Method for gradient thickening of thread coating through combination of multidirectional spray gun and two-stage spraying

Abstract

The invention provides a method for gradient thickening of a thread coating by combining a multidirectional spray gun with two-stage spraying, which comprises the following steps: S1, inserting a rod part of a bolt to be sprayed into a tray with a hole, and putting the tray into a drying oven for preheating; s2, the head of the bolt to be sprayed is sprayed, and then the bolt is put into a drying oven to be pre-cured for half an hour; s3, the tray with the holes is turned over, the bolts to be sprayed are inversely arranged on the fixing plate, a cushion block with a certain thickness is placed between the fixing plate and the tray with the holes, and the tray with the holes is elevated; s4, a multi-directional spray gun is adopted for S-shaped gun walking, and a first-stage spray coating is conducted; s5, the tray with the holes is dismantled for overall spraying; s6, a multi-directional spray gun is adopted for S-shaped gun moving, and second-stage spraying is conducted; and S7, the sprayed bolts and the tray with the holes are put into a drying oven to be cured. According to the thread coating gradient thickening method combining the multidirectional spray gun with two-stage spraying, it can be ensured that the thickness of a thread part is obviously increased, and the thickness of a bolt rod part and the thickness of a bearing face coating do not exceed the standard requirement.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface treatment, and particularly relates to a method for gradient thickening of a threaded coating by combining a multi-directional spray gun with two-stage spraying. Background Art

[0002] In the field of aerospace fasteners, the standard for processing external threaded fasteners is to achieve a coating thickness of 5 - 13 μm on both the bolt bearing surface and the non-bearing surface. The conventional bolt spraying process is as follows: First, place the bolts on a tray, neatly arrange the bolts to ensure uniform spacing and stable position on a special fixture or tray, and then spray the heads; after spraying the heads, enter the pre-curing stage, send the bolts into an oven for pre-curing, turn the bolts over after pre-curing, then perform overall spraying, and finally cure the bolts again.

[0003] The existing spraying methods have the problem that the coating thickness on the threaded bearing surface of external threaded fasteners is less than 5 μm, far from reaching the standard requirement of 5 - 13 μm thickness level. Traditional spray guns and spraying methods are difficult to balance the requirements of spraying efficiency and coating thickness, resulting in easy corrosion, failure, etc. in the threaded connection parts. Summary of the Invention

[0004] In view of this, the present invention aims to propose a method for gradient thickening of a threaded coating by combining a multi-directional spray gun with two-stage spraying to solve the problems that traditional spray guns and spraying methods are difficult to balance the requirements of spraying efficiency and coating thickness, resulting in easy corrosion, failure, etc. in the threaded connection parts.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows:

[0006] The present invention provides a method for gradient thickening of a threaded coating by combining a multi-directional spray gun with two-stage spraying, including: Step S1, according to the specifications of the bolts to be sprayed, select the corresponding perforated tray, insert the rod parts of the bolts to be sprayed into the perforated tray, and put them into an oven for preheating; Step S2, spray the heads of the bolts to be sprayed, and then put them into an oven for pre-curing for half an hour; Step S3, turn over the perforated tray so that the bolts to be sprayed are inverted on the fixed plate, and place a certain thickness of spacer blocks between the fixed plate and the perforated tray to raise the perforated tray; Step S4, use a multi-directional spray gun to perform S-shaped gun movement to form a first-stage spray coating; Step S5, remove the perforated tray and perform overall spraying; Step S6, use a multi-directional spray gun to perform S-shaped gun movement to perform the second-stage spraying to form a second-stage spray coating; Step S7, put the sprayed bolts together with the perforated tray into an oven for curing.

[0007] Further, in step S3, the perforated tray is lifted until the bottom surface of the perforated tray is flush with the last tooth of the threaded part of the bolt to be sprayed. The perforated tray includes a fixed plate at the upper part and rectangular columns fixed at the four corners. At least two rows of a number of fixing holes are provided on the perforated tray along the length and width directions of the tray. The lateral spacing between two adjacent fixing holes in any row is the same, and the longitudinal spacing between any two adjacent rows of fixing holes is the same. The longitudinal center line of the first fixing hole in the second row is located at the central position between the first and the second fixing holes in the first row.

[0008] Further, in step S4, the object of the first-stage spraying is to form a coating with a thickness of 5 - 8 μm on the threaded bearing surface and non-bearing surface parts of the bolt to be sprayed.

[0009] Further, in step S4, a multi-directional spray gun with a caliber of 0.8 mm is used. The multi-directional spray gun forms an angle of ±5° with the horizontal direction, and the muzzle is 2 - 4 cm away from the tail of the bolt to be sprayed.

[0010] Further, when the diameter of the bolt to be sprayed is 4 - 8 mm, the spraying method for 4 threaded surfaces is adopted; when the diameter of the bolt to be sprayed is 8 - 12 mm, the spraying method for 8 threaded surfaces is adopted.

[0011] Further, in step S6, the object of the second-stage spraying is the rod part and the supporting surface part of the bolt to be sprayed.

[0012] Further, in step S6, a multi-directional spray gun with a caliber of 1.0 mm is used. The multi-directional spray gun forms an angle of 45 - 60° with the horizontal direction, and the muzzle is 15 - 20 cm away from the tail of the bolt to be sprayed.

[0013] Further, when the diameter of the bolt to be sprayed is 4 - 8 mm, the spraying method for 8 threaded surfaces is adopted; when the diameter of the bolt to be sprayed is 8 - 12 mm, the spraying method for 8 threaded surfaces is adopted.

[0014] Further, the multi-directional spray gun is driven by a three-axis two-spray gun robotic arm for spraying. Two multi-directional spray guns with different calibers are respectively fixed at the end of the three-axis two-spray gun robotic arm.

[0015] Compared with the prior art, the method for gradient thickening of the threaded coating by combining the multi-directional spray gun and two-stage spraying of the present invention has the following advantages:

[0016] (1) Compared with conventional spray guns, the multi-directional spray gun of the present invention can easily achieve a horizontal spray direction, thereby achieving the purpose of thickening the coating on the bearing surface. Compared with conventional primary spraying, in the two-stage spraying, the first stage first performs horizontal spraying on the threaded part to ensure that there is no coating coverage on the bolt rod part and the bearing surface part during this process. The second stage performs simultaneous spraying on the bolt rod part and the bearing surface part. The combination of the two ensures that the thickness of the threaded part is significantly increased and the coating thickness of the bolt rod part and the bearing surface does not exceed the standard requirements.

[0017] (2) In the present invention, for external thread fasteners of different specifications, gradient thickening can be achieved by increasing the number of spray surfaces. The high-precision rotation of the robotic arm is realized through a three-axis two-spray gun robotic arm for precise spraying. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0019] In the drawings:

[0020] Figure 1 is a schematic diagram of the spraying process of the method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to the embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of placing the bolt to be sprayed in step S1 of the method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to the embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of turning over the bolt to be sprayed in step S3 of the method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to the embodiment of the present invention;

[0023] Figure 4 is a schematic diagram of padding up with a cushion block in step S3 of the method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to the embodiment of the present invention;

[0024] Figure 5 is a schematic diagram of the spraying state of the multi-directional spray gun in step S4 of the method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to the embodiment of the present invention;

[0025] Figure 6 is a schematic diagram of the spraying state of the multi-directional spray gun in step S6 of the method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to the embodiment of the present invention;

[0026] Figure 7 is a schematic diagram of the connection of the three-axis two-spray gun robotic arm of the method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to the embodiment of the present invention.

[0027] Description of reference numerals:

[0028] 1. Pallet with holes; 2. Bolts to be sprayed; 3. Fixed plate; 4. Spacer block; 5. Multi-directional spray gun; 6. Three-axis two-spray gun robotic arm; 7. First multi-directional spray gun; 8. Second multi-directional spray gun. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0032] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0033] See also Figures 1-7As shown in the figure, this embodiment provides a method for gradient thickening of a threaded coating by combining a multi-directional spray gun with two-stage spraying, including the following steps: Step S1, according to the specifications of the bolts to be sprayed, select the corresponding perforated tray 1, insert the rod part of the bolts to be sprayed 2 into the perforated tray, and place them in an oven for preheating; Step S2, spray the heads of the bolts to be sprayed 2, and then place them in the oven for pre-curing for half an hour; Step S3, flip the perforated tray 1 so that the bolts to be sprayed 2 are inverted on the fixing plate 3, and place a cushion block 4 with a certain thickness between the fixing plate 3 and the perforated tray 1 to raise the perforated tray 1; Step S4, use a multi-directional spray gun 5 to perform S-shaped gun travel to form a first-stage spray coating; Step S5, remove the perforated tray and perform overall spraying; Step S6, use a multi-directional spray gun 5 to perform S-shaped gun travel to perform a second-stage spraying to form a second-stage spray coating; Step S7, place the sprayed bolts together with the perforated tray 1 in the oven for curing.

[0034] First-stage spraying: Only spray the threaded part. Adjust the multi-directional spray gun to be in a horizontal direction, that is, perpendicular to the placement direction of the bolts to be sprayed, and perform gun travel near the threaded part. Through S-shaped gun travel, a 5-8 μm coating is evenly formed on the threaded load-bearing surface and non-load-bearing surface parts of all the bolts on the tray. Second-stage spraying: Based on the first-stage spraying, perform overall spraying to cover the rod part and the support surface. At this time, the distance between the spray gun and the bolt should be relatively far to ensure that the overall coating of the bolt is uniform and stable.

[0035] Specifically, in this embodiment, in step S3, the perforated tray 1 is raised until the bottom surface of the perforated tray is flush with the last tooth of the threaded part of the bolts to be sprayed. The perforated tray 1 includes a fixed plate at the upper part and rectangular columns fixed at the four corners. There are at least two rows of a number of fixing holes on the perforated tray 1 arranged along the length and width directions of the tray. The lateral spacing between two adjacent fixing holes in any row is the same, and the longitudinal spacing between any two adjacent rows of fixing holes is the same. The longitudinal center line of the first fixing hole in the second row is located at the central position between the first and second fixing holes in the first row.

[0036] Specifically, in this embodiment, in step S4, the object of the first-stage spraying is to form a 5-8 μm coating on the threaded load-bearing surface and non-load-bearing surface parts of the bolts to be sprayed 2.

[0037] Specifically, in this embodiment, in step S4, a multi-directional spray gun 5 with a caliber of 0.8 mm is used. The multi-directional spray gun 5 forms an angle of ±5° with the horizontal direction, and the muzzle is 2-4 cm away from the tail of the bolts to be sprayed 2.

[0038] Specifically, in this embodiment, when the diameter of the bolts to be sprayed 2 is 4-8 mm, the method of spraying 4-sided threads is adopted; when the diameter of the bolts to be sprayed 2 is 8-12 mm, the method of spraying 8-sided threads is adopted.

[0039] First - stage spraying: Use a multi - directional spray gun with a 0.8 - mm caliber to perform S - type gun movement, spray at an angle of ±5° with the horizontal direction, the muzzle is 2 - 4 cm away from the tail of the bolt, and the gun movement speed is 0.2 m / s. It is determined according to the bolt specifications that under normal circumstances, the liquid output of the spray gun is 3 g / s, and the atomization pressure is 0.2 - 0.4 MPa. When the bolt diameter is 4 - 8 mm, to ensure that the coating thickness at the bearing surface of the bolt meets 5 - 13 μm, the first - stage spraying generally adopts the method of spraying 4 - threaded surfaces; when the bolt diameter is 8 - 12 mm, to ensure that the coating thickness at the bearing surface of the bolt meets 5 - 13 μm, the first - stage spraying generally adopts the method of spraying 8 - threaded surfaces.

[0040] Specifically, in this embodiment, in step S6, the objects of the second - stage spraying are the rod part and the support surface part of the bolt 2 to be sprayed.

[0041] Specifically, in this embodiment, in step S6, use a multi - directional spray gun 5 with a caliber of 1.0 mm. The multi - directional spray gun 5 forms an angle of 45 - 60° with the horizontal direction, and the muzzle is 15 - 20 cm away from the tail of the bolt 2 to be sprayed.

[0042] Specifically, in this embodiment, when the diameter of the bolt 2 to be sprayed is 4 - 8 mm, the method of spraying 8 - threaded surfaces is adopted; when the diameter of the bolt 2 to be sprayed is 8 - 12 mm, the method of spraying 8 - threaded surfaces is adopted.

[0043] Second - stage spraying: Use a multi - directional spray gun with a 1.0 - mm caliber to perform S - type gun movement, spray at an angle of 45 - 60° with the horizontal direction, the muzzle is 15 - 20 cm away from the tail of the bolt, and the gun movement speed is 0.2 m / s; when the bolt diameter is 4 - 8 mm, the second - stage spraying generally adopts the method of spraying 4 - whole surfaces; when the bolt diameter is 8 - 12 mm, the second - stage spraying generally adopts the method of spraying 8 - whole surfaces.

[0044] Compared with a conventional spray gun, a multi - directional spray gun can easily make the spray direction horizontal to achieve the purpose of thickening the coating on the bearing surface. Compared with conventional first - stage spraying, in two - stage spraying, the first stage first performs horizontal spraying on the threaded part to ensure that there is no coating coverage on the rod part and the support surface part of the bolt during this process. The second stage sprays the rod part and the support surface part of the bolt simultaneously. The combination of the two ensures that the thickness of the threaded part is significantly increased and the coating thickness of the rod part and the support surface of the bolt does not exceed the standard requirements.

[0045] For different specifications of external - thread fasteners, gradient thickening can be achieved by increasing the number of sprayed surfaces. It is stipulated that each rotation of the perforated tray is 4 surfaces during spraying. For example: Bolts with a diameter of 4 - 8 mm are first sprayed with 4 - threaded surfaces (rotating 360°), and then the whole bolt is sprayed with 8 - surfaces (rotating 720°); products with a bolt - size specification of 8 - 12 mm are first sprayed with 8 - threaded surfaces (rotating 720°), and then the whole bolt is sprayed with 8 - surfaces (rotating 720°).

[0046] Specifically, in this embodiment, a multi-directional spray gun is driven by a three-axis two-spray gun robotic arm for spraying, and two multi-directional spray guns with different calibers are respectively fixed at the end of the three-axis two-spray gun robotic arm.

[0047] During actual operation, refer to Figure 7 , Figure 7 in which the first multi-directional spray gun 7 and the second multi-directional spray gun 8 are multi-directional spray guns 5 with different calibers in the method. The multi-directional spray gun 5 in the method is combined with a flexible robotic arm to form a three-axis two-spray gun robotic arm 6. The design of the robotic arm is simplified through three-axis linkage, and two multi-directional spray guns with different calibers and adjustable angles are installed at the end of the flexible robotic arm (i.e., Figure 7 the first multi-directional spray gun 7 and the second multi-directional spray gun 8 in ), so as to meet the requirements of separately coating the threads and other parts. This robotic arm for three-axis spraying adopts a composite motion structure, which consists of a chassis rotation axis, a longitudinal rotation axis, and a terminal rotation axis. The chassis rotation axis realizes the high-precision rotation of the robotic arm through a reduction motor, and controls the terminal positioning error within ±3 mm; the terminal rotation axis is equipped with a precision swing mechanism and is adjusted with the assistance of a micro-reducer to reduce the swing angle error to 0.2°, and the interval of -5° - 60° is sufficient to achieve precise spraying. Double-spring SATA spray guns with calibers of 0.8 mm and 1.0 mm are respectively installed at the end of the robotic arm, which can meet the liquid outlet requirements of different spraying stages while realizing precise liquid control (the spray width is continuously adjustable from 50 to 400 mm).

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for gradient thickening of a threaded coating by combining a multi-directional spray gun with two-stage spraying, characterized in that, Including step S1, according to the specifications of the bolts to be sprayed, select the corresponding perforated trays, insert the rod parts of the bolts to be sprayed into the perforated trays, and place them in an oven for preheating; Step S2, spray the heads of the bolts to be sprayed, and then place them in the oven for pre-curing for half an hour; Step S3, turn over the perforated tray so that the bolts to be sprayed are inverted on the fixed plate, place a spacer of a certain thickness between the fixed plate and the perforated tray to raise the perforated tray; Step S4, use a multi-directional spray gun to perform an S-shaped gun movement to apply the first-level spray coating to form the first-level spray coating; Step S5, remove the perforated tray and perform overall spraying; Step S6, use a multi-directional spray gun to perform an S-shaped gun movement to perform the second-level spraying to form the second-level spray coating; Step S7, place the sprayed bolts together with the perforated trays in the oven for curing.

2. The method for gradually increasing the thickness of the threaded coating by combining a multi-directional spray gun with two-stage spraying according to claim 1, wherein In step S3, raise the perforated tray until the bottom surface of the perforated tray is flush with the last tooth of the threaded part of the bolt to be sprayed. The perforated tray includes a fixed plate at the upper part and rectangular columns fixed at the four corners. At least two rows of a number of fixing holes are provided on the perforated tray along the length and width directions of the tray. The lateral spacing between two adjacent fixing holes in any row is the same, and the longitudinal spacing between any two adjacent rows of fixing holes is the same. The longitudinal center line of the first fixing hole in the second row is located at the central position between the first and the second fixing holes in the first row.

3. The method for gradient thickening of a threaded coating by combining a multi-directional spray gun with two-stage spraying according to claim 1, wherein In step S4, the object of the first-level spraying is to form a 5-8 μm coating on the threaded bearing surface and non-bearing surface parts of the bolts to be sprayed.

4. The method for gradient thickening of the threaded coating by combining a multi-directional spray gun with two-level spraying according to claim 3, characterized in that in step S4, a multi-directional spray gun with a caliber of 0.8 mm is used. The multi-directional spray gun forms an angle of ±5° with the horizontal direction, and the muzzle is 2-4 cm away from the tail of the bolt to be sprayed.

5. The method for gradient thickening of the threaded coating by combining a multi-directional spray gun with two-stage spraying according to claim 4, characterized in that, When the diameter of the bolt to be sprayed is 4-8 mm, the method of spraying 4-sided threads is adopted; when the diameter of the bolt to be sprayed is 8-12 mm, the method of spraying 8-sided threads is adopted.

6. The method for gradient thickening of the threaded coating by combining a multi-directional spray gun with two-stage spraying according to claim 1, characterized in that, In step S6, the object of the second-level spraying is the rod part and the supporting surface part of the bolts to be sprayed.

7. The method for gradually increasing the thickness of the threaded coating by combining a multi-directional spray gun with two-stage spraying according to claim 6, characterized in that, In step S6, a multi-directional spray gun with a caliber of 1.0 mm is used. The multi-directional spray gun forms an angle of 45-60° with the horizontal direction, and the muzzle is 15-20 cm away from the tail of the bolt to be sprayed.

8. The method for gradient thickening of the threaded coating by combining a multi-directional spray gun with two-stage spraying according to claim 7, wherein When the diameter of the bolt to be sprayed is 4-8 mm, the method of spraying 8-sided threads is adopted; when the diameter of the bolt to be sprayed is 8-12 mm, the method of spraying 8-sided threads is adopted.

9. The method for gradient thickening of the threaded coating by combining a multi-directional spray gun and two-stage spraying according to claim 1, characterized in that, The multi-directional spray gun is driven by a three-axis two-spray gun robotic arm for spraying. Two multi-directional spray guns with different calibers are respectively fixed at the end of the three-axis two-spray gun robotic arm.

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