| Beam-steered Nd:YAG (Neodymium:Yttrium
| |
| | results without additives; for example,
|
| Aluminum Garnet) laser marking provides a
| |
| | most black polycarbonates produce a
|
| unique combination of speed, permanence,
| |
| | snow-white mark without altering the
|
| and imaging versatility in a noncontact
| |
| | chemistry.Coated PlasticsCoated plastics
|
| marking process. Laser marking can
| |
| | consist of a solid, translucent, or
|
| generate considerable savings in reduced
| |
| | transparent plastic with one or more
|
| manufacturing and tooling costs;
| |
| | coats of ink or paint. The marking image
|
| elimination of secondary processes and
| |
| | is created by achieving vaporization
|
| consumable disposal; and reduced
| |
| | temperature on the surface to remove the
|
| inventory expense, quality-control costs,
| |
| | top coat and expose the underlying
|
| and maintenance downtime. Laser marking
| |
| | plastic or second coat.Coated plastics
|
| frequently improves the aesthetic
| |
| | allow a great deal of control over color
|
| appearance of the marking image, thereby
| |
| | selection and marking contrast.
|
| increasing the product's perceived
| |
| | Transparent plastics allow the designer
|
| value.Of all materials, plastics are the
| |
| | to use an underlying part to establish
|
| most challenging in terms of the laser's
| |
| | the background color (marking image)
|
| interaction with the material and the
| |
| | while the top coat determines the
|
| required image quality. The wide variety
| |
| | foreground color. Solid plastics
|
| of material chemistries and colors and
| |
| | establish their own background with the
|
| the aesthetic requirements of most
| |
| | color of the plastic. Translucent
|
| plastics applications require special
| |
| | plastics are frequently used for back-lit
|
| consideration in both material chemistry
| |
| | applications. The plastic is initially
|
| and imaging techniques. The successful
| |
| | coated with a white paint and overlaid
|
| implementation of laser marking
| |
| | with a dark top coat. The laser removes
|
| technology requires a working knowledge
| |
| | the top coat, exposing the white paint
|
| of the laser marker's function and
| |
| | for daytime visibility. When the part is
|
| capabilities and a committed, team
| |
| | back-lit at night, the lighting
|
| approach by the user.Marking
| |
| | illuminates the translucent plastic from
|
| FundamentalsLaser marking is a thermal
| |
| | behind and the marking image appears in
|
| process that employs a high-intensity
| |
| | the color of the plastic.The paint or ink
|
| beam of focused laser light to create a
| |
| | used must be conducive to laser
|
| contrasting mark on the material surface.
| |
| | processing. Standard paints and inks are
|
| As the target material absorbs the laser
| |
| | neither predictable nor controllable when
|
| light, the surface temperature increases
| |
| | exposed to the laser output. The inks
|
| to induce a color change in the material
| |
| | burn easily and can mix with the
|
| and/or vaporization of material to
| |
| | underlying plastic while in the molten
|
| engrave the surface.Beam-steered laser
| |
| | liquid state. Laser-compatible inks are
|
| marking employs mirrors mounted on
| |
| | mixed with a silicone-based material
|
| high-speed, computer-controlled
| |
| | reflective to the laser output, thereby
|
| galvanometers to direct the laser beam
| |
| | reducing the ink's light absorption and
|
| across the target surface. Each
| |
| | rate of thermal reaction. Paints must be
|
| galvanometer provides one axis of beam
| |
| | suitable for high-temperature processing
|
| motion in the marking field. A
| |
| | and be free of any contaminants that may
|
| multi-element, flat-field lens assembly
| |
| | absorb the laser wavelength and speed up
|
| subsequently focuses the laser light to
| |
| | the thermal rise.To achieve a quality
|
| achieve high power density on the work
| |
| | image, the top coat must be completely
|
| surface while maintaining the
| |
| | removed with minimal impact on the
|
| focused-spot travel on a flat plane. The
| |
| | underlying plastic or secondary coat. To
|
| laser output is gated to blank the beam
| |
| | maximize the ratio of light absorption
|
| between marking strokes.Marking can be
| |
| | between the two layers, the top coat must
|
| accomplished at speeds of up to 5000 mm
| |
| | always be a dark color and the
|
| sec with positioning speeds between
| |
| | contrasting underlying layer must be a
|
| marking strokes of 50,000 mm/sec. Because
| |
| | light color. The dark color will absorb a
|
| the process relies on heat conduction
| |
| | comparatively higher percentage of the
|
| into the plastic, marking speeds are
| |
| | laser light, resulting in a higher
|
| usually slower than the system's maximum
| |
| | surface temperature, while the light
|
| capability to allow sufficient conduction
| |
| | color reflects a higher percentage and
|
| to achieve the desired results.The
| |
| | minimizes the temperature rise. The
|
| beam-steered marker can duplicate
| |
| | underlying plastic, paint, or ink should
|
| virtually any black-and-white image,
| |
| | also be thick enough to tolerate a minor
|
| including variable line widths and images
| |
| | amount of material removal during
|
| as small as 0.0001 inch. Present
| |
| | marking.Marking coated plastics is a
|
| computer-imaging technology produces
| |
| | multi-step process in which the first
|
| highly intricate graphics with line
| |
| | marking pass removes the majority of the
|
| widths, resolution, and accuracy well
| |
| | top coating. The remaining residue is
|
| below 0.001 inch. Because the image is
| |
| | removed with a second, lower-power pass
|
| created by "drawing" with the laser beam,
| |
| | to minimize the effect to the underlying
|
| the marking time is dependent on the
| |
| | material. For precise edge definition,
|
| amount and complexity of the text and
| |
| | the outline of the image is marked prior
|
| graphics. With computer-generated
| |
| | to filling in the image. The outline is
|
| imaging, any graphic element or the
| |
| | marked with a heavy edge pass (i.e., 50
|
| entire marking program can be instantly
| |
| | kHz, 250 mm/sec, 2.5 watts) followed by a
|
| changed before a new part is positioned
| |
| | lower-power cleanup pass (50 kHz, 250 mm
|
| for marking.Nd:YAG lasers amplify light
| |
| | sec,1.75 watts). The image is then
|
| of 1.06mm wavelength in the
| |
| | filled, if desired, with a heavy fill
|
| near-infrared. They are unique among the
| |
| | pass (50 kHz, 650 mm/sec, 6 watts) and
|
| different types of lasers in that they
| |
| | subsequent cleanup pass (50 kHz, 6.50 mm
|
| operate much like an "optical capacitor."
| |
| | sec, 4.5 watts). Care in determining the
|
| In pulsed operation, the Nd:YAG laser
| |
| | process parameters for each pass and the
|
| stores energy between pulses, resulting
| |
| | edge and fill beam paths will result in a
|
| in peak powers of kilowatts of light
| |
| | crisp, high-contrast, high-quality
|
| energy. A Nd:YAG laser emitting 75 watts
| |
| | marking image.Preparation and
|
| of continuous light, pulsed at 1 kHz,
| |
| | InstallationPerhaps the most critical
|
| emits a train of pulses with peak powers
| |
| | element in the successful application of
|
| of 110,000 watts. The "optical capacitor"
| |
| | laser marking is the composition of the
|
| effect provides the peak power necessary
| |
| | part programs. When replacing an existing
|
| to vaporize material. For plastics
| |
| | marking technology, one must allow up to
|
| applications, the laser must also be run
| |
| | six months for conversion of existing art
|
| in a "top hat" mode, where the power
| |
| | work to part-marking computer programs.
|
| distribution is fairly even across the
| |
| | Even if the present artwork resides in
|
| cross section of the laser beam in order
| |
| | AutoCAD files, time must be allotted to
|
| to eliminate "hot spots" in the marking
| |
| | convert the files to optimized marking
|
| path.The beam-steered Nd:YAG marker
| |
| | programs.Many users start with thousands
|
| frequently replaces acid and electro-etch
| |
| | of sheets of Mylar artwork. (Mylar is a
|
| systems, stamping and punching systems,
| |
| | DuPont trade name.) Each Mylar film is
|
| and those other marking systems that
| |
| | scanned to create a bitmap image. The
|
| permanently mark products by imprinting
| |
| | scanned bitmap could be directly
|
| or engraving. It also replaces other,
| |
| | converted to the laser marker format with
|
| less permanent printing systems,
| |
| | good image quality, but the cycle time
|
| including ink jet.Uncoated PlasticsMost
| |
| | would be unnecessarily long, with
|
| uncoated plastics must be doped with a
| |
| | excessive marking line overlap.For best
|
| material reflective to the laser
| |
| | results, import the scanned bitmap into
|
| wavelength to prevent over-absorption of
| |
| | AutoCAD as a positional template. Create
|
| the laser light, which results in loss of
| |
| | a separate marking "logo" for each
|
| control of the temperature rise and
| |
| | alphanumeric character and graphic image,
|
| excessive melting on the surface.
| |
| | and, in AutoCAD, place each logo in
|
| Light-colored plastics are doped with
| |
| | position on a separate layer, using the
|
| mica, titanium dioxide or
| |
| | bitmap template as a positioning guide. A
|
| carbon-containing materials. The heat
| |
| | library of optimized logos facilitates
|
| generated by absorption of the laser
| |
| | the creation of programs from the scanned
|
| light causes the carbon to migrate to the
| |
| | artwork, allows nonstandard text kerning
|
| surface, producing a contrasting dark
| |
| | and line leading, and ensures low cycle
|
| mark against the unaltered background
| |
| | time and high image quality. After all
|
| plastic.Plastics are semitransparent to
| |
| | the logos are in place, the template
|
| the near-infrared wavelength of the
| |
| | layer is removed, and the final CAD file
|
| Nd:YAG laser. Depending on the degree of
| |
| | is converted to the laser marker program
|
| transparency and the laser output power,
| |
| | format.If the art work already exists in
|
| the laser beam can alter the material
| |
| | a CAD file format, the image elements
|
| surface to depths of more than 0.025 mm
| |
| | could be optimized without using a
|
| without achieving vaporization
| |
| | separate library of logos. Every element
|
| temperature on the surface. If material
| |
| | including repetitive elements shared
|
| vaporization occurs, the layer of carbon
| |
| | between drawings must be individually
|
| is thinned and the marking image will
| |
| | optimized. It will take considerably
|
| appear washed out.There has been
| |
| | longer to convert large quantities of
|
| considerable success in altering the
| |
| | files, and there is no guarantee that
|
| depth of carbon migration to create
| |
| | every clement is optimized correctly. It
|
| gray-scale graphics on light plastics.
| |
| | is far more efficient to use the original
|
| Adjusting the power and/or pulse rate of
| |
| | AutoCAD file as the placement template
|
| the laser controls the depth of
| |
| | for optimized logos.Implementation of
|
| penetration and therebv the darkness of
| |
| | beam-steered laser marking requires a
|
| the mark. Increasing the laser power will
| |
| | team effort. With cooperative
|
| increase the overall depth of penetration
| |
| | implementation. manufacturing can ensure
|
| and thickness of the carbon layer.
| |
| | product flow and integration with
|
| Increasing the pulse rate will result in
| |
| | existing controls, the materials
|
| a longer pulse width and lower peak
| |
| | department ensures that plastics and
|
| power. The longer exposure also increases
| |
| | coatings are appropriate for laser
|
| the depth of penetration and associated
| |
| | marking, and engineering will produce
|
| carbon layer.Dark plastic is doped with a
| |
| | part-marking programs with low cycle
|
| material that produces a lighter color as
| |
| | times and high-quality images. Careful
|
| the material expands and the density
| |
| | team planning, preparation, and execution
|
| decreases. As the temperature of the
| |
| | will result in a smooth application of
|
| plastic increases, the plastic expands to
| |
| | laser marking technology and the
|
| form a "blister" on the surface and a
| |
| | associated benefits in manufacturing
|
| lighter-colored mark. As with light
| |
| | efficiencies, quality, and product
|
| plastics, the temperature must be tightly
| |
| | value.Richard Stevenson is the Sales
|
| controlled to avoid over absorption. If
| |
| | Director for Control Micro Systems, Inc.
|
| the temperature rises too high and the
| |
| | a manufacturer of beam-steered laser
|
| blister bursts, material is lost and the
| |
| | marking systems. He has published and
|
| mark will lose contrast.Not all plastics
| |
| | presented numerous technical papers and
|
| require dopant to achieve a contrasting
| |
| | articles on laser marking in trade
|
| mark. Several plastics do yield excellent
| |
| | publications.
|
