Dynamic saturation control method in binder jetting

Abstract

The invention relates to a dynamic saturation control method in binder jetting, which enables the dynamic control of saturation levels in additive manufacturing, as the saturation rate varies with each layer laid.

Description

[0001] DYNAMIC SATURATION CONTROL METHOD IN BINDER JETTING

[0002] The technical field to which the invention relates:

[0003] The invention relates to a method of dynamic saturation control in binder jetting, which enables the dynamic control of saturation levels, as the saturation rate in additive manufacturing is not constant and changes with each layer being laid.

[0004] State of the Art:

[0005] Additive manufacturing (3D printing) technologies are a rapidly developing field that is revolutionizing various industrial applications. In this process, strain gauges, which are specifically used to monitor and optimize material performance, play a crucial role in enhancing the durability and quality of printed parts. Strain gauges detect changes in stress, deformation, and strain within the material during printing, enabling the optimization of printer settings and material selection. Furthermore, the use of these technologies to increase material efficiency and improve print quality is becoming increasingly common, especially in industrial applications.

[0006] Binder jetting is an additive manufacturing method that enables the production of 3D objects from a wide range of materials. In this process, binders are jetted onto the surface in the correct amount and at the appropriate speed, playing a critical role in enhancing material adhesion. To increase the effectiveness of binders, dynamic saturation control is crucial for ensuring accurate application. Furthermore, factors such as binder viscosity, temperature, and surface condition are taken into consideration to determine the optimal jetting parameters for each application.

[0007] Dynamic saturation control ensures the correct application of binders, optimizes material consumption, and improves application quality. This principle can be similarly applied to 3D printing processes; material deformations and stresses are monitored during printing, ensuring production under ideal conditions. For example, because the jetted material must reach a certain saturation level upon interaction with the surface, exceeding or falling short of this level can impact material yield. Therefore, strain gauges and other sensor systems are integrated with dynamic control systems to determine the optimal parameters for each printing process.

[0008] Consequently, the proper integration of both strain gauges and binder jetting techniques in additive manufacturing processes is critical for increasing material efficiency and optimizing application quality. With technological advancements, systems equipped with sensors and microprocessors offer more precise and sustainable solutions that take into account environmental factors and material interactions. Thus, both technologies enable higher productivity and higher-quality results in both additive manufacturing and binder jetting applications.

[0009] While various proposals and applications for dynamic saturation control in binder jetting have been developed within the state of the art, these developments are not sufficient. Some applications related to inventions developed for this purpose are listed below.

[0010] The patent application, numbered "CN113909490A" and currently under development, belongs to the field of additive manufacturing technologies and offers an innovation in the production and near-net forming of metal parts. The application describes the process steps involved in creating a metal starting block using binder jetting technology, which involves mixing metal powder and binders, and pretreating this block (including bleaching and pre-sintering). The resulting pre-sintered part is then coated with silicone rubber to form a sheath, followed by cold isostatic pressing and sintering to increase the density. This method aims to address the challenges of low density, high shrinkage rate, and dimensional control encountered during sintering by providing densification at low temperatures,thereby enabling the fast and mold-free production of high-performance metal parts by increasing the homogeneity of the microstructure.

[0011] The patent application "W02020051635A1," which is currently in the state of the art, describes a specific powder composition and printing method used to create a 3D-printed object. The composition includes cementitious materials, such as Portland cement or Calcium Sulfoaluminate (CSA) cement, to bind the aggregate; accelerators, such as calcium aluminate, plaster of Paris, or lithium salts, to accelerate hardening; and a flow control agent to control the powder's flowability. This powder is then placed on a bed in a 3D printer from a powder feeder, and a binder is jetted onto it to create a printed object. The aim is to accelerate the 3D printing process, enabling the efficient and rapid production of various structures.

[0012] In the state of the art, when the packing ratio changes during layer laying during production, the same amount of binder is delivered, resulting in a change in saturation. This requires a dynamic saturation control method for binder injection, which uses strain gauges and algorithms to maintain saturation at the desired level.

[0013] Consequently, due to the drawbacks described above and the inadequacy of existing solutions, development in the relevant technical area has become necessary.

[0014] Purpose of the Invention:

[0015] The most important purpose of the invention is to enable dynamic control of the saturation level, as the saturation rate is not constant and varies with each layer being laid.

[0016] Another purpose of the invention is to enable precise adjustment of saturation for high-resolution prints with printheads with high resolutions, such as 1200 DPI and 1600 DPI.

[0017] Another purpose of the invention is to dynamically adjust saturation settings, taking into account the effects of varying packing ratios for each layer.

[0018] Another purpose of the invention is to minimize the measurement accuracy and roughness issues that can arise when saturation is not constant. Thus, accurate saturation control enhances print quality and enables smoother surfaces.

[0019] Another purpose of the invention is to dynamically control the energy level of the laser or electron beam in powder bed fusion methods, taking into account variations in the packing ratio for each layer.

[0020] Explanation of the Figures:

[0021] Figure 1: This diagram illustrates the axes defined for the process step of calculating the required binder volume, as per the saturation equation, to maintain constant saturation over the varying packing ratio value of the invention.

[0022] Figure 2: This diagram shows the dynamic saturation control method for binder jetting.

[0023] Reference numbers:

[0024] 10: Checking whether the print head has laid the layer.

[0025] 20: If the layer has been laid, the print head continues operation; if not, it stops.

[0026] 30: Reading the strain gauge under the printing platform.40: Calculating the total weight of the powder on the platform based on the strain gauge reading.

[0027] 50: Calculating the weight of the laid layer by subtracting the previously calculated weight from the calculated total weight.

[0028] 60: Calculating the air-free volume of the layer by dividing the weight of the laid layer by the material density.

[0029] 100: Calculating the weight of the laid layer after the tare operation is completed.

[0030] 200: Calculating the air-free volume of the layer by dividing the weight of the laid layer by the material density.

[0031] 300: Calculating the packing ratio by dividing the calculated air-free volume by the total volume occupied by one layer.

[0032] 400: Calculating the required binder volume from the saturation equation using the packing ratio.

[0033] 410: Determining a fixed saturation value before starting the printing process.

[0034] 420: Calculating the required binder volume from the saturation equation to maintain constant saturation over the changing packing ratio value.

[0035] Description of the Invention:

[0036] The invention relates to a method for dynamic saturation control in binder jetting, enabling the dynamic control of saturation levels as the saturation rate varies with each layer being laid.

[0037] The invention enables precise saturation adjustment for high-resolution prints with printheads with high resolutions, such as 1200 DPI and 1600 DPI. Since the packing rate can vary for each layer, saturation adjustments are made dynamically, taking into account these effects. This minimizes the measurement accuracy and roughness issues that can arise when saturation is not constant. Thus, accurate saturation control enhances print quality and enables smoother surfaces.

[0038] _ V binder > V binder z

[0039] V air (l-PO)xVsolid

[0040] pQ —vpowder (2)

[0041] Vpowder+^air

[0042] $ _ IQOOXV

[0043]

[0044] —(1-(P0))XXXYXZ ' '

[0045] Saturation is the ratio of the binder volume to the total volume of air within the powder. Theoretically, the saturation formula is equation (1).

[0046] In a 3D printer, a strain gauge or load cell is placed under the printing platform (build piston) or under the printing chamber to measure the weight of each layer. Equation (2) enables calculation of the packing ratio of each layer based on the weight of each layer and the material density. Saturation is calculated based on the packing ratio. Alternatively, saturation may be determined using a different calculation formula. Equation (3) is more useful than equation (1) in calculating saturation. It is actually a slightly expanded version of equation (1). It expresses the volume of binder (in picoliters) released from a nodule of the print head in one jet, and print head manufacturers provide this value. "PO" refersto the packing ratio. "X" represents the interdroplet spacing (in microns) on the x-axis, while "Y" represents the interdroplet spacing on the y-axis. "Z" represents the layer thickness. Multiplying X, Y, and Z indicates the micrometer volume covered by a single droplet. This multiplication corresponds to the voxel concept, which is known in additive manufacturing. Many additive manufacturing methods, such as binder jetting, utilize the voxel concept. Calculating the saturation of a voxel is the same as calculating the saturation of the entire part; therefore, formula (3) is used in this invention for convenience.

[0047] Because the packing ratio of each layer is calculated in real time in the invention, the amount of binder required for each voxel of that layer is calculated using formula (3) based on the predetermined optimum saturation value. In this manner, even if the packing ratio of the layers varies, the saturation remains constant by correspondingly adjusting the amount of binder delivered. The invention relates to a control method for dynamic saturation control in binder spraying via a controller on a 3D printer. The method for dynamically controlling saturation in binder jetting, as shown in Figure 2, includes the following process steps:

[0048] • calculating the weight of the layer laid after taring (100);

[0049] • calculating the air-free volume of the layer by dividing the weight of the laid layer by the material density (200);

[0050] • calculating the packing ratio by dividing the calculated air-free volume by the total volume occupied by one layer (300); and

[0051] • calculating the required binder volume from the saturation equation using the packing ratio found (400).

[0052] Calculating the weight of the laid layer by performing the taring process, which constitutes a process step of the dynamic saturation control method in binder jetting (100), wherein performing the taring process includes the following process steps:

[0053] • checking whether the layer has been laid by the print head (10);

[0054] • if the layer has been laid, the print head continues operation; if not, it stops (20);

[0055] • reading the value of the strain gauge under the printing platform or printing chamber (30); • calculating the total weight of the powder on the platform based on the strain gauge reading (40);

[0056] • calculating the weight of the laid layer by subtracting the previously calculated weight from the calculated total weight value (50); and

[0057] • calculating the air-free volume of the layer by dividing the weight of the laid layer by the material density (60).

[0058] In the process of calculating the air-free volume of the layer, the weight of the laid layer is divided by the material density (200), which is a step in the dynamic saturation control method used in binder jetting. The volume is then automatically calculated by dividing the weight of a layer by its material density. The calculated volume here refers to the volume that excludes the air in the powder.

[0059] In the process of calculating the required binder volume using the saturation equation with the found packing ratio (400), a dynamic saturation control method is employed in binder jetting. The binder volume (V) is then calculated from Equation (3) by determining the packing ratio. This is because aspecific saturation (S) value is determined before the printing process begins. In other words, the (S) value is fixed. To maintain constant saturation over the changing packing ratio (PO) value, the binder volume (V) required is calculated according to the saturation equation.

[0060] The method for dynamically controlling saturation in binder jetting includes calculating the required binder volume from the saturation equation using the determined packing ratio (400), which includes the following process steps:

[0061] • determining a specific saturation value before the printing process begins (410); and

[0062] • calculating the binder volume required to maintain constant saturation as the packing ratio varies, based on the saturation equation (420).

[0063] The method in question can be applied in both binder jetting and powder bed fusion processes, including selective laser sintering, selective laser melting, and electron beam melting. Because powder is used in these methods, the packing ratio varies for each layer being deposited. However, these methods do not use a binder; instead, a laser or electron beam is used. In binder jetting, the change in binder volume based on the packing ratio can be achieved by adjusting the energy of the laser or electron beam. In lasers, such energy change can be achieved by adjusting the laser power, focusing area, pulse duration, and pulse repetition frequency. In electron melting, an energy change can be achieved by adjusting the focus and beam current.

[0064] In powder bed fusion methods, the packing ratio varies for each layer, as in binder jetting. Just as saturation is controlled in binder spraying, the energy of the laser or electron beam can be controlled in powder bed fusion methods. Calculating the packing ratio of a layer in powder bed fusion methods is performed in the same manner as the methods described in the invention. Changing the binder volume in binder jetting is achieved by varying the laser or electron beam energy, similar to the approach used in powder bed fusion methods.

Claims

CLAIMS1. A control method for dynamically controlling the saturation of binder jetting using a controller on a 3D printer. It comprises the following steps:• Calculating the weight of the laid layer after taring (100);• Calculating the air-free volume of the layer by dividing the weight of the laid layer by the material density (200);• Calculating the packing ratio by dividing the calculated air-free volume by the total volume occupied by one layer (300); and• Calculating the required binder volume from the saturation equation using the packing ratio (400).

2. A control method for dynamic saturation control in binder jetting via a controller on a 3D printer according to Claim 1. The method includes the following steps:• calculating the weight of the laid layer after the taring process is completed (100);• checking whether the layer has been laid by the print head (10);• continuing operation of the print head if the layer has been laid, stopping the print head if not (20);• reading the value of the strain gauge under the printing platform (30);• calculating the weight of the total powder on the platform based on the strain gauge reading (40);• calculating the weight of the laid layer by subtracting the previously calculated weight value from the calculated total weight value (50); and• calculating the air-free volume of the layer by dividing the weight of the laid layer by the material density (60).

3. A control method for providing dynamic saturation control in binder jetting by means of a controller on a 3D printer according to Claim 1, characterized in that the volume calculated in the process step of calculating the air-free volume of the layer by dividing the weight of the laid layer by the material density (200) corresponds to the volume of the powder that does not contain air.

4. A control method for dynamically controlling saturation in binder jetting using a controller on a 3D printer according to Claim 1. The method includes the following steps:• calculating the required binder volume from the saturation equation using the determined packing ratio (400);• determining a fixed saturation value by the user before the printing process begins (410); and • calculating the required binder volume according to the saturation equation to maintain constant saturation over the changing packing ratio value (420).

5. A control method for dynamic saturation control in binder jetting via a controller on a 3D printer according to Claim 1 or Claim 4, characterized in that the binder volume required to keep the saturationconstant over the changing packing ratio value is calculated according to the saturation equation (420) in the process step, wherein the saturation is calculated as: S=(1000xV) / ((l-(PO)) xXxYxZ)6. A control method for providing dynamic saturation control in binder jetting by means of a controller on a 3D printer according to Claim 1, characterized in that the packing ratio is determined by dividing the calculated air-free volume by the total volume covered by a layer (300). The process step involves adjusting the binder volume according to the packing ratio in binder jetting and adjusting the energy of the laser or electron beam according to the packing ratio in powder bed fusion methods.

7. A control method for providing dynamic saturation control in binder jetting via a controller on a 3D printer according to Claim 1, characterized in that the process step of reading the value of the strain gauge under the printing platform (30) includes reading a strain gauge or load cell positioned beneath the printing chamber or the printing platform.

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