FR3161587A1 - A process for surfacing the surface of a 3D printed object - Google Patents

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: Preparing the printed object (O); Preparing 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

process for surfacing the surface of a 3D printed object

The invention relates to the three-dimensional printing of an object made with mortar or construction material.

Previous art

3D printing of construction materials such as concrete or mortar is a well-known method for creating building components or even entire buildings. This 3D printing process involves using 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 or building.

The resulting object is then composed of a multitude of layers superimposed on one another to form said object.

These superimposed layers have the disadvantage of being visible. This means that the finished object has a non-smooth surface, that is, one that leaves the strata, the layers of material, visible. The result is an unflattering, striated appearance.

One existing method to overcome this drawback involves 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.

Another solution involves a surface finishing step once the hardening process is complete. This finishing step consists of adding or removing material to achieve 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.

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.

In the case of material removal, the risk is that the object will become fragile. Furthermore, this material removal has a negative environmental and economic impact. First, it generates dust. Second, it generates waste. Therefore, to achieve the same level of strength, this material removal must be compensated for by using a larger initial material, thus requiring more resources.

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.

• Se munir de l’objet imprimé ;
• Se munir d’une surface de contact vibrante et d’une surface de conformage ;
• Appliquer des vibrations sur l’objet imprimé pour appliquer des vibrations sur au moins une surface de l’objet imprimé par l’intermédiaire d’une surface de contact vibrante ;
• Conformer la surface de l’objet imprimé traité par la surface de contact vibrante par la surface de conformer, ladite surface de conformage étant appliquée au plus tôt en même temps que ladite surface de contact vibrante.

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.

In one example, the application of the shaping surface is simultaneous with the application of the vibrating contact surface.

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

In one example, the application of the conforming surface is carried out by a second tool.

In one example, the application of vibrations and the application of the forming surface are operated by the same tooling.

• Se munir du système d’impression et imprimer l’objet à l’aide du matériau de construction ;
• Opérer une étape de surfaçage d’au moins l’une des surfaces de l’objet.

The invention further relates to a method for producing an object from 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.

According to one example, the surfacing step is carried out when the printed material forming the object has a threshold constraint with a defined value.

In one example, the value of the threshold constraint is determined theoretically using a database.

According to one example, the threshold stress value is determined with a measuring device that allows obtaining a threshold stress value.

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

According to one example, the threshold stress value is between 50 and 130 kPa for a printable material.

Other features and advantages will become clear from the description given below, which is indicative and in no way exhaustive, with reference to the attached drawings, in which:

- there FIG. 1 represents a view of a printing system according to the invention;

- there FIG. 2 represents a diagram of the printing system according to the invention;

- there FIG. 3 represents a profile view of a printed object;

- THE FIG. 4 represents a vibrating contact surface according to the invention;

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

Detailed description

To the 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 it 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.

The print head 10, visible at the 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.

The printing system 1 also includes a pump 50 to bring the mixture from the reservoir to the print head.

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.

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

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 can take the form of a visible ridge B on the surface of the object O, as seen in FIG. 3 These B-shaped ridges are visible on either the exterior or interior surfaces of the object, depending on its configuration. The surfacing step is preferably performed on an exterior surface but can also be performed on an interior surface, depending on the configuration of the printed object. It is understood that the technical feasibility of performing this surfacing step is essential. This modification of the appearance is achieved with, or preferably without, material removal. If material removal is necessary, it is kept to a minimum.

This surfacing step relies on the use of vibrations. These vibrations are applied to the printed material and used to locally modify it. This local modification involves refluidifying the material. The vibrations cause the bonds formed during its hardening to break. This breaking of bonds allows the material to be reshaped over time.

The vibrations are generated by a vibration generator. This vibration generator can utilize various technologies, such as a pneumatic or ball vibrator. Such a vibrator is capable of generating vibrations of 1700N at a frequency of 16000 VPM (vibrations per minute).

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.

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

The application of vibrations and the application of the 300 shaping surface can be simultaneous or staggered. In the case of staggered applications, the application of the 300 shaping surface occurs after the application of vibrations.

To achieve this, vibration and shaping can be carried out with the same tooling or with different tooling.

With a single tooling 200, it is clear that the application of vibrations and the application of the forming surface are simultaneous, as can be seen in the FIG. 6 Thus, the vibrating contact surface and the forming surface are one and the same. One can also imagine having a tooling surface 200 divided into two portions: the vibrating part and the forming part.

Tool 200, for example, takes the form of a trowel. This trowel is operated manually or mounted on a robotic arm. It comprises a working surface and a vibration generator designed to transmit vibrations to the surface. This working surface can be flat or feature a pattern. This pattern is then replicated on the surface of the object.

The advantage is saving time with surfacing that is done in a single pass.

With two 200 toolings, we understand that the application of vibrations and the application of the forming surface are simultaneous or staggered.

In the case of offset applications, as visible to the FIG. 7 Each tool is used for a specific function. The first tool is used to vibrate 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 tool can take any shape, such as a trowel. Its contact surface is flat to prevent marking. The second tool is designed to have a contact surface. This contact surface displays a pattern intended to be reproduced on the printed object.

Each tool is handled manually or mounted on a robotic arm.

In the case of simultaneous applications as seen in the FIG. 8 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 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 an interlayer. This interlayer is positioned between the first tool and the printed object. It is a flexible material such as a sheet, film, membrane, or strip with two opposing faces. One face contains the pattern to be replicated. The second tool then works in conjunction with the first tool to replicate the pattern. This interaction occurs through vibrations that are not transferred directly to the printed material but rather through the second tool. In this case, the vibrations from the first tool are transmitted to the second tool, which then transmits them to the printed material. The printed material, upon receiving the vibrations, experiences a refluidification of its surface. The pattern arranged on the second tooling is then replicated onto the refluidified surface of the printed material.

The advantage of having two different tool sets is that it allows for greater flexibility since the number of usable tools is larger.

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 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.

The time interval within which surface finishing is possible is linked to a physical quantity called the yield stress. This yield stress is associated with the material's stiffness over time after printing. The range of yield stress values for which the surface finishing step according to the invention is effective has been determined. Indeed, if this yield 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.

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°.

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.

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. This database advantageously includes a multitude of simulations or tests, allowing for values to be obtained for different environmental conditions such as humidity and temperature. It is therefore understood 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 point at which the surfacing stage can begin.

Secondly, this threshold stress value is measured. This measurement is performed by a sensor that allows for the direct measurement of the threshold stress or a physical quantity used to obtain this threshold stress. The measurement is taken continuously or at regular intervals.

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 (11)

a surfacing process for a finished object, made from a construction material and printed by 3D printing, said process comprising the following steps:

• Obtain the printed object (O);
• Provide a vibrating contact surface (210) and a shaping surface (300);
• 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.

surfacing process according to the preceding claim, wherein the application of the shaping surface is simultaneous with the application of the vibrating contact surface. a surfacing process according to any one of the preceding claims, wherein the application of vibrations is carried out by a first tooling. a surfacing process according to any one of the preceding claims, wherein the application of the conforming surface is carried out by a second tool. surfacing process according to claim 2, wherein the application of vibrations and the application of the conforming surface are carried out by the same tooling. method for producing an object from 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) allowing 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 according to any 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, in which the value of the threshold stress is determined theoretically using a database. A method of implementation 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.