Laser Cutting of Plastics

Laser cutting is one of the most versatile and precise methods for processing plastics. It produces clean, narrow kerfs with minimal mechanical stress, making it ideal for intricate shapes, tight tolerances, and high-volume production. This guide covers laser types, cutting parameters, edge quality considerations, and material compatibility — all based on our production experience at PlexiSystem.

How does laser cutting work?

A focused laser beam (typically 0.1–0.3 mm spot size) melts, vaporizes, or burns through the material along a programmed path. An assist gas (compressed air, nitrogen, or oxygen) blows the molten material from the kerf. The process is non-contact, meaning no mechanical force is applied to the workpiece — allowing the cutting of delicate features and thin materials without deformation.

CO&sub2; vs. fiber lasers

CO&sub2; lasers (10.6 μm wavelength)

CO&sub2; lasers are the standard for cutting plastics. The 10.6 μm wavelength is efficiently absorbed by most organic materials (plastics, wood, textiles, paper), making them the optimal choice for acrylic, PET-G, HIPS, foamed PVC, and many other polymers.

Typical power: 40–400 W for plastics cutting
Maximum cutting thickness: up to 30 mm for PMMA, 15 mm for PET-G
Edge quality on PMMA: flame-polished, optically clear (cast PMMA)
Kerf width: 0.1–0.3 mm depending on focal length and material thickness

Fiber lasers (1.06 μm wavelength)

Fiber lasers are primarily designed for metals, but certain types can be used for plastics marking and engraving. Their shorter wavelength passes through many transparent plastics without being absorbed, making them unsuitable for cutting clear PMMA or PET-G. However, they can cut opaque plastics (colored PMMA, ABS, some composites).

Which laser for which plastic?

For virtually all plastics cutting at PlexiSystem, we use CO&sub2; lasers. Fiber lasers are used only for specific metal components and marking applications. If your project involves mixed materials (e.g., acrylic with metal inserts), we process each material on the appropriate machine.

Cutting parameters by material

The following parameters are starting points for a 130 W CO&sub2; laser with compressed air assist. Actual settings depend on the specific machine, lens focal length, material grade, and desired edge quality.

Material	Thickness [mm]	Power [%]	Speed [mm/s]	Edge quality
PMMA (cast)	3	60–70	15–25	Flame-polished, crystal clear
PMMA (cast)	5	75–85	10–18	Flame-polished, crystal clear
PMMA (cast)	10	90–100	4–8	Clear with slight taper
PMMA (extruded)	3	55–65	12–20	Slightly frosted
PET-G	3	65–75	10–16	Matte, slightly rough
PET-G	5	80–90	6–12	Matte, may require polishing
HIPS	2	50–60	15–25	Slight melting, acceptable
Foamed PVC	3	40–50	20–30	Clean, slight discoloration
Foamed PVC	10	80–90	6–12	Clean, yellow tinge at edge
Polycarbonate	3	70–80	8–14	Yellow discoloration, rough

Materials you should NEVER laser cut

PVC (solid/rigid): releases hydrochloric acid (HCl) gas — toxic, corrosive to machine optics and metal parts
Polycarbonate (PC): produces toxic fumes (bisphenol A), very poor edge quality with severe discoloration. CNC machining is the preferred method for PC.
ABS: emits hydrogen cyanide (HCN) at high temperatures — extremely hazardous. Use CNC routing instead.
HDPE / LDPE / PP: melt rather than vaporize, producing a rough, stringy edge. Not recommended for laser cutting.

Foamed PVC note

While solid PVC should never be laser cut, foamed PVC (Forex) can be laser cut in well-ventilated systems with proper fume extraction and filtration. The chlorine content is lower due to the foam structure, and cutting speeds are high, minimizing thermal decomposition. Nevertheless, always ensure your laser system has adequate HCl filtration.

Edge quality factors

Edge quality from laser cutting varies significantly depending on the material, cutting parameters, and laser type. Understanding these differences is essential for specifying the right process for your application.

PMMA (acrylic glass) — the ideal laser material

Cast PMMA produces a flame-polished, optically transparent edge when laser cut with a CO&sub2; laser. This is because PMMA depolymerizes cleanly at laser cutting temperatures, vaporizing into monomer (MMA) rather than charring. The result is an edge that requires no further finishing for most applications — a major advantage over CNC machining, which always requires edge polishing for optical clarity.

Edge quality comparison

Material	Edge appearance	Post-processing needed?
PMMA (cast)	Crystal clear, flame-polished	No (for most applications)
PMMA (extruded)	Slightly frosted / hazy	Optional polishing for optical use
PET-G	Matte, slightly rough	Polishing recommended for visible edges
HIPS	Slight melt, acceptable	Depends on application
Foamed PVC	Clean, minor discoloration	Usually not needed

Kerf width and tolerances

What is kerf?

Kerf is the width of material removed by the laser beam during cutting. It is always wider than the laser spot size due to thermal conduction into the surrounding material. Kerf width must be compensated in the cutting program to achieve accurate part dimensions.

Material thickness	Typical kerf width	Achievable tolerance
1–3 mm	0.10–0.20 mm	±0.05–0.10 mm
4–8 mm	0.15–0.25 mm	±0.10–0.15 mm
10–20 mm	0.20–0.35 mm	±0.15–0.25 mm

Note that thicker materials exhibit more edge taper — the bottom of the cut is slightly wider than the top. For critical fit applications (e.g., container joints), compensate for taper or specify CNC machining for edges that must be perfectly perpendicular.

Laser engraving and marking

In addition to cutting, lasers can engrave (remove material to a controlled depth) and mark (discolor the surface without material removal) plastics. Common applications include:

Raster engraving: bitmap-based surface engraving for logos, text, images. Depth 0.1–2 mm. Produces a frosted appearance on clear PMMA.
Vector engraving: line-based engraving following vector paths. Used for fine text, scales, graduation marks.
LED edge-lit engraving: shallow engraving on clear PMMA that glows when edge-lit with LEDs. Popular for signage and decorative panels.
Serial number marking: surface discoloration without material removal. Fast, suitable for production marking.

Safety considerations

Laser cutting safety

Fume extraction: mandatory for all plastics. HEPA + activated carbon filtration recommended. Some materials (PVC, ABS) produce toxic gases.
Fire risk: PMMA is flammable. Never leave the laser unattended. Keep fire extinguisher accessible.
Eye protection: CO&sub2; laser radiation (10.6 μm) is absorbed by standard glass, but enclosed laser systems with interlocked doors are still required.
Material verification: always confirm the material type before laser cutting. Mislabeled PVC cut as PMMA can damage the machine and endanger operators.

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