Patent Application
20250236090
The present disclosure relates generally to the field of material coatings, and more specifically to the removal of material coatings from a solid surface.
Removal of material coatings, such as exterior decorative and non-decorative finishes, is a common practice as part of maintenance, repair, and overhaul (MRO) activities for objects that are coated with such material coatings, such as a building or a vehicle—e.g., an aircraft. When an object is out of service for MRO activities, the loss of revenue or operational readiness is significant. Thus, MRO technicians are motivated to remove such material coatings as part of MRO activities quickly in order to return the object back to operation.
Conventional techniques for removing material coatings have various issues. As one example, material coatings can be removed from an object via abrasion or sanding. Conventional hand sanding lacks sufficient control to avoid causing damage to an underlying substrate of the object. When sanding is performed by hand, the process is slow and presents ergonomic challenges for operators. Moreover, operators need to wear a significant amount of personal-protection equipment (PPE) to protect themselves from abrasive dust and/or other material particles produced during sanding, which adds to the cost of conventional sanding.
As another example, material coatings can be removed from an object via chemical stripping. Conventional chemical stripping requires a long dwell time for the chemicals to effectively strip a material coating from a surface of an object. Further, conventional chemical stripping generates a significant amount of hazardous waste that has to be handled and disposed of with carefully controlled processes, which increases the cost of conventional chemical stripping. Also, operators need to wear a significant amount of PPE to protect themselves from the hazardous stripping chemicals and the chemical waste that is generated from conventional chemical stripping. Alternatively, to avoid some of the issues related to handling the conventional stripping chemicals, environmentally sustainable strippers can be used instead. However, such environmentally sustainable strippers have even longer dwell times than the conventional stripping chemicals.
As yet another example, material coatings can be removed from an object via top-down laser material removal. Top-down laser material removal is performed by setting a focal point of a laser to a surface of the topmost material layer. Using current laser technology, each layer is removed 25-50 micrometers at a time with each pass of the laser. Laser material removal requires the laser to make several passes over the same area to remove the material layer by layer until an underlying substrate is exposed. Since the laser requires multiple passes to remove all of the layers, top-down laser material removal is still time consuming even if it offers additional benefits relative to conventional sanding and chemical stripping. Removal of more material on a per pass basis is possible via top-down laser material removal in order to speed up the overall process. For example, the laser power can be increased and/or the depth of the focal point of the laser can be increased in order to remove more of the material with each pass. However, these adjustments in the operating parameters of the laser can cause the laser to damage the underlying substrate during top-down laser material removal. Moreover, in some scenarios, the parameters of the laser may not be adjustable.
Examples are disclosed that relate to a material-coating system having properties that are tuned for fast removal via laser ablation. In one example, the material-coating system includes a substrate, a laser-ablation layer deposited on the substrate, and a topcoat layer deposited on top of the laser-ablation layer. The topcoat layer is at least partially transparent to laser light in a designated wavelength. The laser-ablation layer is tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the laser-ablation layer causes the laser-ablation layer and the topcoat layer to collectively de-bond from the substrate.
The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.
Conventional techniques for removing material coatings from an object have various issues. For example, conventional sanding and chemical stripping are slow, tedious, and costly and require operators that perform these processes to wear a significant amount of personal protection equipment (PPE). Top-down laser material removal provides several benefits relative to conventional sanding and chemical stripping. However, top-down laser material removal is still relatively slow and tedious.
Laser ablation is a technology that is becoming more prominent in industrial hygiene and sustainability applications, and more particularly, is being used to remove material coatings from a solid surface. Laser ablation is a process in which a laser generates a highly focused and intense beam of light that is directed onto the surface of the material to be ablated. The material absorbs the laser energy, and this absorption causes the material to undergo various physical and chemical changes. The absorbed laser energy can lead to different processes depending on the laser parameters and the material. These processes may include heating, melting, vaporization, and ionization of the material. As a result of the absorbed energy, the material is either vaporized directly into a plume of particles or undergoes a phase change, such as melting or sublimation. When the material undergoes the phase change, the material becomes de-bonded from the interface of interest. Laser ablation offers a high degree of control and precision. The characteristics of laser light emitted by the laser, such as its intensity and duration, can be carefully adjusted to achieve the desired material removal or modification with minimal damage to the surrounding areas. Laser ablation avoids the issues of conventional sanding and chemical stripping by being faster and less tedious than manual sanding and being faster than the dwell time required for chemical stripping. Moreover, laser ablation produces less waste material relative to conventional sanding and chemical stripping. Furthermore, although top-down laser material removal offers additional benefits relative to conventional sanding and chemical stripping, top-down laser material removal is still time consuming, because the laser requires multiple passes to remove all layers of material from an interface of interest.
Accordingly, there is a desire to remove material coating from an object in a manner that is faster than other conventional approaches while still protecting the underlying substrate of the object when removing material coatings from the substrate. Thus, examples are disclosed that relate to a material-coating system having properties that are tuned for fast removal via laser ablation. In one example, the material-coating system includes a substrate, a laser-ablation layer deposited on the substrate, and a topcoat layer deposited on top of the laser-ablation layer. The topcoat layer is at least partially transparent to laser light in a designated wavelength. The laser-ablation layer is tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the laser-ablation layer causes the laser-ablation layer and the topcoat layer to collectively de-bond from the substrate.
Since the laser-ablation layer is positioned underneath at least the topcoat layer (and one or more additional intermediate layers in some embodiments), when the laser-ablation layer absorbs the energy from the laser in the designated wavelength and becomes de-bonded, the topcoat layer (and any intermediate layer(s)) also become separated from the underlying substrate. In this way, multiple layers of the material-coating system can be removed from the substrate with each pass of the laser. This allows for layers of the material-coating system to be removed at a rate that is at least two to three times faster than top-down laser material removal. Moreover, the material-coating system still benefits from the other advantages of laser ablation relative to conventional sanding and chemical stripping. For example, time, cost, and labor associated with PPE required for conventional sanding and chemical stripping as well as disposal of hazardous waste could be reduced or eliminated by using the laser-based material-coating system.
In the illustrated example, the external surface 102 of the aircraft 100 is coated with a material-coating system 200. The material-coating system 200 is configured to be removed from the external surface 102 quicker and easier than other conventional approaches. In particular, the material-coating system 200 includes a laser-ablation layer 204 (shown in
The laser 104 can be configured to perform any suitable removal operations/routing to apply laser light to the material-coating system 200 in order to remove layers of the material-coating system 200 from the aircraft 100. In one example, the laser 104 performs a scanning removal routine in which the laser 104 scans back and forth across a region 108 of the aircraft 100 to apply laser light to the region 108. Further, the laser 104 can make multiple passes over the same region 108 as part of the scanning routine to ensure that the laser-ablation layer 204 absorbs enough energy from the laser light 106 to de-bond from the substrate 202.
In some embodiments, the laser 104 can be controlled in an automated fashion. For example, the laser 104 can be included in a robotic system that automatically performs laser ablation across the external surface 102 of the aircraft. In other embodiments, the laser 104 can be controlled manually by a human operator. The laser 104 can take any suitable form.
The laser-ablation layer 204 may be tuned to absorb energy from laser light in any suitable wavelength or wavelength range. In some examples, the laser 104 can be configured to emit infrared light or near-infrared light (e.g., at a wavelength of ˜1064 nanometers). As one example, a fiber laser may be employed for removing layers of the material-coating system 200. The fiber laser uses an ytterbium fiber as a lasing material. The fiber laser is highly efficient and easily serviced in the field. In other examples, the material-coating system 200 may be tuned for use with a different type of laser that emits laser light in a different wavelength, such as an excimer laser, a CO2 laser, a fiber laser, or another type of laser that emits laser light in a different wavelength. The choice of laser depends on the specific needs of the application, such as the material properties, the required precision, the desired depth of ablation, and the allowable thermal effects on the surrounding material. The appropriate laser may be selected to optimize the efficiency and effectiveness of laser ablation for MRO activities performed on the aircraft 100.
The laser-ablation layer 204 is deposited on top of the substrate 202 in the material-coating system 200. The topcoat layer 206 is deposited on top of the laser-ablation layer 204. The topcoat layer 206 is at least partially transparent to laser light in a designated wavelength to allow the laser light in the designated wavelength to pass through the topcoat layer 206 to the laser-ablation layer 204. The designated wavelength refers to the wavelength of laser light emitted from a laser and applied to the material-coating system 200 during laser ablation to remove layers of the material-coating system 200 from the substrate 202.
In some embodiments, the topcoat layer 206 can be totally transparent to laser light in the designated wavelength. For example, the topcoat layer 206 can be a visually transparent clear coat that is applied as a protective finish to protect the underlying layers of the material-coating system 200 from environmental exposure.
In some embodiments, the topcoat layer 206 can be partially transparent to laser light in the designated wavelength such that at least some laser light passes through the topcoat layer 206 to the laser-ablation layer 204. For example, the topcoat layer 206 can include some amount of pigment that absorbs some amount of the laser light while still allowing some amount of the laser light to pass through the topcoat layer 206 to the laser-ablation layer 204. In some embodiments, the topcoat layer 206 is a visually opaque paint layer.
In some embodiments, the topcoat layer 206 can be at least partially transparent to light in other wavelengths besides the designated wavelength. In embodiments, the topcoat layer 206 can absorb at least some light in other wavelengths besides the designated wavelength.
In some embodiments, a plurality of topcoat layers 206, 206′, 206″ can be deposited on top of the laser-ablation layer 204. Each of the plurality of topcoat layers 206, 206′, 206″ is at least partially transparent to laser light in the designated wavelength to allow the laser light in the designated wavelength to pass through the plurality of topcoat layers 206, 206′, 206″ to the laser-ablation layer 204. As one example, different topcoat layers of the plurality of topcoat layers 206, 206′, 206″ include different color pigments that make up a color scheme or specific design of the livery of the aircraft 100 shown in
The laser-ablation layer 204 is tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the laser-ablation layer 204 causes the laser-ablation layer 204 and the topcoat layer 206 (and topcoat layers 206′, 206″ when included) to collectively de-bond from the substrate 202. In this way, multiple layers of the material-coating system 200 can be removed from the substrate 202 on a per pass basis when the laser emits laser light on the material-coating system 200.
The laser-ablation layer 204 may be tuned to absorb the laser light in the designated wavelength in any suitable manner. In some embodiments, the laser-ablation layer 204 may be selected or formulated to have material properties that absorb the laser light in the designated wavelength.
In some other embodiments, the laser-ablation layer 204 is doped with an additive material that is tuned to absorb laser light in the designated wavelength.
The additive material 304 can include any suitable type of material that is tuned to absorb the laser light in the designated wavelength. In some embodiments, the additive material 304 comprises nano-sized particles. In some embodiments, the additive material 304 comprises nanodiamonds that are tuned (e.g., formulated or selected) to absorb the laser light in the designated wavelength. In other embodiments, the additive material 304 comprises carbon nanotubes that are tuned (e.g., formulated or selected) to absorb the laser light in the designated wavelength. In still other embodiments, the additive material 304 comprises gold nanoparticles that are tuned (e.g., formulated or selected) to absorb the laser light in the designated wavelength. In still other embodiments, the additive material 304 comprises nanoclay that is tuned (e.g., formulated or selected) to absorb the laser light in the designated wavelength. In still other embodiments, the additive material 304 comprises micron-sized particles that are larger than the other nano-sized particles discussed above. For example, the micron-sized particles can comprise diamonds, gold, clay or other material. The micron-sized particles are tuned (e.g., formulated or selected) to absorb the laser light in the designated wavelength. In still other embodiments, the additive material 304 comprises graphene. In some embodiments, the laser-ablation layer 300 is doped with multiple types of additive materials that are collectively tuned to absorb laser light in the designated wavelength. For example, the laser-ablation layer 300 may include any combination of the additive materials described above and/or any other suitable additive materials. These different types of additive materials have different physical properties that react differently to laser light in different wavelengths. The type of additive material that is used to dope the laser-ablation layer may be selected based on the designated wavelength of the laser light and/or other factors. The nano- and/or micron-sized materials used in the material-coating system may be applied sequentially in different layers or may be combined into “hybrid” layers, or combinations of these, as needed to achieve the desired properties for coating removal. Note that the particles of the additive material 304 are shown schematically and may assume different shapes than those depicted. For example, some types of particles may be planar instead of spherical.
Returning to
In some embodiments, the inclusion of the reflective layer 208 in the material-coating system 200 can depend on the type of material that makes up the substrate 202. For example, if the substrate is formed as a monolithic component, such as with a metal alloy, then the substrate is less likely to need to be repaired or spot repaired during MRO activities. In this case, the substrate does not need to be accessible during MRO activities, so the reflective layer can be included in the material-coating system 200. On the other hand, sometimes the substrate may have known areas that need to be spot repaired as part of MRO activities. For example, such areas may include areas that are susceptible to corrosion. In this case, the reflective layer may be omitted from the material-coating system 200 so that the areas can be addressed as part of the MRO activities. In some examples, the areas may be removed via laser-ablation. Moreover, in some examples, the areas may include material that is tuned to absorb laser light in the designated wavelength in the same manner as the laser-ablation layer 204 so that it can become de-bonded from an interface of interest along with the other layers of the material-coating system 200 via laser ablation.
At time T2, the laser-ablation layer 404 has absorbed enough energy from the laser light 400 and the reflected laser light 406 to begin to de-bond and bubble up from the reflective layer 208 and the substrate 202. The topcoat layer 206 remains bonded to the laser-ablation layer 204, so the topcoat layer 206 also begins to bubble up away from the reflective layer 208 and the substrate 202.
At time T3, the topcoat layer 206 and the laser-ablation layer 204 collectively have fully de-bonded and separated from the reflective layer 208 and the substrate 202. At this point, laser ablation is complete and the topcoat layer 206 and the laser-ablation layer 204 can be collectively removed leaving the reflective layer 208 and the substrate 202 intact in the material-coating system 200. Further, MRO activities can continue with application of a new laser-ablation layer and a new topcoat layer to the remaining reflective layer 208 and substrate 202 to refinish the material-coating system 200.
Because the laser-ablation layer 204 and the topcoat layer 206 collectively de-bond from the reflective layer 208 and the substrate 202, laser ablation can be completed quicker than other conventional coating removal approaches. This allows for an aircraft to undergo MRO activities and return to operational service more quickly than would be possible by performing other conventional material coating removal approaches, which reduces operating costs of the aircraft, among other benefits.
At time T1, laser light 508 in the designated wavelength is emitted from a laser 510 and directed into the material-coating system 500. The laser light 508 is transmitted through topcoat layer 506 and into the laser-ablation layer 504. A focal point or ablation plane 512 of the laser 510 is set to a depth of a top layer of carbon fiber strands 502′. The laser-ablation layer 504 absorbs energy from the laser light 508 as the laser light 300 travels through the laser-ablation layer 504. The laser light 508 further travels into the substrate 502 to the ablation plane 512. The top resin layer 502″ of the substrate 502 is tuned to absorb energy from the laser light 508 in the designated wavelength as well.
At time T2, the laser-ablation layer 504 and the top resin layer 502″ of the substrate 502 have absorbed enough energy from the laser light 508 to begin to de-bond and bubble up from the top carbon fiber layer 502′ of the substrate 502. The topcoat layer 506 remains bonded to the laser-ablation layer 504 and the laser-ablation layer 504 remains bonded to the top resin layer 502″, so the topcoat layer 206 also begins to bubble up away from the substrate 502.
At time T3, the topcoat layer 506, the laser-ablation layer 504, and the top resin layer 502″ collectively have fully de-bonded and separated from the substrate 502. At this point, laser ablation is complete and the topcoat layer 506, the laser-ablation layer 504, and the top resin layer 502″ can be collectively removed leaving the fiber layer 502′ and the remainder of the substrate 502 intact in the material-coating system 500. Further, MRO activities can continue with application of a new layer of resin, a new laser-ablation layer, and a new topcoat layer to the remaining layers of the substrate 502 to refinish the material-coating system 500.
In the illustrated example, the resin layer 502″ is removed during laser ablation to expose the fiber layer 502′ of the substrate. There are various reasons why the resin layer 502′ would be removed from the substrate 502. As one example, the resin layer 502″ could be replaced due to environmental exposure of the material-coating system during operation. As another example, when an aircraft comes to the end of the operation lifecycle, the aircraft can be deconstructed and recycled or disposed of. The resin layer 502″ can be removed via laser ablation during deconstruction so that the material can be properly recycled or disposed of.
In some embodiments, at 602, the method 600 can include applying a reflective layer on top of a substrate of a material-coating system. The reflective layer is configured to reflect laser light in a designated wavelength.
In some embodiments, at 604, the method 600 can include doping a laser ablation an additive material that is configured to absorb laser light in the designated wavelength. In some embodiments, at 606, the additive material can comprise nano-sized particles. In some embodiments, the nano-sized particles may comprise at least one of nanodiamonds, carbon nanotubes, gold nanoparticles, graphene, and nanoclay. In some embodiments, at 608, the additive material can comprise micron-sized particles. In some embodiments, the micron-sized particles may comprise at least one of diamonds, gold, graphene, and clay. In some embodiments, at 610, the additive material can comprise a mixture of nano-sized particles and micron-sized particles. In some embodiments, the laser-ablation layer can be doped with multiple types of additive materials that are collectively tuned to absorb laser light in the designated wavelength. For example, the laser-ablation layer may include any combination of the additive materials described above and/or any other suitable additive materials. These different types of additive materials have different physical properties that react differently to laser light in different wavelengths. The type of additive material that is used to dope the laser-ablation layer may be selected based on the designated wavelength of the laser light and/or other factors. The nano- and/or micron-sized materials used in the coating system may be applied sequentially in different layers or may be combined into “hybrid” layers, or combinations of these, as needed to achieve the desired properties for coating removal.
In other embodiments, the laser-ablation layer can be tuned in a different manner that does not involve doping the laser-ablation layer with additive material. Instead, the material properties of the laser-ablation layer itself can be selected/fabricated to absorb laser light in the designated wavelength.
At 612, the method 600 includes applying the laser-ablation layer on top of the substrate. In some embodiments where the material-coating system includes a reflective layer, at 614, the method 600 can include applying the laser-ablation layer on top of the reflective layer.
At 616, the method 600 includes applying one or more topcoat layers on top of the laser-ablation layer in the material-coating system. In some embodiments, at 618, the topcoat layer(s) can include a visually transparent clear coat layer. In some embodiments, at 620, the topcoat layer(s) can include a visually opaque paint layer.
The method described above can be performed to produce a material-coating system where the laser-ablation layer is positioned underneath at least the topcoat layer (and one or more additional intermediate layers in some embodiments). When the laser-ablation layer absorbs energy from a laser in a designated wavelength and becomes de-bonded, the topcoat layer (and any intermediate layer(s)) also become separated from the underlying substrate. In this way, multiple layers of the material-coating system can be removed from the substrate with each pass of the laser during laser ablation. This allows for layers of the material-coating system to be removed faster than other conventional approaches.
In an example, a material-coating system comprises a substrate, a laser-ablation layer deposited on the substrate, and a topcoat layer deposited on top of the laser-ablation layer, wherein the topcoat layer is at least partially transparent to laser light in a designated wavelength, and wherein the laser-ablation layer is tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the laser-ablation layer causes the laser-ablation layer and the topcoat layer to collectively de-bond from the substrate. In this example and/or other examples, the laser-ablation layer may be doped with an additive material that is tuned to absorb laser light in the designated wavelength. In this example and/or other examples, the additive material may comprise nano-sized particles. In this example and/or other examples, the nano-sized particles may comprise at least one of nanodiamonds, carbon nanotubes, gold nanoparticles, graphene, and nonclay. In this example and/or other examples, the additive material may comprise micron-sized particles. In this example and/or other examples, the additive material may comprise a mixture of nano-sized particles and micron-sized particles. In this example and/or other examples, the topcoat layer may be a visually transparent clear coat layer. In this example and/or other examples, the material-coating system may further comprise a reflective layer deposited in between the laser-ablation layer and the substrate and configured to reflect laser light in the designated wavelength. In this example and/or other examples, the substrate may comprise a metal alloy. In this example and/or other examples, the substrate may comprise a fiber layer and a resin layer, and the resin layer may be tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the resin layer causes the resin layer to de-bond from the fiber layer of the substrate.
In another example, a process for fabricating a material-coating system comprises applying a laser-ablation layer on top of a substrate, and applying a topcoat layer on top of the laser-ablation layer, wherein the topcoat layer is at least partially transparent to laser light in a designated wavelength, and wherein the laser-ablation layer is tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the laser-ablation layer causes the laser-ablation layer and the topcoat layer to collectively de-bond from the substrate. In this example and/or other examples, the process for fabricating the material-coating system may further comprise applying a reflective layer on top of the substrate, and applying the laser-ablation layer on top of the reflective layer. In this example and/or other examples, the process for fabricating the material-coating system may further comprise doping the laser-ablation layer with an additive material that is tuned to absorb laser light in the designated wavelength. In this example and/or other examples, the additive material may comprise nano-sized particles. In this example and/or other examples, the nano-sized particles may comprise at least one of nanodiamonds, carbon nanotubes, gold nanoparticles, graphene, and nanoclay. In this example and/or other examples, the additive material may comprise micron-sized particles. In this example and/or other examples, the additive material may comprise a mixture of nano-sized particles and micron-sized particles. In this example and/or other examples, the topcoat layer may be a visually transparent clear coat layer. In this example and/or other examples, the substrate may comprise a fiber layer and a resin layer, and the resin layer may be tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the resin layer causes the resin layer to de-bond from the fiber layer of the substrate.
In yet another example, a material-coating system comprises a substrate, a reflective layer deposited on the substrate, a laser-ablation layer deposited on the reflective layer, and a topcoat layer deposited on top of the laser-ablation layer, wherein the topcoat layer is at least partially transparent to laser light in a designated wavelength, wherein the laser-ablation layer is doped with an additive material that is tuned to absorb the designated wavelength of the laser light such that the application of the laser light in the designated wavelength to the laser-ablation layer causes the laser-ablation layer and the topcoat layer to collectively de-bond from the substrate, and wherein the reflective layer is configured to reflect laser light in the designated wavelength.
It will be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and/or described may be performed in the sequence illustrated and/or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed.
The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.
