A process for surfacing the surface of a 3D printed object

Abstract

The present invention relates to a method for surfacing a finished object made from a construction material and printed by 3D printing, said method comprising the following steps: Obtaining the printed object (O); Obtaining a vibrating contact surface (210) and a shaping surface (300); Applying vibrations to the printed object to apply vibrations to at least one surface of the printed object via a vibrating contact surface; Shaping the surface of the printed object treated by the vibrating contact surface with the shaping surface, said shaping surface being applied at the earliest simultaneously with said vibrating contact surface. Figure 1

Description

Title of the invention: Method for surfacing the surface of a 3D printed object

[0001] The invention relates to the three-dimensional printing of an object made with a mortar or construction material. Previous art

[0002] Three-dimensional printing of construction materials such as concrete or mortar is known for creating building elements or even entire buildings. This 3D printing process involves a vat of material. A pump is used to transfer the material from the vat to a print head. This print head includes an opening / closing mechanism used to enable or stop printing. This opening / closing mechanism is used during the creation of an object / building.

[0003] The object produced is then composed of a multitude of layers superimposed one on top of the other to form said object.

[0004] These superimposed layers have the disadvantage of being visible. This means that the finished object has a non-smooth surface, that is to say, one that leaves the strata, the layers of material, visible. This results in an unflattering appearance, made up of striations.

[0005] One existing method for overcoming this drawback consists of equipping the print head with at least one smoothing tool. This smoothing tool takes the form of a plate that is applied during printing to smooth the surface simultaneously with the printing process. The disadvantage of this solution is that this step occurs during printing. This necessitates rotating the nozzle and tool assembly during printing, which is difficult for complex shapes.

[0006] Another solution involves a surface finishing step once the hardening is complete. This surface finishing step consists of adding or removing material to obtain a smooth surface. A material is then applied to conceal any striations in the case of material addition, or a tool such as a grinder or sander is used in the case of material removal.

[0007] In the case of adding material, we end up with an object that is composed of two different materials or two blocks of the same material but not linked.

[0008] In the case of material removal, the risk is that the object may become fragile. Furthermore, this material removal has a negative ecological and economic impact. First, this material removal generates dust. Second, the material removal generates waste. Now, to have a Given identical resistance, it is necessary to compensate for this removal of material and have a greater initial input of material, therefore using more resources. Summary of the invention

[0009] The invention then seeks to provide a solution to the aforementioned drawbacks by providing a method for improving and modifying the surface of a three-dimensionally printed object.

[0010] To this end, the invention relates to a method for surfacing a finished object, made from a construction material and printed by 3D printing, said method comprising the following steps: - Obtain the printed item; - Equip yourself with a vibrating contact surface and a shaping surface; - Apply vibrations to the printed object to apply vibrations to at least one surface of the printed object via a vibrating contact surface; - Conform the surface of the printed object processed by the vibrating contact surface by the conforming surface, said conforming surface being applied at the earliest at the same time as said vibrating contact surface.

[0011] According to one example, the application of the shaping surface is simultaneous with the application of the vibrating contact surface.

[0012] According to one example, the application of vibrations is carried out by a first tool.

[0013] According to one example, the application of the conforming surface is carried out by a second set of tools.

[0014] According to one example, the application of vibrations and the application of the shaping surface are operated by the same tooling.

[0015] The invention further relates to a method for producing an object from a construction material by means of a printing system comprising a printing head 10 by which the material is deposited, said printing head 10 being mounted on a structure 2 enabling said printing head to move along at least three axes, said printing head 10 being connected to a reservoir 20, in which the mixture used for printing is stored, by means of a main conduit 40, said method comprises the following steps: - Obtain the printing system and print the object using the construction material; - Perform a surfacing step on at least one of the object's surfaces.

[0016] According to an example, the surfacing step is performed when the printed material forming the object has a threshold stress with a defined value.

[0017] According to one example, the value of the threshold constraint is determined theoretically using a database.

[0018] According to one example, the value of the threshold stress is determined with a measuring device allowing a value of the threshold stress to be obtained.

[0019] According to one example, the threshold stress measurement is carried out continuously or at intervals.

[0020] According to an example, the value of the threshold stress is between 50 and 130 kPa for a printable material. Brief description of the drawings

[0021] Other features and advantages will become clear from the description given below, by way of example and not limitation, with reference to the attached drawings, in which:

[0022] - [Fig.1] represents a view of a printing system according to the invention;

[0023] - [Fig.2] represents a diagram of the printing system according to the invention;

[0024] - [Fig.3] represents a profile view of a printed object;

[0025] - [Fig.4] represents a vibrating contact surface according to the invention;

[0026] - Figures 5 to 8 represent different ways of carrying out the surfacing step of a printed object according to the invention. Detailed description

[0027] In [Fig. 1], a three-dimensional material printing system 1 is shown. The printing system 1 is used to create an object. This object can be a construction item such as a brick or a concrete block, or it can be used to directly create a building. The object can also be something like street furniture. The printing system includes a print head 10 through which the material is deposited. The print head 10 is mounted on a structure 2 that allows the print head to move along at least three axes: length, width, and height, to perform the printing. This structure can be in the form of an articulated arm or gantries. The print head 10 is controlled by a control unit 60, which controls the movement of the print head and its material flow.

[0028] The print head 10, visible in [Fig. 2], is connected to a reservoir 20 via a conduit called the main conduit 40. The reservoir 20 is a tank in which the mixture used for printing is stored. The reservoir 20 is also called a mixer when it is equipped with means for mixing the mixture, such as a screw conveyor or rotating blades.

[0029] The printing system 1 further includes a pump 50 for bringing the mixture from the reservoir to the print head.

[0030] The print head 10 optionally includes opening-closing or sealing means 100, such as a flap or valve, allowing the mixture to exit the print head and be deposited.

[0031] Thus, printing is done by pumping the mixture from the reservoir to the print head while moving said head along a path programmed to produce the object.

[0032] According to the invention, the printed object undergoes a surfacing step. This surfacing step is performed to modify the appearance of at least one surface S of the object O and eliminate the unsightly appearance of the various superimposed layers. This unsightly appearance may be in the form of a ridge B visible on the surface of the object O, as shown in [Fig. 3]. These ridges B are visible on external or internal surfaces of the object, depending on its configuration. The surfacing step is preferably performed on an external surface but may also be performed on an internal surface, depending on the configuration of the printed object. It is understood that it is necessary to be able to technically perform the surfacing step. This modification of the appearance is carried out with, or preferably without, material removal. In the case of material removal, the amount is kept to a minimum.

[0033] This surfacing step is based on the use of vibrations. These vibrations are applied to the printed material and used to locally modify it. This local modification consists of refluidifying the material. Indeed, the vibrations applied to the material cause a break in the bonds that are formed during the hardening of the material. The breaking of these bonds allows the material to be reshaped over a period of time.

[0034] The vibrations are generated by a vibration generator 100. This vibration generator 100 can use different technologies such as a pneumatic or ball vibrator. Such a vibrator is capable of generating vibrations of 1700 N at a frequency of 16,000 VPM (vibrations per minute).

[0035] These vibrations are applied to the printed material by a tool 200 which has a vibrating contact surface 210 as seen in figures 4 and 5.

[0036] These vibrations are accompanied by the application of a shaping surface 300. This shaping surface 300 is used to shape the freshly refluidized material to give it the desired appearance. This appearance can be smooth or have an aesthetic or functional texture.

[0037] The application of vibrations and the application of the shaping surface 300 can be simultaneous or staggered in time. In the case of staggered applications, it will be understood that the application of the shaping surface 300 is subsequent to that of the vibrations.

[0038] To do this, the vibrations and the shaping can be carried out with the same tooling or with different tooling.

[0039] With a single tool 200, it is understood that the application of vibrations and the application of the forming surface are simultaneous, as shown in [Fig. 6]. Thus, the vibrating contact surface and the forming surface are one and the same. One can also imagine having a tool surface 200 divided into two portions: the vibrating part and the forming part.

[0040] The tool 200 takes, for example, the form of a trowel. This trowel is operated manually or mounted on a robotic arm. This trowel comprises a working surface and a vibration generator arranged to transmit its vibrations to the working surface. This working surface may be flat or include a pattern. This pattern is then replicated on the surface of the object.

[0041] The advantage is to save time with surfacing that is done in a single pass.

[0042] With two tooling 200, it is understood that the application of vibrations and the application of the shaping surface are simultaneous or staggered.

[0043] In the case of offset applications as seen in [Fig. 7], each tool is used for a specific function. The first tool is used to impart vibrations and reflow the printed material, while the second tool is used to mark the material and replicate a pattern. The first tool is an application tool designed to be in contact with the printed material. This first tool can take any shape, such as a trowel. Its contact surface with the printed material is flat to prevent marking. The second tool is arranged to present a contact surface. This contact surface has a pattern intended to be reproduced on the printed object.

[0044] Each tool is operated manually or mounted on a robotic arm.

[0045] In the case of simultaneous applications as shown in [Fig. 8], a first tool is used to provide vibrations and reflow the printed material, while the second tool is used to mark said material and replicate a pattern. The first tool is an application tool designed to be in contact with the printed material. This first tool can take any shape, such as a trowel. This first tool has a flat contact surface with the printed material to prevent any marking. The second tool is an interlayer. This interlayer is designed to be placed between the first tool and the printed object. This interlayer is in the form of a flexible piece such as a sheet, film, membrane, or strip comprising two opposing faces. One of the faces includes the pattern to be replicated.The second tool then cooperates with the first tool to replicate the pattern. This cooperation... The process involves vibrations that are not transferred directly to the printed material but rather through the second tooling. In this case, the vibrations from the first tooling are transmitted to the second tooling, which then transmits them to the printed material. The printed material, receiving the vibrations, experiences a refluidification of its surface. The pattern created on the second tooling is then replicated onto the refluidified surface of the printed material.

[0046] The advantage of having two different tooling sets is to allow greater flexibility since the number of usable tools is greater.

[0047] The surfacing step according to the invention is such that it allows the printed material to be momentarily reflowed for resurfacing. This reflowing implies that the bonds between the materials are formed and that hardening is underway. It is therefore necessary to determine the optimal moment to perform the surfacing. Indeed, if the bonds have not yet been formed, the reflowing will be too significant, less localized, resulting in overall deformation or sagging of the printed part. If the bonds are too strong, then the hardening is too advanced and therefore reflowing does not occur.

[0048] The time interval within which surfacing is possible is linked to a physical quantity called the threshold stress. This threshold stress is associated with the material's stiffness over time after printing. The range of threshold stress values ​​for which the surfacing step according to the invention is effective has been determined. Indeed, if this threshold stress value is too low, then overall deformation or sagging of the part may occur due to excessive reflowing, and if this value is too high, then the material is too dry and brittle.

[0049] The threshold stress is, within the framework of the present invention, measured with a falling cone penetrometer of mass 80.1 g and angle 15°.

[0050] For example, this value range is between 50 and 130 kPa for a mortar-based printable material. This value range ensures that the printed material can be resurfaced.

[0051] First, this threshold stress value is taken from a database. This database contains threshold stress values. These threshold stress values ​​are simulated and / or measured during tests. Advantageously, this database includes a multitude of simulations or tests, providing values ​​for different environmental conditions such as humidity and temperature. It is understood, then, that the threshold stress is an intrinsic property of the material, which makes the use of this database possible. Thus, by knowing the start time of printing, it is possible to determine the time from which the surfacing step can take place.

[0052] Secondly, this threshold stress value is measured. This measurement is carried out by a sensor allowing the direct measurement of the threshold stress or a quantity The physical process used to obtain this threshold constraint. The measurement is taken continuously or at regular intervals.

[0053] Of course, the present invention is not limited to the illustrated example but is susceptible to various variants and modifications which will become apparent to those skilled in the art.

Claims

Demands

1. method of surfacing a finished object, made from a construction material and printed by 3D printing, said method comprising the following steps: - Obtaining the printed object (0); - Obtaining a vibrating contact surface (210) and a conforming surface (300); - Applying vibrations to the printed object to apply vibrations to at least one surface of the printed object by means of a vibrating contact surface; - Conforming the surface of the printed object treated by the vibrating contact surface by the conforming surface, said conforming surface being applied at the earliest at the same time as said vibrating contact surface.

2. a surfacing method according to the preceding claim, wherein the application of the conforming surface is simultaneous with the application of the vibrating contact surface.

3. a surfacing method according to any one of the preceding claims, wherein the application of vibrations is carried out by a first tooling.

4. a surfacing method according to any one of the preceding claims, wherein the application of the conforming surface is carried out by a second tool.

5. a surfacing method according to claim 2, wherein the application of vibrations and the application of the conforming surface are carried out by the same tooling.

6. method of making an object out of construction material by a printing system comprising a printing head (10) by which the material is deposited, said printing head (10) being mounted on a structure (2) enabling said printing head to move along at least three axes, said printing head (10) being connected to a reservoir (20) in which the mixture used for printing is stored, by means of a main conduit (40), said method comprises the following steps: - Obtaining the printing system and printing the object using the construction material;

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11. - To perform a surfacing step on at least one of the surfaces of the object according to one of claims 1 to 5. Method of implementation according to the preceding claim, wherein the surfacing step is carried out when the printed material forming the object presents a threshold stress having a defined value. A method of implementation according to the preceding claim, wherein the value of the threshold stress is determined theoretically using a database. A method of embodiment according to claim 7, wherein the value of the threshold stress is determined with a measuring device enabling the obtaining of a value of the threshold stress. method according to the preceding claim, wherein the threshold stress measurement is carried out continuously or at intervals. method according to any one of claims 7 to 10, wherein the threshold stress value is between 50 and 130 kPa for a printable mortar-based material.

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