Abstract:
A first source of radiation generates a first radiation to remove a coating from a component. An amount of the first radiation generated by the first source of radiation depends on an amount of power supplied to the first source of radiation. A controller receives feedback regarding removal of the coating from the component by the first radiation and regarding the amount of power supplied to the first source of radiation, and adjusts the amount of power supplied to the first source of radiation based on the feedback. A second source of radiation generates a second radiation capable of detecting whether the coating is encountered again. The controller restarts the first source of radiation to generate the first radiation in response to the coating being detected by the second radiation, and sets the amount of power supplied to the first source of radiation based on the feedback.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present disclosure is a continuation of U.S. patent application Ser. No. 14/352,831 filed on Apr. 18, 2014, which is the National Stage of International Application No. PCT/US2012/61297, filed Oct. 22, 2012, which claims the benefit of U.S. Provisional Patent Application No. 61/549,818 filed on Oct. 21, 2011. The entire disclosures of the applications referenced above are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to a system and method for removing a coating from a substrate using radiation. 
       BACKGROUND 
       [0003]    Aircraft, vehicles, boats, and many other structures have surfaces which are primed, painted, or otherwise covered with coatings. Over time, the coatings may become dull, peel, or need to be removed such that another coating may be applied to the surfaces. 
       SUMMARY 
       [0004]    A removal system is configured for removing a coating from a substrate of a component. A first energy source is configured to be energized at a first power level to direct a first stream electromagnetic radiation onto the component such that the first stream of electromagnetic radiation produces a first property on the component. A second energy source configured to be energized at a second power level to direct a second stream of electromagnetic radiation onto the component such that the second stream of electromagnetic radiation produces a second property on the component. A sensor is configured for detecting the first and second properties produced by the first and second stream of electromagnetic radiation. A controller is operatively connected to the first and second energy sources and the sensor. The controller is configured to receive the detected first and second properties from the sensor and the associated first and second power levels from the respective first and second energy sources. The controller is configured for transmitting an updated first and second power level to at least one of the first and second energy sources in response to the first and second properties received from the sensor and the associated power level received from the first and second energy sources. 
         [0005]    A method of removing a coating from a substrate includes directing a first stream of electromagnetic radiation onto the component from a first energy source. The first energy source is energized at a first power level such that the first stream of electromagnetic radiation causes a first property to be produced on the component. A second stream of electromagnetic radiation is directed onto the component from a second energy source at a second power level such that the second stream of electromagnetic radiation causes a second property to be produced on the component. The second energy source is energized at a second power level such that the second stream of electromagnetic radiation causes a second property to be produced on the component. The first property of the component and the associated first power level of the first energy source are detected. The second property of the component and the associated second power level of the second energy source are detected. At least one of the detected first and second properties and the associated first and second power levels are transmitted to a controller. A determination is made, in the controller whether the coating is disposed on the substrate of the component, based on the detected first and second property. An updated power level is transmitted to at least one of the first and second energy sources. 
         [0006]    The above features and advantages, and other features and advantages, of the present invention are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the invention, as defined in the appended claims, when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic diagrammatic view of a removal system configured for removing a coating from a substrate of a component; 
           [0008]      FIG. 2  is a schematic diagrammatic view of the removal system; 
           [0009]      FIG. 3  is a schematic diagrammatic view of the removal system illustrating two sensors; 
           [0010]      FIG. 4  is a schematic view of the component having multiple layers of coatings disposed on the substrate; and 
           [0011]      FIG. 5  is a schematic graphical illustration of the wavelength and intensity of detected by the sensor of the removal system during multiple passes of a laser across the component. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to the drawings, wherein like reference numbers refer to like components, a removal system configured for removing a coating  12  from a substrate  14  of a component  15  using a first stream of electromagnetic radiation  16   a , is shown at  10  in  FIG. 1 . The removal system  10  includes a first energy source  18 , a sensor  20 , a controller  22 , and an optional display unit  24 . 
         [0013]    Referring to  FIG. 4 , the coating  12  may be one or more layers  25  of different coatings  12  disposed over one another ( FIG. 4 ). More specifically, the layers  25  may include a first layer  25   a  and a second layer  25   b . It should be appreciated, however, that the layers  25  may be any number of layers. The substrate  14  is an underlying material with one or more layers  25  of coating  12  disposed on the top thereof. Additionally, each layer  25  of coating  12  may have a thickness  26  which is not uniform across the substrate  14 . Furthermore, each layer  25  may have thicknesses  26   a ,  26   b ,  26   c ,  26   d  which are different for each layer  25  across the substrate  14 . The coating  12  may be any type of layer  25  which is attached to the substrate  14  or attached to another layer  25 . The coating  12  may include, but should not be limited to, a cured film formed from a coating composition, barnacles, rust, lead, and the like. The coating composition may include, but should not be limited to, paint, primer, varnish, shellac, lacquer, and the like. 
         [0014]    The first stream of electromagnetic radiation  16   a  may be may be an energy stream of heat and/or light. The first stream of electromagnetic radiation  16   a  may be a laser  16   a . The laser  16   a  may be a fiber neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, a CO2 laser, and the like, which are of sufficient power to remove the coating  12  from the substrate  14  of the component  15 . Removal of the coating  12  may include, but should not be limited to, removal of the coating  12  using thermo mechanical stress induced dislocations, physical ablation, burning, and decomposition of the coating. Physical ablation may include the removal of the coating  12  using vaporization, chipping, and/or other erosive processes. 
         [0015]    Referring again to  FIG. 1 , the sensor  20  and the first energy source  18  are operatively connected to the controller  22 . The sensor  20  is a device which converts a sensed first property  21   a  into a numerable representation. By way of a non-limiting example, the intensity of an electromagnetic source may be represented by numbers ranging from 0 to 100. The sensor  20  may be an optical sensor  20 , such as a wide-wavelength sensor  20 . The sensor  20  may be a spectrum analyzer, and the like. The first energy source  18  is configured for directing the laser  16   a  at a power level which is based on input  32  received from the controller  22 . The controller  22  is a closed loop process controller  22  which is configured for receiving input  28  from the sensor  20  and input  30  from the energy source and providing a signal or input  32  to the energy source  18  to control the power emitted by the laser  16   a , based on these inputs. The sensor  20  may be integrated within a scanning head, which continually scans the component  15  to provide closed loop control of the power level of the laser  16   a  during the coating  12  removal process. Scanning is a systematic process by which a source of the first stream of electromagnetic radiation  16   a  is passed over the surface  17  of the component  15  from which the coating  12  is being removed. This process may include moving the component  15  relative to the source of first stream of electromagnetic radiation  16   a , moving the source of the electromagnetic radiation  16   a  relative to the component  15  directing the beam of electromagnetic radiation  16   a  at a particular portion of the component  15 , and/or providing a beam of electromagnetic radiation  16   a  sufficiently large to encompass the entirety of the component  15 . 
         [0016]    The laser  16   a  is directed to an area of the component  15  which includes the substrate  14  having the coating  12  disposed thereon. Since the coating  12  may have a variable thickness  26   a ,  26   b ,  26   c ,  26   d  over the entire substrate  14  the amount of electromagnetic radiation directed at the component  15  may need to be varied, based on the thickness  26   a ,  26   b ,  26   c ,  26   d  of the coating  12 . When the laser  16   a  is directed at the component  15 , the ablation of the coating  12  produces measurable levels of light (intensity and wavelength), with properties  34  which provide a significant indication of what material the laser  16   a  is impinging upon. Therefore, the sensor  20  is configured to detect a first property  21   a  of the coating  12  where the first stream of electromagnetic radiation  16   a  is being applied. The first property  21   a  may be in the form of a spectral visible and/or invisible radiation. The detected first property  21   a , along with the power level output provided by the first energy source  18 , is transmitted to the controller  22 . The controller  22  analyzes the detected first property  21   a  and transmits the signal  32  to the first energy source  18  to continue removal of the coating  12  from the substrate  14 . If the first property  21   a  transmitted to the controller  22  is consistent with the coating  12  having been fully removed in the area, a signal is sent to the first energy source  18  from the controller  22  to cease removal of the coating  12 . This prevents the electromagnetic radiation  16   a  from penetrating beyond the layer  25  to be removed, and into the substrate  14  or other intermediate layers  25 . This also allows enough precision to remove only the layers  25  desired, while leaving other layers  25  untouched by the laser  16   a.    
         [0017]    The first property  21   a  sensed by the sensor  20  may include any first property  21   a  produced by the application of the first stream of electromagnetic radiation  16   a  which can be measured, either in absolute terms or relative to a baseline value, include, but not limited to, power, phase angle, wavelength, and polarization state of the component  15 . More specifically, one or more sensed properties  34  may be indicative of a layer  25  of a specific type of coating  12  or indicative of the substrate  14 . As the sensor  20  is scanned over the component  15  and the electromagnetic radiation  16   a  is directed onto the layer  25 , the sensor  20  measures one or more sensed properties  34 , as depicted in  FIG. 5 . A change  36  in one or more sensed properties  34  is indicative of a difference in the surface  17  of the component  15 . By way of a non-limiting example, an increased value for certain sensed properties  34  may indicate the present of a layer  25  on the substrate  14 , whereas, a lack of an increased value for certain sensed properties  34  is indicative of the substrate  14 . Referring specifically to the example shown in  FIG. 5 , a spike  36  in the light intensity is indicative of the presence of a layer  25  on the substrate  14 , whereas, no spike  36  or very little spike  36  is indicative of the substrate  14 .  FIG. 5  further illustrates the properties  34  of the component  15  as the laser  16   a  is passed over the same component  15  fourteen times, i.e., Pass  1  through Pass  14 . The varying peak intensities and wavelengths are indicative of different types of coatings  12  and/or the presence of only the substrate  14 . By way of a non-limiting example, Pass  1  is shown as having a peak intensity of approximately 12500 at approximately 589 nm, Pass  14  is shown as having a peak intensity of approximately 250 at approximately 589 nm. The values associated with Pass  1  are equivalent to the removal of a top coat layer  25 , whereas the values associated with Pass  14  are equivalent to only the presence of the substrate  14 . It should be appreciated that these values may vary based on the type of coating  12 , substrate  14 , and/or power level provided by the first energy source  18 . It should also be appreciated that the number of passes required to remove the coating may range from one to as many as desired. 
         [0018]    The power of the laser  16   a  being directed to the component  15  from the power source ranges from no power to that power level necessary to achieve coating removal and in certain embodiments typically may range between 3 kW and 6 kW. More specifically, the power source may direct the laser  16   a  at 3kW of power when the substrate  14  is detected by the sensor  20 , in order to protect the substrate  14 , and direct the laser  16   a  at 6 kW of power when the presence of a layer  25  is indicated, in order to remove the layer  25 . Additionally, if it is desired to remove only layer  25   a  of the coating  12 , and leave a layer  25   b  of a coating  12  beneath the layer  25   a  untouched by the laser  16   a , when the sensor  20  detects the intensity associated with layer  25   b , the energy source  18  may be directed by the controller  22  to reduce the power to 3 kW to prevent removal of the layer  25   b  by the laser  16   a . It should be appreciated that other levels of power may also be used such that the layers  25  are removed and not removed from the substrate  14 , as desired. The adjustment of the power of the laser  16   a  may be continuously adjusted based on the continued feedback the controller  22  received from the sensor  20 . Therefore, more accuracy and control may be achieved through increased sampling rates of the properties  34 . 
         [0019]    Additionally, referring to  FIG. 2 , chip-level light sensors  20  may be used, which are sensitive to a narrow range of wavelengths near a particular wavelength of interest. This sensitivity could be further refined by using an optical filter. These sensors  20   a ,  20   b , with proper biasing, would convert the light level first property  21   a  into an analog voltage or current output. This analog signal would be monitored through a high speed microcontroller  38 . The microcontroller  38  would provide an appropriate operator interface to enable setting of appropriate threshold levels. Then, signal levels rise above the threshold, the power of the laser  16   a  provided from the first energy source  18  would be raised to a maximum level, e.g., 6 kW, and when the signal levels drop below the threshold, the power of the laser  16   a  provided from the first energy source  18  would be dropped to the minimum level, e.g., 3 kW. Dropping the power level to the minimum level will produce significant benefits in terms of avoided substrate  14  damage. Other methods to further reduce unnecessary laser  16   a  application are possible, including shorted “sampling” of laser  16   a  pulses emitted periodically to determine the condition of the surface  17  of the component  15 . Referring to  FIG. 3 , a plurality of sensors  20   a ,  20   b  may also be used. 
         [0020]    The display unit  24  may be configured to provide information to the user as to the state of the removal system  10 . More specifically, the display unit  24  may display the power level of the laser  16   a  being output from the first energy source  18 , the properties  24  being sensed by the sensor, and the like. 
         [0021]    In certain circumstances, dependent on the configuration of the type of coating  12  and substrate  14  configuration, it may be necessary to remove the laser  16   a  of the first energy source  18  once a selected coating  12  has been removed. In order to facilitate initiation of the selected coating removal process when an area of selected coating on the component  15  is again encountered, a second energy source  19  of stimulation may be activated. This second energy source  19  may direct a second laser  16   b , which directs energy, such as a second stream of electromagnetic radiation  16   b , at a second power level, different from the power level of the first energy source  18 , to provide a unique wavelength to provide stimulation to detect a second property  21   b . The ability to detect the second property  21   b  provides a distinct and detectable response difference between the selected coating  12  and the substrate  14 . The sensor(s)  20  compare the responses to these coatings  12  and, when the selected coating  12  is once again encountered, the laser  16   a  energy of the first energy source  18  is re-initiated and the proper energy level is set in response to the sensors  20 . 
         [0022]    The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims.