Continuous Wave VS Pulsed Laser Welding
Laser welding concentrates energy into a tiny spot and turns it into a clean, fast, and precise joining process. But the time profile of that energy matters as much as the amount delivered. In practice, you’ll choose between two modes:
- Continuous Wave (CW): The laser emits steady power with no intentional gaps.
- Pulsed: The laser delivers discrete bursts of energy separated by off-
Both can create strong, repeatable joints. Both can deliver a beautiful surface finish. Yet they behave differently in the melt pool, introduce heat at different rates, and favor different materials, thicknesses, and joint styles. Pick the wrong mode and you’ll fight distortion, porosity, and rework. Pick the right one and you’ll hit first-pass quality at the pace your line needs.
This article explains how CW and pulsed welding work, compares them across the levers that matter (energy delivery, heat control, speed, compatibility, weld quality, and cost), and gives a practical framework to choose and tune the process. No tables, no formulas—just clear guidance, examples, and checklists you can apply in the shop.
Table of Contents
Understanding Continuous Wave (CW) Laser Welding
Description
Continuous Wave laser welding uses a laser that emits constant power throughout the weld. Modern CW sources are primarily fiber lasers near one micrometer wavelength. They offer high electrical efficiency, excellent beam quality, and compact footprints. Power ranges from a few hundred watts for precision work up to multi-kilowatt for thick sections and high line speeds.
CW is the workhorse for long seams and structural joints. If you need deep penetration at speed, CW is usually your starting point.
Working Principle
At the focus, the beam heats the surface and forms a melt pool. Two regimes are common:
- Conduction mode: Heat flows from the surface into the base metal. Cross-sections are shallow and wide. This regime is friendly to thin sheet and cosmetic work, where you want to limit distortion.
- Keyhole mode: With higher intensity, the surface locally vaporizes, opening a narrow cavity. Light reflects inside this cavity and couples energy deeply. The result is a deep, narrow fusion zone and very high travel speeds.
Because the beam is continuous, once a keyhole is established, you can “ride” it along the seam with stable penetration, provided power, focus, and speed stay inside a stable window.
Control levers in CW
- Laser power: Determines whether you can open and sustain a keyhole. It also sets your potential speed at a given depth.
- Spot size and focus position: Smaller spots raise intensity. Focusing slightly below the surface often stabilizes the keyhole; focusing on or above the surface softens intensity for conduction-mode work.
- Travel speed: Balances penetration against total heat input. Faster is cooler but risks keyhole collapse; slower increases penetration and heat-affected zone.
- Shielding gas: Argon is common. Helium (or helium-rich mixes) can suppress plasma above the pool at high powers and promote smoother, deeper welds in some alloys.
- Beam motion strategies: Small oscillations (wobble), power modulation, twin-spot or ring-shaped beams widen beads, improve gap tolerance, and calm the pool.
Advantages
- Speed and penetration: Multi-kilowatt beams maintain open keyholes and weld thick sections rapidly.
- Process continuity: Fewer starts and stops on long welds; consistent bead shape when parameters are stable.
- Automation-friendly: Pairs well with seam tracking, scanners for on-the-fly welding, and inline penetration monitoring.
- Hybrid compatibility: Works with filler wire and hybrid laser-arc processes to widen the fit-up window and adjust metallurgy.
Disadvantages
- Heat input on thin parts: The continuous beam can overheat delicate components, increasing distortion or risking burn-through.
- Keyhole sensitivity: Keyhole instability can trap gas and create porosity if power or focus drifts or travel speed is too high.
- Reflective materials: Initial coupling on copper and aluminum can be challenging; once hot, coupling improves, but ignition can be inconsistent without careful setup.
Typical Applications
- Automotive body-in-white seams, tailored blanks, and closures.
- General fabrication of carbon and stainless steels in the 2–6mm range.
- Heavy industry, including ship panels and structural sections, often with hybrid laser-arc for gap tolerance.
- Battery enclosures and busbars, especially with green/blue CW sources for copper.
Understanding Pulsed Laser Welding
Description
Pulsed laser welding delivers energy in bursts separated by off-times. Each pulse has a defined energy and duration; the instantaneous peak power can be far higher than the average power. This decouples the ability to punch through surface effects from the total heat you pour into the part. Pulsed welding is the go-to for thin gauges, miniature features, and assemblies where distortion or discoloration is unacceptable.
Most industrial pulsed welding uses microsecond-to-millisecond pulses. (Ultrafast nanosecond or femtosecond sources live in a different regime aimed at ablation and micro-machining.)
Working Principle
In seam welding, pulses are overlapped so that each new pulse partly remelts the previous one. The high peak of each pulse helps initiate coupling through oxide or reflectivity. The off-time lets the pool partially cool, which keeps average heat low and narrows the heat-affected zone. Pulse shape matters: a brief ignition spike helps the pulse “bite” into the surface, a flat plateau sustains the pool, and a gentle downslope reduces crater cracking.
Control levers in pulsed welding
- Pulse energy: Sets nugget size and penetration.
- Pulse duration: Longer pulses build a larger conduction pool; shorter pulses limit heat spread.
- Repetition rate and overlap: Higher repetition or lower speed increases overlap and smooths seams; lower overlap leaves scallops.
- Focus strategy: Focus at or slightly above the surface to avoid unintended keyholing unless you want it.
- Shielding gas and fixturing: Gas protects the pool; tight, repeatable clamping ensures consistent overlap and contact between parts.
Advantages
- Thermal control: Low average heat input reduces distortion and narrows the heat-affected zone.
- Precision: Tight control over nugget size and seam width.
- Coupling on difficult surfaces: High peak power helps initiate coupling on reflective or oxidized metals.
- Dissimilar and heat-sensitive joints: Short time at temperature limits intermetallic growth and preserves base properties.
Disadvantages
- Throughput limits: Seam welding with high overlap is slower than CW keyhole welding of similar thickness.
- Risk of lack of fusion: If pulse parameters are off, nugget continuity suffers.
- Fit-up sensitivity: Pulsed seams without filler dislike gaps.
- Complexity: More parameters to control, which requires a disciplined setup.
Typical Applications
- Medical devices (thin stainless steel and titanium tubing, end caps, and hermetic shells).
- Electronics (pins, leads, sensors, housings, and micro-mechanisms).
- Battery tabs and foils (copper to nickel or stainless steel in stacked tabs).
- Jewelry and watchmaking (very small, precise joints with immaculate finish).
- Aerospace instrumentation (thin diaphragms, bellows, pressure cells).
Key Differences Between Continuous Wave and Pulsed Laser Welding
Energy Distribution
- CW feeds energy continuously. Once the melt is established, the pool and any keyhole stay open as you move along the seam.
- Pulsed parcels of energy into short bursts. The instantaneous power can be very high to ensure coupling, while the time-averaged heat stays modest. This time structuring is why pulsed can be both aggressive in the moment and gentle overall.
Heat Input and Control
- CW generally introduces more total heat for a given depth and speed. That can broaden the heat-affected zone and increase distortion on thin parts.
- Pulsed lets you separate ignition strength from total heat. You can break through oxide and still keep the part cool, which preserves geometry and surface finish.
Practical signs you’re in control: consistent plume, stable bead width, no color change on stainless or titanium beyond the accepted range, and parts that stay within dimensional limits without post-straightening.
Welding Speed and Efficiency
- CW wins when you need meters of continuous seam at meaningful depth. It’s the default for structural welds and thicker sections.
- Pulsed is slower in linear seam welding because you must maintain an overlap. That said, for spot arrays and micro-assemblies, pulsed can process hundreds or thousands of spots per hour with near-perfect repeatability.
Material Compatibility
- Steels: Both modes work well. CW keyhole excels above roughly one to two millimeters; pulsed shines on thin sheets or delicate components.
- Aluminum: Pulsed helps with initiation and low heat on thin sections. CW, combined with helium-rich shielding and sometimes beam wobble, handles thicker sections at speed while managing porosity.
- Copper: Coupling at near-infrared is tricky when cold. Pulsed high-peak strategies can initiate on small joints. Where available, green or blue CW sources couple cleanly and raise throughput on busbars and tabs.
- Titanium: Both modes produce beautiful results with immaculate shielding. Pulsed minimizes color change on thin parts.
- Dissimilar metals: Pulsed reduces time at temperature and limits intermetallic growth. CW can join larger sections if you add filler or beam oscillation to manage mixing.
Weld Quality
- CW keyhole: Deep, narrow beads at high speed. Vulnerable to porosity if the keyhole collapses or wobbles; spatter rises with excessive intensity. Countermeasures include slight defocus, helium mixes, beam wobble, and modest power margins to stabilize the cavity.
- Pulsed conduction: Shallow, tidy beads with minimal distortion and excellent cosmetics. The main risks are a lack of fusion between pulses and crater cracking at pulse ends. You control these with adequate overlap, pulse energy, smooth pulse tails, and tight fixturing.
Equipment Cost and Complexity
- CW systems: Higher power sources and robust motion systems raise capex, but the cost per meter is lowest when fully utilized. Integration often includes scanners, seam tracking, and penetration monitoring for critical seams.
- Pulsed systems: Average power can be lower, but you’ll invest engineering time in pulse shaping, overlap control, and precision fixturing. For high-value assemblies, the payoff is lower scrap and minimal post-process correction.
Choosing the Right Mode for Your Application
A Practical Decision Framework
Ask these questions in order:
How thick is the joint, and how deep must you penetrate?
If you need deep, single-pass penetration or long structural seams, choose CW. If you’re in thin sheet, foils, wires, pins, or miniature housings, choose pulsed.
How heat-sensitive is the assembly?
If dimensional stability and cosmetic finish are critical, choose pulsed. If strength and throughput dominate and you can manage distortion with fixturing, choose CW.
What does your fit-up really look like?
If gaps vary and you can’t tighten them with fixtures, plan for CW with filler, CW with beam wobble, or laser-arc hybrid. Pulsed without filler expects intimate contact.
What’s the material pairing?
Steels can go either way. Aluminum often starts pulsed on thin parts and CW on thick. Copper favors green/blue CW if available; otherwise, pulsed IR on small features. Dissimilar stacks generally start with pulsed to control intermetallics unless the joint is large.
What does the business case demand?
If takt time and meters per minute decide profitability, go CW. If the cost of a warped or discolored micro-assembly is high, go pulsed.
Starting Recipes (then tune)
These are productive starting points; expect to adjust based on your laser, optics, and part geometry.
Thin stainless steel lap seam (about half a millimeter, cosmetic)
- Mode: Pulsed conduction.
- Setup: Small spot; moderate pulse duration; high pulse overlap for a continuous, smooth bead.
- Pulse shape: Brief ignition spike, flat plateau, gentle downslope to avoid craters.
- Gas: Clean, laminar argon; add a trailing cup if you want a mirror-bright finish.
- Focus: At the surface or a hair above to soften peak intensity.
Aluminum butt seam around a millimeter
- Mode: Pulsed conduction unless the job is throughput-
- Setup: Use an ignition spike to break through the oxide. Keep the pulse long enough to connect through the thickness without forming a deep keyhole.
- Gas: Helium-rich shielding; weld shortly after cleaning to avoid moisture pickup.
Steel butt seam two to three millimeters
- Mode: CW keyhole.
- Setup: Power high enough to open a keyhole with margin; focus slightly below the surface for stability; travel speed balanced for depth without excessive heat.
- Add-ons: Small beam wobble to widen the bead and improve gap tolerance; gas shielding with argon or a helium mix.
- Monitoring: A simple photodiode or an inline penetration system catches drift before it creates scrap.
Copper tab to nickel or stainless (battery tabs)
- Mode: Green or blue CW if available; otherwise IR pulsed with short, high-peak pulses.
- Setup: Firm mechanical clamping, bright-metal cleaning, and a short pilot pulse before the main pulse sequence often stabilize coupling.
Tuning Knobs and How They Move the Process
- Focus position: Slightly below the surface stabilizes CW keyholes; at or slightly above the surface softens pulsed conduction and widens the pool.
- Travel speed vs. thermal load: Faster is cooler but risks under-penetration; slower deepens penetration but increases distortion. Adjust in small steps and watch both the top bead and the back side.
- Shielding gas: Too little flow invites oxidation; too much flow jets the pool and causes undercut or porosity. Aim for smooth, laminar coverage. Helium mixes can improve stability in high-power CW and on aluminum.
- Beam oscillation (wobble): Widens the bead, improves gap bridging, and reduces crack risk. The trade-off is slightly lower effective penetration at the same power.
- Pulse shaping: A gentle start reduces spatter; a smooth downslope avoids crater cracks; avoid abrupt, square pulses on crack-sensitive alloys.
Managing Common Defects
- Porosity in CW keyhole welds: Improve cleaning; add a little power or reduce speed to stabilize the keyhole; move focus slightly deeper; try a helium-rich gas; consider beam wobble. For highly critical parts, reduced-pressure or vacuum welding can collapse pores.
- Lack of fusion in pulsed seams: Increase pulse energy or duration; increase overlap; slow travel slightly; set focus a touch deeper.
- Crater cracking at pulse ends: Add a downslope; extend overlap at the weld end; reduce part restraint; consider filler on crack-sensitive alloys.
- Excessive spatter: Reduce peak intensity or slightly defocus; smooth the pulse shape; adjust gas flow; add wobble.
- Distortion on thin sheet: Prefer pulsed; if you must use CW, raise speed and lower power while keeping the keyhole stable, and use heat sinks.
Fixturing, Preparation, and Handling
- Cleanliness: Remove oils and oxides. Aluminum and copper demand dry, freshly prepared surfaces. Avoid chlorinated solvents on stainless steel and titanium.
- Fit-up: CW without filler wants tight gaps. Pulsed seams expect intimate contact. If gaps are inevitable, plan filler, wobble, twin-spot beams, or a hybrid process.
- Clamping: Clamp close to the seam; stiff fixtures reduce distortion. Provide heat sinks for CW on thin parts. Use hard stops so pulsed spot arrays land repeatably.
- Shielding discipline: Use laminar nozzles, trailing cups for titanium or high-cosmetic stainless, and hose routes that avoid turbulence.
Monitoring and Control
- Photodiodes: Fast signals that correlate with plume intensity and keyhole stability in CW. Spikes and dropouts warn of trouble.
- Cameras: Coaxial or off-axis views help with seam tracking and surface QA.
- Thermal sensing: Single-point pyrometers or thermal cameras check that heat input stays consistent across batches.
- Inline depth measurement: Optical methods that look into the keyhole during CW welding can hold penetration within a narrow band and pay back quickly on critical lines.
- Data logging: Record parameters and sensor signals. Establish simple alarm thresholds so the line stops before scrap accumulates.
Alloy-Specific Playbooks (Concise but Actionable)
- Low-carbon and HSLA steels: CW keyhole is efficient for medium sections; watch hardness in the heat-affected zone if the chemistry pushes toward martensite. Pulsed gives clean, thin-sheet seams.
- Austenitic stainlesssteel (304/316): Very forgiving; pulsed yields excellent cosmetics on thin parts; CW works well above thin-sheet territory. Nitrogen shielding is sometimes used for austenite balance—avoid on ferritic or martensitic grades.
- Ferritic/martensitic stainlesssteel: Crack sensitive; keep heat input moderate; consider filler or wobble; pulsed reduces molten length on thin parts.
- Aluminum 1xxx/5xxx: Control hydrogen. Clean, dry parts and appropriate gas go a long way. Pulsed for thin; CW for thick, with attention to porosity.
- Aluminum 6xxx/7xxx: Crack sensitive; pulsed conduction for thin; CW with wobble and helium mixes for thicker sections. Filler wire can balance the composition on larger joints.
- Copper and copper alloys: Green/blue CW simplifies life on large joints. For small features with IR sources, short, high-peak pulses, and excellent clamping deliver stable nuggets.
- Dissimilar stacks: Start pulsed to limit intermetallics. Keep the time at temperature short and mixing minimal. For larger joints needing throughput, shift to CW with filler or wobble.
Safety and Compliance
- Treat all welding lasers as Class 4. Enclose where possible; interlock doors; keep eyewear specific to wavelength and power.
- Extract fumes and particulates; stainless and galvanized fumes are hazardous.
- Guard against reflections, especially on bright metals. Use blackened, angled baffles inside cells.
- Maintain protective windows; contamination drifts your focus and power density over time.
- Follow relevant welding acceptance standards for your industry and the laser safety standards in your region.
Economics and ROI
- CW: Higher-power sources and scanners raise capital cost, but the cost per meter is lowest when you exploit the speed. Inline penetration control and seam tracking protect yield.
- Pulsed: Lower average power and minimal distortion, lower rework on delicate assemblies. Even with slower seams, the savings in scrap, polishing, and straightening often carry the business case.
- Integration levers: Robust fixtures, simple monitoring, and beam wobble capability are often better investments than squeezing out another small increment of laser power.
Summary
Continuous Wave and pulsed laser welding are complementary tools built on the same physics but with different time profiles.
- Choose CW when you need depth and speed on longer seams or thicker sections. Stabilize the keyhole with the right focus, shielding, and small oscillations. Add filler or hybridize with an arc when fit-up isn’t perfect.
- Choose pulsed when you need precision, low heat, and beautiful cosmetics on thin or heat-sensitive assemblies, or when you’re joining dissimilar metals. Control pulse energy, duration, overlap, and shape; use careful fixturing and clean parts.
Decide with five questions: How thick? How heat-sensitive? How good is the fit-up? What materials? What does takt time demand? Then tune the few parameters that move the process most—focus, speed, gas, motion, and (for pulsed) pulse timing. Do that, and you’ll stop fighting the weld and start shipping parts that meet spec the first time.
Get Laser Welding Solutions
Selecting between continuous wave and pulsed laser welding is not just about comparing theory—it’s about finding the right solution for your material, geometry, and production goals. That’s where Maxcool CNC adds value. As a professional manufacturer of intelligent laser equipment, we provide not only the hardware but also the expertise to match the right technology to your application.
Our team begins by understanding your needs: part design, material type, thickness, joint configuration, cosmetic expectations, and production speed. From there, we evaluate whether continuous wave or pulsed operation—or a hybrid approach—delivers the best balance of penetration, distortion control, and throughput. In our applications lab, we run sample trials on your actual components, comparing weld morphology, strength, porosity levels, and appearance. You receive documented results and process recommendations that shorten your path to production.
When it comes to equipment, Maxcool CNC offers a full portfolio of CW fiber lasers for deep, fast structural seams and pulsed lasers for precision joining of thin or heat-sensitive parts. We integrate these with advanced motion systems, wobble heads, seam tracking, safety enclosures, and inline monitoring for a turnkey solution. Training, service, and ongoing support ensure your line stays productive.
Whether you’re welding stainless steel, carbon steel, aluminum, copper, or dissimilar metals, Maxcool CNC delivers tailored solutions that let you capitalize on the strengths of both CW and pulsed laser welding.