A continuous feeding method for friction stir additive manufacturing

Abstract

A continuous feeding method of friction stir additive manufacturing, by the cooperation of two clamping mechanisms in the friction stir additive manufacturing process, the continuity and uniformity of the whole additive process can be realized, the axial pressure, rotational motion and forward motion of the additive process rod are consistent, which can effectively improve the performance and quality of the additive structure.

Description

Technical Field

[0001] This invention relates to the field of friction stir additive manufacturing technology for aluminum alloy materials. Background Technology

[0002] Friction stir additive manufacturing of aluminum alloys is a novel solid-state additive technology developed in recent years based on the principle of friction stir welding. The additive manufacturing process eliminates the melting-solidification process of metal materials, avoiding metallurgical defects such as incomplete fusion, voids, and hot cracks that are prone to occur in melting-based additive manufacturing. Furthermore, friction stir additive structures possess refined microstructures and excellent mechanical properties, such as… Figure 1 As shown, it has broad application prospects in the manufacturing of complex structures such as spacecraft hulls and weapon systems.

[0003] The principle is as follows: a driving device rotates a rod-shaped raw material at high speed and applies axial pressure, causing the end of the rod to contact the substrate. The end of the rod has a shoulder made of a material with a higher melting point and strength than the rod. During the additive manufacturing process, under the action of axial pressure, the end of the rod rubs against the substrate, generating a large amount of heat. The interface area between the rod and the substrate becomes plasticized. Under the combined action of heat, rotational force, and pressure, the plastic material flows, mixes, and deposits on the substrate. At the same time, the rod moves forward, and during this process, the material in the plasticized area is continuously deposited on the substrate to form an additive layer.

[0004] In additive manufacturing, as the deposition rate gradually increases, the rod material is continuously consumed. When the rod material is insufficient, it needs to be replaced. However, the additive manufacturing process needs to be interrupted when replacing the rod material. After replacement, axial force, rotational motion, and forward motion need to be reapplied to the rod material to continue the additive manufacturing process. Because the additive manufacturing process is interrupted when replacing the rod material, the heat input, axial pressure, rotational motion, and forward motion are all interrupted, the continuity of the additive manufacturing process is disrupted. As a result, the junction between the replaced deposited material and the original deposited material is prone to defects such as incomplete connection, insufficient connection, and voids. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and proposes a continuous rod feeding method for friction stir additive manufacturing, which can achieve continuity and uniformity throughout the additive process. The axial pressure, rotational motion, and forward motion of the rod are kept consistent throughout the additive process, which can effectively improve the performance and quality of the additive structure.

[0006] The problem of poor quality and various defects at the joint of the additive deposit layer caused by the interruption of additive manufacturing process when replacing consumable rods during friction stir additive manufacturing is that the process is interrupted.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a continuous feeding method for friction stir additive manufacturing, comprising:

[0008] Additive rods are loaded and clamped in the upper and lower clamping mechanisms of the friction stir additive machine, ensuring that the end faces of the two additive rods are in contact, with the lower end of the additive rod inserted into the inner hole of the shaft shoulder.

[0009] When the clamping mechanism located below is about to interfere with the shoulder, control the clamping mechanism to loosen the clamping of the additive bar and move it up along the bar axis to below the clamping mechanism above.

[0010] During the relaxation of the clamping mechanism located below, the lower additive bar is driven to rotate and advance by the shoulder, and the upper additive bar provides downward pressure. During this process, the rotation and forward speeds of the two clamping mechanisms, the shoulder, and the two additive bars are kept the same and constant.

[0011] Once all the additive manufacturing material at the bottom is consumed, the clamping mechanism at the top releases its grip on the additive manufacturing material and moves upward. After moving upward, there is no additive manufacturing material left in the clamping mechanism at the top. At this time, a new additive manufacturing material is installed in the clamping mechanism at the top, and under the action of gravity, its lower end face contacts and adheres to the upper end face of the original additive manufacturing material at the top. After the adherence, the clamping mechanism at the top clamps the newly installed additive manufacturing material. During this process, the rotational speed, downward pressing speed, and forward speed of the clamping mechanism at the bottom remain unchanged; the rotational speed and forward speed of the shoulder also remain unchanged.

[0012] Repeat the above steps to complete the continuous rod replacement in the additive manufacturing process, thereby achieving stability and continuity in the additive manufacturing process when adding new additive rods.

[0013] Preferably, the upper clamping mechanism stops rotating after it is released. After a new additive bar is installed and clamped, it needs to be rotated again, with the rotation speed consistent with that of the lower clamping mechanism and the shoulder.

[0014] Preferably, the upper clamping mechanism maintains its original rotational speed after it is released.

[0015] Preferably, the cross-section of the additive bar is rectangular, triangular, or other shapes, but the cross-section of the inner hole of the shoulder must be the same as that of the additive bar.

[0016] Preferably, the lower surface of the shoulder is a plane, a conical surface, or has other geometric features, including concentric circles and helices.

[0017] Preferably, the clamping mechanism is hydraulically or mechanically driven.

[0018] Preferably, the axis of the shoulder, the two clamping mechanisms, and the clamped additive bar coincide.

[0019] The technical effects achieved by this invention are as follows: This invention proposes a continuous rod feeding method for friction stir additive manufacturing, which can achieve continuity and uniformity throughout the additive manufacturing process. The axial pressure, rotational motion, and forward motion of the rod are kept consistent throughout the additive manufacturing process, which can effectively improve the performance and quality of the additive structure. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the friction stir additive manufacturing principle.

[0021] Figure 2 This diagram illustrates the process of changing the bar stock during continuous stirring friction additive manufacturing as described in this invention.

[0022] Figure 3 This is a schematic diagram illustrating the planar fit structure between a bar stock and a shoulder as described in this invention. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1-3 The present invention will be further illustrated by the embodiments.

[0024] The process of continuous feeding additive manufacturing method is as follows: Figure 2 As shown, the components involved in the method include additive bar 2, additive bar 4, additive bar 8, clamping mechanism 1, clamping mechanism 3, shoulder 5 made of non-consumable material, and base material 6. Among them, additive bar 2, additive bar 4, and additive bar 8 are completely identical, but are used in different situations.

[0025] Clamping mechanism 1 and clamping mechanism 3 are the driving mechanisms for the movement of additive rods during the additive manufacturing process. They have independent motion control functions, can clamp and release the additive rods, and can drive the additive rods to rotate, move up and down, and move along the additive direction.

[0026] Shoulder 5 also has the function of active rotation and forward movement. The inner hole of the shoulder is consistent with the cross-sectional shape and size of the additive bar. After the bar is inserted into the inner hole of the shoulder, the rotation of the shoulder can drive the bar to rotate.

[0027] Shoulder 5, clamping mechanism 1, additive bar and clamping mechanism 3 have their axes coincide.

[0028] Clamping mechanism 1, clamping mechanism 3 and shoulder 5 are all components of the friction stir additive manufacturing machine.

[0029] Additive manufacturing process for changing bar stock:

[0030] 1. First, additive bar 2 and additive bar 4 are loaded into clamping mechanism 1 and clamping mechanism 3 respectively. The lower end of additive bar 4 is inserted into the inner hole of shoulder 5, and the lower end face of additive bar 2 is in contact with the upper end face of additive bar 4. Then, clamping mechanism 1 and clamping mechanism 3 clamp additive bar 2 and additive bar 4.

[0031] 2. Clamping mechanism 1, clamping mechanism 3 and shoulder 5 start to rotate at the same speed and drive additive bar 2 and additive bar 4 to rotate.

[0032] 3. While clamping mechanism 1 and clamping mechanism 3 rotate synchronously, they also press down synchronously and move forward synchronously along the additive manufacturing direction. At this time, the lower end of the additive rod 4 rubs against the substrate 6, generating heat, softening the material in the friction area, and the material in the friction area mixes and deposits on the substrate 6 to form an additive deposition layer 7.

[0033] 4. As the additive manufacturing process proceeds, the lower part of the additive bar 4 continuously softens and deposits onto the substrate 6, and the length of the additive bar 4 gradually decreases. When the clamping mechanism 3 is about to interfere with the shoulder 5, the clamping mechanism 3 releases its grip on the additive bar and moves upward along the bar axis to below the clamping mechanism 1. During the release of the clamping mechanism 3, the additive bar 2 is driven by the clamping mechanism 1, and the clamping mechanism 3 does not clamp.

[0034] During this process, clamping mechanism 1, clamping mechanism 3, shoulder 5, additive bar 2, and additive bar 4 all maintain the same rotation and forward speed.

[0035] During this step, the rotational speed, pressing speed, and forward speed of clamping mechanism 1 remain unchanged.

[0036] During this step, the shoulder 5 drives the additive bar 4 to rotate and move forward, and the additive bar 2 provides downward pressure on the additive bar 4.

[0037] During this step, the rotational speed and forward speed of shoulder 5 remain unchanged.

[0038] 5. After all the additive manufacturing rod 4 has been consumed, the clamping mechanism 1 releases its grip on the additive manufacturing rod 2 and moves upward. After moving upward, there is no additive manufacturing rod in the clamping mechanism 1. At this time, a new additive manufacturing rod 8 is installed in the clamping mechanism 1. Since the clamping mechanism 1 is not clamping at this time, the lower end face of the additive manufacturing rod 8 will contact and adhere to the upper end face of the additive manufacturing rod 2 under the action of gravity. At this time, the clamping mechanism 1 clamps the additive manufacturing rod 8.

[0039] In this step, after the clamping mechanism 1 is released, it can either stop rotating or maintain its original rotation speed. If it stops rotating, after installing and clamping the additive bar 8, it needs to be rotated again, with the rotation speed consistent with that of the clamping mechanism 3 and the shoulder 5.

[0040] During this step, the rotational speed, pressing speed, and forward speed of the clamping mechanism 3 remain unchanged.

[0041] During this step, the rotational speed and forward speed of shoulder 5 remain unchanged.

[0042] 6. At this point, the replacement of one additive manufacturing bar is completed. By repeating the above steps, the bar replacement can be completed continuously in the additive manufacturing process, so as to achieve stability and continuity in the additive manufacturing process when adding new additive manufacturing bars.

[0043] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A continuous feeding method for friction stir additive manufacturing, characterized in that... include: Additive rods are loaded and clamped in the upper and lower clamping mechanisms of the friction stir additive machine, ensuring that the end faces of the two additive rods are in contact, with the lower end of the additive rod inserted into the inner hole of the shaft shoulder. When the lower clamping mechanism is about to interfere with the shoulder, control the clamping mechanism to loosen the clamping of the additive bar and move it up along the bar axis to the lower part of the upper clamping mechanism to re-clamp the upper additive bar. During the relaxation of the clamping mechanism located below, the lower additive bar is driven to rotate and advance by the shoulder, and the upper additive bar provides downward pressure. During this process, the rotation and forward speeds of the two clamping mechanisms, the shoulder, and the two additive bars are kept the same and constant. Once all the additive manufacturing material at the bottom is consumed, the clamping mechanism at the top releases its grip on the additive manufacturing material and moves upward. After moving upward, there is no additive manufacturing material left in the clamping mechanism at the top. At this time, a new additive manufacturing material is installed in the clamping mechanism at the top, and under the action of gravity, its lower end face contacts and adheres to the upper end face of the original additive manufacturing material at the top. After the adherence, the clamping mechanism at the top clamps the newly installed additive manufacturing material. During this process, the rotational speed, downward pressing speed, and forward speed of the clamping mechanism at the bottom remain unchanged; the rotational speed and forward speed of the shoulder also remain unchanged. Repeat the above steps to complete the continuous rod replacement in the additive manufacturing process, thereby achieving stability and continuity in the additive manufacturing process when adding new additive rods.

2. The method according to claim 1, characterized in that: After the upper clamping mechanism is released, it stops rotating. After installing a new additive bar and clamping it, it needs to be rotated again, with the rotation speed consistent with the lower clamping mechanism and the shoulder.

3. The method according to claim 1, characterized in that: After the upper clamping mechanism is released, it maintains the original rotation speed.

4. The method according to claim 1, characterized in that: The cross-section of the additive bar can be rectangular, triangular, or other shapes, but the cross-section of the inner hole of the shoulder must be the same as that of the additive bar.

5. The method according to claim 1, characterized in that: The lower surface of the shoulder is a plane, a cone, or has other geometric features, including concentric circles and helices.

6. The method according to claim 1, characterized in that: The clamping mechanism is driven by hydraulic or mechanical power.

7. The method according to claim 1, characterized in that: The axis of the shoulder, the two clamping mechanisms, and the clamped additive bar coincide.

Images