Method for consolidating an additively manufactured piece
11858180 · 2024-01-02
Assignee
Inventors
Cpc classification
B29C64/30
PERFORMING OPERATIONS; TRANSPORTING
B29C64/386
PERFORMING OPERATIONS; TRANSPORTING
B29C39/10
PERFORMING OPERATIONS; TRANSPORTING
B33Y50/00
PERFORMING OPERATIONS; TRANSPORTING
B33Y40/20
PERFORMING OPERATIONS; TRANSPORTING
B29C2043/562
PERFORMING OPERATIONS; TRANSPORTING
B29C43/12
PERFORMING OPERATIONS; TRANSPORTING
B22F2998/10
PERFORMING OPERATIONS; TRANSPORTING
B22F2998/10
PERFORMING OPERATIONS; TRANSPORTING
B33Y40/00
PERFORMING OPERATIONS; TRANSPORTING
International classification
B29C43/10
PERFORMING OPERATIONS; TRANSPORTING
B29C39/10
PERFORMING OPERATIONS; TRANSPORTING
B29C43/12
PERFORMING OPERATIONS; TRANSPORTING
B29C64/30
PERFORMING OPERATIONS; TRANSPORTING
B29C64/386
PERFORMING OPERATIONS; TRANSPORTING
B33Y40/00
PERFORMING OPERATIONS; TRANSPORTING
B33Y40/20
PERFORMING OPERATIONS; TRANSPORTING
Abstract
Methods and systems for consolidating an additively manufactured piece. In one embodiment, methods include the step of combining the additively manufactured piece with another piece, for example with another additively manufactured piece or with a piece that is not additively manufactured (e.g. an insert, foam, etc.), so that during a consolidation step, those pieces are assembled or connected together.
Claims
1. A method for consolidating an additively manufactured piece, the method comprising the steps of: placing a first additively manufactured piece in a cavity of a thermally conductive container, filling the cavity with one of a liquid and a semi-liquid material, so that the material directly contacts and completely surrounds the first piece, the material having a maximum operating temperature higher than a matrix melt temperature of the first piece, and the material having a positive relative thermal coefficient of expansion, sealing the cavity, curing the material, so that the cured material restricts movement of the first piece in the cavity, heating the container, wherein, while the temperature within the container is increased by the heating, the cured material expands and then creates a pressure on the first piece, and wherein the temperature is increased by the heating until the temperature reaches a process temperature equal or higher than the matrix melt temperature of the first piece and lower than the maximum operating temperature of the material, and maintaining the process temperature within the container so as to consolidate the first piece; wherein during the steps of heating and maintaining, the cured material is an in-situ created monobloc mould for the first piece.
2. The method of claim 1, wherein the first piece has a complex geometry.
3. The method of claim 1, wherein before the curing step, any cracks in an outer surface of the first piece are covered.
4. The method of claim 1, further comprising a step of connecting the first piece with a second additively manufactured piece during the maintaining step.
5. The method of claim 4, further comprising a step of forming seal-tight junction points of the first and second pieces before the curing step.
6. The method of claim 1, further comprising a step of positioning the first piece in the cavity before filling the cavity.
7. The method of claim 1, further comprising a step of cooling the cavity.
8. The method of claim 7, wherein the step of cooling includes: cooling the cavity to reach a predetermined temperature, maintaining the predetermined temperature for a time interval, and further cooling the cavity to reach a room temperature.
9. The method of claim 8, wherein a first rate of cooling during the step of cooling the cavity to reach the predetermined temperature is lower than a second rate of cooling during the step of cooling the cavity to reach room temperature.
10. The method of claim 1, further comprising a step of separating the consolidated piece from the cured material.
11. The method of claim 10, wherein the step of separating includes programming the path planning of a tool for the separating based on a 3D model file for the piece prepared prior to the curing step.
12. The method of claim 1, further comprising a step of generating controlled pressure on the first piece during the step of heating.
13. The method of claim 1, further comprising a step of filling the cavity with a cured filler material before the curing step.
14. The method of claim 1, comprising a step of manufacturing the first piece on a build platform; and wherein the step of placing the first piece in the cavity comprises placing the build platform on which the first piece is manufactured and the first piece in the cavity.
15. The method of claim 1, wherein before the curing step, the method includes embedding a core in the first piece.
16. The method of claim 1, further comprising planning a path based on a 3D model of the piece for a tool for separating the piece from the cured material.
17. The method of claim 1, further including controlling a piston facing the cavity for generating a controlled force or pressure on the first piece.
18. A system for consolidating an additively manufactured piece, the system comprising: a thermally conductive container comprising a cavity, the cavity including an additively manufactured piece and a liquid or semi-liquid material, so that the material completely surrounds or envelops at least a portion of the piece, the material having a maximum operating temperature higher than a matrix melt temperature of the piece and having a positive relative thermal coefficient of expansion, curing means for curing the material, so that the cured material restricts the movement of the piece in said cavity, and temperature controlling means configured for heating the cavity, wherein while the temperature is increased by the heating, the cured material expands and then creates a pressure on the piece, and wherein the temperature is increased by the heating until reaching a process temperature equal or higher than the matrix melt temperature of the piece and lower than the maximum operating of the material, the temperature controlling means being configured also for maintaining the process temperature so as to consolidate the piece; wherein during the heating and during the maintaining, the cured material is an in-situ created monobloc mould for the piece.
19. The system of claim 18, further including a build platform for supporting the piece, wherein the build platform forms a closing of the cavity.
20. The system of claim 18, further comprising a piston facing the cavity.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention will be better understood with the aid of the description of an embodiment given by way of example and illustrated by the figures, in which:
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
DETAILED DESCRIPTION
(15)
(16) The steps 1000 and 2000 are made up by operations and movements that are preferably executed sequentially, as indicated by the sense of the arrows.
(17) Those operations and movements can be executed in a manual, semi-automatic or fully-automatic manner. Semi or fully automatic operations or movements can be driven by direct feedback from, e.g. sensors, user input or self-learning algorithms, or by preconfigured settings.
(18) In the example of
(19) The piece to be consolidated with the method according to the invention can be made by homogenous and/or composite material. An example of this piece is given in
(20)
(21) The bracket 10 comprises an outer lateral surface (perimeter) 1 and a core 2. In one embodiment, the lateral surface 1 and the core 2 are made of a homogeneous material, e.g. plastic. In another embodiment, the lateral surface 1 and the core 2 are made of a heterogeneous material, e.g. carbon fiber reinforced plastic. In another embodiment, the lateral surface 1 and the core 2 are made of different materials: for example, the lateral surface 1 can be made of hybrid plastic and the core 2 by carbon fiber reinforced plastic, or vice-versa.
(22) With the method according to the invention it is possible also to consolidate and at the same time assemble or connect together multiple pieces. At least one and possibly all those pieces is (are) additively manufactured.
(23) In other words, the pieces can be combined before consolidating them. During their combination, connection means can be used (if possible) for maintaining the relative position between the pieces so as to handle the composed piece. Connection means comprise mechanical locks, adhesives, fasteners, knitting, etc.
(24) In one preferred embodiment, the method according to the invention not only allows the consolidation of at least one of those pieces, but it allows also the connection of the combined pieces together so that they form a monobloc piece.
(25) Those pieces can be chemically linked or cannot be chemically linked. An example of pieces that can be chemically linked is given in
(26)
(27) The first component 10 of the bracket, visible in
(28) With the method according to the invention it is possible also to assemble or connect together multiple pieces that cannot be chemically linked. At least one and possibly all those pieces is(are) additively manufactured. The method according to the invention establishes a mechanical lock and/or provides adherence between those pieces. An example is given
(29)
(30) A metal core 10.sup.iv, e.g. a printed metal core or a core manufactured with other techniques, is encapsulated by two printed carbon fiber end cups 10.sup.v, as illustrated by the arrows F1. A printed carbon fiber hollow cylinder (sleeve) 10.sup.vi is then inserted on the encapsulated metal core, as illustrated by the arrows F2. The obtained pressure vessel is illustrated in in
(31) As will be discussed, the method according to the invention allows the metal core 10.sup.iv to adhere to the two printed carbon fiber components 10.sup.v and the printed carbon fiber components 10.sup.v and the printed carbon fiber hollow cylinder 10.sup.vi to cohere.
(32) If the additively manufactured pieces 10 must be assembled as in the examples of
(33) It is also sometimes necessary or useful to insert or encapsulate one or more functional elements in an additively manufactured piece or in a group of combined pieces, comprising at least one additively manufactured piece.
(34) Non-limitative examples of such functional elements comprise: elements for enhancing a function as e.g. fasteners, sensors, actuators, cables, etc.; elements for enabling load introduction as e.g. inserts; and/or elements for increasing mechanical properties, e.g. metal, ceramic, glass, fiber reinforced plastic rods and/or other structures.
These elements may be partially inserted and/or may be encapsulated only when multiple pieces are assembled.
(35) In one preferred embodiment, those elements have a melt point higher than the process temperature.
(36) It is also sometimes necessary or useful to embed one or more structural core in the additively manufactured piece, e.g. a lattice, foam and/or honeycomb core.
(37) In one preferred embodiment, the core has a melt point higher than the process temperature.
(38) The step of embedding a core is illustrated by the reference 130 in
(39) Preparing the piece 10 can include also to create in the piece 10 air channels (not illustrated) so as to accommodate air leaving the piece 10 during its consolidation.
(40) Preparing the piece 10 can include a step during which the outer surface (shell) of the piece 10 is made crack free as much as possible, as to avoid the curable material to enter in the cracks and then break the piece 10 during the curing step. In one preferred embodiment, this step comprises to manufacture the piece 10 so that at least a portion of its outer surface is made of a crack free material only, e.g. of plastic. In another embodiment, this manufacturing step is made as proper as possible, so that the bonding between the layers of the piece 10 is crack free as much as possible.
(41) In one embodiment, preparing the piece 10 can include a step during which the piece 10 is put into an air tight bag, which covers the outer shell of the piece 10. This air tight bag may be connected to the ambient environment outside the cavity through a channel (e.g. a tube), as to accommodate air escaping from the bag that escapes from the piece 10 during the consolidation step. The air tight bag can in this embodiment also be held under vacuum by generating an under pressure through the channel, which in this case would be connected to a vacuum pump.
(42) In another embodiment, at least part of the piece 10 is covered by and/or wrapped into an airtight seal/sheet.
(43) The presence of an air tight bag, seal and/or sheet allows to avoid the curable material 30 to enter in possible cracks in piece 10 and then break the piece 10 during the curing step.
(44) If combined pieces must be consolidated, after their combination junction point(s) or area(s) of two or more pieces are seal-tight, so as to avoid curable material to enter in between and the separate pieces. In one embodiment, the pieces before the curing step are at least partially covered by a crack free material (e.g. plastic), e.g. by sheet a crack free material or by spraying a crack free material on at least a portion of the outer surface of the pieces.
(45) Once the piece (or the combined pieces) 10 has been prepared, it is placed in a cavity of a container, e.g. in the cavity 21 of the container 20 illustrated in
(46) The illustrated container 20 is substantially cylindrical, but any other shape or size of the container can be imagined. It can also have a variable volume.
(47) The container 20 is (at least partially) made of a thermally conductive material. In one preferred embodiment, it is metallic.
(48) The container 20 is arranged so as to support high pressures, i.e. pressures belonging to the range 1 Bars-10 Bars or higher, typically in the range 3 Bars-7 Bars.
(49) In one embodiment, part of the container 20 and/or its lid 22 can be perforated so as to accommodate during the consolidation step air exchange with the surrounding environment. In one preferred embodiment, those (not illustrated) perforations should not inhibit pressure build-up in the container 20.
(50) In one preferred embodiment, the method according to the invention comprises the step of positioning the piece(s) 10 in the cavity 21 by using (not illustrated) positioning means. Examples of positioning means comprise spacers, holders, pins, etc.
(51) In one preferred embodiment, illustrated in
(52) In one embodiment, the piece 10 is automatically stuck on the build platform 28 during the manufacturing step 110. In another embodiment, connection means (as adhesive, glue, etc.) are used for connecting the build platform 28 to the piece 10.
(53) The cavity 21 is at least partially filled with a liquid or semi-liquid material 30, before or after positioning piece 10 into the cavity 21, so that the material 30 directly contacts at least an outer portion of the piece 10, by perfectly surrounding or enveloping this portion. In one preferred embodiment, it completely surrounds the piece 10.
(54) In one embodiment, air channels (not illustrated) are added to or created in the curable material 30, before or after the curing step, as to accommodate air leaving the piece 10 during the consolidation step to leave the cavity 21, or at least so as to not trap air leaving the piece 10 between the monobloc mould and the piece 10. This improves the compaction and fusion of the piece 10.
(55) According to the invention, this material 30 is curable, has a maximum operating temperature higher than the lower melt temperature of the piece to be consolidated, and has a positive relative thermal coefficient of expansion. In one preferred embodiment, it does not degrade, soften, deteriorate, melt and/or burn with high pressures, i.e. pressures belonging to the range 1 Bars-10 Bars or higher.
(56) Examples of this material 30 comprises rubber (e.g. natural or synthetic), silicone, elastomer, thermoplastic, thermoset and/or starch based elastomers or plastics (biodegradable).
(57) If the cavity 21 is not completely filled by the material 30, a filler (not illustrated) can be used for filling the remaining volume or vice versa.
(58) In one preferred embodiment, the filler comprises a previously cured material 30 that has been pre-processed before re-using it as a filler, e.g. so as to reduce it in granulate.
(59) In another embodiment, sand, plastic and/or metal particles can be used as a complementary or alternative filler and may be added to the material 30 before filling the cavity 21.
(60) The placing step and the filling step form the potting step 210 of
(61) The cavity 21 is then sealed, e.g. by closing the open part of the container 20 with a lid 22, visible in
(62) Mechanical, electrical and/or magnetic forces can be used so as to restrict expansion of the cured material 30 to build up pressure in the cavity 21.
(63) The material 30 is then cured, so that the cured material 30 restricts the movement of the piece 20 in the cavity 21. Depending on substance's curing properties, its curing can be performed by, e.g. time, exposure to gas(es), exposure to UV and/or to heat. Since the curable material is cured, it becomes solid.
(64) The container 20 (and then its cavity 21) is then heated to a temperature equal or higher than the lower melt temperature of the piece to be consolidated, but lower than the maximum operating temperature of the material. In one embodiment, the heating step is 30 seconds to 5 minutes long. In one preferred embodiment, the container 20 comprises or is connected to means (not illustrated) for controlling the time and the temperature and possibly the pressure in the cavity 21 during the heating step.
(65) The heating step is illustrated in
(66) During the heating step 240, the heat causes expansion, reduction, relative movement and/or deformation of the cured material 30 and of the piece 10, depending on relative heat expansion coefficient and other physical properties.
(67) Since the material 30 has a positive thermal coefficient of expansion, once the cured material is heated, it expands in the cavity 21 so as to generate a substantially homogenous pressure on the piece 10. During this expansion, the cured material remains solid and maintains close control of the geometry of the piece 10.
(68) In one preferred embodiment, the container 20 comprises or is connected to means for controlling the pressure in the container during the heating step. In one preferred embodiment, the container comprises or is connected to a piston so as to generate a controlled force or a controlled pressure on the piece during the heating step. In one embodiment, illustrated in
(69) Although
(70) In the example of
(71) According to the invention, the temperature is increased until reaching a process temperature equal or higher than the lower melt temperature of the piece to be consolidated, but lower than the maximum operating temperature of the material.
(72) To create more pressure on the piece(s) 10, the temperature can be increased so to a process temperature T2, to expand cured material more. More pressure could mean also better consolidation. In one example, T2 belongs to the range 200 C.-400 C., for example T2=250 C.
(73) In the example of
(74) The process temperature T2 is then maintained for a certain time interval (t.sub.3t.sub.2), typically ranging from 30 minutes to 6 hours, so as to consolidate the piece 10. The consolidation step is illustrated in
(75) Consolidation takes place also due to the homogenous pressure that is applied to piece(s) 10. This consolidation step 250 causes fusion (bonding), compaction and/or crystallization of or within piece(s) 10 and can result in air leaving the piece(s) 10.
(76) For example, the method according to the invention allows the printed metal core 10.sup.iv of
(77) According to the invention, during the heating step and during the maintaining step, the cured material 30 is an in-situ created monobloc mould for the piece 10. It is the unique or sole mould in the cavity 21 and it is created in the cavity 21, after the piece has been placed in the cavity 21.
(78) In one embodiment, the material 30 filling the cavity can be a recycled material, i.e. a material that has been cured and that has been processed so as to come back to a liquid or semiliquid and still curable state.
(79) In the embodiment of
(80) In one preferred embodiment, as visible in
(81) In one preferred embodiment, the piece comprises a matrix, e.g. a thermoplastic matrix, and this predetermined temperature T3 is the glass transition temperature of the thermoplastic matrix. The difference in the coefficients of thermal expansion between the fibers and the (e.g. thermoplastic) matrix as well as the density change for semi-crystalline polymers may lead to residual stresses and warping. To prevent this and to relieve such residual stresses, the glass transition temperature T3 is maintained for a time interval (t.sub.5t.sub.4). This applies also for a piece made of a homogeneous material as well. In one example, T3 belongs to the range 50 C.-350 C., for example T3=100 C.
(82) In one embodiment, the cooling rate during the time interval (t.sub.4t.sub.3) is lower than the cooling rate after t.sub.5. Typical cooling rates range from 5 C./min to 50 C./min.
(83) In one preferred embodiment, the method according to the invention, after the cooling step, comprises the step of separating the consolidated piece(s) from the cured material. This step is illustrated in
(84) In one preferred embodiment, the separating step comprises programming the path planning of a tool (e.g. a knife, a drill, a mill etc.) based on a 3D model file that was entered by the user and/or by probing and/or by scanning the piece prior to the curing step.
(85) Once the in-situ created mould is separated from the piece 10, it can be optionally reused as a tradition mould or shredded to be used as granular filler.
(86) Optionally, post-processing may take place to clean, surface smoothen, paint and/or coat the consolidated piece(s) 10 (step 280 in
REFERENCE NUMBERS USED IN THE DRAWINGS
(87) 1 Outer lateral surface of the bracket 2 Core of the bracket 3 Hole 4 End of the bracket 5 Aperture of the first component of a bracket 6 Protruding part of the second component of a bracket 7 Base of the second component of a bracket 10, Additively manufactured piece 10 to 10.sup.vi Examples of additively manufactured pieces 10 Bracket 10 First component of a bracket 10 Second component of a bracket 10.sup.iv Printed metal core of a pressure vessel 10.sup.v Printed carbon fiber components 10.sup.vi Printed carbon fiber hollow cylinder 14 Holes of the container 20 Container 21 Cavity of the container 22 Lid 24 Means for generating a controlled pressure in the container (piston) 26 Lateral surface of the container 28 Build plate 30 Curable material 40 Fixation means (screw) 110 Piece additive manufacturing step 120 Combining pieces step 130 Embedding core step 140 Adding elements step 250 Consolidating step 260 Cooling step 270 Separating step 280 Post-processing step 1000 Steps for preparing the piece to be entered in the cavity 2000 Steps after preparing the piece to be entered in the cavity F1, F2 Arrow T0 Room temperature T1 Matrix (thermoplastics) melt temperature T2 Process (consolidation) temperature T3 Matrix (thermoplastics) glass transition temperature t1 to t6 Time 1 Reinforcement fibers 2 Matrix 3 Hole 4 Aperture 10, 10 to 10.sup.vi Additively manufactured piece 14 Holes of the container 20 Lateral surface of the container 22 Top surface of the container (lid) 24 Means for generating a controlled pressure in the container (piston) 28 Bottom surface of the container 30 Curable material 40 Fixation means (screw) 110 Potting piece step 120 Sealing step 130 Curing step 140 Heating step 150 Consolidating step 160 Cooling step 170 Separating step 180 Post-processing step 210 Piece additive manufacturing step 220 Combining pieces step 230 Embedding core step 240 Adding elements step T0 Room temperature T1 Matrix (thermoplastics) melt temperature T2 Process (consolidation) temperature T3 Matrix (thermoplastics) glass transition temperature t1 to t6 Time