What are the reasons for deformation of workpieces cut by laser cutting machines? Deformation or warping during laser cutting is a common challenge, particularly when working with thin metals or complex geometries.1 It is fundamentally caused by the imbalance of internal stresses within the material.2+1
The main reasons for workpiece deformation can be categorized into four key areas:
1. Thermal Stress and the Heat-Affected Zone (HAZ)
The most common cause of warping is the extreme temperature gradient created by the laser.
- Expansion and Contraction: As the laser melts the metal, the heated area expands.3 Because the surrounding material remains cold, it resists this expansion.4 When the area cools and shrinks, “residual stress” is locked into the part, causing it to bow or twist.5+2
- HAZ Impact: A larger Heat-Affected Zone (the area around the cut that didn’t melt but was changed by heat) increases the likelihood of deformation.6 This is often caused by slow cutting speeds or excessive laser power.7+1
2. Release of Residual Material Stress
Most sheet metals are not perfectly “relaxed” when they arrive from the factory.8
- Mill Stresses: Processes like cold-rolling or coiling lock internal stresses into the metal.9
- The “Release” Effect: When you cut a shape out of a sheet, you are removing the structural material that was holding those internal stresses in balance.10 Think of it like cutting a rubber band—once the support is gone, the material “springs” into a new, warped shape.11+1
3. Improper Cutting Sequence and Nesting12
The order in which the laser travels significantly affects heat buildup.13
- Heat Accumulation: If the laser cuts many small features in one localized area without moving away, the “base” temperature of that section rises too high.
- Lack of Support: Cutting the outer contour of a part before the internal holes can cause the part to shift or sag as it loses its connection to the main sheet, leading to dimensional errors.14
4. Technical and Parameter Errors
Sometimes the setup of the machine itself leads to uneven heating:
- Inappropriate Assist Gas: Using Oxygen creates an exothermic reaction that adds extra heat to the cut.15 For sensitive parts, Nitrogen is preferred because it acts as a coolant while blowing away molten metal.16+1
- Focus Position: If the focus is not centered correctly relative to the material thickness, the kerf (cut width) may be wider on the top than the bottom, causing uneven cooling and “camber” deformation.
How to Prevent Deformation
| Strategy | Description |
| Path Optimization | Use “leapfrog” or staggered cutting sequences to allow the material to cool between cuts. |
| Micro-Joints (Tabs) | Leave tiny “tabs” connecting the part to the scrap frame to keep it supported and flat until the end. |
| Increase Speed | Faster travel speeds reduce the amount of heat absorbed by the surrounding metal. |
| Lead-ins/Lead-outs | Strategically place start points away from delicate corners to prevent localized melting. |
Would you like me to explain how to optimize nesting software settings to automatically reduce thermal stress during a production run?
Understanding Thermal Stress and Part Distortion
This video provides a practical look at how thermal stress develops during laser cutting and offers visual demonstrations of how to adjust your process to keep parts flat and accurate.