Laser Marking on Plastic

The Best Type of Laser to Mark Plastic: UV Laser

Different types of lasers can be used to mark plastic, each differing mainly in the way the beam is focused and in the wavelength. Selecting the right system depends on the material and application.

CO2 Lasers

CO2 lasers have been around since the 1960s and are commonly used for general-purpose marking, since they produce deep, high-contrast, and durable marks through thermal processes. Due to their longer wavelengths (typically between 9,300 nm and 10,600 nm), CO2 lasers are more often used to process  metals, wood, cardboard,  and other  materials. Heat is the main mechanism to change the color of the part by slightly burning, engraving or ablating the material. Spot sizes (resolution) are generally larger than other laser standards, but can work for many applications.

Fiber Lasers

Fiber lasers use infrared light to produce precise markings on various materials. Their wavelengths range from 780 nm to 2200 nm; this range of infrared light tends to react well with metals and plastics. 

But infrared lasers also produce heat and can cause unwanted charring, along with debris and particulates that risk contaminating the surface. This often requires an extra cleaning step, and therefore some manual downtime.

UV Lasers

When it comes to precision and versatility, UV lasers are the best choice to mark plastics. They’re the only lasers with the ability to mark extremely small codes, with standard spot sizes down to  7 um micron. These spot sizes simply cannot be achieved with fiber or CO2 lasers for marking.

One of the main advantages of UV lasers is their ability to interact with several materials through photochemical mechanisms. UV lasers are frequently called “cold lasers,” as the desire is to use them to mark products and not  heat up the surface surrounding or underneath the marked area.

UV lasers can induce color changes on substrates to create high-contrast marks. While fiber lasers can also achieve this effect, they produce heat on the surfaces, and are limited to certain substrates.

Laserax’s DPSS UV lasers offer the largest marking field in the industry at 1 meter, compared to 300 mm for competitors. They also feature a variable focal distance and deliver average power levels of up to 55 W, ensuring effective and high-contrast marking on plastics.

Why are fiber and CO₂ lasers less effective than UV lasers for plastics?

CO2 and fiber lasers have limitations when it comes to marking certain types of plastics. On water bottles and other similar plastics, for example, fiber lasers are often unsuitable because their infrared wavelength can pass through the material, without producing the intended mark.

CO2 lasers at  10.6 um can use their laser induced heat to mark the materials by melting or engraving the surface. This leads to heat-related distortion or deformation, which can be fine for an application such as marking water bottles. But the accuracy and distortion of the CO2 laser mark is not appropriate for high-resolution application marks.

Which Plastics Can Be Laser Marked with UV Lasers

Commonly markable plastics:

• Polybutylene terephthalate (PBT)
• Polycarbonate (PC), transparent and colored
• Polyethylene (PE), including HDPE and LDPE, as well as PETE
• Polyester (PES)
• Polyamide (PA)
• Acrylonitrile butadiene styrene (ABS)
• Polyethylene terephthalate (PET), transparent and colored
• Polyimide (PI)
• Polyoxymethylene (POM), e.g., Delrin®
• Polypropylene (PP)
• Polyphenylene sulfide (PPS)
• Polystyrene (PS), transparent
• Polystyrene (PS), colored, including HIPS (High Impact PS)
• Polyurethane (PUR)
• Foam (PVC free)
• PVC, transparent and colored
• Acrylics (PMMA), clear and colored/tinted
• PEEK
• Polytetrafluoroethylene (PTFE), especially colored
• BioPlastics, such as colored PFA
   

Non-plastic materials that act like plastics:

• Silicones
• Rubber

Additives

While Fiber and CO2 lasers sometimes require the use of additives (like mica), UV lasers do not in most cases.

Types of Laser Marking for Plastics

Color Change (Discoloration)

UV lasers can produce markings by changing the color of the plastic: light colors turn dark through photochemical reactions, while dark colors turn white through photo bleaching. 

Foaming

When the laser hits the material, gas bubbles (foam) form within the plastic, which causes the surface to rise and appear whitish. This method is typically used on dark materials to get white marks and can be performed with UV, CO2, fiber, or green lasers. Foaming is only suitable when the change in dimension doesn’t matter.

Carbonization

Marking through carbonization involves heating up the material close to its combustion point. This process requires the presence of carbon in the material, since it is the carbon that turns dark.

Engraving

Engraving is when the fiber, CO2, or UV laser goes deep into the material (UV lasers are slower to engrave than other lasers, due to low power levels) Engraving produces deep & permanent marks that are more resistant to mechanical abrasion, but it does alter the surface of the material and heat & stress can potentially damage the material.

Ablation

Similar to engraving, ablation removes material, but typically on a micron scale, without heating the surrounding surface.

Safety Considerations for Laser Marking

Eyes

Polycarbonate shielding is sufficient for protecting the eyes when using a UV or CO2 laser. Fiber and green lasers, however, require specially coated plastics or glass for eye protection, which are more costly.

Fumes and Particles

Regardless of laser type, fume extraction is always important when marking plastic. In general terms, UV lasers produce the least amount of fumes, fiber lasers produce more, and CO2 lasers produce the most fumes.

Industries that Benefit from Plastic Laser Marking

The versatility of laser marking on plastics makes it a highly effective solution for a wide range of industries:

Automotive

Laser marking is used in the automotive industry to mark essentially any plastic part for identification and traceability. This includes buttons, headlight lamps, wires, electronic components, and more.
Not only does this technique improve production efficiency, but it also ensures companies are compliant with regulatory standards.

Electronics

UV laser marking is particularly useful in the electronics industry because of its ability to label very small components with highly accurate and clear results: microchips, wires, cables, connectors, plastic encapsulated circuits, and other electronic parts.

Medical

Since manufacturers of medical devices are under strict government regulations to ensure the well-being of all patients, the safety and reliability of laser marking makes it a preferred method for the permanent identification of plastic components.

This applies to catheters, catheter hubs, mouthguards, dental appliances, IV bags, tubes, and more.

Packaging

Every packaging material made of plastic that requires branding, traceability, or identification benefits from laser marking technology: plastic bags, containers, clamshells, etc. 

Consumer Goods

This can be just about anything: cosmetics, water bottles, toys, USB drives, bottle caps…