Electric heating – Metal heating – By arc
Reexamination Certificate
2003-02-19
2004-09-21
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121720
Reexamination Certificate
active
06794604
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION(S)
None.
BACKGROUND OF THE INVENTION
The present application relates to an apparatus for securing and advancing a web material for laser processing. More particularly, the present invention relates to a technique for using a web-securing drum to secure and advance the material under a lager or high energy beam for processing.
Generally, laser or e-beam processing of a moving web involves directing a focused beam onto the surface of the web material as the web material is advanced. As the beam touches the surface of the moving web, the beam vaporizes and/or melts the web material. Traditionally, laser processing systems have used vacuums located beneath the cutting surface for drawing away smoke and debris from the cutting areas. Additionally, laser processing systems have used vacuums for work piece retention on flat surfaces. Such vacuums are known in the art.
Laser processing of a moving web or a continuous substrate requires consideration of a number of factors. For example, flapping and fluttering of the web, shifting of the web material transverse to the direction of movement, wrinkling and creasing of the web material, varying tensions across the web, varying thickness of the web, and varying web composition contribute to inaccuracy and inefficiency in the process.
Typically, laser processing requires the minimization of flapping and shifting of the web material, while advancing the web under the laser beam. Rollers positioned on opposite sides of the laser hold the web material in tension and advance the web material through the cutting zone underneath the laser beam. However, tensioning the web material lacks precision, because the chemical structure of the web material can vary across the sheet, affecting the elasticity of the sheet material. In other words, the rollers may hold some areas in tension while other areas of the web material can flap and flutter as the web is advanced by the rollers particularly at high speeds.
Additionally, web materials may not be uniform in thickness, width, length or composition. For example, a web material that is rolled may be longer along the edges than in the middle. The thickness of the web may vary. The edges of the web may be wavy or uneven. Finally the web material for example may be non-homogenous, such that the thermal coefficients of the substrate can vary across the substrate, or woven, such that internal stresses can vary across the substrate. These inconsistencies can lead to undesirable wrinkling, creasing or tearing of the web material. Additionally, such variations can cause the beam to move in and out of focus, can contribute to inaccuracies and inefficiencies (such as higher power usage), can contribute to inconsistencies in the score or cut pattern depth, and can cause the size of the focal point to vary at the surface of the web.
One solution for limiting such web movement involves increasing the tension. However, with some web materials (particularly very thin materials) and with some laser processes (such as cross-cutting, shape cut-outs, and the like) increasing the tension on the web material is not an option. Specifically, increasing the tension on a very thin material may cause the web to break. Increasing the tension on thicker materials where the laser process involves a cross-cut (a cut that is transverse to the direction of the moving web) or a shape cut-out with a substantial area can cause the web material to tear. In such instances, the laser process may sufficiently weaken the web material that the tension rollers cannot be used. Moreover, tensioning does not resolve issues relating to web thickness variations, compositional variations, or dimensional variations, and may exacerbate creasing and wrinkling of the substrate.
In some instances, the web material is manufactured in such a way that it has internal stresses. Woven fabrics and certain non-homogenous materials may have such internal stresses. These stresses can impact the accuracy of the laser process because the internal stresses are relieved to some degree by the laser processing, which may cause the web material to shift or move. With web materials that have varying internal stresses, tension alone may be insufficient to prevent the web material from shifting before or during the laser processing operation. For example, when cutting strips from a moving web of material that contains such internal forces, the laser cutting process releases the internal stresses of the material. As the web material is cut into strips, the downstream strip (the strip after laser cutting) becomes difficult to control. Moreover, as the positioning of the web material entering the “cutting zone” is partly dependent on the downstream components in a conventional “tensioning” system, the material may shift before, during, and after laser processing such that the score line or cut line can vary across the sheet material.
In general, in laser processing, precision laser processing requires precise location and positioning of the laser spot as well as accurate power modulation. When the web material shifts or flaps, the precision of the laser spot placement and the modulation of the power are affected. Specifically, shifting or inaccuracy in the cut or placement of the spot affects the power level at which the laser must be run in order to perform the laser process. When the web material flaps a great deal, the laser has to be run at a higher power level in order to be cut because the position of the laser spot cannot be controlled to maintain peak efficiency. As a result, sometimes the laser processing must be slowed down in order to minimize the flap and flutter of the web material.
Cut out shapes or patterns on a moving web present additional difficulties. If the cut out areas constitute a significant surface area of the web material, tensioning of the web material during the cut out process can cause the web material to either pull apart or shrink up so that it cannot be rewound on a roller on the other end. Moreover, flapping of the web material during the cut out process may cause the objects to fall out of the moving web into the cutting zone vacuum.
With certain film materials, which are simply too thin or too elastic to tension across the rollers, prior art systems sometimes used a conveyor to secure and advance the film material under the laser beam. However, even with guide edges to hold the material on the moving conveyor, the material can shift during laser processing on the conveyor such that the accuracy of the laser process is compromised by the movement of the material in a direction that is often transverse to the movement of the conveyor.
Finally, with respect to cutting of strips of material, in the prior art, the thickness of the strips was in part determined by a spacing of the laser heads. For example, the focusing lenses and mirrors of the fixed beam laser apparatus, or any other laser beam set up takes a certain amount of space relative to one another. When positioned adjacent to one another, the beams are necessarily spaced from one another. In certain applications, in order to achieve a narrower cutting area, the laser heads are aligned longitudinally in the direction of the cut for a closer lateral arrangement without interfering with each other. However, with respect to previously described materials that contain internal stresses, stacking the lasers in such a manner results in widely varying cuts. Specifically, as the first laser beam initiates its first cut, the materials internal stresses are somewhat relieved and the material downstream will begin to shift thereby affecting the accuracy of the laser cuts at the downstream laser beams.
Therefore, it is desirable in the industry to have a laser processing apparatus with improved efficiency. More specifically, it is desirable to have a laser processing apparatus capable of handling materials that have internal stresses, with sufficient versatility to handle any laser processing task. Additionally, it is desirable to have a laser processing system c
Herke Donald
Lawson William E.
Miller Dan B.
Zik John J.
Heinrich Samuel M.
Preco Laser Systems, LLC
Westman Champlin & Kelly P.A.
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