Solving quality issues with in-process weld depth inspection using OCT (Optical Coherence Tomography)
In laser welding processes, "weld depth inspection" is considered difficult to achieve.
To address this, we have implemented in-process weld depth inspection using OCT (optical coherence tomography measurement) technology with a galvano scanning optical system. With this technology, it is now possible to move from conventional destructive sampling inspection to real-time, non-destructive, 100% inspection.
This page introduces the features of the latest "OCT-based weld depth inspection (LW + OCT)," the advantages of its implementation, and several use cases.
In laser welding processes, "weld depth inspection" is considered difficult to achieve.
To address this, we have implemented in-process weld depth inspection using OCT (optical coherence tomography measurement) technology with a galvano scanning optical system. With this technology, it is now possible to move from conventional destructive sampling inspection to real-time, non-destructive, 100% inspection.
This page introduces the features of the latest "OCT-based weld depth inspection (LW + OCT)," the advantages of its implementation, and several use cases.
Table of Contents
1. What Is OCT for Laser Welding?
1-1. What Is OCT?
1-2. Principles of OCT
1-3. Using OCT for Laser Welding
2. Features of OCT-based Weld Depth Inspection (LW + OCT)
3. Advantages of Introducing OCT-based Weld Depth Inspection (LW + OCT)
4. Use Examples of OCT-based Weld Depth Inspection (LW + OCT)
4-1. OCT-based Weld Depth Inspection Example 1: Wobbling Welding of Aluminum Materials
4-2. OCT-based Weld Depth Inspection Example 2: Changing Laser Power Output for Copper Welding
1. What Is OCT for Laser Welding?
1-1. What Is OCT?
OCT stands for Optical Coherence Tomography, and is also referred to as an optical coherence tomography method. In the history of OCT, its principles were reported in 1985. It was developed as an ophthalmic examination technique and later expanded to industrial applications.
In industrial settings, OCT's features are used in various applications, including imaging the interior of devices (such as SD cards), as shown in the images on the left.
1-2. Principles of OCT
The principles of OCT involve measuring distances by analyzing the interference of reflected and scattered light from an object. This can be understood as "precise distance measurement using optical interference."
* As shown in the figure on the left, the distance to the measured object is determined by analyzing the interference between light from the object and reference light from the reference mirror.
1-3. Using OCT for Laser Welding
OCT utilization is broadly classified into the following three categories.
- Pre-weld inspection: Pre-weld height inspection, pre-weld position inspection, seam tracking
- During-weld inspection: Weld depth inspection
- Post-weld inspection: Bead width inspection, bead height inspection
As shown in the figure, measuring the position of the keyhole bottom can be used for "weld depth inspection," as it correlates with the penetration depth.
* A "keyhole" refers to a small hole (or depression) formed during laser welding.
2. Features of OCT-based Weld Depth Inspection (LW + OCT)
- The galvano scanning optical system enables OCT-based weld depth inspection.
- Keyhole measurement is possible while tracking the wobbling movements of the laser beam during welding.
- Even a single-mode fiber laser can be used for measurements.
(Micro-keyholes can also be measured.) - OCT-based inspection can even be applied to weld depth measurement of aluminum materials, which is considered difficult.
* For detailed specifications, please contact us or refer to the whitepapers or catalogs.
3. Advantages of Introducing OCT Weld Depth Inspection (LW + OCT)
The typical advantages of introducing this inspection equipment include the following:
- Enables real-time, non-destructive, 100% inspection instead of destructive sampling inspection (expandable to in-process weld assurance).
- Reduces other inspection processes and inspection labor hours while improving operating rates, resulting in lower total costs.
- Evidence data supporting the quality of all welds can be collected and stored, enabling traceability.
On the other hand, there are currently the following issues in mass production processes:
- Losses due to excessive inspection and maintenance work
- Losses from follow-up investigations of sudden defects
To address the above two issues, introducing OCT-based weld depth inspection can optimize welding inspection frequency and equipment maintenance timing, reducing total costs and further improving the efficiency of laser welding processes.
4. Examples of OCT-based Weld Depth Inspection (LW + OCT)
Here are some examples of OCT-based weld depth inspections. For more detailed information, please download and read the whitepapers (Basics and Advanced Editions).
Here are some examples of OCT-based weld depth inspections. For more detailed information, please download and read the whitepapers (Basics and Advanced Editions).
4-1. OCT-based Weld Depth Inspection Example 1: Wobbling Welding of Aluminum Materials
4-2. OCT-based Weld Depth Inspection Example 2: Changing Laser Power Output for Copper Welding
