Laser-cut plate must meet the required geometry and dimensions. Assessing cutting quality also means examining the condition of the cut edge.
Residue beneath the edge, surface irregularities, through-thickness inclination and heat-induced material changes each reveal a different aspect of quality. They can affect the need for additional processing and subsequent assembly and welding.
Four key aspects help explain laser-cut edge quality: dross, surface roughness, perpendicularity and the heat affected zone.
A close-up view of the cut edge and through-thickness profile of a steel plate component.
Dross Reveals How Effectively Molten Metal Is Removed
During laser cutting, the material melts and the assist gas expels molten metal from the kerf. Material that is not fully expelled may adhere to the lower edge and solidify. This residue is known as dross.
Assessment considers not only the amount of dross, but also its distribution and adhesion. Is it limited to isolated areas or continuous along the cut? Can it be removed easily?
Heavy or firmly attached dross may require additional cleaning before fabrication. Cutting speed, focal position and gas conditions can influence its formation, so the combination of process parameters should be reviewed.
Surface Roughness Is Assessed by Texture and Consistency
Striations can form on a laser-cut edge as molten metal is removed. Their presence alone does not mean that the cut is defective. The size and depth of surface irregularities, and their consistency across the edge, should be considered.
Visual inspection helps identify deep grooves or locally rough areas. However, appearance alone cannot provide a numerical roughness value. Where quantitative assessment is required, surface roughness is measured and compared with the specified criteria.
Acceptable roughness depends on the component application, drawing and customer requirements. It can also help indicate whether additional machining is needed.
Perpendicularity Describes Accuracy Through the Plate Thickness
A component can appear accurate when viewed from above while its cut edge is inclined through the plate thickness. For a nominally square cut, perpendicularity describes how closely the edge follows a right angle to the plate surface.
Deviation between the upper and lower edges can affect joint gaps or contact during fit-up. Plan-view dimensions should therefore be considered alongside the through-thickness geometry.
Intentional weld bevels are assessed separately. Their acceptance depends on the bevel angle and geometry specified in the drawing, rather than on a square-edge requirement.
The Heat Affected Zone Requires More Than Visual Inspection
Laser cutting uses heat. Next to the cut edge, material that has not melted may undergo changes in microstructure or properties. This region is known as the heat affected zone, or HAZ.
Although a laser concentrates energy into a narrow area, the process is not free from thermal effects. These effects should be considered in relation to material type, thickness and processing conditions.
Surface discoloration alone cannot establish the extent or severity of microstructural changes. Depending on the material and project requirements, assessment may involve cross-sectional examination or hardness testing.
A Good Cut Edge Meets Its Intended Requirements
These four aspects describe different features of cut quality. Low dross does not establish perpendicularity, and a smooth surface does not confirm the absence of heat-induced material changes.
Quality assessment should consider geometry, dimensions, edge condition and material-specific requirements together. Acceptance criteria should reflect the drawing, customer requirements and intended use, rather than applying one universal threshold to every material and thickness.
Material-Specific Cutting Conditions at JL Heavy Industries
JL Heavy Industries draws on its experience with materials including high-manganese steel, nickel steel and stainless steel to review laser cutting conditions suited to each material and thickness.
Cut quality is not determined by machine power alone. Power, cutting speed, focal position and assist-gas conditions must work together with the characteristics of the material.
JL Heavy Industries considers processing speed, edge condition and the need for additional work when developing appropriate cutting conditions. For special steels, the focus extends from whether a material can be cut to how it can be processed to meet the required quality.
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