3 to polymerize can be used as the light source 22. A deflection mirror 25 is provided approximately in the middle above the container 1, which is gimbally suspended and can be pivoted by a schematically indicated pivoting device 26 such that the light beam 24 directed at the mirror 25 is reflected by the mirror 25 as a reflected light beam 27 at each point Surface 2 can be positioned.

Furthermore, a computer 28 is provided which is coupled to the lighting device 21, to the swivel device 26, to the displacement device 18 and to the height adjustment device 6 for carrying out the steps described below.

In operation, data about the shape of the object 7 are first created or stored in the computer 28 on the basis of a construction program or the like. These data are prepared for the production of the object 7 in such a way that the object is broken down into a multiplicity of horizontal layers which are thin in comparison to the object dimension and the shape data, for example in the form of data records, e.g. CAD data are provided for each layer 7a ... 7d of this large number of layers. The creation and preparation of the data for each layer can take place before the production or at the same time as the production of each layer.

The container is then filled with plastic 3 to such an extent that the free surface 2 of the plastic bath is higher than the bottom area 10 of the channel 9, but lower than the upper edge of the edge areas 11, 12. The amount by which the channel dips into plastic 3 from above (which is shown in FIG. indicated immersion depth d), is chosen so that unevenness of the surface 2 is safely above the underside of the bottom region 10 during operation.

To produce the first layer 7a, the computer 28 controls the height adjustment device 6 such that there is a distance between the top of the carrier plate 5 and the underside of the bottom region 10 that corresponds precisely to the intended thickness of the first layer 7a. The shifting device 18 is moved into a starting position, preferably at a lateral edge of the layer to be produced, and then horizontally or continuously by the computer in the shifting direction horizontally over the area of the carrier plate 5 on which the first layer is produced. During this shift, the computer 28 controls the illuminating device 21 and the swiveling device 26 in such a way that the light beam 27 in the manner indicated in FIG Place the liquid plastic layer between the base area 10 and the carrier plate 5. This is done in such a way that the deflecting mirror 25 is moved synchronously with the displacement of the channel 9 in such a way that the light beam 24, 27 is deflected in the longitudinal direction of the channel 9 to the intended locations. As a result, the plastic is solidified at the points of incidence of the light beam in a line or row along the longitudinal direction of the channel and below it by polymerization. If the gutter shifted konti¬ ously, the displacement movement of de _^ channel 9 arises by the superposition with the movement of the light beam 27 along the trough an inclined or sawtooth-like movement of the reflected light beam 27 across the surface 2, is completely solidified until the layer . When the trough is advanced step by step, it is shifted from the first shifting position by a distance corresponding to the shape data to a new position and the deflecting mirror is moved by the computer by means of the swiveling device 26 pivoted accordingly so that when the next row is exposed while the channel is stationary, the reflected light beam again strikes the plastic 3 through the bottom area 10 of the channel. The lateral swiveling of the light beam can take place in such a way that the points to be solidified are approached in a targeted manner and faded out in between or driven at a higher speed.

After the first layer 7a has solidified in this way, the computer 28 moves the channel 9 back to the starting position and lowers the support plate 5 via the height adjustment device 6 to such an extent that now between the top of the first layer 7a and the bottom of the bottom region 10 there is a distance corresponding to the thickness of the second layer 7b. Then the second layer 7b is solidified in the same manner as the first layer 7a. The other layers are then produced analogously.

After the lowering of the carrier plate after the completion of a layer 7a ... 7d, the liquid plastic 3 flows from the edges of the layer to the center and initially forms a liquid layer with a thickness that decreases towards the center. This irregularity in the layer thickness compensates more or less quickly, depending on the viscosity of the plastic. In the method described, however, this irregularity is irrelevant as long as it does not exceed the immersion dimension d at any point. However, this is already ^{significant, "is} present ahout the case, as a required for the known method a uniform layer thickness. Thus, a considerable acceleration results in the process. Furthermore, occurring Unregelmä¬ are ßigkeiten the layer thickness without affecting the JSxaktheit during the solidification of a layer of the Layer thickness and thus the shape of the object 7, since the lateral displacement of the channel immersed in the plastic always ensures an exact layer thickness.

In the embodiment shown in FIG. 4, the body is 8 formed as a hollow body in the form of a downwardly open channel 29, which is arranged relative to the container 1 in the same way as the channel 9. The channel 29 has a light-permeable or radiation-permeable upper side 30 and on both sides thereof a downwardly protruding edge region 31, 32, the lower ends of which are arranged below the surface 2 and therefore protrude into the plastic 3. The upper side 30 and the edge regions 31, 32 thus form a cavity 33 which, on its underside immersed in the plastic, has a slot-like opening 34 which extends in the longitudinal direction of the channel 29 and is closed at the bottom by the plastic 3. The cavity 33 is connected to a supply 37 for inert gas, preferably nitrogen, via a line 35 and a pressure regulator 36. Alternatively, a liquid which is immiscible and does not react with the material 3 can also be selected.

In operation, in the embodiment according to FIG. 4, the height adjustment device 6 is actuated in such a way that the distance between the lower edge of the edge regions 31, 32 is slightly larger than the thickness of the layer to be consolidated (and preferably by an amount of 0.01 to 0.1mm). The pressure in the cavity 33 is now adjusted or regulated with the aid of the regulator 36 such that the interface 38 between the gas in the cavity and the plastic 3 is arched out of the cavity downward by the same amount. This has the consequence that in the focus 39 of the light beam 27 entering through the upper side 30, the layer thickness of the liquid plastic corresponds exactly to the thickness of the layer to be solidified and can thus be solidified. Due to the bulging out of the interface 38, the lower edge of the edge regions 31, 32 remains at a corresponding distance above the upper side 40 of the solidified layer with each movement, so that sticking of the channel to the object is avoided. The movement of the channel 29 and the consolidation of successive layers then take place in the same way as in the embodiment in FIG. 3. Various modifications of the described device and the method are possible. For example, instead of the liquid plastic, plastic or metal powder can also be used and solidified by the action of light or laser (laser sintering). Depending on its properties, the material can also be solidified by other forms of electromagnetic radiation or thermal radiation. Instead of lowering the carrier plate after each layer, the level of the plastic surface 2 together with the channel 9 or 29 or the body 8 can also be raised accordingly. The channel itself can also be formed in one piece from a radiation-permeable material and in other cross-sectional shapes, for example semicircular or rectangular, and be inclined or tilted or provided with different edge areas, so that one of the edge areas, preferably the front area in the feed direction, further immersed in the material 3. It is also possible to omit the base region 10 or the top side 30, so that the body 8 consists only of two profiles which extend transversely across the container and which are so small, preferably smaller, on their underside which dips into the material than 1mm, have that the material 3 due to its surface tension not in the. Space between the profiles occurs. The method according to the invention can also be carried out with a single profile of this type if the radiation action for solidification is carried out on the rear side in the displacement direction of the profile in the region formed there during the displacement with the surface 2 lowered, that is to say directly adjacent to the profile .

The non-stick coating can be obtained by choosing the material of the channel or by means of appropriate coatings, coatings, foils, etc. Alternatively or additionally, the body 8 can be vibrated by means of a vibration device, for example an ultrasound source, in order to reduce the adhesion. As a further possibility for reducing the liability it can be provided that the distance of the base region 10 of the carrier plate 5 or the preceding layer is selected to be slightly larger than the layer thickness of the layer to be solidified, so that a thin liquid film remains underneath the base region 10. In this case, the exact layer thickness is obtained by adjusting the focus of the light beam 24, 27 by a corresponding amount below the underside of the floor area, which acts as a reference surface.

Furthermore, it is also possible to mount the scanner consisting of light source 22 and deflecting mirror 25 on channel 9 or 29 or to couple it to displacement device 18, so that light beam 24, 27 is deflected only in the longitudinal direction of channel 9 or 29 got to. Instead of the light beam 24, 27 deflected via the mirror 25, one or more glass fiber light guides can also be used, which are either shifted along the channel or the body accordingly or at a plurality of locations along the channel corresponding to the shape data or the body are firmly attached, so that a displacement in the longitudinal direction of the channel or the body is no longer necessary. Permanently installed light sources are also possible at these points of the channel or the body. The body 8 can also be cup-shaped with an open top according to the embodiment according to FIG. 3 or an open bottom according to the embodiment according to FIG. 4 and not only in one direction from the displacement device 18, but also in synchronization with the light beam 27 or in any direction in the horizontal plane above the carrier plate 5, the individual layers and thus the plane of displacement not necessarily being parallel to the surface, but also obliquely thereto.

Claims

Method for producing a three-dimensional object by solidifying layers of the object lying one above the other, in which a subsequent layer is solidified on an already solidified layer in a bath of initially liquid or powdery material which can be solidified by the action of electromagnetic radiation, corresponding to the shape of the object characterized in that the distance between a base plate or the already solidified layer and the surface of the bath is set so that it is greater than the thickness of the layer to be solidified, that at the location of the radiation in the bath an area with a to the thickness of the solidifying layer corresponding dimension of the lowered surface is formed and that the area is moved along with the location of the radiation effect to solidify the object along the surface of the bath.

A method according to claim 1, characterized in that the displacement parallel to the base plate or ^' . to the previously solidified layer. ; • ^{• "}

The method of claim 1 or'ϊ?, Characterized gekennzeir≤hnet that a body permeable to electromagnetic radiation is immersed in the material and the radiation effect takes place through this body.

Method according to one of claims 1 to 3, characterized in that the surface in the Area is lowered by the action of a fluid.

5. The method according to claim 4, characterized in that an inert gas under increased pressure is used as the fluid.

6. The method according to claim 5, characterized in that the lowering of the surface takes place in the area to the desired level by adjusting or regulating the pressure.

7. The method according to any one of claims 3 to 6, characterized in that the body is displaced in a defined plane and the object is lowered after the solidification of a layer.

8. The method according to any one of claims 1 to 7, characterized in that the solidification takes place by means of egg nes light or laser beam, the direction of which is changed synchronously with the displacement of the area.

#

9. The method according to any one of claims 1 to 8, characterized in that a polymerizable liquid plastic is used as the material.

10. Device for carrying out the method according to claim 1, with a container (1) for holding a bath of liquid or powdery material (3) that can be solidified by the action of electromagnetic radiation, a carrier (4) for holding the object ( 7) and a device (20) for solidifying a layer of the material by means of electromagnetic radiation,

-___.___ characterized in that a body (8) dipping into the material (3) from above and a device (18) for displacing the body (8) along the surface (2) of the material (3) In such a way that an area with a surface (2) corresponding to the thickness of the layer to be solidified is formed in the region of the body (8), and that the solidifying device (20) is connected to the body (8) is coupled that it acts on the area with the lowered surface.

11. The device according to claim 10, characterized in that the body (8) as a transversely to the direction of displacement over the container (1) er¬ extending profile and that a Vorrich¬ device (6) for vertical adjustment of the height of the body (8) perpendicular to the carrier (4) and to the surface (2) of the material (3) is provided.

12. The apparatus of claim 10 or 11, characterized in that the body (8) is at least partially transparent to radiation and that the consolidation device (20) acting on the free top of the body (8) device (21, 25) for radiating through the body with the electromagnetic radiation.

13. The apparatus according to claim 12, characterized in that the body (8) has a radiation-permeable bottom region (10) which forms the underside of the body (8) facing the carrier (4), and an edge region (11 , 12) - = -.

14. The apparatus according to claim 13, characterized in that the bottom region (10) and / or the edge region (11, 12) made of a non-adhering material, preferably PTFE, to the material to be solidified (3), or is coated with such a material .

15. Device according to one of claims 10 to 14, characterized in that the body (8) is formed as an open-topped channel (9) which extends transversely to the direction of displacement across the container (1).

16. The apparatus according to claim 15, characterized in that the bottom area of the channel (9) forming the bottom area (10) is designed as a translucent window that extends over substantially the entire length of the channel (9) or width of the container ¬ ters (1) extends.

17. Device according to one of claims 10 to 12, characterized in that the body (8) is designed as a hollow body with a downward opening (34) and a device (35,36,37) for supplying one for the radiation used has transmissive fluids in the cavity.

18. The apparatus according to claim 17, characterized in that the top (30) of the hollow body is radiation-transmissive.

19. The apparatus according to claim 17 or 18, characterized in that the feed device (35,36,37) has a control device (36) for adjusting or regulating the pressure of the fluid.

20. Device according to one of claims 17 to 19, characterized in that the hollow body is designed as a downwardly open channel (29) which extends transversely to the direction of displacement over the container (1).

21. Device according to one of claims 15, 16 or 20, characterized in that the displacement device (18) the channel (9; 29) in a horizontal, substantially transverse to the longitudinal direction of the channel (9; 29) stretching direction shifts.

22. The device according to one of claims 10 to 14 and 17 to

19, characterized in that the displacement device (18) displaces the body (8) in a horizontal plane in a first direction and in a second direction substantially perpendicular thereto.

23. Device according to one of claims 10 to 22, characterized in that the vertical Einteilvor¬ device (6) has a device for moving and adjusting the carrier (4) in a direction perpendicular to the horizontal plane of displacement of the body (8).

24. Device according to one of claims 10 to 23, characterized in that the solidification device (20) has a light source (22, 23) for generating a bundled light beam (24), a deflection mirror (25) for the light beam (24) and has a control (26, 28) coupled to the displacement of the body for adjusting the deflection mirror (25). .

25. Device according to one or more of the preceding

Claims, characterized in that a plurality of light sources are provided side by side in the longitudinal direction of the body (8) and are controlled in parallel by a control J_28 ^" ) in accordance with the shape of the object.

26. Device according to one of claims 10 to 23, characterized in that the solidification device (20) a light source and one or more, with the

—-.__ body-coupled light guide for supplying the radiation into the body.