Decorative thermoplastics with laser markings have taken longer than expected 10 years ago to gain acceptance. However, laser technology has replaced ink marking technologies (such as embossing and inkjet printing) in some applications and the situation has changed.
The so-called "non-aesthetic" applications currently account for 90% of the plastic laser markings. Some of the markings are made using a CO2 laser machine, including part numbers, manufacturing dates, and expiration dates. Usually these markings are black letters and numbers on a transparent or light background, or pure white markings on a black background.
“Aesthetics” laser marking accounts for 10% of the market and has great potential for replacing ink technology. This is a typical white marking on black engineering plastics. It is printed on a solid-state Nd:YAG laser. This laser is easy to program and is suitable for clear marking of products in any shape.
Applications that have been successfully commercialized for laser marking include ABS keyboards for commercial machines, HDPE, PP, PET, and PVC rigid containers and closures; Nylon and PBT automotive and non-automotive electrical connectors; hood components such as fuse boxes and air caps. . There are other applications including TPE ear tags for cattle and pigs, electrical devices such as HDPE switch buttons on cleaning and drying equipment, PVC fittings such as fittings and fittings.
The initial applications include light switch covers, cosmetic packaging materials, automotive interior buttons and door handles, and instrument panels. In recent years, the latter has become an important application market.
In the last decade, technological advances in computer-programmed laser marking equipment have been accompanied by the development of a wider variety of laser-markable resins. Specially-made colorants and packaging additives can be used in a wide variety of plastics. Such as polyolefins, ABS, PVC, polyester, polycarbonate, nylon, polyoxymethylene and thermoplastic elastomers.
Today's laser marking plastics have a high contrast ratio. Sometimes it is not so much black and white as a contrasting color. Even dark contrast is possible. According to Patrick Schlather, marketing manager of Rofin-Baasel, a major supplier of plastic laser equipment, these color variations are one of the trends that are giving rise to greater interest in laser decorative plastics.
Laser marking applications include light switch covers, cosmetic packaging materials, automotive interior buttons and door handles, and instrument panels. In recent years, the latter has become an important application market, but also meets the development needs of printing large amounts of data on even smaller plastic parts. For example, two-dimensional barcodes with a data density of 10 times that of conventional barcodes have been studied. Compared with previously used barcodes, printing two-dimensional barcodes requires more precision and higher resolution. According to Schlather, laser marking satisfies these requirements. In the 0.001-inch range, the dot size and position can be repeated—these properties are difficult for imprint or ink printers to achieve.
Environmental issues are another driving force for the development of laser marking. Laser marking does not use inks or solvents, nor does it require high-intensity energy drying processes such as ink marking. Schlather said that for a three-shift printing production, inks and chemicals cost between 20,000 and 40,000 U.S. dollars, while printed plates cost 100,000 U.S. dollars per year or more. In contrast, a three-shift laser marking machine costs less than $3,000 a year for electricity, and other costs such as lamps and filters cost less than $3,500.
Printing Labeling Basics Although there are many existing laser sources for decorative plastics, sealed carbon dioxide lasers are currently the most widely used, followed by lamp-pumped solid-state Nd:YAG lasers and recent diode pumping. Nd:YAG device.
Most laser devices use high-speed beam-controlled galvanometer marking technology. This control device scans the laser beam with two computer-controlled mirrors or galvanometers that can move in the X or Y direction. “When the programmed laser path is completed, the new part is in place and repeats this cycle. Because the laser mode is completely in software, tools or masks are not required.”
Software that allows plastic marking with rotating beam control is also available from several laser equipment suppliers. This kind of equipment is essentially the same technology, but is suitable for continuous rotary production such as conveyor belt or substrate conversion, Barbero explained, "The advantage of this equipment is that it can be easily retrofitted to existing production lines, The productivity is maximized. The code is fed back to the computer and the computer makes appropriate adjustments to track the moving target in real time." Schlather went on to say, "The current device uses simple and straightforward graphics generation software, which is easy to program. Single data is printed on each and every rotating part."
In recent years, the proceduralization, standardization and troubleshooting of laser marking have become easier and the speed of marking has also been greatly improved. Barbero said, "Today's software is suitable for printing more than 400 words per second, and only 40 per second were printed 10 years ago." Most laser machine software has the ability to print serial and multiple models Bar code and text of any model (including company logo). With the Window-based “Help” option, laser marking suppliers added service and standardization techniques as well as fault clearing software.
Another development is the use of a laser light source to simultaneously print two parts. In addition to a deformation head and a programmed beam splitter, with the same information, a laser machine can print two parts at the same time. Schlather pointed out that this type of device can be used to print large areas or large quantities of parts that do not move parts.
Cost is a key factor in the ever-popular CO2 laser equipment. A complete set of CO2 turnkey equipment sells for between $25,000 and $35,000, while a tube-pumped or diode-pumped Nd:YAG device sells for between $60,000 and $75,000.
The CO2 laser etched the plastic surface and cleaned the material by evaporation, resulting in a contrasting mark but with little or no real color change. Plastics suitable for printing on carbon dioxide lasers are PVC, ABS and most polyesters. Mica-filled commercial resins, such as PP, are marked with a CO2 laser to produce a frosty gray marking. Although the CO2 output power can reach 200W, the most common range for printing plastics is 10 to 25W, and sometimes 50W.
In the coding process of the bottling line, speed is critical, or large letters are also needed, and carbon dioxide lasers are generally used. Steve Bone, president and chief executive officer of the FOBA North American Laser Equipment Group, said that carbon dioxide engines use matrix printing marks twice as fast as Nd:YAG machines, albeit at a fraction of a second.
"Now laser marking plastics have a high contrast ratio. Sometimes it is not so much black and white as a contrasting color. Even dark contrast is possible."
Control Microsystems' main market focus has always been on car hoods and electronic/electrical devices. Stevenson, the company's company, said that when considering a plastic marking, the first thing to do is to try to use a CO2 laser. “If you do not get the required contrast or get an excessive amount of melting, go to the YAG laser.” Heating the plastic on a solid Nd:YAG laser causes thermochemical reactions (such as foaming) and also produces more color changes. Since the wavelength of the laser light generated by this laser is short, high definition can be obtained. The shorter the wavelength, the less heat is induced by the plastic substrate (cold print). FOBA's Bone said that the 100-watt Nd:YAG device used for plastic marking is currently popular (due to its high output), but devices with output power of 30-50W are also available. YAG lasers are generally used for high quality marking of parts such as electronic connectors, hood components, lock caps, and surgical equipment.
Schlather of Rofin-Baasel recommends that processors consider the required production volume and the aesthetic requirements of the printed label when considering a solid-state laser. For example, if you want a high-contrast, out-of-measured off-scale mark, the high-frequency laser performs best. However, this depends on whether the device's low output power suits your productivity requirements.
There is also a new type of diode with a power between 3 and 100 W. A diode can be used as a laser light source instead of the electron tube of the vacuum pump device. It is said that the diode is 50% more compact than the electron tube and the energy efficiency is increased by 20% to 30%. Tube equipment needs water cooling, and the diode type needs water or air cooling. The electron tube generally needs to be replaced every 1000 hours, and the lifetime of the diode is 10,000 hours. The disadvantage is that diodes are relatively new and expensive. For example, the FOBA50W diode pump laser is 10% more expensive than a 100W tube device. However, FOBA anticipates that the prices of diode devices may fall in the next few months, and they will eventually replace the tube pump equipment.
“Environmental issues are another driving force for the development of laser marking. Laser marking does not use inks or solvents, nor does it require high-intensity energy drying processes like ink marking.”
Schlather of Rofin-Baasel summarized the choice of YAG type: “If you need to perform maintenance every 600-800 hours, then the pump investment is minimal, but you can get the maximum productivity. If you use a 3-60W diode pump device can achieve the desired marking Then diode pump equipment will cost less than tube pump equipment in 5 years." Formulation for lasers If the correct choice of additive formula is used, FOBA's Bone says that almost any plastic can be printed on any type of laser machine. . The supplier of the recipe or masterbatch needs to know the resin, the final application, the type of icon needed. For example, some plastics such as high density polyethylene and polycarbonate can be printed with YAG lasers in some colors without any additives. Carbon dioxide lasers, on the other hand, do not print well when they are printed without special additives.
The limitation of the prior art is that the ability to obtain a well-tuned laser marking is limited, and the laser-preferred plastic cost is also higher than the market price by 10% to 15%, and sometimes higher.
Bill Blasius, director of technology development at the Clariant Group, acknowledges that laser marking is limited in pigment choice and color transparency. He said, “We know more about how to use pigments and additives than we did 10 years ago. We hope to use laser light to make full use of chemical reactions that occur between special resins and certain additives and pigments. ”
Due to the development of compounding technology, we can obtain almost white markings on black or blue acetal copolymers or pure white markings on black ABS. With special recipes and laser machine parameters, we can even get tuned colors. Schlather explained that “In this way, etched laser markings can be tuned to Pantone, Munsell or other industry standards. The pigments in the resin determine the color and hue, and the laser determines the strength or concentration.” Many laser marking colors The additives are based on surface-treated mica, such as the popular Afflair and Laser Flair formulations formulated by EM Industries. But other additives such as copper and tantalum are also used in the patent formula.
“Although there are many existing laser sources for decorative plastics, sealed carbon dioxide lasers are currently the most widely used, followed by lamp-pumped solid-state Nd:YAG lasers and diode pumped Nd:YAG in recent years. Device."
The companies that produce plastics for laser marking are BASF, Bayer, Ticona and RTP. The main suppliers of specialty pigments and additive masterbatches for laser marking are Clariant and PolyOne.
Focusing first on automotive parts, Ticona introduced two laser-markable black acetal copolymers, Celcon LM90 and LM90Z. The LM90 is used to print engine hoods and fuel device components. The LM90Z is a UV-stabilized type of interior trim, such as for speaker grills and release levers. Tom Miller's automotive marketing manager said that patented additives are best suited for Nd:YAG lasers.
Ticona's latest research product is the Celcon UV140LG, which is said to be the first low-gloss acetic acid aldehyde copolymer for laser marking. It also has anti-ultraviolet effect. At the 2001 and 2002 model year auto show, it was mainly used for radio buttons, hazard lights, and cruise controllers. Tico

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