Method and device for producing an article

Abstract

The invention relates to a method for producing a three-dimensional article by way of an additive manufacturing method, wherein at least one manufacturing material is introduced in a flowable state into a support material from at least one introduction opening of an introduction needle and is then hardened, and a stiffening material is introduced into the support material and then hardened.

Description

[0001] Method and device for producing an object

[0002] The invention relates to a method for producing a three-dimensional object using an additive manufacturing process, in which at least one production material is introduced in a flowable state into a support material from at least one insertion opening of an insertion needle and then cured. The invention also relates to a device for carrying out such a method.

[0003] Additive manufacturing processes are now known in many forms from the state of the art and are used to produce a wide variety of 3-dimensional objects. Traditionally, additive manufacturing processes are hardly suitable for producing large quantities of the respective objects, as the production of individual objects is very time-consuming. In additive manufacturing processes, especially 3D printing, the object to be manufactured is constructed from a multitude of very thin, stacked layers, often only a few micrometers thick. The production of large objects, in particular, is therefore very time-consuming.

[0004] In recent years, great progress has been made in this field. For example, MIT has developed a 3-dimensional printing process that was published in US 2018 / 281295 A1. This process is called “rapid liquid printing” (RLP). The object to be manufactured is created in a container containing a gel suspension or another material as support material that does not chemically react with the production material. It serves exclusively to support the production material as long as it has not yet sufficiently cured. In the context of the present invention, “curing” is also understood to mean crosslinking or another process by which the flowable production material changes into a state in which its flowability is limited or no longer present. Such a restriction of flowability occurs, for example, through crosslinking.In this process, the production material is introduced into the support material in a flowable state, for example, in liquid or gel form, at the desired position. For this purpose, at least one insertion needle is used, which has at least one insertion opening.

[0005] This process made it possible to use manufacturing materials that exhibit elastic properties after curing. It is thus possible to produce a 3-dimensional, elastic object using an additive manufacturing process.

[0006] This is particularly interesting for a whole range of orthopedic devices, such as prosthetic liners. A prosthetic liner is typically made of silicone or polyurethane. It serves as an intermediate layer between an amputation stump and a prosthetic socket, to which additional prosthetic components can be arranged and attached. The prosthetic liner has an open proximal end into which the amputation stump is inserted, and a closed distal end. The direction extending from the distal end to the proximal end, or vice versa, is referred to as the longitudinal direction of the prosthetic liner. Prosthetic liners are often standard elements that are not adapted to the individual circumstances of the respective amputation stump. They frequently have a circular cross-section that usually tapers from the proximal end to the distal end.This design has the advantage that such a standard liner can be used for many different amputation stumps, eliminating the need to keep a large number of different liners on hand. Instead of a circular cross-section, the cross-section can also be oval, ellipsoidal, or freely shaped. However, each liner has a closed cross-section. In addition to these standard liners, there are also custom-made liners on the market that are adapted to the specific conditions of the amputation stump. These also have a closed cross-section. This can also be circular, oval, ellipsoidal, or freely shaped. Regardless of the type of liner, the shape of the cross-section can also change depending on its position along the longitudinal direction.

[0007] It is known to produce prosthetic liners using an RLP process, as this can also be used to manufacture elastic components and objects. However, the elasticity of a prosthetic liner is preferably not homogeneous. While the liner must have high elasticity in the circumferential direction in order to be sufficiently expanded when the liner is applied to the amputation stump, thereby achieving sufficient adhesion, the elasticity of the liner should be significantly lower along the longitudinal direction of the liner. Preferably, the liner is almost or completely inelastic along this direction. This avoids the "milking effect" known from the prior art. Such a liner, which, for example, has different elasticity and stretch behavior in the longitudinal and circumferential directions, cannot be produced using the RLP processes of the prior art.

[0008] The invention is therefore based on the object of further developing a method in such a way that these disadvantages are eliminated or at least reduced.

[0009] The invention solves the stated problem by a method according to the preamble of claim 1, which is characterized in that a stiffening material is introduced into the support material and then hardens. After hardening, the stiffening material has different mechanical properties, in particular a different elasticity, preferably a lower elasticity than the hardened production material. In this way, the elasticity of the manufactured object can be changed and influenced in a spatially resolved manner, i.e. to different extents at different locations. Advantageously, the stiffening material contains solid particles. The amount and type of these solid particles can be constant throughout the stiffening material. This is then referred to as a homogeneous distribution of the solid particles.However, the quantity and / or type of solid particles can also vary in the stiffening material, so that the distribution of the solid particles is referred to as inhomogeneous.

[0010] The solid particles are arranged in a flowable stiffening material when they are introduced into the support material. This flowable stiffening material can therefore also be referred to as the matrix for the solid particles.

[0011] The solid particles preferably comprise fibers. The fibers include, for example, inorganic fibers, such as boron fibers, silica fibers, carbon fibers, quartz fibers, and / or silicate-based fibers, for example, basalt fibers, glass fibers, or ceramic fibers. Alternatively or additionally, the fibers include organic fibers, such as aramid fibers and / or carbon fibers, polyester fibers, nylon fibers, polyethylene fibers, and / or polymethyl methacrylate fibers. Alternatively or additionally, the fibers include natural fibers made, for example, from flax, hemp, wood, sisal, and / or cotton.

[0012] While in natural fibers, the fibers are primarily bonded to the matrix, such as a silicone matrix, through mechanical bonding, inorganic and organic fibers are generally bonded through chemical bonding. In a matrix that exclusively or predominantly contains polyurethane, the bonding is preferably chemical.

[0013] Alternatively or additionally, the solid particles contain glass particles, preferably glass spheres. This also allows the mechanical properties of the stiffening material and thus of the 3-dimensional object to be influenced. Advantageously, the solid particles, especially the fibers used, exhibit lower elasticity than the manufacturing material. Particularly preferably, the fibers also exhibit lower elasticity than the matrix of the stiffening material. It has proven advantageous to use inelastic fibers.

[0014] The stiffening material is preferably introduced into the support material in such a way that it comes into contact with previously introduced production material. Advantageously, at least one introduction needle with at least one introduction opening is used to introduce the stiffening material. The stiffening material is preferably introduced into the support material through the at least one introduction opening of the at least one introduction needle in such a way that it comes into contact with the already present production material upon or immediately after emerging from the introduction opening. The stiffening material is therefore injection-molded onto the production material already introduced into the support material. It is not necessary, but advantageous, if the entire stiffening material is introduced in such a way that it already comes into contact with previously introduced production material.

[0015] In a preferred embodiment, the production material is not yet fully cured when it comes into contact with the stiffening material. The stiffening material is also not cured at this point, so that the two materials, in particular the production material and the matrix of the stiffening material, can cure together. This preferably results in a chemical bond between the matrix of the stiffening material and the production material, creating a good and sufficiently strong bond between the two materials. It is advantageous if the matrix of the stiffening material and the production material are identical. Alternatively, the matrix of the stiffening material and the production material can both be a silicone or a polyurethane, although different silicones and polyurethanes can be used.Advantageously, at least a portion of the stiffening material, but preferably the entire stiffening material, is introduced into the support material simultaneously with the production material. Particularly if the matrix corresponds to the production material, the stiffening material can be introduced into the support material using the same insertion needle as the production material. The stiffening material preferably replaces the production material at least partially, preferably completely, at least in some areas. This can be achieved particularly simply by adding stiffening elements, for example, solid particles, to the production material.In a particularly preferred embodiment, both the production material and the stiffening material are each introduced into the support material with at least one insertion needle, so that preferably at least two insertion needles are used simultaneously and are located in the support material.

[0016] Preferably, the production material incorporated into the support material forms a base body of the 3-dimensional object to be produced, with the stiffening material being arranged on this base body. This preferably occurs on an outer side of the base body, i.e., the side that is not associated with or facing the skin or a body part of the wearer in the finished 3-dimensional object. Thickened portions and additionally applied materials, such as the stiffening material, are generally easy to arrange on the outer side of the base body, whereas on the opposite inner side of the base body, they often lead to problems, pressure sores, or pain when wearing the finished 3-dimensional object.

[0017] The fibers preferably contain short fibers, long fibers, and / or continuous fibers. Short fibers are fibers with a maximum length of 1 mm. Long fibers are fibers that are longer than short fibers and have a maximum length of 50 mm. Fibers with a length of more than 50 mm are referred to as continuous fibers. If the stiffening material is introduced into the support material using at least one insertion needle, this insertion needle moves along a predetermined pressure path through the support material. A predetermined amount of stiffening material is introduced into the support material along this pressure path. The fibers are advantageously aligned at least partially in the direction of movement of the insertion needle.Preferably, at least 50% of the fibers in the introduced stiffening material, preferably more than 70% of the fibers, particularly preferably more than 90% of the fibers are aligned along the direction of movement of the insertion needle. The longer the fibers, the easier they are to align by the movement of the insertion needle. Preferably, particularly long fibers, for example continuous fibers or long fibers, are fed to the stiffening material via a separate feed. As a result, they are already aligned in the stiffening material when the latter is introduced into the support material. The solid particles, preferably the fibers, are present in an unaligned manner in a storage container in which the matrix of the stiffening material is mixed with the solid particles, preferably the fibers, and from which the insertion needle is fed.

[0018] The fibers, which are aligned along the direction of movement of the insertion needle, are arranged such that their longitudinal extension forms an angle of at most 30°, preferably at most 20°, and particularly preferably at most 10°, with the direction of movement. The longitudinal extension of a fiber preferably extends from one end of the respective fiber to the other end of the fiber. In this way, a longitudinal extension direction can be defined even if the fiber does not extend in a straight line.

[0019] The fibers give the stiffening material greater mechanical stability along their longitudinal direction. In a direction perpendicular to the longitudinal direction, however, the stability is only slightly affected or not affected at all. By selecting the direction of movement of the insertion needle, it is thus possible to influence the direction along which stability is increased, i.e. the direction in which the structure is to be stiffened. In advantageous embodiments of the invention, the direction of movement of the insertion needle is therefore selected so that different regions, areas, or locations of the stiffening material are stiffened in different directions. It is advantageous to determine the anticipated loads to which the object will be exposed before manufacturing the object, for example by computer simulation. From these loads, it is then determined in which areas the object should be stiffened against loads in which direction.This is used to determine the pressure path that the insertion needle follows when producing the object and which thus defines the direction of movement of the insertion needle.

[0020] Preferably, the stiffening material creates an auxetic structure. An auxetic structure has the property that a strain of the structure in a first direction, for example, due to the action of an external force, results in a strain in a second direction, which is, for example, perpendicular to the first direction.

[0021] Preferably, the 3-dimensional object is a liner with a base body having an outer surface, wherein the base body is preferably made from the production material and wherein the stiffening material is preferably arranged on the outer surface of the base body. Particularly preferably, the stiffening material is arranged on the base body in a distal-proximal direction, preferably in distal-proximal strips. The arrangement of the stiffening material in a distal-proximal direction means that the insertion needle, which is used to introduce the stiffening material into the support material, moves through the support material along this direction, i.e. from distal to proximal or vice versa. Sections of the pressure path that form an acute angle to this direction are also considered to be in the distal-proximal direction.As already explained, the use of such a shaped pressure path results in fibers located in the matrix of the stiffening material forming along this direction. If the fibers are inelastic or low-elasticity fibers, the elasticity of the stiffening material is reduced in the distal-proximal direction by the fibers aligned in this way. Since the stiffening material is bonded to the manufacturing material, the mechanical properties, in particular the elasticity, of the manufacturing material bonded to the stiffening material are also reduced in this direction. However, in a direction perpendicular to this, such as the circumferential direction, they are not or only slightly impaired.

[0022] The distal-proximal strips, in which the stiffening material is preferably arranged, can also be referred to as fingers and preferably extend from the distal end of the base body of the liner. Particularly preferably, at least four, more preferably at least six, more preferably at least eight, and particularly preferably at least ten such fingers or distal-proximal strips are produced. These fingers or distal-proximal strips are preferably arranged equidistantly around the circumference of the base body of the liner.

[0023] Preferably, at least a part of the stiffening material, but particularly preferably the entire stiffening material, is arranged on the outside of a part of the object to be produced made from the production material.

[0024] The invention further achieves the stated object by a device for carrying out a method described here. Such a device has a container, for example a box or a container, in which the support material is located and in which the 3-dimensional object is produced. The device also has at least one insertion needle with at least one insertion opening through which the production material is introduced into the support material. Advantageously, the device has at least one further insertion needle with at least one insertion opening through which the stiffening material is introduced into the support material.

[0025] An example of an embodiment is explained in more detail below with the help of the attached drawings.

[0026] Figure 1 - the schematic representation of a 3-dimensional object which is produced by means of a method according to an embodiment of the present invention Figure 2 - the schematic representation of the effect of fibers on the

[0027] Elasticity and

[0028] Figure 3 - the schematic representation of a device for

[0029] Performing a procedure described here.

[0030] Figure 1 shows a 3-dimensional object comprising a base body 2 manufactured from a production material using an additive manufacturing process. It has an outer side 4, an open proximal end 6, and a closed distal end 8. The object is a prosthetic liner. A stiffening material is applied to the outer side 4 of the base body 2 via an insertion needle 10, which is embedded in the support material (not shown). This occurs in distal-proximal strips 12.

[0031] Figure 2 shows the influence of fibers on the elasticity of a matrix in which they are arranged. In the right-hand part of Figure 2, the fibers, which are represented by short lines, are undirected. The arrows show that the elasticity of the matrix is ​​immediately influenced, i.e. is equally great in all directions. In the left-hand part of Figure 2, the fibers are predominantly, in the example embodiment shown even completely, aligned up and down along the directions of the arrows. As a result, a stiffening material in which the fibers are aligned in this way has severely limited elasticity in the direction of alignment, i.e. up and down, while the elasticity perpendicular to this, i.e. to the left and right in the illustration shown, is hardly or not at all influenced.

[0032] Figure 3 shows a schematic diagram of an apparatus for carrying out a method described here. The support material, which is not shown in Figure 3 for the sake of clarity, is located in a container 14. The insertion needle 10 is shown within the container 14, through which stiffening material 16 is introduced from a reservoir 18 into the support material and the container 14. The fibers of the stiffening material 16, shown as short lines, are present in an undirected manner in the reservoir 18 and are aligned along the direction of movement of the needle on their way through the insertion needle 10. The schematic representation in Figure 3 makes the insertion needle 10 appear to be immobile relative to the container 14. However, this is incorrect and is only due to the clarity of the representation.The insertion needle 10 is preferably movable along three independent directions, which are particularly preferably perpendicular to one another, although combinations of these directions are also possible. Located inside the container 14 is a base body 2, which was manufactured from a production material in a previous process step. On the outside of the base body, a distal-proximal strip 12 can be seen, which is made of the stiffening material 16, represented by the fibers shown as small lines.

[0033] List of reference symbols

[0034] 2 basic bodies

[0035] 4 Outside

[0036] 6 proximal end

[0037] 8 distal end

[0038] 10 insertion needle

[0039] 12 distal-proximal stripe

[0040] 14 containers

[0041] 16 stiffening material

[0042] 18 Reservoir ii

Claims

Patent claims 1. A method for producing a 3-dimensional object by means of an additive manufacturing method, in which at least one production material is introduced in a flowable state into a support material from at least one introduction opening of an introduction needle and then hardens, characterized in that a stiffening material is introduced into the support material and then hardens.

2. Method according to claim 1, characterized in that the stiffening material contains solid particles.

3. The method according to claim 2, characterized in that the solid particles contain fibers, for example inorganic fibers such as basalt fibers and / or glass fibers and / or ceramic fibers and / or quartz fibers, and / or organic fibers such as aramid fibers and / or carbon fibers, and / or natural fibers such as flax and / or hemp and / or cotton.

4. Process according to claim 2 or 3, characterized in that the solid particles contain glass particles, preferably glass spheres.

5. Method according to one of the preceding claims, characterized in that the stiffening material is introduced into the support material in such a way that it comes into contact with previously introduced production material.

6. Method according to one of the preceding claims, characterized in that the production material is not yet completely cured when it comes into contact with the stiffening material.

7. Method according to one of the preceding claims, characterized in that at least a part of the stiffening material, preferably the entire Stiffening material is introduced into the support material at the same time as the manufacturing material.

8. Method according to one of the preceding claims, characterized in that the production material introduced into the support material forms a base body on which the stiffening material is arranged.

9. Method according to one of the preceding claims, characterized in that the stiffening material is introduced into the support material by means of a second introduction needle.

10. Method according to one of the preceding claims, characterized in that the fibers contain short fibers, long fibers and / or continuous fibers.

11. Method according to one of the preceding claims, characterized in that the 3-dimensional object is a liner with a base body having an outer surface, wherein the base body is preferably made of the production material and wherein the stiffening material is preferably arranged on the outer surface.

12. Method according to claim 11, characterized in that the stiffening material is arranged on the base body in the distal-proximal direction, preferably in distal-proximal strips.

13. Method according to one of the preceding claims, characterized in that at least a part of the stiffening material, preferably the entire stiffening material, is arranged on an outer side of a part of the 3-dimensional object to be produced, which part is made from the production material.

14. Apparatus for carrying out a method according to one of the preceding claims.

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