FIELD OF THE INVENTION

The present invention relates generally to methods and systems of removing a coaling or masking layer or an aluminum oxide layer from an area of a part, for the purpose of being able to combine individually desirable material properties on the same part.

BACKGROUND OF THE INVENTION

Aluminum is well established in many industries as a base metal with a wide range of favorable material properties: It is light-weight, readily available, can easily be recycled, and can be deformed into nearly any shape without great effort in toolmg and machinery. Typical aluminum alloys used for these applications include the materials covered in industry standards designated in 1000, 3000, 5000 and 6000 series aluminum alloys of varying grades of tempering (base hardness), but other alloys could also be considered for the application of the proposed process. These materials are commonly used in manufacturing applications in the form of coils in varying widths and thicknesses, where the efficiencies of continuous processing are advantageous, or sheets of various shapes and sizes, where smaller production volume and simplicity of handling are preferred.

For estlietical and other reasons, aluminum can also be covered with a coating which can be colored in various ways. One commonly applied process is the practice of anodizing the raw aluminum, to create a thin layer of very small pores of Aluminum Oxide, These pores will readily absorb certain dyes to provide a foil spectrum of colors, while, at the same time, forming a protective, wear-resistant surface due to the very high hardness of the Aluminum Oxide. Commercial anodizing processes are designated as Type Π or III anodizing defined in industry and military standards like MIL-A-8625 or MIL-STD-171. In other applications, conventional coatings with paints, lacquers or other coatings with special formulations have also been applied to achieve sufficient levels of hardness, wear resistance and color.

There are certain applications, where the goal is to combine the wear-resistance and color-carrying properties of the coating layer, with the high degree of pliability of the base aluminum, The above mentioned layers of hard coatings tend to peel, chip or crack once exerted to certain high levels of strain induced stress.

For example, there have been attempts to change some of the parameters of the anodizing process to reduce the thickness of the anodizing layer and/or its hardness and increase the degree of deformability of the anodized aluminum, but it has been found that these variations can change the properties of the aluminum oxide layer only to a very small degree, which does not nearly reach the ratios of deformation of raw aluminum, which can easily exceed strains of 20% and more, while typical strain levels achievable with aluminum oxide without severe structural damage to the anodizing layer are limited to 1- 2% or less. These desirable high degrees of strain of 20% or more are typically encountered in forming operations like the forming of small radii, effecting diameter increases or reductions and other deformations for purposes of aesthetic effects or increased structural strength, or dimensional or shape changes e.g. accomplished in operations like deep-drawing, in transfer presses or progressive die-sets, crimping or other manufacturing or assembly operations requiring large degrees of deformation.

Attempts have also been made to "mask" those areas of the aluminum material that are required to maintain their high level of deformability with certain compounds that prevent the formation of the oxide layer in the anodizing process. However, these compounds are difficult to apply, are difficult to remove after anodizing, and generally can interfere with the anodizing operation: In addition to the obvious surface and process contamination issues from the removed masking compounds, there are challenges in the cross-reaction of these masking compounds with the electrical and chemical parameters of the anodizmg process. SUMMARY OF THE INVENTION

In a first preferred embodiment, the present invention relates generally to a method of at least partially removing a coating or masking layer from an area of each of a plurality of parts, the method comprising the steps of:

a) orienting the plurality of parts; and

b) removing the area of the coating or masking layer from each of the plurality of parts using a pl urality of removal devices. In a second preferred embodiment, the present invention relates generally to a method of at least partially removing an aluminum oxide layer from an area of each of a plurality of anodized aluminum parts, the method comprising the steps of:

a) orienting the plurality of anodized aluminum parts; and

b) removing the area of the aluminum oxide layer from each of the plurality of anodized aluminum parts using a plurality of removal devices. hi a third preferred embodiment, the present invention relates generally to a method of at least partially removing a coating or masking layer from an area of a part, the method comprising the steps of:

a) orienting the part; and

b) removing the area of the coating or masking layer from the part using at least one removal device.

In a fourth preferred embodiment, the present invention relates generally to a method of at least partially removing an aluminum oxide layer from an area of an anodized aluminum part, the method comprising the steps of:

a) orienting the anodized aluminum part; and

b) removing the area of the aluminum .;oxidc layer from the anodized aluminum part using at least one removal device. The present invention also relates generally to systems for removing a coating or masking layer or an aluminum oxide layer from an area of a part,

In a first preferred embodiment, the present invention relates generally to a system for at least partially removing a coating or masking layer from an area of each of a plurality of parts, the system comprising:

a) at least one path for maintaining alignment and spacing of the plurality of parts, and

b) a plurality of removal devices arranged about the at least one path for at least partially removing the coating or masking layer from the area of each of the plurality of parts as said plurality of parts move relative to the plurality of removal devices.

In a second preferred embodiment, the present invention relates generally to a system for at least partially removing an aluminum oxide layer from an area of each of a plurality of anodized aluminum parts, the system comprising:

a) at least one path for maintaining alignment and spacing of the plurality of anodized aluminum parts, and

b) a plurality of removal devices arranged about the at least one path for at least partially removing the aluminum oxide layer from the area of each of the plurality of anodized aluminum parts as said plurality of anodized aluminum parts move relative to the plurality of removal devices.

In a third embodiment, the present invention relates generally to a system for at least partially removing a coating or masking layer from an area of a part, the system comprising:

at least one removal device positioned for at least partially removing the coating or masking layer from the area of the part. In a fourth embodinieni, the present invention relates generally to a system for at least partially removing an aluminum oxide layer from an area of an anodized aluminum part, the system comprising:

at least one removal device positioned for at least partially removing the aluminum oxide layer from the area of the anodized aluminum part.

In yet another preferred embodiment, the present invention relates to a method of at least partially removing at least one of a coating and a masking layer from an area of at least one part, the method comprising the steps of:

a) orienting the at least one part; and

b) removing the area of the at least one of coating and masking layer from the at least one part using at least one removal device.

In still a further preferred embodiment, the present invention relates to a system for at least partially removing at least one of a coating and masking layer from an area of at least one part, the system comprising:

at least one removal device positioned for at least partially removing the at least one coating and masking layer from the area of the at least one part.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of believed characteristic of the invention are set forth in the claims. The invention itself, however, as well as other features and advantages thereof, will be best understood by reference to the descriptions which follow, read in conjunction with the accompanying drawings, wherein:

Fig. 1 shows a process flow diagram of a combined Anodizing and Finishing Line Fig, 2 shows an Integrated Handling System to handle some of the movements of parts and components through the process

Fig. 3 shows the process flow diagram of the Removal Station in the Finishing Workcell where the actual removal process takes place Fig. 4 shows the detailed parameters that need to be established and controlled for a successful Implementation of the removal process

Fig, 5 shows a first implementation example, where the part is acted on during the removal operation inside a Removal Workcell

Fig. 6 shows a second implementation example, where the part is in linear and rotary motion through the Removal Workcell during the removal process

Fig. 7 shows a third implementation example, where a plurality of removal systems act on a part inside the Removal Workcell

Fig, 8 shows a fourth implementation example, where a plurality of parts are acted on by a plurality of removal systems as they move through the Removal Workcell

For a fuller midersianding of the inventi on, reference is had to the following descriptions, taken in connection with the accompanying figures 1-8 described above,

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is a puipose of this disclosure to establish that a novel way to achieve the combination of the above described favorable material properties of alummum and aluminum oxide on the same part is, to anodize the part in the conventional way, including the process steps of dyeing and sealing the aluminum oxide pores, and then partially or entirely removing the entire aluminum oxide layer in those areas where high degrees of deformation on the finished part are required, This is accomplished by combining technologies of first creating special layers with the desired properties on a suitable base material, and then partially removing these layers in those areas where these properties are undesired, to create parts that exhibit a combination of these indi vidually desirable specific properties on the same part, to facilitate the use of these parts for their intended purposes.

One particularly favorable process to remove the aluminum oxide layer is by means of a laser device, for example used in engraving operations to apply graphics and patterns to suitable surfaces, including raw or anodized alummum. These engraving lasers are commercially available, with modem controls that allow adjustments for the size and shape of the part, the size and depth of the area in which all or a portion (certain depth) of the aluminum oxide layer is to be removed, processing speeds, etc. Depending on the size, shape and location of the area of removal, a manipulation of the parts themselves, the laser beam, or a combination of both may have to be employed.

One particularly beneficial implementation of this process is achieved in so-called rack- or belt-anodizing, where the parts, typically small sizes and/or large quantities, are oriented and aligned on fixtures to maximize process efficiency and provide the proper electrical contact during anodizing. This process implementation is typically found in industries and applications like cosmetics, medical or pharmaceutical packaging, where large volumes, high quality standards and cost efficiencies are required. The required pails handling volume in these applications can reach several hundred million parts per year. Since the parts are already aligned in a defined orientation, it is advantageous to implement the process step of removing controlled areas of the aluminum oxide after the completion of the anodizing process. This can be accomplished by using the anodizing racks or belts directly, or by automatically ti-ansferring the parts from their attachments to the racks or belts into secondary fixtures while maintaining their orientation, for proper alignment in the removal process. In many cases, these parts are fairly thin, with thicknesses ranging from a few micrometers to one millimeter or more, which makes it desirable to minimize the need to handle the parts with the risk of damage to the shapes and surfaces.

The following is a list of required operational steps and parameters for one successful implementation of the above outlined process, incorporated within a combined Anodizing and Finishing Line, see Fig. 1. To maximize the efficiency of the overall process, the Finishing Workcell of the Removal Station is preferably set up to operate directly in-line with the Anodizing Line, but near-line or off-line implementations can also be

advantageous for smaller batches and production runs or other operational considerations. The transfer of parts and components between stations and workcells may be manual or automatic, or a combination thereof. A plurality of parts are assembled onto a titanium or aluminum rack in a defined orientation, to be processed in a combined Anodizing and Finishing Line, see Fig. 1. The parts are aligned closely next to each other to maximize process efficiency. One such rack could have dimensions of e.g. 500mm x 500mm, and hold up to 1200 or more parts of a diameter of 10mm or less.

Such rack could consist of a plurality of clamping strips being loaded off-line with an integrated handling system, see Fig. 2, with a certain number of the parts, e.g. 40 on each strip; the au tomated loading system could install e.g. 30 of these clamping strips onto said rack in a discrete operation. Another commonly applied system is to install these strips on a belt, where the belt is used to carry the strips through the tanks of the anodizing process in a continuous operation.

The integrated handling system in Fig. 2 could include an automated visual inspection system to check for dimensional tolerances and other quality defects in the raw parts being supplied to the system.

A plurality of such racks could then be transferred to a larger frame that can hold 14 or more of these racks per side, totaling 33,000 parts or more to be processed simultaneously or on a continuous belt system in a suitable anodizing line.

After anodizing the parts to achieve the desired surface hardness, surface finish, color, etc specified for the anodizing process, the racks are manually or automatically unloaded from the frames, and transferred to an automatic unloading system, see Fig. 2, where the aforementioned clamping strips are disengaged from the racks or transport belt, and the anodized parts from each strip are automatically undamped and transferred into a set of tracks or other means that maintain alignment and spacing of the parts, while the empty strips are returned within the automatic loading/unloading system to be reloaded with a set of new parts, to be sent into the anodizing process.

Upon automated quality inspection of the anodized parts for deviations in process parameters like surface finish, color, etc., the parts are automatically transferred into a workcell station, see Fig. 3, where the actual process of removing a portion of the anodizing layer is performed. These areas of desired removal could be located on either of the surfaces of flat parts, or the "inside" and/or "outside" surfaces of a wide variety of shapes of hollow parts. These surfaces could be substantially flat, or curved to a certain degree.

The finishing workcell could consist of one or a plurality of devices to perform the removal operation, see Fig. 4, aligned in a matter so as to engage in certain defined areas to make up the entirety of the removed surface area defined by the application, namely those areas where the hardness of the anodized layer would interfere with the desired deformability of the underlying aluminum. Fig. 4 outl ines some of the parameters of the process and the parts that need to be controlled for a successful implementation of the removal process. The source of the energy for the removal process can be either continuous over larger areas (e.g. a chemical reaction) or focused at discrete locations , like using a waterjet, grit- blast or laser application. The interaction of this energy can therefore be concurrent in nature, like a semi-continuous sweep over larger areas, or discrete and highly localized, like in a dot-matrix pattern.

One embodiment of such removal is to expose the required areas of each part in front of the removal device in a rotational motion around one or more of its axes, see Fig. 5. In the illustration for this application example, a cup-shaped part moves in and out of the workstation before and after the removal process. During the removal process, the part rotates in a defined position in front of a first and a second removal systems, where the first removal system may be focused to remove the areas on the outside of the part and the portion of the rim areas exposed to it, while the second removal system is focused on removing the inside areas and the remaining exposed rim areas. It is understood that the same removal operation could be performed by a single removal system, by making two passes of rotation of the part, while sequentially performing the abo ve described operations of both removal systems, and adjusting the focus between the removal passes at the inside and outside surfaces. A s a tradeoff for the savings of only requiring one removal system, the process time would increase for having two passes, plus any adjustment time for switchmg the focus and any other associated parameters of the single removal system. S uitable removal systems are able to provide adequate quality of removal of the selected areas over a wide range of angles of incident, as required to perform the removal on the surfaces on the inside of the shown cup-shaped part. Depending on the shape and form-factor of the part, the angle of incidence may range between from 90 degrees to the surface of removal down to 45 degrees or l ess. One successful implementation for a small and narrow part was achieved with angles of incidence of abou t 60 degrees from the surfaces of the part,

Another embodiment of the invention limits the motion of each part to the movement through the workcell in Fig. 6, and the removal systems follow each part on its path by controlling the direction of the energy of the removal system. For example, commercial laser systems include this "tracing" feature by controlling the beam direction by means of optical lenses and mirror systems as a standard feature. As the parts move through the workcell, they rotate around their respective axes. The translatory and rotational motions are synchronized with the controls for the removal systems, so that the removal systems always focus and point at the apex of the parts. The removal parameters are chosen so that the removal time is short enough to maintain the required energy densities to avoid the need to adjust the focus of the removal systems as the part moves through the removal zone of the workcell. A sensor triggers the start of the removal systems, and the linear velocities and part spacing are optimized to match the jump time for the removal system to move their focus to the next part that enters the removal zone after the removal process for the preceding part is finished as it exits the removal zone. This process could also equally be performed by a single removal system, switching between the desired areas of remo val, as described in the preceding paragraph.

Another embodiment would be to employ a plurality of removal devices in the workcell according to Fig. 7, each aligned independently to remove only a defined partial area, the sum of these partial areas adding up to comprise the total area to be removed. The trade-off between these two approaches lies in the investment and operational cost of the number of removal stations included in the removal system, in relation to the achievable removal rate for each removal device and hence the overall system throughput for the entire process, hi the shown application example, five removal systems are arranged along the path of the parts through the workcelL Four removal systems are designated to act on the outside and inside of the cup-shaped part shown as an illustration, while a fifth removal system in this example is designated solely to act on the rim area of the part, to ensure adequate removal by maintaining an optimal angle of incident on the surface to be removed. Each of the four removal systems acting on the perimeter of the part is set up to act on a segment of the total circumferential area, covering 90 degrees or one-fourth of the total circumferences of the respective inside and outside areas, plus a small area of overlap between the segments. The width of this area of overlap depends on the accuracy of the focusing and positioning controls of the chosen removal systems and can range from under one millimeter to several millimeters. In one successful implementation, an area of overlap between the removal systems of one millimeter was implemented,

Yet another embodiment would allow the single or multiple removal systems to switch focus between multiple parts, as these move through the workcell in parallel paths, see Fig. 8, to further increase throughput performance. In the shown application example, a continuous stream of parts is arranged in parallel paths of defined spacing in the indicated x- and y-directions. The parts are moved through the workcell in x-direction, and the removal systems are sequentially controlled to act on defined areas of the parts in each track along the y-direction, as the parts move along their respective defined paths through the workcelL Implementations of the above described process were successfully perfomied by using commercial laser removal devices. These devices can be of C0 ₂ , Nd:YAG, Nd: YV 0 ₄ , Yb:fiber or other base design to create a laser beam. Power control can be accomplished using mode-locked or Q-switched technique. Preferably, a Yb:fiber based, pulse switched laser system is used.

The applications advantageously use laser devices with wavelengths in the range from 300— 1200nm. Particularly successful was the application in the infrared range of around 1062nm, which is especially suitable for the range of colors in the dye used in the anodizing process, as well as compatible with the relevant material properties of both the base aluminum and the aluminum oxide of the anodizing layer.

Average power levels of the laser systems of 5W to 750W are suitable to perform the operation successfully. A level of 20-30W is adequate, however, higher power levels will allow to reduce the cycle time and result in higher system throughput and overall performance.

The laser beam is directed and focused on each of the removal surfaces for optimum removal quality, and the combination of available process control parameters adj usted in relation to the number and relative position of "dots" removed with each pulse to achieve complete removal of the anodizing layer across the entire defined surface area.

One successful implementation of such removal was achieved with a focal distance of 160mm and a laser beam focus diameter of 70μτη. Other combinations of focal distance (in the range between 100 - 500mm) and beam focus diameters (between 10 and 1 ΟΟΟμιη) may be employed, depending on the particular system properties and selected operation parameters of the selected laser system, especially those of the optical lenses and mirrors employed in the beam path and the particular properties of the layer of material to be removed.

In particular, it is possible to select a laser system which allows to set the beam focus diameter to the full width of the surface area to be removed, e.g. 1mm or more, and simplifying the efforts needed to control the above described motion of the part and/or direction of the laser beam to follow the length and width of the shape of the area to be removed; this requires higher levels of power of each of the removal systems at a higher initial cost, but may result in higher system throughput.

The pulse repetition rate can be set to 100kHz or higher, typically in a range from 25-lOOGkHz, depending on the particulars of the selected laser system; operating modes can be of the "modulated or "continuous wave" mode form or a combination thereof.

The pulse duration can be in the order of magnitude of nanoseconds or less, depending on the beam focus diameter, system power and other specifics of the selected laser system and the material to be removed; typically, the pulse width can range from less than lOps to 700ns or more,

20. The maximum required pulse energy can range between 25 and 250μΙ, depending on the selected laser application control settings that result in the best removal rate and quality.

21, The fumes and dust particles from the removed particles from the removal

operation are collected in an exhaust system, where the removed particles of the anodized layer are retained in a filtering subsystem and properly disposed of.

22, it may be desirable to add a second pass of the removal operation, applying the same or a different set of operating process parameters, as an additional cleaning operation. Another purpose for one or more additional passes with the same or different parameters may be to further alter the surface properties of the parts, like hardening, softening, smoothing, or other changes of the properties of the finished surface.

23. Upon successful removal of the desired areas of the anodizing layer on each part and achieving an acceptable surface finish of the removed areas, the parts may- pass through a final automated inspection system, where parts are deemed "pass" or "fail", based on defined acceptance criteria. The passing parts are transferred to an automated packaging station, while the failing parts are collected to be reviewed and reused or recycled as standard aluminum recyclable material.

It will be obvious to those skilled in the art of metal finishing that the above exemplifies only one suitable range and set of parameters in a process with a wide range of interdependencies between the parts (size, shape, color, etc.; see table 1 below), the application requirements (size, shape, depth, etc. of the areas to be removed; see table 2 below) and the specifics of the selected removal system and the design of the automated handling system as outlined above, including their interface with the anodizing line and its own process parameters, as indicated before. It is therefore understood that other combinations of overall process parameters exist that lead to equally acceptable process results. It is understood that the matrices in the tables below are meant to indicate that any parameter in a row or column can be combined with any other parameter in another row or column of the same table.

It is furthermore understood, that the means to provide the required energy to remove the anodizing layer are not limited to employing the highly focused energy of laser systems, which generally have the ad van tage of being commercially avai lable and very precise in the controls of their operating parameters. Alternatively suitable, with little concern for less quality in the result of the layer removal, are removal systems based on the mechanical energy of water-jets (with or without the addition of abrasive media) or abrasive blasting (e.g. employing silica sand or aluminum oxide as abrasive medium in a controlled stream of high-pressure air or other gases), provided the stability in part position and orientati on can be maintained against the impact of the media, or the chemical energy of certain material removal processes, as long as the residue of the process can. be adequately captured and disposed of.

It is also understood, that the above removal process is not limited to the removal of the hard aluminum oxide layer obtained after the anodizing process. The removal process can also be successfully employed to solve the above described challenge of removing a masking layer, which may have been introduced and applied onto the raw metal prior to the anodizing process, to protect certain areas from being anodized in the first place. If the masking is detrimental to the final use of the parts and must be removed in a controlled manner, the above described methods can be applied to remove such a layer of masking material in very much the same fashion as described above to remove the anodizing layer in those exact same areas.

Naturally, the above described processes can be equally successful when implemented at smaller scales of volume and productivity, e.g. at a lab level down to processing only a single part, or volumes of only a few hundred or tho usand parts per ran cycle, if the cost of the implementation can be justifi ed. it is equally implied that the removal of layers of insufficient ductility is not limited to layers of aluminum oxide created in an anodizing process. Other layers of coatings, like paints, lacquers and specially formulated coatings based on various chemical substrates and compounds can equally be removed taking advantage of the benefits of the above described processes, provided the process and operational parameters are adequately adjusted to match the properties of such materials. One example of such applications include pre-lacquered or pre-anodized sheet or coil materials, with anodized layers on one or both sides, to achieve a match in the desired color for the application. Another example is the anodizing in a bulk process, where parts of sufficient stiffness to withstand the mechanical stresses encountered in bulk applications are anodized in large batches, with a trade-off in color consistency and anodizmg quality. Finally, the above described processes can be applied on parts of any shape or size, small or large, thin walls or thicker parts made from bar stock. Castings or otherwise machined parts, in quantities down to single prototypes, can be successfully processed, where localized, defined areas of an. applied coating need to be removed, for purposes of improved ductility or other reasons.

It is also contemplated that the removal processes and systems described herein can be used for removing coating or masking layers and/or oxide layers from other materials, including for example, various metal alloys, including aluminum alloys, steel, including stainless steel, brass, and other similar materials.