Source: Metal Forming Magazine
The efficiencies inherent in automated welding cannot be denied, as the process has proven itself for OEMs and Tier One and Two suppliers alike. But a longstanding challenge remains: automating the welding of materials with irregular, inconsistent or difficult-to-access joint interfaces. Fortunately, advances in sensing technology allow automated welding to tackle such variables and, combined with cost-competitive robotic-welding options, enable automated welding to expand all along the fabricated-part supply chain.
With sensor packages selected, installed and trained (programmed) correctly, the capabilities of robotic arms in combination with controllers are significantly extended. For example, in robotic-welding systems the introduction of sensors provides the adaptive capability of touch and sight to address the challenges of a “moving” weld seam or component. Previously prohibited joint tolerances and configurations now are effectively produced with acceptable quality and weld integrity.
Sensoring has positively addressed inconsistent-joint challenges in these phases of the automated-welding process:
- Joint-edge detection—finding the edge or start of a weld seam
- Joint-seam tracking—maintaining the desired weld path
- Measuring the width or profile of a joint.
For this article, we’ll focus on joint-seam tracking. In some instances the start or edge of the joint may be relatively simple to control within the tooling or fixturing. The seam itself, however, may vary due to manufacturing methodology or thermal influences of the process. Tracking of the seam by various methods can overcome this shortcoming of manufactured parts, offering another opportunity to automate the welding of previously prohibited joints and components.
Three main methodologies can facilitate seam tracking, with each providing varying levels of investment, complexity and capability:
- Vision solutions
- Laser scanning
- Through-the-arc sensors
Historically, most vision applications have been employed in situations where quality requirements were uncompromising, often with significant safety implications. Today sees greater availability of lower-cost and increasingly capable solutions. Consider each system on its own merit, as not all vision/laser solutions offer the same capabilities.
Laser-scanning technologies fall into the categories of 1D, 2D, 3D, spot, line and circle. All frequently combine with some form of CCD-style camera to capture images for processing with algorithms. Such setups usually are managed by a host PC (often combined with the camera as a space saver) that calculates the input data and produces the necessary output for the robot to execute its task.
To ensure the effective deployment of vision/laser solutions, ask the following:
- When sizing up the task, what is the smallest object or feature to be tracked/detected?
- When viewing the feature or part, what level of measurement accuracy is required to meet the process criteria?
- What size of field of view is required to capture essential information when tracking?
- What is the speed of recognition and processing time required to meet output-cycle requirements?
When selecting the right laser/camera combination, consider environmental aspects. Temperature, vibration, illumination and humidity all can affect the quality and reliability of results. Note that some cameras are best suited for static capture and others perform better for linear tracking.
The combination of process-head and component geometry also may dictate what size lens and camera arrangement can be installed on the end of the robot arm. Time spent with quality 3D-simulation software is very important. Simulating the movement of the robot and its end-of-arm-tooling minimizes risk by thoroughly identifying what welds can be accessed, as well as any potential compromises that may arise with certain camera/lens configurations. Beyond the physical constraints, determine whether your company has the expertise to configure the equipment, and the level of the support that’s needed for system startup and operation.