The present disclosure concerns systems and methods for automatic spray coating of large workpieces, and in particular robotically applied sprayed coatings of large workpieces.
Some examples of large artifacts that can require painting or other material coating include aircraft wings, aircraft fuselages, aircraft engine blades, wind-turbine blades, wind-tower shafts, artifacts concerning space and defense industries such rocket and missile bodies, commercial and transportation truck bodies, rail vehicles and boats.
The surfaces of such artifacts that require coating can include surfaces that have complex features including but not limited to 3-dimensional surface shapes, uneven adjacent surfaces, tapered or wedge shapes and other shapes. Such large and complex surfaces can require coating or painting with several layers of material. Further, successive coats can be of the same or different materials, and can have varying thicknesses.
Due to the characteristics of some coatings, proper application of certain coats should be performed when the underlying coating is still sufficiently wet. For example, this is required when bonding between layers occurs only when the underlying coat is sufficiently wet upon application of the subsequent overlying coat. Unless such application is made while the underlying surface is sufficiently wet, the quality of the overall coating is diminished.
A system and method of coating a workpiece is disclosed. A controller is in electronic communication with a robotic manipulator having a coating dispenser. A layer of coating is applied to a surface of the workpiece by the robot. A wet-surface time is determined corresponding to the areas of the surface upon which the layer of coating is applied. A second layer of coating is automatically applied prior to the expiration of the wet-surface time of the first layer. The layers of coating in adjacent segments can be applied in an overlapping manner within the boundary regions of the segments.
In the accompanying drawings, structures and methods are illustrated that, together with the detailed description provided below, describe aspects of a system and method for coating large and complex artifacts. It will be noted that a single component may be designed as multiple components or that multiple components may be designed as a single component.
Further, in the accompanying drawings and description that follow, like parts are indicated throughout the drawings and written description with the same reference numerals, respectively. The figures are not drawn to scale and the proportions of certain parts have been exaggerated for convenience of illustration.
Various forms of coatings can be applied to workpieces according to the present teachings, including epoxy-based or urethane-based primers and paints, examples of which are coatings qualified under the SAE standard AMS 3095. Other examples of coatings that can be implemented according to the present teachings are automotive and industrial paints and primers, coatings on which additional layers are applied while still sufficiently wet and coatings applied on a base layer that is sufficiently wet.
The workpiece 104 has several surfaces that can require coating, such as the surfaces of the upper skin panel 110, lower skin panel 112, the front spar 114 and rear spar 116.
Robots 118a,b are disposed within the booth 102 and are secured to arms 120a,b that extend from towers 122a,b. Two articulated robots 118a,b are illustrated in
The combination of the range of motion of the robots 118a,b, the vertically moveable arms 120a,b and the rotatable, moveable towers 122a,b allow the system 100 to position the coating dispensers 128a,b in all of the positions required to completely coat the surfaces of workpiece 104. Such coatings can include primer coats, top coat, clear coats or other forms of coatings. According to other aspects of the present teachings, the robots 118a,b can be fitted with finishing tooling. For example, in lieu of having coating dispensers 128a,b mounted to the robots 118a,b, the robots 118a,b can instead be fitted with a sander, pressure washer fitting or other tooling that can be required to prepare the workpiece 104 surfaces for coating or painting.
Controllers 146a,b are in electrical communication with robots 118a,b through physical connections 148a,b. While physical connections are shown, wireless connections can also be implemented according to the present disclosure. The controllers 146a,b can include, for example, a central processing unit that executes computer-readable instructions stored on a non-transient medium and a power supply for the individual robots 118a,b and their corresponding dispensers 128a,b. According to other aspects of the present teachings, the illustrated robots 118a,b can be connected to a single controller that provides the functionality of the two individual controllers 146a,b illustrated in
With reference to
According to one aspect of the present teachings, one or more robots such as robots 118a,b can be implemented to apply layers of coating on the workpiece. Where one robot 118 is utilized, multiple different layers of material can be deposited on the workpiece 104 by switching the coating provided by a dispenser such as dispensers 128. Where multiple robots 118 are implemented, any particular layer within a surface area of the workpiece 104 surface can be applied by any of the multiple robots 118 with access to the surface area and able to apply the necessary coatings at the required time. According to one aspect of the present teachings, one of the robots 118a,b can apply a complete layer of coating over one or more of the segments 350. According to still other aspects of the present teachings two or more robots 118a,b apply a complete layer of coating over one or more of the segments 350. Under certain circumstances, one or more robots 118a,b can reach the entirety of a particular segment 350, allowing for flexibility in determining which robots 118a,b will be assigned to apply the particular layers of coatings of the particular segments 350.
The selection of the shape and size of the segments 350 is also based in part on the amount of time required for one or more of the layers of coating to dry. In particular, the size and shape of the segments 350 can be selected such that the robots 118a,b and associated coating dispensers 128a,b can complete an application of a layer of coating within a segment 350 before any of the portions of the particular layer within the segment 350 dry such that a required wet-surface is not maintained in the segment 350. The duration from the point in time at which coating is first applied to a portion of the surface to the point in time at which the coating at that portion is too dry to apply a desired subsequent coat can be denoted as the wet-surface time duration or TWET. Such a parameter can depend upon, for example, the chemical composition of the layer of coating, the ambient temperature, atmospheric pressure and humidity, the temperature of the workpiece, the thickness of the layer of coating and other factors.
The speed at which the applicators can apply coating will depend on the shape of the surface. The presence of, for example, pylons 340, flap track fairings 342, 343 or other contours can affect the duration of time required to completely coat a segment 350 of the workpiece 104. For segments 350 of the workpiece 104 that have such relatively complex three-dimensional shapes, the parameters under which coating is applied can change, such as the flow rate of coating material, the spray pattern and the speed of motion of the dispensing robot 118. As just one example, when a complex surface is encountered, the flow rate of coating material from the dispenser 128 can decrease, the spray pattern shape can be narrowed so to cover less area per unit time and the rate of translational movement of the dispenser 128 relative to the segment 350 can decrease to ensure sufficient coating thickness is achieved. Other parameters can affect the speed, and therefore the time required to apply one or more layers of coating. Such parameters include but are not limited to the required coating thickness and the rate of flow of coating material from the dispenser 128.
As shown in
According to one aspect of the present teachings, one or more robots 118 can be implemented to apply layers of coating such as those shown in
With further reference to
As shown in
With reference to
The controller 146a is connected to robot 118a through electrical connection 148a, such as one or more cables. A robot interface 612 manages communication between the robot 118a and controller 146a, transmitting electrical signals and optionally operating power to the robot 118a. According to one aspect of the present teachings, upon execution of the instructions 603 stored on at least one of the RAM 604 or storage 606 by the CPU 602, the CPU 602 provides signals to the robot interface 612 through the bus 614 that cause to the robot interface 612 to communicate signals to the robot 118a though connection 148a. The signals provided by robot interface 612 in turn cause the robot 118a to move and dispense coating as directed by the CPU 602. The robot interface 612 can, for example, cause the robot 118a to move to a particular position or move with a particular velocity along a determined path. According to one aspect of the present teachings, the controller 146a can cause the robot 118a having a coating dispenser 128a as shown in
A user input/output (I/O) 616 such as a keyboard or remote control can be used to input instructions 603 into controller 146a. The user I/O 616 communicates with the user I/O interface 618 through connection 620. The user I/O 616 can be used to input instructions 603 into the controller 146a. According to one aspect of the present teachings, the user I/O 616 can be used to input a travel path, which can be defined by the coordinates Φk, where k=1 to 6 accounting for the 6 degrees of freedom, that will be followed by the robots 118a,b during the coating process, a speed and coating flow rate along the path Φk, k=1 to 6, and storing the path, speed and flow rate to at least one of the RAM 604 or storage 606. According to another aspect of the present teachings, the RAM 604 or storage 606 can have instruction 603 written upon them to execute coating processes described herein with regard to
Several coating process parameters can be stored in the controller, and can be adjusted by, for example, accessing the user I/O 616. Such parameters include but are not limited to robot speed, the overall path of the robot and orientation of the dispenser relative to the workpiece surface, paint or coating material flow rate, coating spray pattern and shape, level of electrical potential between applicator and workpiece and blending constraints.
A network interface 608 permits connection between controller 146a and a network 610 through physical connection 621a, such as an Ethernet connection. It should be noted that wireless connections can also be implemented instead of or in addition to physical connection 621a. Additional controller 146b is also connected to the network 610 though connections 621b allowing the controllers 146a,b to be in communication and further allowing the controllers 146a,b to synchronize the actions of robots 118a,b during application of coating on a workpiece 104. It should be noted that the aspects of controllers 146a,b described herein can be distributed, such as by providing computing resources and memory through a computer workstation, and providing the robot interface within a separate unit that communicates with the workstation through a communication linkage such as a wireless connection or suitable cabling.
The method 700 shown in
In step 706 the three-dimensional structures of the workpiece 104, such as when the surface of the workpiece 104 transitions from a flat surface to a protrusion such as pylons 340, flap track fairings 342, 343 or other contours shown in
Segments 350 can also be chosen based in part on other parameters that can differ between adjacent coated surfaces of the workpiece 104, such as occurs when the drying times of a particular layer between two adjacent surfaces differs, even if the complete sequence of coating layers is otherwise identical in its composition and thickness. In step 708, the contiguous areas are further divided into areas based on the time required to complete application of at least one of the layers of coating over the particular area and the required wet-surface time duration TWET. If the calculated time required to complete a segment 350 is greater than the calculated wet-surface time duration for any portion of the segment 350, the segment 350 can be changed (e.g., reduced in size) to reduce the time required to complete the layer within the segment 350 to be less than the wet-surface time.
A determination of the wet-surface time duration for a layer of coating can be calculated based on one or more of the chemical composition of the layer of coating, the ambient temperature, atmospheric pressure and humidity, the temperature of the workpiece, the thickness of the layer of coating and other factors. Wet-surface time durations can also be predetermined values for ranges of various coating layer characteristics such as thickness and atmospheric conditions.
According to one aspect of the present teachings, the wet-surface time can be calculated based on a characteristic drying time. Such a predetermined characteristic drying time can reflect the drying time for a coating over a range of layer thicknesses and atmospheric conditions. Within those ranges, the wet-surface time can simply be the characteristic drying time. Such a time value can be adjusted when the variables on which the drying time of a surface depends vary greatly from the range of values for which the wet-surface time is the characteristic time. As one example, if the coating process takes place at high altitude where pressure is much lower than the range over which the characteristic drying time is applicable, the wet-surface time can be determined by subtracting a predetermined amount of time from the characteristic time. The amount of time subtracted in turn depends on the amount by which the pressure varies from the normal pressure range. Similar application can be made with other parameters, such as temperature, layer thickness and others parameters. TWET can also be determined by a computer processor such as processor 602 calculating the wet-surface time based on TWET written as a numerical function dependent on one or more of the parameters referred to herein, such as ambient temperature, atmospheric pressure and humidity, the temperature of the workpiece, the thickness of the layer of coating and other factors.
By determining the wet-surface time duration TWET for a location on the workpiece 104 on which a layer of coating is applied and the time at which that layer was applied at the location, the point in time at which the wet-surface time TWET will expire for that location can be calculated. By determining this point in time, a robot 118 can be positioned in sufficient time to begin to apply the second layer atop the first layer before the first layer becomes excessively dry.
With reference to
With continued reference to
The controller 146a can track the time at which a layer of coating is applied over a particular portion of the workpiece surface 802, and the wet-surface time for the portions if the surface 802. For example, the controller 146a can record such information in real-time on a non-transient computer-readable medium. According to one aspect of the present teachings, the controller 146a tracks the duration of time coating has been applied over part or all of the workpiece surface 802. Such a surface can include a subsection of a workpiece 104 such as the segments 350 chosen in process 700 described herein in connection with
According to another aspect of the present teachings, the controller 146a also determines the time required to prepare the robot 118a to apply a second or subsequent layer of coating. Such a time interval can be incorporated into the calculation of when to begin instructing the robot 118a to apply the second layer of coating. Such time can include but is not limited to the time required to move robot 118a into the desired position from its current position and the time required to switch the coating being applied by the robot 118a, if necessary. With reference to
According to another aspect of the present teachings, multiple robots such as robot 118a can be implemented so that when a wet-surface time duration is elapsing for a particular portion of a workpiece surface 802 before the first layer is completely applied, a second robot 118b can begin to apply a second layer of coating while the first robot 118a is completing the first layer of coating. In this way, the first robot 118a need not interrupt the application of the first layer of coating in order for the second layer of coating to be applied while a wet-surface is present.
With reference to
In recording the locations on the workpiece where the first layer of coating is applied to the workpiece in step 908 or recording wet-surface times and corresponding locations in step 910, the location can be recorded as the position along the travel path of the coating dispenser, such as path 804 referred to herein and in connection with
With continued reference to
The method 900 can be performed with one or more robotic coating dispensers 128. When a single robot 118a is implemented according to the present teachings, the robot 118a applies the first layer of coating until the first layer is completed or TELAPSED+ΔT=TWET. At such a point in time, the robot 118a can cease applying the first layer and start to apply the second layer of coating once in position to do so. The inclusion of ΔT in the comparison of the wet-surface time and the elapsed time allows the robot 118a to begin applying the second layer of coating prior to the wet-surface time being reached. According to one aspect of the present teachings, the robot 118a can apply the second layer of coating by following the same path as followed while applying the first layer of coating, starting at the location where the first layer of coating was first applied. According to another aspect of the present teachings, the location on the workpiece 104 surface at which the robot 118a ceased to apply the first coat is recorded, allowing the robot 118a to continue applying the first layer of coating at a later time.
Where a second robotic coating dispenser 128b is available to paint the particular subsection, the second robotic dispenser 128b can start applying the second coating over the first coating without interrupting the first robot 118a in its application of the first layer of coating. Thus, at the point in time where TELAPSED+ΔT=TWET, the second robot 118b will proceed to apply the second coat once in position to do so. Alternatively, the first robot 118a can return to the start of the segment and begin applying the second layer of coating, and the second robot 118b can continue the application the first coating where the first robot left off. In another aspect of the present teachings, more than two robots 118 having coating dispensers 128 can be implemented. For example, a first robot 118 can apply a first layer of coating, a second robot 118 can apply a second layer of coating over the first, and a third robot 118 can continue to apply the first coat from where the first robot 118 left off. In yet another aspect of the present teachings, where a segment 350 requires a first and second layer of coating applied over one another such that the first layer of coating is still sufficiently wet during the application of the second layer of coating, the controller 146 can determine which robots 118 can access the area to apply a first coating, determine which robots 118 can access the area to apply a second coating, select a robot to apply the first coating from the from the first list of robots 118 and select a robot 118 to apply the second coating from the second list of robots 118.
Although the finishing operations can be performed automatically according to the present teachings, some finishing operations can be performed by human operators. As one example, human operators can override the automated coating process and control the coating dispensing robots directly. Such intervention can be necessary under circumstances, for example, where the coating dispensing robots malfunction, or where the workpiece has uncommonly intricate surfaces requiring coating.
According to yet other aspects of the present teachings, sensors are implemented that can detect the level of wetness of a particular portion of a coated surface of a workpiece 104. Such detection can be performed with infrared or other spectroscopic sensors, for example such as can be mounted to a robot 118. Such sensors can be used to detect the level of wetness of a layer of coating, particularly the uppermost layer on a portion of the workpiece 104, by detecting the spectrum emitted by the layer of coating and comparing such a spectrum with the known spectrum of the particular coating at various levels of wetness.
According to other aspects of the present teachings, the system includes detection equipment that can determine the shape of the workpiece 104. Such rendering can be performed by cameras positioned within the painting booth 102 or by cameras mounted on the robot 118 and used with, for example, image processing software that renders three-dimensional shapes based on color, level of reflection or refraction and boundary detection.
For the purposes of this disclosure and unless otherwise specified, “a” or “an” means “one or more.” To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” As used herein, “about” will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term. From about A to B is intended to mean from about A to about B, where A and B are the specified values.
While the present disclosure illustrates various embodiments, and while these embodiments have been described in some detail, it is not the intention of the applicant to restrict or in any way limit the scope of the claimed invention to such detail. Additional advantages and modifications will be apparent to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's claimed invention. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.
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