Among the parameters used in laser cutting, power and speed form the most fundamental pair. Laser power determines the energy delivered per unit time, while cutting speed determines how much of that energy is distributed along each unit length of the kerf. When the two are poorly matched, the result may be incomplete penetration or excessive heating of the cut edge. This guide explains the underlying relationship and a practical adjustment method using recorded process data for carbon steel, stainless steel, aluminum and brass.

1. Core Concept: Linear Energy Input

Power–speed matching is fundamentally about controlling linear energy input: the amount of laser energy delivered per unit length of cut.

Linear energy input, E (J/mm) = laser power, P (W) ÷ cutting speed, v (mm/s)

The following examples are calculated from the recorded cutting parameters:

For the 6 mm plate, the calculated energy input per unit length is approximately 70 times that of the 1 mm plate. These values represent nominal laser energy per length, not energy actually absorbed by the material.

1. A minimum energy input is needed for full penetration. The necessary amount generally increases substantially with material thickness, contributing to the sharp decline in attainable cutting speed as thickness increases. It is not a universal exponential relationship.

2. More energy is not always better. Excessive heat input can widen the kerf, round the top edge, expand the heat-affected zone and distort thin sheets.

3. Power and speed both affect nominal linear energy, but they are not interchangeable in all respects. Their effects on peak intensity, melt flow and process stability differ; select the parameter to adjust based on the observed defect.

2. Cutting Speed Versus Thickness: Recorded 1,500 W Data

The following values are cutting speeds in m/min from the supplied process table at the stated 1,500 W setting. Carbon steel uses air or oxygen as indicated; the other listed materials use compressed air.

· Cutting speed decreases nonlinearly as thickness increases. For stainless steel, speed falls from 35 m/min at 1 mm to 2 m/min at 3 mm—approximately one seventeenth of the original speed.

· For the 1 mm conditions shown, the speed order is stainless steel > carbon steel > aluminum > brass. This is specific to these recorded conditions, rather than a universal ranking for all thicknesses and gas selections.

· Carbon steel behaves differently when the gas process changes. At 4 mm, the table switches from air to oxygen. Exothermic oxidation supplies additional heat and changes the power–speed relationship.

3. Power Setting: Use High Power Where Appropriate

The source process notes describe most conditions as using 100% laser power, with an exception noted for 0.5 mm brass (70%). High-power cutting may support higher throughput when the material, optics, gas delivery and machine ratings allow it. However, 100% power is not a requirement for every thickness or contour.

4. Higher available laser power can enable faster processing, provided cut quality, gas flow and machine limits remain acceptable.

5. A power margin can help maintain penetration under some process disturbances, but it does not replace stable gas pressure, proper focusing or clean optics.

6. When excessive heat input causes edge rounding or dross, test speed and other process settings as appropriate. Do not assume that reducing peak power is always wrong; use the actual result to choose the adjustment.

Cases where lower or dynamically controlled power may be appropriate:

· Thin, highly reflective materials: the recorded 0.5 mm brass setting uses 70% power. Back-reflection protection and approved machine parameters remain essential.

· Piercing: staged/progressive piercing and duty-cycle settings help control heat input and spatter during the piercing operation.

· Small holes and sharp corners: enable validated speed-dependent power control, where supported, to limit overheating during machine deceleration.

4. How to Set Cutting Speed

7. Start with the process table. Select parameters for the specific material and thickness; the recorded speed assumes matching nozzle, focus, gas and pressure settings.

8. Find the upper speed limit by test-cutting. Increase speed from the table value in approximately 5–10% increments until dross increases or penetration becomes unreliable. Then reduce the speed by roughly 10–15% from the demonstrated limit as an initial production setting.

9. Distinguish a successful test cut from stable batch production. A speed that cuts one sample may not remain reliable over an eight-hour production run as lens condition, material or pressure changes.

10. Confirm the cut-edge appearance. Slightly trailing striations can be normal. Strongly trailing striations may indicate excessive speed; a wide cut and rounded top edge may indicate excessive heat input or slow speed. Confirm with penetration and dross observations rather than relying on appearance alone.

5. Frequency and Duty Cycle: Fine Control of Delivered Energy

The influence of pulse frequency and duty cycle depends on the laser source and how the controller implements modulation. Where true pulsed or gated output is used, these settings affect the distribution of delivered energy and, together with laser power and speed, the effective heat input.

· Lower-frequency examples in the recorded data: 6 mm stainless steel at 1,000 Hz, and 3–4 mm aluminum at approximately 1,000–2,000 Hz. These values are process-specific; lowering frequency does not automatically increase penetration or decrease average power unless the other pulse settings make that true.

· Piercing duty cycle: a lower duty cycle may reduce average delivered power at a given peak power, helping manage spatter and heating during a staged piercing operation.

In summary, available laser power influences processing capacity; speed strongly affects throughput and linear energy; frequency and duty cycle refine energy delivery when modulation is enabled.

6. Practical Guidelines for Matching Parameters

11. Save matched parameters as complete process layers. Power, speed, frequency, duty cycle, focus and gas pressure form a linked set. Store validated settings by material and thickness and recall the entire layer.

12. Enable speed-dependent power adjustment if supported and validated. Machines slow down at corners and small arcs; appropriately reduced output helps prevent local overheating.

13. Observe sparks, cut edges and striations. Spark direction and consistency can provide clues, but do not treat a single spark pattern as a definitive speed diagnosis. Confirm first-article quality before batch production.

14. Leave a production margin of approximately 10–15% below the verified maximum speed as an initial guideline; adjust to actual process stability and quality requirements.

15. Improve throughput systematically. Evaluate nozzle size, assist-gas choice and purity, and focus position before simply increasing programmed speed. Changes in assist-gas process must be validated for the specific material and finish requirement.

16. Include environmental and optical conditions in routine checks. If previously reliable parameters begin to cause incomplete cuts, inspect protective windows, nozzles and gas supply before changing the saved recipe.

7. Conclusion

Matching power and speed means keeping energy delivery inside a practical cutting window: high enough to penetrate the workpiece reliably, but controlled enough to prevent excessive edge heating. Use validated material/thickness settings as a baseline, establish a safe production-speed margin, and optimize modulation and speed-dependent power control for corners and other demanding features. Record the final parameters as reproducible process recipes.

Technical note: All numerical cutting data and example values in this guide are taken from the supplied article and should be validated on the specific Thunder AccuMetal machine and material batch before production.