On the Cutting Edge with PETG and Lasers

Lasers are growing in popularity among fabricators working with a wide range of materials. For plastic applications in the store fixture and highend point-of-purchase (P.O.P.) market, lasers offer speed, flexibility and pinpoint accuracy, enabling the creation of virtually any shape to exacting specifications.

Offering exceptional clarity, toughness, high chemical resistance and excellent forming capabilities, PETG sheet can be a valuable companion material to laser cutting. The material’s unique combination of properties can reduce fabricators’ overall cost of operations and increase design flexibility for retail fixtures and displays created using lasers.

Despite these advantages, however, there continues to be a lack of a strong knowledge base between laser equipment manufacturers, fabricators who use lasers and plastics suppliers. This has resulted in industry misconceptions about the compatibility between laser cutting and PETG sheet.

The following article provides an overview of the correct laser settings for cutting PETG sheet, as well as how PETG sheet and laser cutting can contribute to a fabricator’s total operational efficiency.

The Right Settings

PETG sheet is an excellent material to work with in regards to laser cutting. However, because the material has not yet been as widely adopted for this technique as alternative materials, the fabrication community has been less informed of proper PETG laser-cutting parameters.

Many lasers have a setting for generic plastic sheet, or acrylic in specific, which is preset in the system. Using these system presets can result in less than optimal performance with PETG sheet, since this material often exhibits less heat resistance than other types of plastic sheet. This can lead many fabricators to incorrectly assume that PETG sheet and lasers are not a workable solution.

Eastman Chemical Company, producer of Eastman Spectar ™ copolyester for PETG sheet applications, has conducted extensive research at its internal facilities and with the Auburn University School of Design to determine optimal settings for laser cutting PETG sheet. Using these settings, PETG sheet can be used with lasers as effectively as other plastics and can even boost overall efficiency.

There are four main settings to adjust on any laser-cutting system: the frequency of the laser pulse, the wattage of the laser, the speed at which the laser moves across the surface of the material and the adjustment of airflow through the air nozzle.

Eastman’s research, gathered during tests using a 75-watt laser, has shown that the frequency setting can be the most critical in terms of successfully cutting PETG sheet. Adjusting the pulse frequency of a laser to between 2,700 and 3,000 pulses per second (pps) is optimal for PETG sheet. This allows the laser to more evenly distribute heat across the PETG sheet surface, preventing burning of the material. To complement this calibration, air nozzle settings of 26 – 30 pounds per square inch (psi) are also optimal, as well as a cutting speed of about 25 inches per minute. Wattage, however, did not test as a significant factor in optimizing settings for PETG sheet.

These settings have shown to efficiently cut PETG sheet in thicknesses up to 100 mm. In addition, use of a pintable to elevate the sheet during laser cutting also optimizes aesthetic results as it can prevent smoke clouding from occurring. Smoke clouding can easily be wiped clean from PETG sheet, but this adds a preventable step to the process, which can cut down on overall operational efficiency. Leaving the protective masking on the PETG sheet during the laser cutting process will eliminate surface whitening that may otherwise appear. This will help assure fabricators provide displays and fixtures with high quality aesthetics for the store environment.

Enhancing Laser Efficiency

Beyond the fact that PETG sheet can be cut using a correctly calibrated laser, the material can actually work in conjunction with this cutting technology to create an overall efficient operation.

Most fabricators invest in laser-cutting equipment to increase production efficiency through faster cutting, lower maintenance costs and greater flexibility. PETG sheet adds to this drive for overall efficiency because the material is tougher than many other types of plastic sheet. For example, PETG sheet can absorb over 80 joules of force during dart impact testing. Impact-modified acrylic, by comparison, scores around 30 joules. The toughness and durability of PETG sheet means that the material can be downgauged for POP display and store fixture applications without sacrificing integrity or durability. This can help to reduce material, shipping and inventory costs.

The ability of PETG sheet to be downgauged can also translate into faster laser cutting, as less time is needed to cut thinner sheet. So, while PETG sheet has less heat resistance compared to alternate materials, its toughness actually adds to the speed already gained in a laser-cutting environment.

In addition to downgauging, there are several other PETG sheet processing benefits that can add to the overall efficiency of a fabricator’s laser-cutting operation. For example, laser cutting is often one of many fabrication processes that a plastic sheet can undergo during the creation of retail fixtures and displays. For designs calling for this technique to be used in conjunction with thermoforming, PETG sheet can improve thermoforming cycles by up to 20% and eliminate the need for pre-drying. Because PETG sheet is thermoformed at lower temperatures, a fabricator also has the flexibility to decorate with paints, coatings or vinyl prior to thermoforming.

Together, these time-saving factors can lead to enhanced overall efficiencies and improve the return on investment on the laser-cutting unit, helping to create a lower total cost of operation.

Versatility

Another reason for investing in laser technology is the design freedom that it offers. Lasers operate from programmable print drivers with easy to understand graphic user interfaces (GUIs) that are simple to program, even with the most intricate designs. This enables a laser to accurately cut any design that can be printed on paper.

PETG sheet adds to this design versatility both directly with its laser-cutting compatibility and indirectly through its own inherent versatility. For example, the material exhibits uniform distribution during thermoforming, which can result in deeper draws and more detailed designs. In addition, surface scratches can be easily removed with a hot air gun, extending the lifecycle of retail fixtures and displays

Versatility also extends to end-users. For POP displays and store fixtures, cleaning on a regular basis is necessary – a process that can expose plastics to random aggressive chemical agents. PETG sheet, however, offers a high level of chemical resistance, ensuring that end users do not have to worry about special care instructions. Adding a laser to a fabrication operation can enhance production efficiency and design flexibility to help meet brand owner and retailer demands. PETG sheet can add to this overall flexibility both in the shop and for the end-user.

Obtaining a Leading Edge

Investment in new technology is ultimately about creating competitive advantage. These benefits can come through greater efficiency or better products and services. Combining PETG sheet with laser cutting offers fabricators a rare moment of enhanced efficiency, improved service and a superior product. By leveraging Eastman’s research in studying the interaction of PETG sheet and lasers, fabricators can achieve this unique combination and gain a leading edge in the marketplace.

Eastman Chemical Company (NYSE:EMN) manufactures and markets chemicals, fibers and plastics worldwide. It provides key differentiated coatings, adhesives and specialty plastics products; is one of the world’s largest producers of PET polymers for packaging; and is a major supplier of cellulose acetate fibers. As a Responsible Care® company, Eastman is committed to achieving the highest standards of health, safety, environmental and security performance. Founded in 1920 and headquartered in Kingsport, Tennessee., Eastman is a FORTUNE 500 company with 2006 sales of $7.5 billion and approximately 11,000 employees.

Written by Chad Alan Frazier, Technician Associate, Specialty Plastics Film and Sheet, Eastman Chemical Company. For additional information, contact Lucy Stewart, Eastman Chemical Company, P.O. Box 431, Kingsport, TN 37662, 423-229-4229, E-mail: lstewart@ eastman.com. Web: www.eastman.com.

For more information, Lucy Stewart, Eastman Chemical Company, P.O. Box 431, Kingsport, TN 37662, 423-229-4229, E-mail: lstewart@eastman.com. Web: www.eastman.com.