WO2016193498A1 - Improved process for photopolymerisation of a resin, preferably for 3d printing of an article by stereolithography - Google Patents

Improved process for photopolymerisation of a resin, preferably for 3d printing of an article by stereolithography Download PDF

Info

Publication number
WO2016193498A1
WO2016193498A1 PCT/EP2016/062794 EP2016062794W WO2016193498A1 WO 2016193498 A1 WO2016193498 A1 WO 2016193498A1 EP 2016062794 W EP2016062794 W EP 2016062794W WO 2016193498 A1 WO2016193498 A1 WO 2016193498A1
Authority
WO
WIPO (PCT)
Prior art keywords
resin
cavity
depression
gas
photopolymerization
Prior art date
Application number
PCT/EP2016/062794
Other languages
French (fr)
Inventor
Pascal Tiquet
Jacqueline Bablet
Original Assignee
Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commissariat A L'energie Atomique Et Aux Energies Alternatives filed Critical Commissariat A L'energie Atomique Et Aux Energies Alternatives
Publication of WO2016193498A1 publication Critical patent/WO2016193498A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/01—Processes of polymerisation characterised by special features of the polymerisation apparatus used
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
    • B29C37/006—Degassing moulding material or draining off gas during moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/3403—Foaming under special conditions, e.g. in sub-atmospheric pressure, in or on a liquid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
    • B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
    • B29C64/129—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask
    • B29C64/135—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask the energy source being concentrated, e.g. scanning lasers or focused light sources
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/46—Polymerisation initiated by wave energy or particle radiation
    • C08F2/48—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/46—Polymerisation initiated by wave energy or particle radiation
    • C08F2/48—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light
    • C08F2/50—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light with sensitising agents
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0037—Production of three-dimensional images
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
    • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
    • B29C2035/0827—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using UV radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
    • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
    • B29C2035/0833—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using actinic light
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2063/00—Use of EP, i.e. epoxy resins or derivatives thereof, as moulding material

Definitions

  • the present invention relates to the field of the manufacture of objects by photopolymerization of a resin. It is preferably applied to the production of objects by 3D stereolithography printing technique.
  • a resin comprises monomers whose overall volume decreases during photopolymerization.
  • the origin of this decrease is both chemical due to the formation of covalent bonds between the monomers, and thermal because of the exothermic reaction and the variation of the coefficient of thermal expansion between the liquid and solid resin.
  • This phenomenon called “shrinkage” occurs either linearly or volumetrically. It thus corresponds to the dimensional variation between the volume of liquid resin and the corresponding volume polymerized.
  • free volume is the volume or space in which monomers and macromolecules can move. This free volume is much larger than the volume occupied solely by the monomers, called Van der Waals volume.
  • photopolymerizable resins such as acrylate monomer resins
  • this liquid resin comprises photoinitiators, or inorganic and / or organic fillers.
  • the free space is the space in which all these constituents can move. After the polymerization, the free volume decreases, the polymerized / crosslinked network taking up less space than the monomers. The free volume is then reduced to a space in which segments of macromolecular chains or macromolecular cells can move. The aforementioned withdrawal phenomenon is thus materialized by the decrease of the free volume. It can be problematic for the manufacture of objects, especially when these objects are large.
  • the table below shows the dimensional variations for different scales of parts with a photo-crosslinkable resin whose linear shrinkage is about 2.5%.
  • the dimensional variability for a 2.5% linear shrinkage resin is proportional to the size of the part.
  • the inaccuracy varies for example from 2.5 ⁇ for 0.1 mm pieces, to 25 mm for 100 cm pieces. Such inaccuracies may be unacceptable.
  • it may require the implementation of one or more steps of discounting the manufactured object, to achieve the required level of accuracy. These additional steps, performed for example by machining, obviously impact the time and cost of manufacturing the object.
  • the invention therefore aims to at least partially meet the need identified above.
  • the invention firstly relates to a photopolymerization process of a resin containing gas, said method comprising a step of illuminating said resin and being characterized by the implementation of a step of expansion of the gas contained in the resin, said relaxing step being carried out by placing the resin in a depression cavity during at least part of said illumination step.
  • the invention thus has the particularity of judiciously using the gas usually contained in the resin, by providing for the expansion of this gas to compensate for all or part of the shrinkage observed during the photopolymerization.
  • the invention can also use the most resin-soluble gases such as CO 2 to maximize the effect of the expansion, in combination or not with oxygen or air to preserve the chemical stability of the resin.
  • the depression applied to the resin allows the gas to relax in a larger space within this resin.
  • This increase in volume at the molecular level advantageously compensates for the phenomenon of shrinkage at the molecular level, and therefore participates in obtaining polymerized objects having precise dimensions.
  • the need for retouching operations advantageously becomes reduced or zero, and without altering the composition of the resin which then retains all the desired properties, including its optical properties.
  • the shrinkage can be maintained at less than 0.1%.
  • the invention furthermore preferably provides at least any of the following optional technical characteristics, taken alone or in combination.
  • said depression increases, preferably at a vacuum speed of between 7 and 300 mbar / s, and even more preferably between 40 and 100 mbar / s.
  • Said illumination step is initiated at a time t2, and the depression of the cavity is initiated at a time t1 earlier than the instant t2.
  • the instants t1 and t2 could alternatively be merged, without leaving of the scope of the invention.
  • the first vacuum velocity VI applied during times t1 and t2 is preferably less than the second vacuum velocity V2 applied after time t2, during the illumination step.
  • the depression is of the order of 800 to 400 mbar, and at a time t3 of end of illumination of a layer of resin, the depression is of the order of 300 to 100 mbar.
  • the method comprises, prior to the depression of the cavity, a step of conditioning the resin in this cavity, said conditioning step being initiated at a time t0 and having a duration D0 preferably less than 3s.
  • This conditioning step may for example consist of a solubilization of a gas such as CO 2 and / or a mixture of gases such as CO 2 -air.
  • This step makes it possible to condition the surface layers of the bath of the resin, in order to prepare the depression during the subsequent phase initiated at the moment tl.
  • This conditioning step initiated at time t0 may have a duration OD of the order of 0 to 30 seconds. It increases the expansion capacity of the resin, especially when it is viscous (by nature or because of a load with mineral and / or organic fillers).
  • the resin comprises acrylate monomers.
  • Other types of resins are also conceivable, such as epoxy resins.
  • the gas enclosed in the resin is carbon dioxide.
  • Other gases can of course be envisaged, without departing from the scope of the invention.
  • the volume fraction of this dissolved gas can reach values greater than or equal to 1% of the total volume of the resin.
  • a resin packaged under pressure of carbon dioxide will initially contain more gas and will therefore be more sensitive to the expansion technique volume by the expansion of its dissolved gas, also said solubilized gas, which is distributed in the resin to the molecular scale.
  • the invention also relates to an installation for implementing the method as described above, comprising:
  • a cavity defined in part by a wall configured to be traversed by said light radiation
  • the pump system comprises means for regulating a vacuum speed as well as the value of the depression within the cavity.
  • the subject of the invention is also a method for 3D printing an object by stereolithography, said method comprising a step of producing of a layer of the object by photopolymerization of a resin layer produced by the implementation of the method described above.
  • the realization of each layer of the object is carried out by the implementation of this photopolymerization process.
  • FIG. 1 shows a schematic front view of an installation for implementing a method according to the invention, for the 3D printing of an object by stereolithography;
  • FIG. 2 is a graph showing the synchronization between the expansion step of the gas enclosed in the resin, and the step of illuminating this resin with a view to polymerizing it, the axis of the abscissae representing the time in seconds, and the ordinate axis representing the air pressure (in mbar) within the cavity;
  • FIG. 3 is a graph showing the linear shrinkage effect as a function of the speed of depression between times t1 and t2;
  • FIG. 4 is a graph showing the linear shrinkage effect as a function of the time between the times t0 and t1.
  • FIG. 1 there is shown an installation 1 for the implementation of a method according to the invention, for the 3D printing of an object by stereolithography.
  • the object A is thus intended to be produced in slices or in layers C1,
  • the resin 2 used comprises acrylate monomers and contains a gas, said dissolved and solubilized gas.
  • This gas, distributed at the scale in the resin and under the pressure of which this resin has been conditioned, is preferably carbon dioxide.
  • the installation 1 comprises means 4 for illuminating the resin 2, also called insolation means, for generating a light radiation 6 for the photopolymerization of the resin.
  • These means 4 are located facing a cavity 8 defined in part by receptacle 10 made of steel, closed by a glass wall 12 transparent to the light radiation 6, preferably UV radiation.
  • a seal 14 is provided between the two elements 10, 12 defining the cavity 8.
  • the installation 1 comprises a pump system 16 for putting the cavity 8 in depression.
  • the system 16 comprises in particular a pump 18 for evacuation of the cavity 8, with which this pump communicates via a pipe 20.
  • the system 16 also comprises means 22 for regulating a vacuum speed as well as the value of the depression within the cavity 8, these means 22 preferably taking the form of micrometer screws.
  • the installation 1 shown in FIG. 1 is represented in a state in which the photopolymerization of the upper layer of resin 2 is carried out.
  • This layer 2 is located above the layer Cn + 1 of the object A which has already polymerized, in a process identical or similar to that which will now be described in relation to the resin layer 2 on which the light radiation 6 is focused.
  • One of the peculiarities of the invention resides in the fact that the process of photopolymerization of the resin layer 2 not only implements a conventional step of illumination of this resin, but also a step of expansion of the gas contained in the resin.
  • the cavity 8 is depressed during at least part of the illumination step, as will be described below.
  • This vacuum setting advantageously increases the free volume of the resin, due to the expansion of the gas contained therein.
  • a step of conditioning the resin in the cavity 8 is initiated.
  • This step is initiated at a time t0, and operated for a duration D 0 between 0 and 30 seconds.
  • this step is carried out under atmospheric pressure Patm, or even at a higher pressure, for example from 1163 mbar to 1263 mbar depending on the gas used to increase the quantity of the solubilized gas (air, oxygen, CO 2 or a mixture thereof ).
  • the step of conditioning the resin preferably consists in solubilizing a gas such as CO 2 and / or a mixture of gases such as CO 2 -air. This step makes it possible to condition the surface layers of the resin so as to prepare the depression during the subsequent phase initiated at a time t1, and thus to increase the expansion capacity of the resin.
  • the time t1 corresponds to the end of the step of conditioning the resin, and also to the initiation of the depression of the cavity.
  • the gas pressure within the cavity 8 is equal to or close to the atmospheric pressure Patm.
  • a depression is formed in the cavity through the pump system 16, the vacuum being formed at a first vacuum speed VI, preferably constant.
  • the pressure in the cavity 8 thus decreases during the duration D1, until a time t2 at which the depression da ns the cavity 8 reaches an intermediate value Pint of the order of 800 to 400 mbar.
  • the illumination step is initiated using dedicated means 4, capable of generating the radiation 6 for a duration D2 with an energy pa example of the order of 42 mJ.
  • the depression continues to increase in the cavity 8, at a second depression velocity V2 which remains preferably stable, and which is greater than the speed VI for obtaining an even better result.
  • the speed V2 is for example between 40 and 100 mbar / s, and even more preferably between 33 and 50 mbar / s. This speed V2 is maintained until the end of the illumination of the resin layer, that is to say until a time t3 corresponding to the end of the duration D2, which is relatively short and for example of the order of 3 seconds.
  • the Pmin depression is between 300 and 100 mbar.
  • the speed VI is less than 40 mbar / s, while it remains nt preferentially less than or equal to the speed V2.
  • the graph in Figure 3 shows In this respect, for speeds VI less than 40 mbar / s, significant gains are observed in terms of limiting the withdrawal effect, which is inversely proportional to the speed VI.
  • the graph of FIG. 4 shows that the shrinkage effect is reduced for short OD durations, preferably less than 3 seconds, for which the observed shrinkage is less than 0.3% (measurements carried out with a vacuum speed VI between 33 and 50 mbar / s).
  • Instants t2 and t3 thus define the duration D2 during which the step of expansion of the gas by depression is continued, and carried out concomitantly with the illumination step.
  • the ratio between the durations D1 and D2 can be between 1 and 23.
  • the increase in the volume of the resin 2 observed between times t1 and t3 advantageously compensates for the shrinkage phenomenon, in whole or in part.
  • This compensation also results from the fact that the expansion of the gas within the resin causes a decrease in temperature of this gas, which is conducive to limiting the extent of the shrinkage phenomenon.
  • the invention can also provide for the implementation of other known means, such as the choice of monomers whose structure is deemed appropriate vis-à-vis the problematic of the withdrawal.
  • the long and flexible structures of the acrylate monomers tend to reduce the phenomenon of shrinkage.
  • the reduction of the illumination temperature also known as the insolation temperature, also makes it possible to limit the volume or linear shrinkage.

Abstract

The invention relates to a process for photopolymerisation of a resin (2) containing gas, the process comprising a step of illuminating the resin and also a step of expansion of the gas contained in the resin, this expansion step being carried out by placing the resin (2) in a cavity (8) placed under vacuum for at least one portion of the illuminating step. The invention also relates to the 3D printing of an article by stereolithography, carried out with the aid of the photopolymerisation process mentioned above.

Description

PROCEDE AMELIORE DE PHOTOPOLYMERISATION D'UNE RESINE,  IMPROVED METHOD FOR PHOTOPOLYMERIZING A RESIN,
DE PREFERENCE POUR L'IMPRESSION 3D D'UN OBJET PAR STEREOUTHOGRAPHIE  PREFERABLY FOR THE 3D PRINTING OF AN OBJECT BY STEREOUTHOGRAPHY
DESCRIPTIONDESCRIPTION
DOMAINE TECHNIQUE TECHNICAL AREA
La présente invention se rapporte au domaine de la fabrication d'objets par photopolymérisation d'une résine. Elle s'applique de préférence à la réalisation d'objets par la technique d'impression 3D par stéréolithographie. The present invention relates to the field of the manufacture of objects by photopolymerization of a resin. It is preferably applied to the production of objects by 3D stereolithography printing technique.
ETAT DE LA TECHNIQUE ANTERIEURE STATE OF THE PRIOR ART
Une résine comprend des monomères dont le volume global diminue lors de la photopolymérisation. L'origine de cette diminution est à la fois chimique du fait de la formation de liaisons covalentes entre les monomères, et thermique du fait de la réaction exothermique et de la variation du coefficient d'expansion thermique entre la résine liquide et solide. Ce phénomène appelé « retrait » se produit de manière linéique ou volumique. Il correspond ainsi à la variation dimensionnelle entre le volume de résine liquide, et le volume correspondant polymérisé. A resin comprises monomers whose overall volume decreases during photopolymerization. The origin of this decrease is both chemical due to the formation of covalent bonds between the monomers, and thermal because of the exothermic reaction and the variation of the coefficient of thermal expansion between the liquid and solid resin. This phenomenon called "shrinkage" occurs either linearly or volumetrically. It thus corresponds to the dimensional variation between the volume of liquid resin and the corresponding volume polymerized.
A cet égard, il est noté que conventionnellement, dans le domaine de la physique des polymères, le « volume libre » correspond au volume ou à l'espace dans lequel les monomères et les macromolécules peuvent se mouvoir. Ce volume libre est largement plus grand que le volume occupé uniquement par les monomères, dit volume de Van der Waals. Dans les résines photopolymérisables comme les résines à monomères acrylates, il existe un volume de gaz renfermé dans la résine liquide. En outre, cette résine liquide comprend des photoinitiateurs, ou encore des charges inorganiques et/ou organiques. Le volume libre est l'espace dans lequel tous ces constituants peuvent se mettre en mouvement. Après la polymérisation, le volume libre diminue, le réseau polymérisé / réticulé occupant moins de place que les monomères. Le volume libre se réduit alors à un espace dans lequel des segments de chaînes macromoléculaires ou des mailles macromoléculaires peuvent se mouvoir. Le phénomène de retrait précité se matérialise donc par la diminution du volume libre. Il peut s'avérer problématique pour la fabrication d'objets, surtout lorsque ces objets sont de dimensions importantes. In this respect, it is noted that conventionally, in the field of polymer physics, "free volume" is the volume or space in which monomers and macromolecules can move. This free volume is much larger than the volume occupied solely by the monomers, called Van der Waals volume. In photopolymerizable resins such as acrylate monomer resins, there is a volume of gas enclosed in the liquid resin. In addition, this liquid resin comprises photoinitiators, or inorganic and / or organic fillers. The free space is the space in which all these constituents can move. After the polymerization, the free volume decreases, the polymerized / crosslinked network taking up less space than the monomers. The free volume is then reduced to a space in which segments of macromolecular chains or macromolecular cells can move. The aforementioned withdrawal phenomenon is thus materialized by the decrease of the free volume. It can be problematic for the manufacture of objects, especially when these objects are large.
Pour illustrer ce propos, le tableau ci-dessous montre les variations dimensionnelles pour différentes échelles de pièces avec une résine photo-réticulable dont le retrait linéique est d'environ 2,5%.  To illustrate this, the table below shows the dimensional variations for different scales of parts with a photo-crosslinkable resin whose linear shrinkage is about 2.5%.
Figure imgf000004_0001
Figure imgf000004_0001
Globalement, la variabilité dimensionnelle pour une résine de 2,5% de retrait linéique est proportionnelle à la taille de la pièce. L'imprécision varie par exemple de 2,5 μιη pour des pièces de 0,1 mm, à 25 mm pour des pièces de 100 cm. De telles imprécisions peuvent ainsi s'avérer inacceptables. Malgré l'anticipation du retrait par des outils numériques, cela peut nécessiter la mise en œuvre d'une ou plusieurs étapes de remise aux cotes de l'objet fabriqué, afin d'atteindre le niveau de précision requis. Ces étapes supplémentaires, réalisées par exemple par usinage, impactent évidemment les temps et coûts de fabrication de l'objet. Overall, the dimensional variability for a 2.5% linear shrinkage resin is proportional to the size of the part. The inaccuracy varies for example from 2.5 μιη for 0.1 mm pieces, to 25 mm for 100 cm pieces. Such inaccuracies may be unacceptable. Despite the anticipation of the withdrawal by digital tools, it may require the implementation of one or more steps of discounting the manufactured object, to achieve the required level of accuracy. These additional steps, performed for example by machining, obviously impact the time and cost of manufacturing the object.
Plusieurs solutions techniques ont été envisagées pour solutionner au moins partiellement la problématique du phénomène de retrait. Par exemple, dans le cas d'une impression 3D par stéréolithograhie, il est possible d'envisager un prétraitement de l'image numérique, de manière à anticiper les retraits. Ce traitement nécessite d'importantes ressources en mémoire et requiert un flux élevé d'informations numériques à gérer en parallèle. Les limites des processeurs réduisent les possibilités en matière de rapidité des traitements. Une autre solution réside dans l'ajout d'une charge micrométrique dans la résine, pour réduire son taux de conversion qui est directement corrélé à l'amplitude du retrait. Encore une autre solution consiste à mettre en œuvre des moyens permettant de faire baisser la température de la résine durant la photopolymérisation, car la température est également directement corrélée à l'amplitude du retrait observé. La réduction de la température peut être effectuée par l'ajout de charges conductrices ou de charges à fortes capacité calorifique. Several technical solutions have been envisaged to at least partially solve the problem of the shrinkage phenomenon. For example, in the case of 3D stereolithography printing, it is possible to envisage preprocessing of the digital image, so as to anticipate withdrawals. This process requires large memory resources and requires a high flow of digital information to be managed in parallel. The limitations of processors reduce the possibilities for fast processing. Another solution lies in the addition of a micrometric charge in the resin, to reduce its conversion rate which is directly correlated with the amplitude of the withdrawal. Yet another solution is to implement means for lowering the temperature of the resin during photopolymerization, because the temperature is also directly correlated to the amplitude of the observed shrinkage. The reduction of the temperature can be carried out by adding conductive fillers or charges with a high heat capacity.
Malgré l'existence de plusieurs solutions pour limiter le phénomène de retrait, il subsiste un besoin d'optimisation du procédé de manière à le rendre plus simple, et éviter l'adjonction dans la résine d'additifs susceptibles d'altérer certaines de ses propriétés, comme ses propriétés optiques. EXPOSÉ DE L'INVENTION  Despite the existence of several solutions to limit the shrinkage phenomenon, there remains a need for optimization of the process so as to make it simpler, and avoid the addition in the resin of additives likely to alter some of its properties , like its optical properties. STATEMENT OF THE INVENTION
L'invention a donc pour but de répondre au moins partiellement au besoin identifié ci-dessus. Pour ce faire, l'invention a tout d'abord pour objet un procédé de photopolymérisation d'une résine renfermant du gaz, ledit procédé comprenant une étape d'illumination de ladite résine et étant caractérisé par la mise en œuvre d'une étape de détente du gaz renfermé dans la résine, ladite étape de détente étant réalisée en plaçant la résine dans une cavité mise en dépression pendant au moins une partie de ladite étape d'illumination. The invention therefore aims to at least partially meet the need identified above. To do this, the invention firstly relates to a photopolymerization process of a resin containing gas, said method comprising a step of illuminating said resin and being characterized by the implementation of a step of expansion of the gas contained in the resin, said relaxing step being carried out by placing the resin in a depression cavity during at least part of said illumination step.
L'invention présente ainsi la particularité d'utiliser judicieusement le gaz habituellement renfermé dans la résine, en prévoyant la détente de ce gaz pour compenser tout ou partie du retrait observé durant la photopolymérisation. L'invention peut aussi utiliser les gaz les plus solubles dans la résine comme le C02 pour maximiser l'effet de la détente, en association ou non avec l'oxygène ou l'air pour préserver la stabilité chimique de la résine. The invention thus has the particularity of judiciously using the gas usually contained in the resin, by providing for the expansion of this gas to compensate for all or part of the shrinkage observed during the photopolymerization. The invention can also use the most resin-soluble gases such as CO 2 to maximize the effect of the expansion, in combination or not with oxygen or air to preserve the chemical stability of the resin.
La dépression appliquée à la résine permet en effet au gaz de se détendre dans un espace plus important au sein de cette résine. Cette augmentation de volume à l'échelle moléculaire compense alors avantageusement le phénomène de retrait à l'échelle moléculaire, et participe donc à l'obtention d'objets polymérisés présentant des cotes précises. Le besoin en opérations de retouche devient avantageusement réduit ou nul, et ce sans altérer la composition de la résine qui conserve alors l'ensemble des propriétés désirées, notamment ses propriétés optiques. Typiquement, avec l'invention, le retrait peut être maintenu à une valeur inférieure à 0,1%. The depression applied to the resin allows the gas to relax in a larger space within this resin. This increase in volume at the molecular level advantageously compensates for the phenomenon of shrinkage at the molecular level, and therefore participates in obtaining polymerized objects having precise dimensions. The need for retouching operations advantageously becomes reduced or zero, and without altering the composition of the resin which then retains all the desired properties, including its optical properties. Typically, with the invention, the shrinkage can be maintained at less than 0.1%.
Du fait de la détente du gaz au sein de la résine, la température de ce gaz diminue et réduit avantageusement l'étendue du phénomène de retrait, du fait de la corrélation entre ces deux paramètres.  Due to the expansion of the gas within the resin, the temperature of this gas decreases and advantageously reduces the extent of the shrinkage phenomenon, due to the correlation between these two parameters.
L'invention prévoit par ailleurs, de manière préférentielle, au moins l'une quelconque des caractéristiques techniques optionnelles suivantes, prises isolément ou en combinaison.  The invention furthermore preferably provides at least any of the following optional technical characteristics, taken alone or in combination.
Durant au moins une partie de ladite étape d'illumination, ladite dépression s'accroît, de préférence à une vitesse de dépression comprise entre 7 et 300 mbar/s, et encore plus préférentiellement comprise entre 40 et 100 mbar/s.  During at least a portion of said illumination step, said depression increases, preferably at a vacuum speed of between 7 and 300 mbar / s, and even more preferably between 40 and 100 mbar / s.
Ladite étape d'illumination est initiée à un instant t2, et la mise en dépression de la cavité est initiée à un instant tl antérieur à l'instant t2. A cet égard, il est noté que si un mode de réalisation préféré de l'invention consiste en effet à débuter la mise en dépression avant d'initier l'étape d'illumination, les instants tl et t2 pourraient alternativement être confondus, sans sortir du cadre de l'invention.  Said illumination step is initiated at a time t2, and the depression of the cavity is initiated at a time t1 earlier than the instant t2. In this regard, it is noted that if a preferred embodiment of the invention is indeed to start the depression before initiating the illumination step, the instants t1 and t2 could alternatively be merged, without leaving of the scope of the invention.
La première vitesse de dépression VI appliquée durant les instants tl et t2 est de préférence inférieure à la seconde vitesse de dépression V2 appliquée après l'instant t2, durant l'étape d'illumination.  The first vacuum velocity VI applied during times t1 and t2 is preferably less than the second vacuum velocity V2 applied after time t2, during the illumination step.
A titre indicatif, à l'instant t2 du début de l'étape d'illumination, la dépression est de l'ordre de 800 à 400 mbar, et à un instant t3 de fin d'illumination d'une couche de résine, la dépression est de l'ordre de 300 à 100 mbar.  As an indication, at time t2 of the beginning of the illumination step, the depression is of the order of 800 to 400 mbar, and at a time t3 of end of illumination of a layer of resin, the depression is of the order of 300 to 100 mbar.
De préférence, le procédé comprend, préalablement à la mise en dépression de la cavité, une étape de conditionnement de la résine dans cette cavité, ladite étape de conditionnement étant initiée à un instant tO et présentant une durée D0 préférentiellement inférieure à 3s. Cette étape de conditionnement peut par exemple consister en une solubilisation d'un gaz comme le C02 et/ou un mélange de gaz tel que C02-air. Cette étape permet de conditionner les couches superficielles du bain de la résine, dans l'optique de préparer la dépression durant la phase ultérieure initiée à l'instant tl. Cette étape de conditionnement initiée à l'instant tO peut présenter une durée DO de l'ordre de 0 à 30 secondes. Elle permet d'accroître la capacité d'expansion de la résine, surtout lorsque celle-ci est visqueuse (par nature ou à cause d'un chargement avec des charges minérales et/ou organiques). Preferably, the method comprises, prior to the depression of the cavity, a step of conditioning the resin in this cavity, said conditioning step being initiated at a time t0 and having a duration D0 preferably less than 3s. This conditioning step may for example consist of a solubilization of a gas such as CO 2 and / or a mixture of gases such as CO 2 -air. This step makes it possible to condition the surface layers of the bath of the resin, in order to prepare the depression during the subsequent phase initiated at the moment tl. This conditioning step initiated at time t0 may have a duration OD of the order of 0 to 30 seconds. It increases the expansion capacity of the resin, especially when it is viscous (by nature or because of a load with mineral and / or organic fillers).
De préférence, la résine comprend des monomères acrylates. D'autres types de résines sont également envisageables, comme les résines époxy.  Preferably, the resin comprises acrylate monomers. Other types of resins are also conceivable, such as epoxy resins.
De préférence, le gaz renfermé dans la résine est du dioxyde de carbone. D'autres gaz peuvent bien évidemment être envisagés, sans sortir du cadre de l'invention. Cependant, il est noté que la concentration du gaz dans la résine est proportionnelle à la solubilité et la pression partielle du gaz dissous, selon la Loi de Henri [C]=S.p(gaz). Or grâce à l'importante solubilité du dioxyde carbone, la fraction volumique de ce gaz dissous peut atteindre des valeurs supérieures ou égales à 1% du volume total de la résine. Ainsi, une résine conditionnée sous pression de dioxyde de carbone contiendra initialement plus de gaz et sera par conséquent plus sensible à la technique d'expansion volumique par la détente de son gaz dissous, également dit gaz solubilisé, qui est distribué dans la résine à l'échelle moléculaire.  Preferably, the gas enclosed in the resin is carbon dioxide. Other gases can of course be envisaged, without departing from the scope of the invention. However, it is noted that the concentration of the gas in the resin is proportional to the solubility and the partial pressure of the dissolved gas, according to the Law of Henri [C] = S.p (gas). However, thanks to the high solubility of carbon dioxide, the volume fraction of this dissolved gas can reach values greater than or equal to 1% of the total volume of the resin. Thus, a resin packaged under pressure of carbon dioxide will initially contain more gas and will therefore be more sensitive to the expansion technique volume by the expansion of its dissolved gas, also said solubilized gas, which is distributed in the resin to the molecular scale.
L'invention a également pour objet une installation pour la mise en œuvre du procédé tel que décrit ci-dessus, comprenant :  The invention also relates to an installation for implementing the method as described above, comprising:
- des moyens d'illumination de la résine, permettant de générer un rayonnement lumineux pour la photopolymérisation de la résine ;  - Illumination means of the resin, for generating a light radiation for the photopolymerization of the resin;
- une cavité définie en partie par une paroi configurée pour être traversée par ledit rayonnement lumineux ; et  a cavity defined in part by a wall configured to be traversed by said light radiation; and
- un système de pompe permettant de mettre ladite cavité en dépression.  - A pump system for putting said cavity in depression.
De préférence, le système de pompe comprend des moyens permettant de réguler une vitesse de dépression ainsi que la valeur de la dépression au sein de la cavité.  Preferably, the pump system comprises means for regulating a vacuum speed as well as the value of the depression within the cavity.
Enfin, l'invention a également pour objet un procédé d'impression 3D d'un objet par stéréolithographie, ledit procédé comprenant une étape de réalisation d'une couche de l'objet par photopolymérisation d'une couche de résine réalisée par la mise en œuvre du procédé décrit ci-dessus. Finally, the subject of the invention is also a method for 3D printing an object by stereolithography, said method comprising a step of producing of a layer of the object by photopolymerization of a resin layer produced by the implementation of the method described above.
De préférence, la réalisation de chaque couche de l'objet est effectuée par la mise en œuvre de ce procédé de photopolymérisation.  Preferably, the realization of each layer of the object is carried out by the implementation of this photopolymerization process.
D'autres avantages et caractéristiques de l'invention apparaîtront dans la description détaillée non limitative ci-dessous.  Other advantages and features of the invention will become apparent in the detailed non-limiting description below.
BRÈVE DESCRIPTION DES DESSINS BRIEF DESCRIPTION OF THE DRAWINGS
Cette description sera faite au regard des dessins annexés parmi lesquels ; This description will be made with reference to the appended drawings among which;
- la figure 1 représente une vue schématique de face d'une installation pour la mise en œuvre d'un procédé selon l'invention, visant à l'impression 3D d'un objet par stéréolithographie ;  - Figure 1 shows a schematic front view of an installation for implementing a method according to the invention, for the 3D printing of an object by stereolithography;
- la figure 2 est un graphe montrant la synchronisation entre l'étape de détente du gaz enfermé dans la résine, et l'étape d'illumination de cette résine visant à la polymériser, l'axe des abscisses représentant le temps en secondes, et l'axe des ordonnées représentant la pression d'air (en mbar) au sein de la cavité ;  FIG. 2 is a graph showing the synchronization between the expansion step of the gas enclosed in the resin, and the step of illuminating this resin with a view to polymerizing it, the axis of the abscissae representing the time in seconds, and the ordinate axis representing the air pressure (in mbar) within the cavity;
- la figure 3 est un graphe montrant l'effet de retrait linéique en fonction de la vitesse de dépression entre les instants tl et t2 ; et  FIG. 3 is a graph showing the linear shrinkage effect as a function of the speed of depression between times t1 and t2; and
- la figure 4 est un graphe montrant l'effet de retrait linéique en fonction de la durée entre les instants tO et tl.  FIG. 4 is a graph showing the linear shrinkage effect as a function of the time between the times t0 and t1.
EXPOSÉ DÉTAILLÉ DE MODES DE RÉALISATION PRÉFÉRÉS  DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
En référence tout d'abord à la figure 1, il est représenté une installation 1 pour la mise en œuvre d'un procédé selon l'invention, visant à l'impression 3D d'un objet A par stéréolithographie. Referring firstly to Figure 1, there is shown an installation 1 for the implementation of a method according to the invention, for the 3D printing of an object by stereolithography.
L'objet A est ainsi destiné à être réalisé par tranches ou par couches Cl, The object A is thus intended to be produced in slices or in layers C1,
C2, ... Cn, Cn+1, chacune d'elles résultant de la photopolymérisation d'une couche de résine 2 initialement à l'état liquide. La résine 2 utilisée comprend des monomères acrylates et renferme un gaz, dit gaz dissous et solubilisé. Ce gaz, distribué à l'échelle moléculaire dans la résine et sous la pression duquel cette résine a été conditionnée, est préférentiellement du dioxyde de carbone. C2, ... Cn, Cn + 1, each resulting from the photopolymerization of a resin layer 2 initially in the liquid state. The resin 2 used comprises acrylate monomers and contains a gas, said dissolved and solubilized gas. This gas, distributed at the scale in the resin and under the pressure of which this resin has been conditioned, is preferably carbon dioxide.
L'installation 1 comporte des moyens 4 d'illumination de la résine 2, également dits moyens d'insolation, permettant de générer un rayonnement lumineux 6 pour la photopolymérisation de la résine. Ces moyens 4 sont situés en regard d'une cavité 8 définie en partie par réceptacle 10 en acier, fermé par une paroi en verre 12 transparente au rayonnement lumineux 6, de préférence un rayonnement UV. Un joint d'étanchéité 14 est prévu entre les deux éléments 10, 12 définissant la cavité 8.  The installation 1 comprises means 4 for illuminating the resin 2, also called insolation means, for generating a light radiation 6 for the photopolymerization of the resin. These means 4 are located facing a cavity 8 defined in part by receptacle 10 made of steel, closed by a glass wall 12 transparent to the light radiation 6, preferably UV radiation. A seal 14 is provided between the two elements 10, 12 defining the cavity 8.
En outre, l'installation 1 comporte un système de pompe 16 permettant de mettre la cavité 8 en dépression. Le système 16 comporte en particulier une pompe 18 pour la mise sous vide de la cavité 8, avec laquelle cette pompe communique par le biais d'une canalisation 20. Le système 16 comporte également des moyens 22 permettant de réguler une vitesse de dépression ainsi que la valeur de la dépression au sein de la cavité 8, ces moyens 22 prenant de préférence la forme de vis micrométriques.  In addition, the installation 1 comprises a pump system 16 for putting the cavity 8 in depression. The system 16 comprises in particular a pump 18 for evacuation of the cavity 8, with which this pump communicates via a pipe 20. The system 16 also comprises means 22 for regulating a vacuum speed as well as the value of the depression within the cavity 8, these means 22 preferably taking the form of micrometer screws.
L'installation 1 montrée sur la figure 1 est représentée dans un état dans lequel il est opéré la photopolymérisation de la couche supérieure de résine 2. Cette couche 2 est située au-dessus de la couche Cn+1 de l'objet A qui a déjà été polymérisée, lors d'un procédé identique ou analogue à celui qui va à présent être décrit en relation avec la couche de résine 2 sur laquelle le rayonnement lumineux 6 est focalisé.  The installation 1 shown in FIG. 1 is represented in a state in which the photopolymerization of the upper layer of resin 2 is carried out. This layer 2 is located above the layer Cn + 1 of the object A which has already polymerized, in a process identical or similar to that which will now be described in relation to the resin layer 2 on which the light radiation 6 is focused.
L'une des particularités de l'invention réside dans le fait que le procédé de photopolymérisation de la couche de résine 2 met non seulement en œuvre une étape conventionnelle d'illumination de cette résine, mais également une étape de détente du gaz renfermé dans la résine. Pour assurer cette détente au sein de la résine et compenser ainsi en tout ou partie le phénomène de retrait observé classiquement lors de la polymérisation, la cavité 8 est mise en dépression durant au moins une partie de l'étape d'illumination, comme cela sera décrit ci-après. Cette mise en dépression augmente avantageusement le volume libre de la résine, du fait de la détente du gaz renfermée dans celle-ci.  One of the peculiarities of the invention resides in the fact that the process of photopolymerization of the resin layer 2 not only implements a conventional step of illumination of this resin, but also a step of expansion of the gas contained in the resin. To ensure this relaxation within the resin and thus completely or partially compensate for the phenomenon of shrinkage conventionally observed during the polymerization, the cavity 8 is depressed during at least part of the illumination step, as will be described below. This vacuum setting advantageously increases the free volume of the resin, due to the expansion of the gas contained therein.
Dans un mode de réalisation préféré du procédé de photopolymérisation schématisé sur le graphe de la figure 2, il est tout d'abord mis en œuvre une éta pe de conditionnement de la résine dans la cavité 8. Cette étape est initiée à un instant tO, et opérée pendant une durée DO comprise entre 0 et 30 secondes. De préférence, cette étape est réalisée sous la pression atmosphérique Patm, voire à une pression supérieure, par exemple de 1163 mbar à 1263 mbar selon le gaz utilisé pour augmenter la quantité du gaz solubilisé (air, oxygène, C02 ou mélange de ceux-ci). En effet, l'étape de conditionnement de la résine consiste de préférence en une solubilisation d'un gaz comme le C02 et/ou un mélange de gaz tel que C02-air. Cette étape permet de conditionner les couches superficielles de la résine de manière à préparer la dépression durant la phase ultérieure initiée à un instant tl, et faire ainsi en sorte d'accroître la capacité d'expansion de la résine. In a preferred embodiment of the photopolymerization process schematized on the graph of FIG. 2, it is firstly A step of conditioning the resin in the cavity 8 is initiated. This step is initiated at a time t0, and operated for a duration D 0 between 0 and 30 seconds. Preferably, this step is carried out under atmospheric pressure Patm, or even at a higher pressure, for example from 1163 mbar to 1263 mbar depending on the gas used to increase the quantity of the solubilized gas (air, oxygen, CO 2 or a mixture thereof ). Indeed, the step of conditioning the resin preferably consists in solubilizing a gas such as CO 2 and / or a mixture of gases such as CO 2 -air. This step makes it possible to condition the surface layers of the resin so as to prepare the depression during the subsequent phase initiated at a time t1, and thus to increase the expansion capacity of the resin.
L'instant tl correspond à la fin de l'étape de conditionnement de la résine, et également à l'initiation de la mise en dépression de la cavité. A cet insta nt tl, la pression de gaz au sein de la cavité 8 est égale ou proche de la pression atmosphérique Patm. A partir de cet instant tl et pendant une durée Dl, une dépression se forme dans la cavité grâce au système de pompe 16, le vide étant réalisé à une première vitesse de dépression VI, préférentiellement constante. La pression da ns la cavité 8 diminue donc pendant la durée Dl, jusqu'à un instant t2 auquel la dépression da ns la cavité 8 atteint une valeur intermédiaire Pint de l'ordre de 800 à 400 mbar.  The time t1 corresponds to the end of the step of conditioning the resin, and also to the initiation of the depression of the cavity. At this insta nt tl, the gas pressure within the cavity 8 is equal to or close to the atmospheric pressure Patm. From this moment tl and during a duration Dl, a depression is formed in the cavity through the pump system 16, the vacuum being formed at a first vacuum speed VI, preferably constant. The pressure in the cavity 8 thus decreases during the duration D1, until a time t2 at which the depression da ns the cavity 8 reaches an intermediate value Pint of the order of 800 to 400 mbar.
A cet instant t2, l'étape d'illumination est initiée à l'aide des moyens 4 dédiés, capables de générer le rayonnement 6 pendant une durée D2 avec une énergie pa r exemple de l'ordre de 42 mJ. La dépression continue de s'accroître da ns la cavité 8, à une seconde vitesse de dépression V2 qui reste préférentiellement stable, et qui est supérieure à la vitesse VI pour l'obtention d'un résultat encore meilleur. La vitesse V2 est par exemple comprise entre 40 et 100 mbar/s, et encore plus préférentiellement entre 33 et 50 mbar/s. Cette vitesse V2 est conservée jusqu'à la fin de l'illumination de la couche de résine, c'est-à-dire jusqu'à un instant t3 correspondant à la fin de la durée D2, qui est relativement courte et par exemple de l'ordre de 3 secondes. A cet instant t3, la dépression Pmin est comprise entre 300 et 100 mbar.  At this time t2, the illumination step is initiated using dedicated means 4, capable of generating the radiation 6 for a duration D2 with an energy pa example of the order of 42 mJ. The depression continues to increase in the cavity 8, at a second depression velocity V2 which remains preferably stable, and which is greater than the speed VI for obtaining an even better result. The speed V2 is for example between 40 and 100 mbar / s, and even more preferably between 33 and 50 mbar / s. This speed V2 is maintained until the end of the illumination of the resin layer, that is to say until a time t3 corresponding to the end of the duration D2, which is relatively short and for example of the order of 3 seconds. At this time t3, the Pmin depression is between 300 and 100 mbar.
Par ailleurs, la vitesse VI est inférieure à 40 mbar/s, tout en resta nt préférentiellement inférieure ou égale à la vitesse V2. Le graphe de la figure 3 montre à cet égard que pour des vitesses VI inférieures à 40 mbar/s, des gains significatifs sont observés en termes de limitation de l'effet de retrait, qui est inversement proportionnel à la vitesse VI. Furthermore, the speed VI is less than 40 mbar / s, while it remains nt preferentially less than or equal to the speed V2. The graph in Figure 3 shows In this respect, for speeds VI less than 40 mbar / s, significant gains are observed in terms of limiting the withdrawal effect, which is inversely proportional to the speed VI.
En outre, le graphe de la figure 4 montre que l'effet de retrait est réduit pour des durées DO courtes, de préférence inférieures à 3s pour lesquelles le retrait observé est inférieur à 0,3% (mesures réalisées avec une vitesse de dépression VI comprise entre 33 et 50 mbar/s).  In addition, the graph of FIG. 4 shows that the shrinkage effect is reduced for short OD durations, preferably less than 3 seconds, for which the observed shrinkage is less than 0.3% (measurements carried out with a vacuum speed VI between 33 and 50 mbar / s).
Les instants t2 et t3 définissent ainsi la durée D2 pendant laquelle l'étape de détente du gaz par dépression est donc poursuivie, et réalisée concomitamment avec l'étape d'illumination. A cet égard, il est noté que le rapport entre les durées Dl et D2 peut être compris entre 1 et 23.  Instants t2 and t3 thus define the duration D2 during which the step of expansion of the gas by depression is continued, and carried out concomitantly with the illumination step. In this respect, it is noted that the ratio between the durations D1 and D2 can be between 1 and 23.
L'augmentation du volume de la résine 2 observée entre les instants tl et t3 compense avantageusement le phénomène de retrait, en tout ou partie. Cette compensation résulte également du fait que la détente du gaz au sein de la résine entraîne une diminution de température de ce gaz, propice à une limitation de l'étendue du phénomène de retrait. Pour limiter encore davantage cette étendue du retrait au cours de la photopolymérisation, l'invention peut également prévoir la mise en œuvre d'autres moyens connus, comme le choix de monomères dont la structure est réputée appropriée vis-à-vis de la problématique du retrait. A titre indicatif, les structures longues et flexibles des monomères acrylates tendent à réduire le phénomène de retrait. La diminution de la température d'illumination, également dite température d'insolation, permet également de limiter le retrait volumique ou linéique.  The increase in the volume of the resin 2 observed between times t1 and t3 advantageously compensates for the shrinkage phenomenon, in whole or in part. This compensation also results from the fact that the expansion of the gas within the resin causes a decrease in temperature of this gas, which is conducive to limiting the extent of the shrinkage phenomenon. To further limit this extent of shrinkage during photopolymerization, the invention can also provide for the implementation of other known means, such as the choice of monomers whose structure is deemed appropriate vis-à-vis the problematic of the withdrawal. As an indication, the long and flexible structures of the acrylate monomers tend to reduce the phenomenon of shrinkage. The reduction of the illumination temperature, also known as the insolation temperature, also makes it possible to limit the volume or linear shrinkage.
Bien entendu, diverses modifications peuvent être apportées par l'homme du métier à l'invention qui vient d'être décrite, uniquement à titre d'exemples non limitatifs.  Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples.

Claims

REVEN DICATIONS REVEN DICATIONS
1. Procédé de photopolymérisation d'une résine (2) renfermant du gaz, ledit procédé comprenant une étape d'illumination de ladite résine et étant caractérisé par la mise en œuvre d'une étape de détente du gaz renfermé dans la résine, ladite étape de détente étant réalisée en plaçant la résine (2) dans une cavité (8) mise en dépression pendant au moins une partie de ladite étape d'illumination. 1. A method of photopolymerizing a resin (2) containing gas, said method comprising a step of illuminating said resin and being characterized by the implementation of a step of expansion of the gas contained in the resin, said step detent being performed by placing the resin (2) in a cavity (8) depressed during at least a portion of said illumination step.
2. Procédé selon la revendication 1, caractérisé en ce que durant au moins une partie de ladite étape d'illumination, ladite dépression s'accroît, de préférence à une vitesse de dépression comprise entre 7 et 300 mbar/s, et encore plus préférentiellement comprise entre 40 et 100 mbar/s. 2. Method according to claim 1, characterized in that during at least a portion of said illumination step, said depression increases, preferably at a vacuum speed of between 7 and 300 mbar / s, and even more preferentially between 40 and 100 mbar / s.
3. Procédé selon la revendication 1 ou la revendication 2, caractérisé en ce que ladite étape d'illumination est initiée à un instant t2, et en ce que la mise en dépression de la cavité est initiée à un instant tl antérieur à l'instant t2. 3. Method according to claim 1 or claim 2, characterized in that said illumination step is initiated at a time t2, and in that the depression of the cavity is initiated at a time tl prior to the instant t2.
4. Procédé selon la revendication 3, caractérisé en ce que la première vitesse de dépression VI appliquée durant les instants tl et t2 est inférieure à la seconde vitesse de dépression V2 appliquée après l'instant t2, durant l'étape d'illumination. 4. Method according to claim 3, characterized in that the first vacuum velocity VI applied during times t1 and t2 is less than the second vacuum velocity V2 applied after time t2, during the illumination step.
5. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il comprend, préalablement à la mise en dépression de la cavité, une étape de conditionnement de la résine dans cette cavité, ladite étape de conditionnement étant initiée à un instant tO et présentant une durée D0 préférentiellement inférieure à 3s. 5. Method according to any one of the preceding claims, characterized in that it comprises, prior to the depression of the cavity, a step of conditioning the resin in this cavity, said conditioning step being initiated at a time tO and having a duration D0 preferably less than 3s.
6. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que la résine (2) comprend des monomères acrylates. 6. Method according to any one of the preceding claims, characterized in that the resin (2) comprises acrylate monomers.
7. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le gaz renfermé dans la résine (2) est du dioxyde de carbone. 7. Method according to any one of the preceding claims, characterized in that the gas enclosed in the resin (2) is carbon dioxide.
8. Installation (1) pour la mise en œuvre du procédé selon l'une quelconque des revendications précédentes, comprenant : 8. Installation (1) for implementing the method according to any one of the preceding claims, comprising:
- des moyens (4) d'illumination de la résine (2), permettant de générer un rayonnement lumineux (6) pour la photopolymérisation de la résine ;  - means (4) for illuminating the resin (2), for generating a light radiation (6) for the photopolymerization of the resin;
- une cavité (8) définie en partie par une paroi (12) configurée pour être traversée par ledit rayonnement lumineux (6) ; et  - a cavity (8) defined in part by a wall (12) configured to be traversed by said light radiation (6); and
- un système de pompe (16) permettant de mettre ladite cavité (8) en dépression.  - A pump system (16) for putting said cavity (8) in depression.
9. Installation selon la revendication précédente, caractérisée en ce que le système de pompe (16) comprend des moyens (22) permettant de réguler une vitesse de dépression ainsi que la valeur de la dépression au sein de la cavité (8). 9. Installation according to the preceding claim, characterized in that the pump system (16) comprises means (22) for controlling a vacuum speed and the value of the depression within the cavity (8).
10. Procédé d'impression 3D d'un objet (A) par stéréolithographie, ledit procédé comprenant une étape de réalisation d'une couche (Cl, C2, Cn, Cn+1) de l'objet (A) par photopolymérisation d'une couche de résine (2) réalisée par la mise en œuvre du procédé de photopolymérisation selon l'une quelconque des revendications 1 à 7. 10. A process for 3D printing an object (A) by stereolithography, said method comprising a step of producing a layer (C1, C2, Cn, Cn + 1) of the object (A) by photopolymerization of a resin layer (2) produced by carrying out the photopolymerization process according to any of claims 1 to 7.
11. Procédé d'impression 3D selon la revendication précédente, caractérisé en ce que la réalisation de chaque couche de l'objet (A) est effectuée par la mise en œuvre du procédé de photopolymérisation selon l'une quelconque des revendications 1 à 7. 11. 3D printing method according to the preceding claim, characterized in that the realization of each layer of the object (A) is performed by the implementation of the photopolymerization process according to any one of claims 1 to 7.
PCT/EP2016/062794 2015-06-04 2016-06-06 Improved process for photopolymerisation of a resin, preferably for 3d printing of an article by stereolithography WO2016193498A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1555104 2015-06-04
FR1555104A FR3037064B1 (en) 2015-06-04 2015-06-04 IMPROVED METHOD OF PHOTOPOLYMERIZING A RESIN, PREFERABLY FOR 3D PRINTING AN OBJECT BY STEREOLITHOGRAPHY

Publications (1)

Publication Number Publication Date
WO2016193498A1 true WO2016193498A1 (en) 2016-12-08

Family

ID=53801049

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2016/062794 WO2016193498A1 (en) 2015-06-04 2016-06-06 Improved process for photopolymerisation of a resin, preferably for 3d printing of an article by stereolithography

Country Status (2)

Country Link
FR (1) FR3037064B1 (en)
WO (1) WO2016193498A1 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5110513A (en) * 1987-09-11 1992-05-05 Framatome Process for producing an article made of resin by photopolymerization and applications of this process
US20110014499A1 (en) * 2008-03-07 2011-01-20 Showa Denko K.K. Uv nanoimprint method, resin replica mold and method for producing the same, magnetic recording medium and method for producing the same, and magnetic recording/reproducing apparatus
WO2012150497A1 (en) * 2011-05-03 2012-11-08 Dws S.R.L. Perfected method for manufacturing three-dimensional objects in layers and perfected stereolithography machine using said method
US20130324629A1 (en) * 2011-02-17 2013-12-05 Nitto Denko Corproation Resin foam and process for producing the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5110513A (en) * 1987-09-11 1992-05-05 Framatome Process for producing an article made of resin by photopolymerization and applications of this process
US20110014499A1 (en) * 2008-03-07 2011-01-20 Showa Denko K.K. Uv nanoimprint method, resin replica mold and method for producing the same, magnetic recording medium and method for producing the same, and magnetic recording/reproducing apparatus
US20130324629A1 (en) * 2011-02-17 2013-12-05 Nitto Denko Corproation Resin foam and process for producing the same
WO2012150497A1 (en) * 2011-05-03 2012-11-08 Dws S.R.L. Perfected method for manufacturing three-dimensional objects in layers and perfected stereolithography machine using said method

Also Published As

Publication number Publication date
FR3037064B1 (en) 2017-06-23
FR3037064A1 (en) 2016-12-09

Similar Documents

Publication Publication Date Title
Zheng et al. Long-range effects on polymer diffusion induced by a bounding interface
Chiche et al. Role of surface roughness in controlling the adhesion of a soft adhesive on a hard surface
WO2007044320A3 (en) Methods and systems for inspection of a wafer
MXPA01006445A (en) Methods for producing films having a layer containing a mixture of fluoropolymers and polyacrylates.
FR2948192A1 (en) OPTICAL CHARACTERIZATION METHOD
EP0964741B1 (en) Method for improving vacuum in a very high vacuum system
WO2016193498A1 (en) Improved process for photopolymerisation of a resin, preferably for 3d printing of an article by stereolithography
Raibaut Singularités à l'infini et intégration motivique
CA2152887C (en) Non destructive examination process for surface finish
FR3043699A1 (en) METHOD FOR FORMING OXIDE AND / OR ALUMINUM NITRIDE AND DEVICE FOR CARRYING OUT SAID METHOD
EP1544599A2 (en) Method and device for measuring physical characteristics of a porous solid sample
Escobar et al. Reproducing Superhydrophobic Leaves as Coatings by Micromolding Surface‐Initiated Polymerization
EP2157301B1 (en) Method for controlling combustion in a diesel engine by means of combustion phasing control
FR3057355A1 (en) METHOD AND DEVICE FOR MEASURING THE RESISTANCE OF SOLID MATERIALS BY IMPACT OF NON-SHOCK PLATES
CA2851126A1 (en) Process and installation for producing radioisotopes
WO2016169644A1 (en) Method for determining actual lengths of short intervals of a toothed target of a crankshaft
Mínguez Fonctions zêta ℓ-modulaires
EP4037889B1 (en) Method of manufacturing a film containing cavities with determination of stretch profiles, density, thickness and/or porosity of the film
Wylie Water surface profiles in divided channels
Bouzeboudja et al. Study of the evolution of the fractal dimension of a granular material’s grains during mechanical tests
EP2113924A2 (en) Method for measuring an anisotropic surface diffusion tensor or surface energy anisotropies
Wilson et al. Single-shot transient absorption spectroscopy of an organic film
Kössler Simple polynomials
Joshi et al. Temperature dependence of critical stress for wall slip by debonding
FR2790790A1 (en) METHOD FOR DETERMINING THE PRESSURE IN THE FUEL INJECTION RAMP OF AN INTERNAL COMBUSTION ENGINE AND CORRESPONDING DEVICE

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 16728912

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 16728912

Country of ref document: EP

Kind code of ref document: A1