Case Study: Why laser cut surfaces are covered with vertical lines (streaks)

The Laser cut surface is full of vertical lines (striations). We’ve changed the nozzle and lens. What’s the hidden problem?

What causes the laser cut surface to be covered with vertical lines (streaks)?

Our client, whom we shall call Arabian Flow Systems (AFS), is a verifiable fabrication and manufacturing firm based near Dammam, Saudi Arabia. AFS is a key supplier in the booming Middle East Energy Sector, specializing in cutting and welding heavy-duty components, including large-diameter pipe sections, flange plates, and structural supports for gas processing and utility infrastructure. Their primary materials are thick-gauge carbon steel and various high-tensile alloys, which require an exceptionally smooth, burr-free cut edge for welding preparation and compliance with industrial standards (e.g., API, ASME).

AFS had previously purchased a high-power fiber laser cutting machine from another Chinese manufacturer. When persistent quality issues arose, AFS’s engineering team, frustrated by unresponsive local support, sought help where modern professionals often turn: online forums.

The AFS lead engineer, a seasoned fabrication expert but a relative fiber laser novice, posted a detailed query on an international manufacturing forum, later drawing the attention of YIHAI LASER’s digital outreach team:

CQ: “The cut surface is full of vertical lines (striations). We’ve changed the nozzle and lens. What’s the hidden problem?”

The vertical lines, or striations (also known as drag lines), are ridges left on the cut face as the molten material solidifies. While minor striations are inherent to the process, excessive, deep vertical lines indicate serious turbulence in the melt flow. AFS’s efforts to replace peripheral optics (nozzle and lens) had correctly addressed common surface issues, but the persistence of the striations signaled an issue rooted deeper than basic consumables.

YIHAI LASER’s Deep-Dive Remote Diagnosis

The YIHAI LASER technical team, recognizing the complexity of the symptom, provided a two-part solution that moved beyond surface-level fixes.

YIHAI LASER Solution: These striations are a tell-tale sign of an incorrect focus position or issues with the laser beam mode quality. Action: Perform a full focus check. If the problem persists, the issue might lie in the laser source itself. YIHAI LASER uses world-renowned laser sources (like IPG, Raycus) to guarantee stable beam quality.

The Focus Position (The Primary Cause)

The technician first directed AFS to perform a detailed focus calibration test, explaining the physics behind the striations:

• The Physics: Striations are created by the chaotic, turbulent flow of the molten material down the kerf. The primary driver of this turbulence is usually an improperly positioned focal point.
• The Problem: The focal point was likely too high or too low, causing the laser’s energy density to be misaligned with the material thickness. An incorrect focus leads to a non-optimal melt pool shape, which the assist gas struggles to efficiently evacuate. This uneven ejection leaves behind the solidified, visible ridges.
• The Action: The YIHAI team remotely guided the engineer through adjusting the focus offset in the CNC software, providing a range of tested parameters for thick steel alloys, aiming for the “sweet spot” where the melt flow is smoothest.

Beam Mode Quality (The “Hidden Problem”)

When initial focus adjustments failed to eliminate the striations completely, the YIHAI team suspected the “hidden problem”: degraded laser beam mode quality. This highly technical issue is a weakness often found in lower-cost laser sources used by less reputable manufacturers.

• The Metric: Laser beam quality is quantified by M² the factor. An ideal beam has M² = 1.0(a perfect Gaussian beam); a higher M² indicates a diverging, less focused beam.
• The Implication: If the non-YIHAI machine used a compromised laser source, its M² factor might be deteriorating. A poor-quality beam cannot maintain the necessary spot size and energy density throughout the thickness of the material, leading to a broader, weaker cut profile. This inherent lack of precision results in severe, unavoidable striations, regardless of the focus setting.
• The YIHAI Difference: The team used this moment to showcase a core competitive advantage. YIHAI LASER strictly integrates only world-renowned, high-end laser sources (such as IPG, Raycus, and MAX), which come with certified, stable M² values (typically near 1.0) and high service life guarantees. This ensures the foundation of the cutting process is always stable and high-quality, preventing such deep-seated beam problems.

Striations Diagnostic Chart

Cut Surface Defect	Primary Cause	Secondary/Hidden Cause	YIHAI LASER Solution Strategy
Deep Vertical Striations	Incorrect Focus Position	Deteriorating Beam Mode Quality (M2>1.2).	1. Optimize Focus Offset. 2. Verify Laser Source M2 Stability (requires specialized equipment).
Excessive Slag/Dross	Gas Pressure too Low	Contaminated Assist Gas (Moisture/Oil).	Increase Gas Pressure & Check Gas Filtration System.
Rough Top Edge	Improper Nozzle-to-Material Distance (Too High).	Worn or Damaged Nozzle Tip.	Adjust Capacitive Height Sensor Setting.

From Reddit to Riyadh: Securing a Partnership

The AFS engineer, under YIHAI’s remote guidance, discovered that the former supplier’s laser source exhibited unstable power output and an increasing M² value—a clear case of component degradation leading to poor cut quality.

While YIHAI could not repair the faulty component from a competitor’s machine, the detailed diagnosis and the educational consultation proved invaluable. AFS finally understood the root cause of their poor quality, validating YIHAI LASER’s technical expertise.

The engineer closed his forum thread, publicly acknowledging YIHAI LASER’s superior, free-of-charge support: a testimonial that instantly bolstered YIHAI’s credibility across the global manufacturing community. This act transformed a frustrated customer of a competitor into a highly satisfied advocate for YIHAI LASER.

The digital collaboration culminated in a pivotal physical meeting. At a recent major Saudi Manufacturing and Energy Exhibition, the AFS leadership team, including the general manager, sought out the YIHAI LASER booth.

The discussion went beyond the previous technical fix. AFS praised YIHAI’s integrity, technical depth, and commitment to client education—qualities they valued highly over a low upfront cost. Recognizing YIHAI LASER’s reliance on high-quality, reliable core components (IPG, Raycus, etc.), AFS initiated discussions for a new equipment purchase.

Currently, AFS is in advanced negotiation to acquire a YIHAI LASER Fiber Tube Cutting Machine. This strategic investment will allow AFS to produce high-precision tubular components essential for their energy sector contracts, ensuring the dimensional accuracy and weld-ready edge finish that the old machine could never guarantee.

YIHAI LASER: The Standard-Bearer for Global Laser Cutting Support

Credibility through Expertise: Our ability to diagnose a complex M² issue remotely, despite the customer being a laser novice, cemented our reputation as a trusted technical partner.

Future-Proofing the Investment: By using only top-tier laser sources, YIHAI LASER guarantees the long-term stability of the beam mode, minimizing the risk of recurrent, difficult-to-solve quality problems like deep striations.

In the high-stakes world of Saudi energy components, the difference between success and failure is often measured in microns. YIHAI LASER’s Service commitment to delivering reliable machines backed by world-class, human-centric technical expertise, ensures our clients, from China to Saudi Arabia, are equipped to succeed.