Plastic and nonmetallic article shaping or treating: processes – Laser ablative shaping or piercing
Reexamination Certificate
1999-02-19
2001-08-21
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Laser ablative shaping or piercing
C264S101000, C264S102000, C219S121690, C219S121860
Reexamination Certificate
active
06277319
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a method and apparatus for trimming a shaped plastic workpiece such as a paint film laminate that is to be used to form an injection molded automotive or truck part. The method uses a laser beam positioned and directed by a robotic arm along a pre-programmed path to trim the edges of the paint film laminate workpiece as the workpiece is held against a positioning block.
BACKGROUND OF THE INVENTION
A variety of injection molded parts are made and used for automobile body and trim parts. For example, bumpers, spoilers, body panels, doors, filler panels, wheel covers, dashboards, arm rests and other parts are commonly made by the injection molding of thermoplastic materials.
In order to provide a painted or other decorative surface for injection molded plastic trim parts, film lamination techniques are commonly employed. A paint film laminate is insert molded or, as it is sometimes referred to, co-molded, with the desired thermoplastic to fuse the film over the injection molded substrate. The resulting injection molded film-plastic part is ready for assembly without subsequent painting.
The paint film laminate used in these insert molding techniques may comprise a backing sheet to which paint, other pigment-containing, or clear layers are adhered. Typically, the backing sheet comprises an extruded thermoplastic sheet. The paint or pigment layer may contain colored pigments or reflective flake pigments such as aluminum or mica flakes to provide for example a metallic finish.
The paint film may consist of a monocoat; a clear coat over a base coat; or a clear coat and a base coat with interposed print or design. The paint film, including base coat, clear coat and print or design, if desired, may range from about 0.5-4 mil. (13-100 &mgr;m) in thickness.
Laminated paint films are well known in the art and are available, for example, from Avery Dennison Decorative Films Div. of Schererville, Ind., or Rexham Decorative Products of Charlotte, N.C. For example, laminated paint films are described in U.S. Pat. No. 5,514,427, the disclosure of which is incorporated herein by reference. The films are typically provided in a roll, unwound and then “preformed” to a size and shape approximating that of the final injection molded film-plastic part.
The paint film laminate preform is next usually trimmed and placed along the cavity side of an injection mold with the painted side or “show” side thereof facing the mold cavity surface. Trimming may be accomplished by hand or in some instances by the use of heavy stamping machines that require the use of expensive tooling.
After trimming, the paint film laminate preform is ready for the molding process where it may be placed along the core side of the mold. The mold is then clamped and the desired molten resin is injected into the mold cavity. Heat and pressure conditions in the mold partially melt the backing sheet and a melt bonding or fusion of the injected resin and the backing sheet of the film occur. Injection molds used for these processes are rear or edge gated so that the molten resin is directed along the backside of the film.
Techniques for preforming paint film laminates and insert molding film-plastic parts are disclosed in U.S. Pat. Nos. 5.599,608; 5,759,477; and 5,783.287. The disclosure of these patents is incorporated herein by reference.
While the prior art process described above has proven effective in many respects, there is a need in the art to improve upon the trimming step for the paint film laminate so that this operation can be conducted economically and more accurately. At the same time, it is desirable to minimize the use of heavy stamping or cutting machines that require large spatial areas and expensive cutting tools and dies.
It is even more desirable to provide a laser trimming operation wherein operation of the laser is conducted in an enclosed atmosphere, shielding workers from the laser beam and from soot and vapors that emanate from the cutting operation. Another desirable goal is to provide an automated laser trimming apparatus wherein soot and vapors from the laser cutting area are immediately removed from the trimming area to a bag house or other filter mechanism and wherein the trimmed workpiece does not contain burned or charred areas surrounding the laser trimming line.
SUMMARY OF THE INVENTION
These and other objects are met by the paint film laminate trimming apparatus and process of the present invention. Basically, the apparatus comprises a rotatable wall carrying a work platform with the platform including a plurality of convex positioning blocks mounted thereon. Each positioning block is contoured to correspond in shape and dimension to a desired work piece such as an automobile or truck trim part.
In a first work station, the operator, which can include manual or robotic means, loads a plurality of “preformed” and roughly trimmed paint laminate films over each of the positioning blocks. The roughly trimmed paint films are dimensioned so that they snugly fit over the corresponding positioning blocks. After all of these paint films are properly positioned over their corresponding positioning blocks, the wall and associated platform are rotated to an enclosed work chamber wherein a laser performs a final, highly accurate trimming of the paint laminate films.
In the laser cutting operation, X, Y, and Z coordinates of the desired cutting pattern are contained in the memory of a microprocessor. The microprocessor then provides this information to a laser controller which in turn moves the laser along the desired cutting pattern to finally trim the paint film laminates, each of which is positioned on its associated positioning block.
The positioning blocks each include a plurality of suction ports positioned along the path of travel of the laser. These ports communicate with a manifold and plenum chamber so that a suction source in operative association with the manifold and plenum chamber draws particulates and vapors from the laser cutting area to a bag house or other effective filter mechanism. This suction action also helps to grip or secure the paint film laminate to the positioning blocks.
The laser includes a source that generates a laser beam which is used to cut the workpiece along the path of travel. The projector is in optical communication with the laser source, preferably through a flexible or jointed optical conductor, so that the projector receives the laser beam from the laser source and projects it onto the workpiece positioned on one of the convex positioning blocks.
The robot positions and orients the projector to direct the laser beam toward the convex positioning block and workpiece mounted thereon. A channel or groove is formed in the positioning block and extends substantially parallel to the desired cutting line. The laser photons pass through the workpiece providing a clear cut therein and then terminate in the channel without reflecting out of the channel onto the back of the workpiece.
Most preferably, the robot includes a first arm or spar having proximal and distal ends. The spar includes a wrist portion near its proximal end on which the projector is mounted. The robot also includes a second arm or boom having a proximal end pivotally supported by a base. The boom has a distal end near which the boom pivotally supports the proximal end of the spar.
The controller electrically communicates with robot electric motors positioned near the wrist portion as well as near the proximal ends of the spar and the boom to enable the robot to move the projector so that the laser beam traces the path of travel programmed into the controller. Most preferably, the controller signals the robot electric motors to orient the projector so that the laser beam remains normal to the tangent of the path of travel and maintains a constant angle with a plane containing that path as the laser beam traces the path.
The invention will be further described in conjunction with the attached drawings and in the ensuing detailed description.
REFERENCES:
p
Hardgrove William H.
Swartz Michael A.
Yorde Andrew G.
Biebel & French
Green Tokai Co. Ltd.
Silbaugh Jan H.
Staicovici Stefan
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