Electric heating – Metal heating – By arc
Reexamination Certificate
2000-04-03
2001-11-06
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121760, C219S121780
Reexamination Certificate
active
06313433
ABSTRACT:
SEQUENCE LISTING
Not Applicable
CROSS-REFERENCES TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Fields of the Invention
The present invention relates generally to apparatuses and methods for engraving and cutting materials using multiple lasers the beams of which can be combined for cutting and deep engraving applications or separated for high speed raster engraving.
2. Discussion of Background and Prior Art
a. Prior Laser Material Processing Systems and Beam Delivery Systems
Typically a laser material processing system includes a laser source, a power supply, a CPU for receiving a computer program to control beam positioning and corresponding laser modulation, a control panel, and a beam delivery system.
1. One typical embodiment of an X-Y beam delivery system includes parallel tracks supporting a transverse rail having a reciprocable carriage with a mirror and focusing lens assembly which delivers the laser beam downwardly onto the workpiece under the control of the CPU. See, Garnier U.S. Pat. No. 4,985,780 and Sukhman U.S. Pat. No. 5,051,558 hereby incorporated herein by reference.
2. Another type of beam delivery system is known in the art as a Galvanometer type wherein two mirrors are each supported on orthogonally placed axes of limited-rotation, moving iron type, servo motors with highly linear torque characteristics over a relatively large angle of rotation with position feedback and servo amplifiers. The combined action of the mirrors produces X and Y movements of the laser beam.
Typically, images are engraved onto materials using a raster motion of the laser beam (“raster mode engraving”). As used herein, raster mode engraving means affecting the surface of a workpiece by engraving, removing, modifying, marking, or otherwise interacting with the surface of the workpiece. Using this method, an image is defined by a number of dots of a certain resolution (e.g., 500 dots/inch). The image is then recreated on a material by passing a laser beam back and forth over the material along one axis to engrave one line of dots with each pass in accordance with the information from the original image while stepping in very small increments along an orthogonal axis until the image is completed.
Typically, patterns are cut from materials using a vector motion of the laser beam (“vector mode cutting”). As used herein, vector mode cutting means cutting into or through the surface of a workpiece. Using this method a pattern is applied to a material by moving a beam delivery system simultaneously along X and Y axes in accordance with the path of the desired pattern while applying a controlled amount of laser energy to cut into or through the material.
b. The Problem of Limited Productivity Of Traditional Systems
Productivity is limited by different factors for raster mode engraving and vector mode cutting.
On the one hand, high productivity in raster mode engraving involves removal or modification of a surface of a workpiece at maximum speed at a predetermined power level. However, such high beam delivery motion speeds and the associated high laser beam pulse rates do not produce good results with most materials, and, are accompanied by other serious disadvantages, as set forth below:
1. At high beam delivery system speeds, the required laser pulsing rate can greatly exceed the laser response rate. E.g., if the user is using 1000 dots/inch and the X-Y based beam delivery system is traveling at 100 inches/second, then the laser must be pulsed at 100 kHz. However, CO
2
lasers typically achieve 100% modulation only below 5-7 kHz, and above these frequencies the lasers are only partially modulated, making power more and more difficult to control. In the above example, at 100 kHz the laser produces a CW beam, and no image can be produced. Also, high frequency pulsing is difficult to achieve with NdYAG lasers due to Q-switch limitations and variations in peak power for the broad range of modulation frequencies required.
2. High speed beam delivery systems require more expensive motors, drivers, mechanical components, and support electronics, and produce more wear and tear on those components.
3. Speed also affects energy density when a laser pulse is applied to a material. A laser pulse applies a fixed amount of energy to a material. As a beam delivery system moves faster, each pulse is spread over more of the material surface, thereby reducing the energy density.
4. As the beam delivery system operates, it must decelerate in order to change directions and accelerate again to reach operating speed after changing directions. At high speeds it becomes more and more challenging to control laser power and material marking consistency during direction changes, thus, requiring more sophisticated control electronics and motion algorithms. Each change in direction slows down the process, and an increase in top speed alone does not necessarily recover all of the lost time.
On the other hand, high productivity in vector mode cutting involves deep penetration into or through a material at maximum available power at a predetermined speed. However, these high power levels are usually unnecessary in raster mode engraving and the vector mode cutting predetermined speeds are too slow for efficient raster mode engraving applications.
Accordingly, there is still an unfilled need for, and it is an object of the present invention to provide, high productivity in raster mode engraving while overcoming the problems intrinsic to higher speeds and while simultaneously preserving the high productivity of vector mode cutting.
c. Prior Electrophotographic Laser Printers With High Speed Raster Output Scanners
The addition of multiple lasers to increase productivity is well known in the reprographics industry for electrostatically discharging drums to form latent images thereon. In a prior system to Genovese in U.S. Pat. No. 5,777,659 there is disclosed the well known technology of the laser printer in which a raster output scanner (“ROS”) provides a laser beam that switches on and off according to electronic image data associated with the desired image to be printed exposing the surface of an electrostatically charged photoreceptor (a photosensitive plate, belt, or drum) point by point as the beams are reflected by the facets of a rotating polygon and move across its surface thereby forming a raster of closely spaced scan lines containing a latent image which is then developed with toner and transferred to a sheet of copy paper as in the well known process of electrophotography. In order to obtain an increase in the effective writing speed of the laser imaging system by increasing the rate at which pixels were processed and a desired image completed, Genovese employed dual, independently operated laser beams which simultaneously scanned across or traversed the photoreceptor surface two parallel scan lines spaced apart by a predetermined number of scan lines thereby effectively doubling the throughput capability of the printer. (FIG.
1
). Genovese used a single light sensor to measure the intensity of the two light sources which operated the lasers in alternating fashion to maintain uniformity in the image.
An improvement to such a system was disclosed by Ito in U.S. Pat. No. 5,786,594 in which at least one of the multiple lasers was rotatable about an axis parallel to the axis of the photoreceptor whereby the pitch of the multiple scan lines could be controllably adjusted. (FIG.
2
).
The same techniques used by Genovese and Ito above were further applied in a system by Balz in U.S. Pat. No. 5,808,268 to facilitate identification and tracking for quality control purposes in a computer controlled, data driven, marking process of scribing or engraving high density indicia, such as, alphanumeric serial numbers or other symbols, on the surface of ceramic substrates or wafers used in the manufacture of electronic components, such as, direct access storage device integrated circuits.
However, none of the above systems dis
Gorham Edwin W.
Risser Christian J.
Schultz David W.
Sukman Yefim P.
Abelman ,Frayne & Schwab
Heinrich Samuel M.
Universal Laser Systems, INC
LandOfFree
Laser material processing system with multiple laser sources... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laser material processing system with multiple laser sources..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laser material processing system with multiple laser sources... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2570551