Jusheng

Two surgeons at once perform an operation: one is a minimally invasive surgery specialist, performing only precise surface sutures with minimal damage. The other has to make incisions deeper into the tissue, rebuilding and welding internal parts.

Laser welding, in the same way, is a 'materials surgeon'. The depth of its 'surgery', i.e., penetration depth, directly correlates with the stability and strength of the connection.

This article covers the basic definition, importance, influencing factors, optimization methods, and maintenance of penetration depth of welds. With reference to real laser welding conditions, it answers theoretical questions and provides practical references for custom sheet metal manufacturing production.

Summary of Core Answers

Section	Core Concepts / Influencing Factors	Key Parameters / Methods	Application Value
Core Mode	Conduction Welding / Deep Penetration Welding.	Conduction welding: depth of penetration ≤ 1 mm. Deep Penetration Welding: depth of penetration in the millimeter order.	Choose the mode of welding based on the thickness of the workpiece (thin/thick).
Influencing Factors	Power of the Laser / Welding Speed ​​/ Beam Quality.	Power of 1000 W supplied to 0.8 mm copper: depth of penetration 0.5-0.7 mm.	Avoid burn-through/spatter and have a fine control over depth of penetration.
Optimization Method	DoE Experiment / Blue Laser.	DoE experiment saves time by 40%. Blue laser (BPP < 0.9).	Consistent penetration depth (±0.05 mm), improving efficiency by 40%.
Maintenance and Calibrations	Daily Cleaning / Weekly Calibration.	Variation in laser power ≤ ±5%, clean lens daily.	Regulate penetration depth variation to ≤ ±5%, reducing rework.

Why Believe This Guide? JS Team's Best Practices Uncovered

JS Precision Manufacturing has over 15 years of actual experience in laser welding and sheet metal production and has catered to clients in 12 industries, including new energy vehicles, medical appliances, and aerospace.

Our technical staff not only has experience in welding six main materials like steel, aluminum, and copper but also possesses a rich process parameter library to process sheet metal fabrication parts with a thickness range of 0.3mm-10mm based on various requirements.We have also made effective solutions to over 30 complex questions.

This manual is the result of combining this operational data, customer feedback, and industry knowledge, all substantiated with real projects.Whether an online sheet metal fabrication consumer seeking a pilot small batch run or an at-scale custom sheet metal fabrication manufacturer, this guide is a reliable reference.

JS has vast knowledge in custom sheet metal fabrication manufacturing. Just do not hesitate to provide us with your requirements, and we will offer end-to-end support from design to production delivery. Select us for hassle-free precision welding services.

Beyond The Surface: Revealing Laser Welding Penetration Depth

We first need to determine the straightforward definition of laser welding penetration depth:

It is the distance along the vertical between the surface of the workpiece and the deepest position at which the resulting pool of molten metal is after the laser beam strikes the workpiece. This distance determines directly whether the weld can support the requirements of sheet metal fabrication parts.

This depth of penetration relies chiefly on two basic welding modes, which are extremely different in the ability of penetration and applicability of use. The incorrect one to use will lead to weld failure directly.

Comparison of the Two Core Laser Welding Modes:

Comparison Dimensions	Heat Conduction Welding	Deep Penetration Welding
Penetration Depth	Shallow, typically ≤1mm.	Deep, between several and tens of millimeters.
Energy Application	The laser energy only acts on the surface and propagates inward through heat conduction.	High concentration of energy density to form a keyhole, allowing for direct penetration into deeper layers.
Weld Characteristics	Shallow and wide with smooth surface.	Narrow and deep with high aspect ratio.
Applicable Applications	Thin-walled sheet metal fabrication parts (e.g., 0.3-0.8mm stainless steel parts).	Thick plate structural parts (e.g., 2-10mm carbon steel parts, battery modules).
Representative Applications	Sealing of sheet metal medical devices by welding.	Chassis connections of sheet metal for new energy vehicles.

Why Is 'Depth' So Important? More Than Just Strength

The depth of laser welding has an impact greater than on weld strength alone, it sets to work immediately on workpiece performance, safety, and expense. It is defined through three significant factors:

Determining Structural Safety

For load-carrying sheet metal fabrication parts (e.g. automobile chassis connectors), a poor weld depth can create a 'weak point' in the weld that tends to crack under long-term vibration. When shallow penetration heat conduction welding is used on heavy plate parts (e.g. 5mm carbon steel), the weld does not reach into the workpiece and is highly prone to fracture during use.

Effect on Functional Conformance

Sheet metal fabrication parts from different industries have varying depth requirements: Copper busbars for new energy batteries require a penetration depth of ≥0.6mm, or overheating by way of high resistance will happen, non-uniform penetration depth in transport pipes for fluids may cause leakage, going against the food and medical industry standards.

Controlling Production Costs

Insufficient penetration depth can increase sheet metal manufacturing costs: too much power input in thin-walled components may quickly cause burn-through (scrap rate of 10%+), rework on thick plate components wastes labor, raising unit cost by 30%.
'Proper depth' holds the secret to finding a balance between laser welding quality and cost.

Desire to manage sheet metal fabrication prices without sacrificing weld depth? JS will find the balance between cost and quality. Transparent processes and streamlined manufacturing provide complete control from communication to delivery.

Achieving 'Depth': Five Key Factors Influencing Penetration Depth

To precisely manage the penetration depth of laser welding, the following five fundamental factors should be well understood.

Laser Power

• Fundamental Correlation: With other parameters unchanged, more power tends to lead to deeper penetration. Yet, going beyond the critical value can cause greater burn-through and spatter.
• Practical Reference: Different powers are linked with a specific range of copper penetration depth. An appropriate power needs to be selected based on the thickness of the material.

Copper penetration depth for different laser powers (welding speed 1m/min, beam quality BPP = 1.0)

Laser Power (W)	Copper Thickness (mm)	Penetration Depth (mm)	Applications
500	0.5	0.3-0.4	Fabrication parts of thin-walled sheet metal fabrication parts.
1000	0.8	0.5-0.7	Battery copper busbars.
2000	2.0	1.2-1.5	Thick sheet metal structural components.
3000	3.0	2.0-2.3	Heavy machinery sheet metal connectors.

Welding Speed

• Core Relationship: Negatively with penetration depth—higher speeds relate with less energy input and lower penetration depth, lower speeds can easily burn through and increase the sheet metal manufacturing price.
• Tip: Trial welding in small batches during production is needed to determine the optimal power and speed combination.

Beam Quality

• Measurement Criteria: Tested with the beam penetration (BPP) value. The smaller the BPP, the more the energy will be concentrated, and the deeper the penetration.
• Practical Utility: In welding copper, a blue laser with a BPP <0.9 can provide more than a 30% increase in penetration depth over an infrared laser with a BPP of 1.5, with less spatter. When JS processes high demand sheet metal fabrication parts, low BPP equipment is preferred.

Material Properties

• Key Influences: The higher the reflectivity and thermal conductivity of the material, the more difficult it is to improve the penetration depth (e.g., copper has an infrared laser reflectivity >95% and thermal conductivity 401 W/(m·K), hardest to weld).
• Adaptation Strategy: Blue lasers are employed on copper workpieces. Aluminum alloys require power and speed adjustments to minimize heat dissipation.

Shielding Gas

• Function and Choice: To prevent weld pool oxidation and stabilize the keyhole, argon (approximately $1.50/m³) is suitable for medium power and low power levels, while helium (approximately $8/m³) can increase penetration depth by 15%.

From Theory To Practice: How To Optimize Laser Welding Penetration Depth

Optimization of penetration depth can be achieved through a systematic approach. The three approaches given below can be utilized for most sheet metal fabrication cases.

Parameter Combination Optimization

Core Technique: Using laser power, welding speed, and focus position as the parameters, try many times to get the optimal combination in terms of a balance between depth, quality, and efficiency.

Practical Outcomes: With the parameters for the best 0.8mm copper busbar determined, the 0.7mm depth was achieved, representing a 40% efficiency gain over the trial-and-error methods. This also reduces waste and minimizes sheet metal fabrication price.

Equipment Selection by Material Property

Choice Logic: Lasers are selected based on the reflectivity and thermal conductivity of the material. Blue lasers are utilized for copper (absorption rate improved to 35%). In the case of thick aluminum alloy plates, a beam shaping system is employed for the improvement of depth uniformity.

Service Benefits: In our online sheet metal fabrication services, JS pre-matches equipment to sheet metal fabrication parts material to create a successful first-pass weld.

Application of Innovative Process Technologies

Key Process: '∞-shaped' oscillating welding increases laser contact time, and copper busbar depth stability improves to ±0.05mm from ±0.1mm. 'Layered welding' prevents shallow depth or burn-through on multi-layered components.

Application Example: Complex sheet metal fabrication parts can utilize two processes simultaneously to meet both weld depth and appearance requirements.

JS possesses skill in optimizing laser welding depth and offers online sheet metal fabrication solutions. Simply give us your workpiece specifications online, and we will quickly design a solution with openness and fast delivery. Choose us to easily achieve optimal weld depth.

Depth Consistency: Daily Maintenance And Calibration

Daily Maintenance

• Cleaning of optical lenses daily (to reduce energy loss).
• Check of laser power weekly (adjustment if deviation exceeds ±5%).
• Accuracy check of motion system every two weeks (re-adjust if displacement deviation exceeds 0.02mm).
• Check of cooling system every month (water temperature 20-25°C).

JS Guarantee of Maintenance

Early Warning System: Equipment parameters outside specified limits will automatically generate an alert to avoid quality risk.

Periodic Inspection: 10 common 0.8mm copper sheets have depth consistency checked every six months. In case of deviation exceeding 0.1mm, a comprehensive inspection is conducted to control depth variation to ±5%, reducing rework and sheet metal fabrication prices.

In addition to welding in custom sheet metal fabrication manufacturing, JS also provides equipment maintenance guides. Partner with us for expert complete-cycle service.

Real Case Study: Deep-Piercing Welding Challenges For New Energy Vehicle Battery Modules

Customer Requirements and Initial Pain Points

A new energy company had to weld 10 pieces of 0.3mm thickness aluminum battery structural module parts. The key requirements were 1.5mm penetration depth (complete penetration with a maximum of 5 pieces) and no welding distortion.

Project Challenges

• Material challenges: Aluminum has a thermal conductivity of 237W/(m·K), and laser energy diffuses very quickly, making it difficult to form a deep weld pool and achieve the required depth of 1.5mm.
• Structural Risks: Joint gap of ≤0.05mm between different layers of sheet metal fabrication parts caused laser energy leakage, which not only reduces depth but also increases the risk of porosity.
• Temperature Restrictions: Cells of the battery are sensitive to temperatures. Weld area temperatures exceeding 200°C can destroy cells and compromise the performance of batteries.

JS Precision Manufacturing Solution

• Equipment Selection: 2000W BPP 1.0 infrared laser was selected along with a beam shaper system to shape the laser beam into a 0.5mm x 1mm rectangle. This maximizes the surface area of energy effect and reduces heat dissipation.
• Process Optimization: It employed a 'pre-pressing + layered welding' process—first applying 0.5MPa pressure on the zone to eliminate gaps, and welding three layers (0.5mm thick) to avoid extremely high temperatures from being produced by one weld.
• Temperature Control Measures: A 15°C cooling water channel was installed near the region of weld for draining heat in real-time, and keeping the surrounding temperature below 180°C and protecting battery cells.

Results

High-strength, spatter-free full-penetrating welding has been achieved, with consistent penetration depth of 0.7mm, equal interface width, and extremely low and consistent resistance, satisfying the battery's demands fully for high current and low loss. The yield rate has been increased from 70% to over 99.5%.

How Do You Guarantee Your Products Receive The Optimal Weld Depth?

Explaining the Essential Criteria for Optimal Weld Depth

Perfect weld depth is not a single numerical value, but a triple standard of performance, stability, and cost.It must meet workpiece functional requirements (e.g., minimum resistance for conductive parts, maximum strength for structural parts), have a range of penetration depth variation ≤±0.05mm, reduce rework caused by erroneous parameters.

This means developing a clear standard framework through the combination of laser welding attributes with custom sheet metal fabrication manufacture specifications.

JS's Three Core Capabilities for Perfect Weld Depth

Proper Material-Equipment Matching: JS uses a material database (steel, aluminum, copper, etc.) to match lasers to workpieces with varying reflectivity and heat conductivity (e.g., reflective parts have blue lasers). This correctly converts the energy and avoids shallow weld depth resulting from 'equipment mismatch'.

Process Innovation and Optimization: Meeting challenging welding environments such as high thermal conductivity and thin walls, we have developed processes such as '∞-shaped oscillation' and 'layered welding' to mitigate molten pool instability, maximize weld depth uniformity, and extend to online sheet metal fabrication services and mass production.

Calibration of Scientific Parameters: With the application of Design of Experiments (DoE) rather than trial-and-error methods, we quickly adjust parameter sets such as power, speed, and focus with an enormous time saving in commissioning, even weld depths, and material.

Full-Scenario Weld Depth Assurance Support

JS processes involve the entire procedure from first design to mid-term control of production up to maintenance after production.

Small orders may be readily compared to parameters through an online system, whereas volume-based customized mass production is controlled through automated production lines. Maintenance guidance for machine tools is also provided in an attempt to prevent weld depth deviations through lengthy use, which makes it possible to produce ideal weld depth under any condition.

FAQs

Q1: Why is high power sometimes the cause of shallow or unstable weld penetration?

This typically occurs as a result of the plasma/vapor shielding effect. Because of the constant delivery of high power, large amounts of plasma or high-temperature vapor are formed on the workpiece surface. These substances act as a 'barrier' to block laser light, preventing it from penetrating effectively deep into the workpiece,thereby ending up in shallow or unstable weld penetration.

Q2: How to detect and measure the penetration depth of welds?

The most accurate method is destructive metallographic examination, including cutting the workpiece in a way to inspect weld penetration and being utilized for precise verification. Ultrasonic testing,and other non-destructive methods are commonly used in industry, which do not require damage to the workpiece and are more suitable for sampling and deep evaluation of batch products.

Q3: What is the maximum possible thickness in laser welding?

This depends on material, laser source, and process. With single-pass welding, fiber lasers can weld 20-30mm thickness carbon steel and 15-20mm aluminum alloys. With multi-pass welding or high-power arrays of lasers and ideal processes, theoretical weld thickness has no maximum.

Q4: Why it is so very difficult to laser weld copper and aluminum?

The intrinsic reasons are two-fold: First, copper and aluminum have very high reflectivity for lasers (copper's infrared laser reflectivity is over 95%), which results in energy reflection and loss, second, they have high heat conductivity, which results in the dispersal of heat quickly. Increased power density and custom processes are required to form and maintain a stable 'pinhole effect.'

Summary

Penetration Depth is not an absolute number, but a 'manipulable variable' able to be modified within a flexible parameter as per the needs of sheet metal fabrication parts. For every manufacturing practitioner, controlling the scientific logic and optimization techniques behind laser welding is about taking this 'sharpest blade of light' from technology to an art.

Whether you are working on small-batch production or high-volume custom manufacturing, if penetration depth problems crop up in laser welding, JS can provide individualized solutions. We understand that only the 'proper' penetration depth will provide the best quality at the lowest cost for your product.