What causes cracking in acrylic during laser cutting?

What causes acrylic to crack during laser cutting?

Cracking in acrylic during laser cutting is usually caused by internal stress in the sheet combined with localized heat from the laser. Improper storage, transport damage, bending, clamping, or an unfavorable cutting strategy can also trigger cracks. In addition, the difference between cast acrylic and extruded acrylic can affect how the material reacts.

Most common causes

• Internal stress in the acrylic

Stress already present in the sheet becomes visible as hairline cracks or fractures during cutting.

• Heat buildup around small details or corners

Heat can accumulate locally, especially at sharp inner corners, small holes, and narrow shapes.

• Damaged or improperly stored sheets

Edge damage, scratches, bending, or pressure points make acrylic more susceptible to cracking.

• Unsuitable cutting order or overly aggressive settings.

If small parts come loose too early or stress builds up around the cutting path, cracks can form.

• Material type.

Cast and extruded acrylic do not always react the same way to laser heat. Extruded acrylic naturally contains more internal stress in the sheet. 

How do you identify the cause?

If you see stress lines or hairline cracks even before cutting, the cause is often related to the material or handling. If cracks consistently appear in the same place in the design, it usually points to heat buildup or a process issue.

How do you minimize cracking?

Inspect sheets beforehand for edge damage and stress. First, test a small sample piece. Adjust settings step by step. Pay extra attention to small details and sharp corners. Consciously choose the right type of sheet for your application.

For a suitable material choice, also check out the acrylic range at Laser Cut Supply.

For additional context on selection and safety, read Why acrylic gets hot and sticky during laser cutting.