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Laser Pulse Overlap and Heat Input Calculator

Whether you are marking, scribing or seam welding with a pulsed laser, the combination of speed, repetition rate and spot size decides if pulses land as separate dots or a continuous line. This calculator makes the geometry and line energy explicit.

Your numbers

um
1,000 mm/s
kHz
W
%

Fraction of power absorbed by the material at the wavelength used.

Your results

Pulse spacing
10
um between pulse centers.
Pulse overlap
80%
Linear overlap of consecutive spots; zero means gaps.
Pulses per spot
5
Average number of pulses hitting any point on the line.
Pulse energy
0.3
mJ.
Absorbed line energy
0.012
J per mm of travel.

Geometry and energy bookkeeping only. Real material response depends on thermal diffusion, melt dynamics and surface condition; validate on test coupons.

Save results:

Pulse overlap (%) vs travel speed (mm/s)

Sweeps Scan or travel speed from 10 to 8000, holding your other inputs fixed.

Control laser recipes in your routings

Optional expert review of how to version and release process parameters through your ERP.

Optional. The tool and every export work without this. No spam.

How to use the calculator

Enter the spot diameter, the relative speed between beam and part, the pulse repetition rate, the average power and an estimate of absorptivity. The pulse spacing is speed divided by repetition rate. Overlap is one minus spacing divided by spot diameter. The sweep chart shows how overlap drops as speed increases, and where a seam turns from continuous to dotted. Use it to set parameter windows before running coupons.

  • Seam welding usually targets 60 to 90 percent overlap for continuity.
  • Marking and scribing often use lower overlap to limit heat.
  • Pulses per spot is a quick proxy for cumulative thermal load.

Formulas

Pulse spacing in micrometers is speed in mm/s divided by repetition rate in kHz. Linear overlap equals one minus spacing divided by spot diameter, expressed as a percentage. The number of pulses seen by any point on the line is approximately spot diameter divided by spacing. Pulse energy in millijoules equals average power in watts divided by repetition rate in kHz. Absorbed line energy equals power times absorptivity divided by speed, in joules per millimeter.

Worked example

At 100 kHz, 1000 mm/s and a 50 um spot, pulses land 10 um apart, giving 80 percent overlap and about five pulses per spot. With 30 W the pulse energy is 0.3 mJ. If 40 percent is absorbed, line energy is 0.012 J/mm. Doubling speed to 2000 mm/s moves the spacing to 20 um and overlap to 60 percent, and halves the line energy, which may be fine for marking but not for welding thick sections.

Common mistakes

Using galvo scan speed without accounting for acceleration at corners produces local overheating where overlap rises. Another is using the focused spot size from theory when the true working spot is larger because of defocus or beam clipping. Absorptivity varies with temperature, surface roughness and oxide, so treat it as a rough input and calibrate. Record the validated parameter sets against part numbers and revisions in your routing so changes are controlled.

Frequently Asked Questions

What overlap is correct for laser welding?

There is no universal value. Seam welding commonly uses high overlap, often well above 50 percent, for a continuous bead, but material, thickness and joint design decide. Confirm with metallographic sections and tests.

Does this apply to continuous-wave lasers?

Pulse overlap does not, since there are no pulses. The line energy output still applies for CW lasers if you set absorptivity and power correctly.

How do I handle 2D hatch overlap?

Hatch overlap between adjacent lines follows the same logic using line pitch and spot diameter: one minus pitch divided by spot diameter. Calculate it separately and combine with pulse overlap to get total pulses per area.

Why is overlap capped at zero?

When spacing exceeds the spot diameter pulses do not touch, and the formula would give a negative overlap. The calculator reports zero, and the pulses per spot output falls below one to show the gap.

Netray can help store validated laser process parameters against ERP routings and work orders so operators always run the approved recipe.

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