JP2002361121A - Powder coating method and coating apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the re-adhesion of an aluminum powder in an unapplied powder paint to an article to be coated when a magnesium metal molded product is coated with the powder coating by one coating system. SOLUTION: The powder coating is applied to the article to be coated by parallelly performing a process for feeding the article to be coated along the axis extending in the longitudinal direction of a feed unit from the upstream side of the axis to the downstream side thereof, a process for spraying the powder coating on the article to be coated fed by the feed unit from a discharge gun in a coating booth and a process for forming air streams flowing in the direction crossing the feed direction of the feed unit in the coating booth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a metallic powder coating to a magnesium alloy molded product, and a coating apparatus for performing the method.

[0002]

2. Description of the Related Art In recent years, ease of recycling, light specific gravity,
Magnesium alloys are attracting attention from the viewpoint of good heat dissipation, and as a group of products in which magnesium alloys are used practically, home appliances such as TVs, notebook computers,
There are exterior parts such as portable MDs and wheels related to vehicles. Magnesium alloy is mainly AZ9 for casting.
There are 1 type and AD31 type for sheet metal, but most are for casting and are formed by die casting and thixomolding.

[0003] The coating of molded products having medium or large dimensions, such as notebook PCs and TV exterior parts, is generally performed as follows. Due to the problem of foaming from metal wrinkles and burrows at the time of painting, metal molds made of magnesium alloy are coated with 3 to 4 coats and putty treatment is performed to prevent hot water wrinkles. Specifically, it is processed in the order of primer coating, putty coating, putty shaving, primer coating, and top coating (in some cases, coating twice). After painting, there is a baking process.

[0004] As described above, there are problems that the number of coating steps is large and that the putty processing is interrupted to perform continuous processing. Therefore, the processing capacity is limited and the cost is increased.

[0005] In order to solve these problems, the applicant has applied one coat (one coating) of powder paint.
Is disclosed in Japanese Patent Application No. 2000-372186. Specifically, the method secures a coating film thickness of 80 μm or more, and secures an average surface roughness of the coating film after baking of 10 μm or more to improve the concealing effect of hot water lines. It is characterized in that the curing start temperature of the paint is set to 140 ° C. or lower in order to suppress the foaming of the paint.

[0006]

The powder coating used in this method is a metallic powder coating containing 3% or more of aluminum powder in order to easily conceal hot water lines. The powder coating is prepared by dry mixing resin powder and aluminum powder. As the aluminum powder, a powder in the form of a scale-like flake is often used.

As aluminum powder, for example, an average particle size of 2
When using a material having a thickness of 8.3 μm and a thickness of 0.7 μm,
Since this aluminum powder has a specific gravity of 1.7 to 1.8 and is in the form of a flake on a scale, once discharged into an open space, it easily floats in the air and hardly sediments. It has the characteristic.

In the powder coating apparatus, a transport unit extends from the upper side to the lower side, and a discharge unit is disposed at a position in the middle of the transport unit. When the object to be coated is sent from the upper side to the lower side of the transport unit in a state of being suspended by the transport unit, powder paint is sprayed from a discharge gun provided in the discharge unit.

[0009] Not all of the powder paint discharged from the discharge gun adheres to the object to be coated, and the powder paint that does not adhere to the object to be coated is collected by the collection unit provided with the suction device. It is provided at one end, and is collected by the collection unit by forming an airflow toward the collection unit in the coating apparatus by suctioning the suction device.

However, as described above, aluminum powder has a large tendency to float in the air, while resin powder exhibits a different floating behavior, in which the tendency is small. for that reason,
The powder coating that has not been applied to the object to be coated flows separately into a flow of the resin powder and a flow of the aluminum powder in the airflow toward the collection unit.

For example, as shown in FIG. 3 (a), even when an airflow toward the collection unit is formed in the coating booth, the aluminum powder is relatively high (high portion) in the entire airflow. ), While
The flow of the resin powder is a flow flowing relatively lower (lower portion) in the entire airflow. Therefore, when the workpiece is transported in the relatively upper portion of the coating booth, the flow of the aluminum powder may overlap with the transport path of the workpiece once powder-coated. In some cases, a phenomenon occurs in which the aluminum powder is re-adhered to an object to be coated that has been subjected to a predetermined coating process.

As a result, the surface of the coating film having the desired properties is formed on the surface of the object to be coated by the predetermined coating process, and the aluminum powder is further adhered to the surface. There has been a problem that the surface of the article to be coated cannot be obtained with the desired properties because the surface is roughened or the coating surface is abnormally roughened. Therefore, the invention according to this application was made for the purpose of solving the above problems.

[0013]

SUMMARY OF THE INVENTION According to one aspect of the present invention, there is provided a method of performing powder coating, comprising the steps of: applying an object to be coated along a transport path extending through a relatively upper portion in a coating booth; It communicates with the transport unit that transports, the discharge unit that discharges the powder coating material to the object to be coated while being transported along the transport path, and the collection port provided in the relatively lower part of the coating booth. A method of performing powder coating by a powder coating apparatus having a collection unit having an air suction device, wherein the coating is performed from an upper side to a lower side along an axis extending in a longitudinal direction of a transport unit. Sending things,
In the coating booth, the powder paint is sprayed from the discharge gun toward the object to be transported by the transport unit, and the air is sucked in by the suction device. It is characterized by forming.

[0014] In the above method, the direction of the airflow formed by the suction device may be substantially perpendicular to the conveying direction.

The invention of a magnesium alloy molded product according to the present application is characterized in that the coating is performed by the above method.

The invention of the powder coating apparatus according to this application is as follows.
In one gist, a transport unit that transports a workpiece along a transport path that extends through the inside of a coating booth, and a discharge that discharges powder paint to the workpiece while being transported along the transport path A powder coating apparatus comprising a unit and a collection unit provided with an air suction device, wherein a discharge unit is arranged on one side around an axis extending in the longitudinal direction of the transport unit, and the other. Is characterized in that a collection unit is arranged on the side of.

In the above powder coating apparatus, a partition intersecting an axis extending in the longitudinal direction of the transport unit is provided between the discharge unit and the collection unit in the coating booth. Has a main opening in a region that does not overlap with the transport unit, and mainly guides the airflow formed in the coating booth to the opening.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, each invention according to the present application will be described with reference to the drawings.

[Embodiment 1] A powder coating apparatus according to the present application and a method for performing powder coating using the powder coating apparatus will be described with reference to FIG. FIG. 1A is a plan view showing a basic configuration of a powder coating apparatus according to the present application, and FIG. 1B is a view showing a cross section thereof.

The powder coating apparatus basically includes a coating booth 7
A transport unit 11 for transporting the workpiece 10 along a transport path 13 extending therethrough, and a discharge unit for discharging powder paint to the workpiece 10 during transport along the transport path 13 It comprises a unit 1 and a recovery unit 6 provided with an air intake device 9.

The painting booth 7 is a booth having a rectangular parallelepiped shape as a basic shape and substantially surrounded by six surfaces. The transport path 13 passes through a relatively upper portion in the coating booth 7 in the longitudinal direction thereof.
Extend through the walls (upper side wall and lower side wall) located at both ends in the longitudinal direction. Both ends of the transport path 13 are supported by support means provided outside the upper side wall and outside the lower side wall of the coating booth 7. The transport path 13 is, specifically, a chain, a cable,
It may be a known means used for transporting articles along a predetermined route, such as a rail. In the embodiment shown in FIG. 1, a chain is used. The transport path 13 which is a chain is driven by a transport motor 14 attached to a support means provided outside the upper side wall.

The article to be coated 10 is a magnesium-based alloy molded article to be subjected to powder coating. The object to be coated 10 is suspended on a transport path 13 by a hanger 12. Therefore, when the transport path 13 is driven by the transport motor 14, the object 10 is transported along the transport path 13 from the upper side to the lower side in the coating booth 7.

A discharge gun 2 is provided at a position on the side of the object to be coated which is being sent along the transport path 13. The discharge gun 2 is supported by a reciprocator 3 arranged outside the powder coating apparatus. Reciprocator 3
Is controlled by control means (not shown) provided outside the powder coating apparatus, so that the discharge gun 2 can be moved in the vertical direction (vertical direction on the paper surface in FIG. 1B). .

The discharge gun 2 is connected by a supply tube 5 to a paint tank 4 arranged outside the powder coating apparatus. Therefore, the powder paint is supplied from the paint tank 4 to the discharge gun 2 through the supply tube 5.

A collection unit 6 is provided on the lower side of the coating booth 7, preferably on the lower side. The recovery unit 6 has a recovery port 8 communicating with an opening provided in a part of the wall of the coating booth 7 and an air intake device 9. The spaces are connected by ducts.

In the embodiment shown in FIG. 1, in the coating booth 7, the discharge unit 1 is disposed relatively upstream, and the recovery unit 6 is disposed relatively downstream.
Between the discharge unit 1 and the recovery unit 6, a partition 16 intersecting an axis extending in the longitudinal direction of the transport unit 11 is provided. Regarding the invention of this application, the axis extending in the longitudinal direction of the transport unit 11 is an axis that is assumed to be an axis along a transport path 13 extending from the upper side to the lower side in the coating booth 7. Therefore, it can be generally considered that the axis extending in the longitudinal direction of the transport unit 11 substantially coincides with the transport path 13. FIG.
In the embodiment shown in FIG. 1, the partition 16 is a wall provided in a direction substantially perpendicular to an axis extending in the longitudinal direction of the transport unit 11.

The partition 16 is not provided over the entire cross section of the coating booth 7, but has a main opening 20 in a region not overlapping with the transport unit 11. In the region to be coated, there are provided a transport path 13 of the transport unit 11 and an opening 15 through which the object 10 suspended on the transport path 13 can pass.

Therefore, when the intake device 9 starts intake,
As shown in FIG. 3B, an airflow is formed from the discharge unit 1 side to the collection unit 6 mainly through the main opening 20 in the coating booth 7. Although part of the airflow can pass through the opening 15, the main opening 20 with respect to the characteristics and the operating conditions of the suction device 9 and the cross-sectional area of the painting booth 7.
By setting the conditions such as the size and shape setting conditions, the cross-sectional area of the workpiece 10 and the transport path 13 and the size and shape setting conditions of the opening 15 to appropriate conditions, the airflow in the coating booth 7 is improved. The main portion can be set so as to pass through the main opening 20.

A method of coating the object 10 made of a magnesium alloy using the powder coating apparatus having such a configuration will be described below. The article to be coated 10 made of a magnesium alloy is an article that has been formed by a thixomolding machine manufactured by Japan Steel Works using AZ91D as a raw material, and has been subjected to secondary processing such as gate cutting and deburring. It is a housing of a television.

Thereafter, a magnesium phosphate coating is formed on the surface of the article 10 through a degreasing treatment, a surface conditioning treatment, and an oxide coating treatment as a base rust prevention treatment. In this way, the pre-treated object 10 is conveyed to the powder coating step.

As described above, the object to be coated 10 is suspended at the predetermined conveying speed from the upper side wall to the lower side wall in the coating booth 7 while being hung on the conveying path 13 by the hanger 12. Sent.

As the powder coating, epoxy resin powder containing 5 to 7% by weight of scale-like aluminum powder was used. This powder paint is supplied from the paint tank 4 to the discharge gun 2 through the supply tube 5, and is discharged from the discharge gun 2 toward the workpiece 10. In this embodiment, a corona discharge gun is used as the discharge gun 2.

The powder coating is applied while moving the discharge gun 2 up and down with respect to the workpiece 10 which is fed from the upper side wall side to the lower side wall side in the coating booth 7, for example, at a conveying speed of 2 m / min. By discharging, even when the object to be coated 10 is an article having a long dimension in the vertical direction (vertical direction of the paper surface in FIG. 1B), the entire surface of the object to be coated 10 on the side of the discharge gun 2 can be applied. Powder coating can be applied.

The object 10 to which the powder coating is applied passes through the opening 15 provided in the partition 16 and is sent to the lower side of the coating booth 7.

In parallel with the step of discharging the powder paint from the discharge gun 2 as described above, the suction device 9 is operated. Main opening 20 mainly from the discharge unit 1 side
, An airflow toward the recovery unit 6 is formed. Therefore, after being discharged from the discharge gun 2,
The aluminum powder that has not adhered to 0 is guided by the above-described airflow from a position around the transport path 13 to the main opening 20 and further guided to the collection unit 6. Therefore, the aluminum powder discharged from the discharge gun 2 and not adhered to the workpiece 10 floats in the coating booth,
It can be effectively prevented from re-adhering to the object to be coated which has already been subjected to the predetermined coating treatment. As a result, a desired smooth painted surface can be obtained from the object 10 to which the predetermined coating has been applied in the powder coating apparatus according to the present invention as described above.

Thereafter, the object to be coated 10 is transferred to a firing furnace,
By performing baking in an atmosphere of 180 to 200 ° C. for about 25 minutes, a coating film in a final form is formed on the surface of the workpiece 10.

[Embodiment 2] Another embodiment of a powder coating apparatus according to the present application and a method of performing powder coating using the powder coating apparatus will be described with reference to FIG.

FIG. 2A is a plan view showing a basic configuration of the powder coating apparatus according to the present application, and FIG. 2B is a view showing a cross section thereof. This powder coating apparatus is called up, down, left, and right, corresponding to the up, down, left, and right directions of the paper surface in FIG.

The basic configuration of the powder coating apparatus of this embodiment is as follows.
Around the axis extending in the longitudinal direction of the transport unit 11,
The configuration is substantially the same as that of the first embodiment except that the discharge unit 1 is arranged on one side and the collection unit 9 is arranged on the other side, and that no partition is used. The same is true. Therefore, the object 10 to be coated is sent through the coating booth 7 by the transport unit 11,
And a discharge gun 2 that moves up and down toward the object 10 to be coated.
The operation relating to the application of the powder paint is the same as in the first embodiment.

In the coating booth 7, the discharge unit 1 is arranged on one side and the collection unit 9 is arranged on the other side, with the axis extending in the longitudinal direction of the transport unit 11 as the center. Accordingly, the discharge unit 1 and the collection unit 6 are provided on a pair of opposed side walls of the coating booth 7, respectively. Further, no partition is provided as in the case of the first embodiment.

In such a configuration, when the suction device 9 starts suction, for example, as shown in FIG.
An airflow is formed toward This airflow is an airflow that flows in a direction crossing the transport path 13. For example, in the embodiment illustrated in FIG. 2, an airflow in a direction substantially orthogonal to the transport path 13 is formed. For example, in the embodiment shown in FIG. 2B, the object to be coated 10 is sent from the back side to the near side of the paper of FIG. The powder paint is discharged toward the object 10. In parallel with this, by operating the suction device 9, an airflow flowing downward from the discharge unit 1 to the collection unit 6 is formed.

Accordingly, the aluminum powder in the powder coating that has not been applied to the object 10 is guided by this air flow and flows downward in the coating booth 7, so that the aluminum powder is discharged from the discharge gun 2 and is discharged. It is possible to effectively prevent the aluminum powder that has not adhered to 10 from floating in the coating booth and re-adhering to the workpiece already subjected to the predetermined coating treatment. As a result, the object 10 to which a predetermined coating is applied in the powder coating apparatus according to the present invention as described above,
A desired smooth painted surface can be obtained.

In the first and second embodiments, the corona discharge gun is used as the discharge gun of the coating machine. Alternatively, a tribo gun may be used. However, since the charging polarity of the powder used differs between the corona discharge gun and the tribo gun, it is necessary to select the powder coating material according to the powder coating material used.

[0044]

According to the invention of the method for performing powder coating according to the present invention, a transport unit for transporting an object to be coated along a transport path extending through a coating booth, and transported along the transport path. A method in which powder coating is performed by a powder coating apparatus having a discharge unit that discharges a powder coating material to an object to be coated on the way and a collection unit having an air suction device, wherein a longitudinal direction of a transport unit is provided. Feeding the workpiece from the upper side to the lower side along an axis extending in the direction, spraying powder paint from a discharge gun toward the workpiece transported by the transport unit in the coating booth, and Adopting the feature that the air flow that flows in the direction intersecting the transport direction of the transport unit in the painting booth is performed in parallel by suctioning by the intake device. Therefore, when the object is conveyed in the relatively upper part of the coating booth, the conveying path of the object once the powder coating has been performed, and the object is discharged from the discharge gun but is applied to the object. It is possible to prevent the air current of the aluminum powder in the uncoated powder coating from overlapping, and to obtain a coated surface having a desired surface condition.

In the above method, when the direction of the air flow formed by the suction device is set to a direction substantially perpendicular to the conveying direction, the object to be coated covers the relatively upper part of the coating booth. When transported, the transport path of the object once coated with the powder and the air current of the aluminum powder in the powder coating discharged from the discharge gun but not applied to the object are over Wrapping can be reliably prevented, and a painted surface having a desired surface condition can be obtained.

The magnesium alloy molded product coated by the above method is subjected to powder coating once, and then discharged from the discharge gun but not coated on the object to be coated. Since the powder is prevented from re-adhering, it is possible to have a painted surface having a desired surface condition.

The invention of the powder coating apparatus according to the present application comprises a transport unit for transporting an object to be coated along a transport path extending through the inside of a coating booth, and a coating unit to be transported along the transport path. A powder coating apparatus comprising: a discharge unit that discharges a powder coating material onto a product; and a collection unit that includes an air suction device. The discharge unit is arranged on the side and the collection unit is arranged on the other side. The flow of the body paint, particularly the flow of the aluminum powder, can be formed so as to flow from the discharge unit to the collection unit. Therefore, when the object is conveyed in the relatively upper part of the coating booth, the conveying path of the object once the powder coating has been performed, and the object is discharged from the discharge gun but is applied to the object. It is possible to reliably prevent the aluminum powder in the unpainted powder coating from overlapping with the airflow, and to obtain a coated surface having a desired surface condition.

In the above powder coating apparatus, a partition intersecting an axis extending in the longitudinal direction of the transport unit is provided between the discharge unit and the collection unit in the coating booth. In the cross section, it has a main opening in a region that does not overlap with the transport unit, and when adopting a configuration in which the airflow formed in the coating booth is mainly guided to the opening, the object to be coated is When transporting the relatively upper part of the painting booth, the transport path of the workpiece once powder coated, and the powder paint discharged from the discharge gun but not applied to the workpiece It is possible to reliably prevent the air flow of the aluminum powder inside from overlapping, and obtain a coated surface having a desired surface condition.

[Brief description of the drawings]

FIG. 1A is a plan view illustrating a basic configuration of a powder coating apparatus according to a first embodiment of the present application, and FIG.
(B) is a figure which shows the cross section.

FIG. 2A is a plan view showing a basic configuration of a powder coating apparatus according to a second embodiment of the present application.
(B) is a figure which shows the cross section.

FIG. 3 (a) shows an airflow in a coating booth in a conventional example, and FIG. 3 (b) shows an airflow in a powder coating apparatus according to the first embodiment of the present application. FIG. 3C shows the flow of the air flow in the powder coating apparatus according to the second embodiment of the present application.

[Explanation of symbols]

1 ... Discharge unit, 2 ... Discharge gun, 3
... reciprocator, 4 ... paint tank, 5 ... supply tube, 6 ... collection unit, 7 ... painting booth, 8 ... collection port, 9 ... suction device,
10: object to be coated, 11: transport unit, 1
2 hanger, 13 transport chain, 14 transport motor, 15 opening, 16 partition.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B05D 3/00 B05D 3/00 C 7/14 7/14 D 7/24 301 7/24 301A F-term ( Reference) 4D075 AA01 AA09 AA25 AA35 AA56 AA60 AA65 AA71 AA76 AD16 BB49Y CA48 DA23 DB01 DC19 EA02 EB33 EC01 EC23 4F034 AA01 BA07 BA36 CA11 CA14 CA21 DA05 DA14 DA17

Claims (6)

[Claims] A conveying unit for conveying an object to be coated along a conveying path extending through a relatively upper portion in a coating booth, and a powder to be applied to the object while being conveyed along the conveying path. Powder coating is performed by a powder coating apparatus having a discharge unit that discharges body paint and a collection unit having an intake device that communicates with a collection port provided at a relatively lower portion of the coating booth. A method for feeding an object to be coated from an upper side to a lower side thereof along an axis extending in a longitudinal direction of a transport unit, a discharge gun toward an object transported by the transport unit in a coating booth. Forming a gas flow flowing from a conveying path to a collection port in a coating booth by spraying a powder coating material from the inside and sucking the powder coating material through a suction device. 2. The method according to claim 1, wherein the direction of the airflow formed by the suction device is substantially perpendicular to the direction of conveyance. 3. A magnesium alloy molded article coated by the method according to claim 1. Description: 4. A conveying unit for conveying an object to be coated along a conveying path extending through a coating booth, and discharging a powder paint to the object to be coated while being conveyed along the conveying path. A powder coating apparatus comprising a discharge unit and a collection unit having an air suction device, wherein the discharge unit is arranged on one side around an axis extending in a longitudinal direction of the transport unit, A powder coating apparatus, wherein a collection unit is provided on the other side. 5. A partition intersecting an axis extending in a longitudinal direction of the transport unit between the discharge unit and the collection unit in the coating booth, wherein the partition is transported in a cross section of the coating booth. The powder coating apparatus according to claim 4, further comprising a main opening in a region not overlapping with the unit, and guiding an airflow formed in the coating booth mainly to the opening. 6. A method for performing powder coating of a magnesium alloy, wherein the powder coating is performed by the powder coating apparatus according to claim 4. Description: