Technical field

The subject of this invention is a device for creating a metallic powder bed during additive manufacturing process using a recoater blade which is mounted on a recoating arm of a 3D printer.

Background art

A blade - shaped recoating element mounted on a recoating arm is used to create layers of metallic powder during the additive manufacturing process. A variety of blades ranging from stiff materials, such as ceramic or metal, to pliable materials, such as polymer or carbon fibre brushes, are used depending on the character of the manufacturing process. During the melting process of individual layers, unpredictable phenomena can occur that affect the homogenity of the subsequent layer deposition, which leads to defect formation and possibly even deterioration of the manufactured part. Current devices do not allow an exchange of the recoating elements based on its stiffness continuously during the manufacturing process in the case of such defect formation. The most common type of defect leading to the process interruption is a build-up of the material that protrudes above the level of powder bed, which causes undesired stumbling and vibrations of the blade and eventually stopping the printing process. Even the stumbling and vibrating is problematic, since it affects the quality of the deposited layer and thus the melting process stability in other places across the powder bed as well, which may lead to chaining other defects. If the process is stopped, the printed part starts to deform. After finishing, a dear line is visible at the level of interruption which can later lead to problems during loading of the part. Also, the process often cannot be resumed once it has been interrupted, and it is necessary to repeat it from the beginning. A dangerous aspect is also the ability of the recoater to overcome certain defects without revealing them, which may lead to identifying them only after the part has been printed and material wasted. Even spotting such a defect can be difficult if it stays enclosed inside the printed part. These problems can be overcome by the exchange of the stiff blade for a pliable one during the 3D printing process.

A recoating device for additive manufacturing was presented in document WO2017143145A1, that allows mounting multiple recoating elements with different stiffness at once, separately or simultaneously. However, this solution does not allow an adaptive change of the blades depending on the current status of the ongoing process.

Disclosure of invention

The subject of this invention is a device for creating a metallic powder bed during additive manufacturing process of the metal part using a recoater blade which is mounted on a recoating arm of a 3D printer. The recoater arm is switchable flipping and is equipped with a pair of recoater blades with different stiffness. The use of one or another is determined by the current state of the powder bed and is switched either manually or automatically, which mitigates the collision risk during the process.

Mutual parallelism of the blades is desirable for their effective interchangeability.

Adaptability of the solution is based on the possibility of easy exchange of the individual recoater blades. This is ensured by an easy clamping bar mechanism for the mounting of the recoater blades on the recoater arm.

Descrition of drawings

Fig. 1 shows complete view on the device assembly, the recoater arm with the pair of recoater blades is depicted in Fig. 2, and the crosssection view of the recoater arm is shown in Fig. 3.

Description of example embodiment

Recoater arm 2 is equipped with a pair of recoater blades 3a. 3b with different stiffness. First blade 3a is made of stiffer material, in this case ceramic or metal, while the second blade 3b is made of pliable material, for example carbon fibre brush. The recoater arm 2 is switchable flipping, mounted to the frame of the 3D printer 1, controlled by a motor 11. The motor 11 is connected to the recoater arm via elastic element 12. A connecting rod 21 is placed on the recoater arm 2 for the purpose of connection with the elastic element 12. Mutual parallelism of the recoater blades 3a. 3b is ensured for effective interchangeability by flipping the recoater arm 2. Recoater blades 3a, 3b are mounted on the recoater arm 2 using a clamping bar 4, which is connected to the recoater arm 2 with bolts 41. Recoated arm 2 is flippable between two bounding positions, either manually by the operator, who oversees the process, or by electronics 5, which monitors vibrations during the recoating cycle of each layer. Controlling electronics 5 are connected to an external computer, which evaluates the measured vibration. When a vibration threshold is exceeded, a negative phenomenon is indicated and the system flips the recoater arm 2, switching between the recoater blades 3a, 3b. Flipping to a pliable recoater blade helps overcoming the critical area and minimizing the defect formation without interrupting the printing process. After stabilisation of the recoating process, the recoater arm 2 is flipped back to its original position, proceeding with the stiffer recoater. Controlling electronics 5 further measure the vibrations, which helps deciding whether it is safe to proceed with the printing process without devaluating the part. This is an adaptable solution for achieving a high quality.