The decorative thermoplastic with laser marking took longer than expected a decade ago to get people's approval. Nonetheless, laser technology has replaced ink marking technology (such as imprinting and inkjet printing) in some applications, and the situation has changed. At present, the so-called "non-aesthetic" applications are estimated to account for 90% of plastic laser markings. Some markings are made with carbon dioxide laser machines, including part models, manufacturing dates, and expiration dates. Usually these marks are black letters and numbers on a transparent or light background, or pure white marks on a black background. "Aesthetic" laser marking accounts for 10% of the market and has great potential for development in replacing ink technology. This is a typical white marking on black engineering plastics. It is printed with a solid-state Nd: YAG laser machine. This laser machine is easy to program and is suitable for clear marking of products on any shape.
Applications for laser marking that have been successfully commercialized include ABS keyboards for commercial machines, HDPE, ie, PET and PVC rigid containers and lids, nylon and PBT automotive and non-automotive electrical connectors, hood components such as fuse boxes and gas cap . There are other applications, including TPE ear tags for cattle and pigs, electrical components such as HDPE switch buttons on cleaning and drying equipment, and PVC fittings such as joints and fittings.
The first 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 ten years, the technological progress of computer-programmed laser marking equipment has been accompanied by the development of more varieties of laser-markable resins. Specially-made colorants and packaging additives can be used in a variety of plastics. Such as polyolefin, ABS, PVC, polyester, polycarbonate, nylon, polyoxymethylene and thermoplastic elastomers.
Today's laser-printed plastics have high contrast. Sometimes, it is more a contrasting color than black and white. Even dark and dark contrast becomes possible. According to Patrick Schlather, marketing manager of Rofin-Baasel, a major supplier of plastic laser equipment, these color variations are one of the popular trends. This trend is making people more interested in laser decorative plastics.
Applications for laser marking 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, while also meeting the development needs of printing large amounts of data on even smaller plastic parts. For example, two-dimensional barcodes with a data density 10 times higher than traditional barcodes have been studied. Compared with the previously used barcodes, printing two-dimensional barcodes requires more accuracy and higher definition. According to Schlather, laser marking meets these requirements. In the range of 0.001 inches, the size and position of the dots can be repeated-these performances are difficult to achieve with embossing or ink printing machines.
Environmental issues are another driving force for the development of laser marking. Laser marking does not use ink or solvents, nor does it require a high-intensity energy drying process like ink marking technology. Schlather said that for a three-shift label production, inks and chemicals cost $ 20,000-40,000, while printing plates costs $ 100,000 / year or more. In contrast, a three-shift laser marking equipment costs less than $ 3,000 per year in electricity, and other costs such as lamps and filters cost less than $ 3,500.
Basics of marking equipment
Although there are many existing laser light sources for decorative plastics, the sealed carbon dioxide laser is currently the most widely used, followed by the solid-state Nd: YAG laser pumped by the lamp tube and the Nd: YAG laser diode pumped in recent years .
Most laser devices use high-speed beam-controlled galvanometer marking technology. This control device scans the laser beam with a mirror or galvanometer that can be moved in the Z direction by two computers. "When the laser path of the programmed program is completed, the new part is put in place, repeating this cycle. Because the laser mode is completely in the software, no tools or masks are needed."
Software that allows plastic marking with rotating beam control is also available from several laser equipment suppliers. This equipment essentially uses the same technology, but is suitable for continuous rotation 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, Maximize productivity. The code is fed back to the computer, and the computer makes appropriate adjustments to track the moving target in real time. "Schlather continued." The current equipment uses simple and clear graphics generation software. This software is easy to program. A single piece of data is printed on each and every rotating part. "
In recent years, it has become easier to program, standardize and troubleshoot laser marking, and the speed of marking has also been greatly improved. Barbero said: "Today's software is suitable for printing more than 400 spaces per second, while 10 years ago it was only able to print 40." Most laser machine software has the ability to print serial and multi-model Bar code and text of any model (including company logo). With N1ndow-based "Help" options, laser marking suppliers have added services and standardized technologies and fault-clearing software.
Another development is the simultaneous printing of two parts with a laser light source. Plus 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 equipment can be used to print large areas or large numbers of parts without moving parts.
Cost is a key factor in the growing popularity of carbon dioxide laser equipment. A complete set of CO2 turnkey equipment is priced between US $ 25,000 and US $ 35,000, while a Nd: YAG device with tube or diode pumping is priced between US $ 60,000 and US $ 75,000.
The carbon dioxide laser machine etched the plastic surface and cleaned the material by evaporation to obtain a contrasting mark, but with little or no real color change. Plastics suitable for printing with carbon dioxide lasers include PVC, ABS and most polyesters. Commercial resins filled with mica, such as gray-white marks that produce frost when marked with a carbon dioxide laser machine. Although the output power of the carbon dioxide machine can reach 200W, the most common range for printing plastics is 10-25W, sometimes 50W (due to its high output), but there are also devices with output power of 30-50W. YAG laser machines are generally used for high-quality marking of parts, such as electronic connectors, hood components, lock caps and surgical equipment. Rofin-Baasel's Schlather recommends that processors consider the required production volume and the aesthetic requirements of the printed label when considering the purchase of solid-state lasers. For example, if you want a high-contrast, unmarked interrupt mark on the surface, a high-frequency laser machine performs best. However, it depends on whether the low output power of the device is suitable for your productivity requirements.
There is also a new type of diode with a power between 3 and 100W. You can use the diode as a laser machine light source to replace the tube of the tube pump equipment. It is said that the diode is 50% more compact than the electron tube, and the energy efficiency is increased by 20% -30%. Electronic tube equipment requires water cooling, while the diode type requires water cooling or air cooling. The electron tube generally needs to be replaced every 1000 hours, and the service life of the diode is up to 10000 hours. The disadvantage is that diodes are relatively new and expensive. For example, FOBA50W diode pump lasers are 10% more expensive than 100W tube devices, but FOBA expects the price of diode devices to fall in the coming months, and they will eventually replace tube pump devices.
"Environmental issues are another driving force for the development of laser marking. Laser marking does not require inks or solvents, nor does it require a high-intensity energy drying process like ink marking technology."
Rofin-Baasel's Schlather summarized the choice of YAG type: "If you want to perform maintenance every 600-800 hours, then the tube pump investment is the least, but you can get the maximum productivity. If you use 3-60W diode pump equipment to complete the desired mark , Then the cost of the diode pump equipment will be less than the tube pump equipment in 5 years. "[Next]
Laser recipe
If the correct additive formula is used, FOBA's Bone says that almost any kind of plastic can be printed by any type of laser machine. Suppliers of formulas or masterbatches need to understand the resin, the final application, and the type of icon required. For example, some plastics such as high-density polyethylene and polycarbonate can be printed very well in some colors using YAG lasers without any additives. On the other hand, carbon dioxide lasers do not print well without special additives when printing these two plastics.
The limitation of the prior art is that the ability to obtain color-adjusted laser markings is limited, and the preferred plastic cost of lasers is also higher than the market price by 10% to 15%, sometimes higher.
Bill Blasius, director of the masterbatch technology development department of the Clariant Group, admitted that laser marking is limited in pigment selection and color transparency. He said: "We know more about how to use pigments and additives than we did a thousand years ago. We hope to make full use of chemical reactions when using laser lights. This chemical reaction occurs between special resins and certain additives and pigments." Due to the development of compounding technology, we can get almost flat white mark on black or blue acetaldehyde copolymer, or pure white mark on black ABS. With special formulas and laser machine parameters, we can even get adjusted colors. Schlather explained: "In this way, the etched laser marking can be adjusted to Pantone, Munsell or other industry standards. The pigment in the resin determines the color and hue, and the laser machine determines the intensity or concentration." / Licking 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 antimony are also used in patented formulations.
"Although there are many existing laser light sources for decorative plastics, sealed carbon dioxide lasers are currently the most widely used, followed by solid-state Nd: YAG laser pumped by lamps and diode-pumped Nd in recent years: YAG device. "
Companies producing dry laser-printable plastics include BASF, Bayer, Ticona and RTP. The main suppliers of special pigments and additive masterbatches for laser marking are Clariant and PolyOne.
Focusing on auto parts first, Ticona introduces two black acetal copolymers that can be laser marked, Celcon LM90 and LM90Z. The LM90 is used to print engine hoods and fuel equipment components. The LH90Z is a UV-stabilized interior part, such as speaker grilles and release levers. Tom Miller's automotive marketing manager said that additives with patented technology are most suitable for Nd: YAG lasers.
Ticona's latest research product is Celcon UVl40LG, which is said to be the earliest snake acetate aldehyde copolymer for low gloss laser marking. It also has anti-ultraviolet effect. Ticona also offers laser-markable, smooth, glass-fiber-filled and mineral-purple glass-fiber-filled Celanex PBT, which is used to mark automotive and electrical / electronic components that do not require aesthetics. Laser-markable V6ndar PBT based on mixtures and alloys is designated as the inner component of automotive inner tubes. The new laser-printable Celanese nylon 66 is also being evaluated for the application of automotive interior components. According to Miller of Ticona, most cars
Car parts require a black substrate with a pure white printed label and a white printed label. "Not only the density of the special black should be compared with the specifications of 0EM, but also the color of the color. The density of the white obtained depends mainly on the additional packaging."
Laser etching, more precisely, engraving has been applied to day / night reflective components since the mid-1980s, such as fluorescent screens, buttons and switches for car stereo surround control, and mirror housings. Some components are particularly transparent polycarbonate or ABS, which are first painted white and then painted black. Use a laser machine for black etching. When the part is reflective, the white color is revealed. Ticona's Miller said: "With creative product design and manufacturing techniques (such as two-component molding), it is possible to eliminate these two processes." "The carbon dioxide laser machine etched the plastic surface and cleaned the material by evaporation. Mark, but there is little or no real color change. "
RTP supplies several smooth and enhanced laser-printable plastic compounds. These plastics are PP, nylon (6, 66, 12, 11, 612), ABS, LLDPE, acetaldehyde copolymer, thermoplastic polyurethane, polybutylene terephthalate, syndiotactic polystyrene, polysulfone, PPS , TPO, acrylic, PC / acrylic, PC / ABS, LPC. StuartSwain, the manager of the paint department, said: "There are huge business opportunities for printing different colors on a black background into white, yellow, and green. "
The German BASF laser marking laboratory research shows that the addition of glass fiber only slightly weakens the printing performance of plastics, but some fillers, flame retardants and re-grinding shreds can greatly reduce the printing. performance. The resins that BASF produces for laser marking include Terluran ABS, UltraformacetaI, Luran S ASA, Ultramid nylon, Luran SAN and Ultradur PBT black pigments.
German Bayer is doing similar work, the company provides polycarbonate, ABS, PBT that can be used for laser marking.
Most of Clariant's laser marking masterbatches are customized. We have our own laser marking powder base, which is both mica base material formula and patented additive formula, we hope to use these formulas to produce special master batch). The pigment effects currently achievable by Clariant are firstly a gradient from white to gray to black on any pigment substrate. On very black substrates, Clariant can provide blue, red or green marks. Blasius expects to achieve a wider range of colors in the next few years.
David Bates, marketing manager of FastMark of PolyOne Group, said that their company's new masterbatch is suitable for making pure black marks with high contrast on white substrates and pure white marks on black substrates. PolyOne also provides masterbatch, which can provide virtually any color mark (usually on black parts). The company combines a variety of special-purpose colorants with additives for laser marking to create a greater possibility of printing shiny labels on naturally colored containers. These new formulas present huge business opportunities—on some high-end SAN cosmetic packaging materials, polyolefin shampoos and thermostat bottles and caps, which are as good as toys. PolyOne has developed FastMar additives for polyolefins, polycarbonate, PC / ABS, and SAN that are both smooth and can be filled with glass fibers or minerals.
Several other companies have also provided laser marking formulas on a low-key basis, including Ferro Group, Jiulu Schulman and LNP Engineering Plastics. Schulman manufactures laser-printed compound ingredients and PolyBatch masterbatches for automotive cabins. lNP provides laser-printed StarFlam flame retardant nylon type compound for electrical devices, Stat-Kon formulation of polyphenylene sulfide for medical containers, ABS, PC and acetaldehyde formulations for surgery.
Plastic product marking in China-the prospect of laser marking
Many plastic final products, such as computer and other office machine shells and accessories, electrical appliance shells and accessories, various electrical connectors, and automotive interior parts need to be marked with product trademarks, specifications, materials used, manufacturers, manufacturing dates, expiration dates, etc. Some such as plastic pipes also need to be marked with the model of the molding machine. Some of them are to meet the requirements of business activities, and some are mandatory requirements of quality assurance regulations. There are a variety of plastic product marking methods, such as direct molding (ie, engraving directly on the injection molding mold), embossing, hot embossing, inkjet, laser, etc. Either way requires that the marking is clear, durable, and will not disappear due to mechanical, chemical, and physical factors.
Due to economic reasons, direct forming, embossing and hot embossing methods are currently used in China. Inkjet printing has increased (especially on the pipe production line), and laser marking methods are rare. The laser marking method has no application of ink and solvent, good environmental adaptability, flexible control of the shape of the mark through the computer, and a large density of markable data. Its application range is constantly expanding, especially in the automotive interior parts. The application is growing rapidly. However, the laser marking method also has shortcomings. In order to carry out clear laser marking of plastics, the material needs to be appropriately modified with special additives.
With the expansion of the application range of laser marking methods and the maturity of technology, costs are falling. China is a big country in the production and application of plastic products. In 2001, according to the statistics of enterprises with an output value of more than 5 million yuan, the production of plastic products reached 11853 kt, and the apparent consumption calculated according to the production and import and export of resin reached 25,000 kt Around (estimated value), a lot of plastic products need to be marked. As a new-generation marking method, laser marking method has broad development prospects in China's plastic products industry.
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