Scrap and rework cost can sometimes seem unavoidable with the welding process. However, when operators can clearly see deviations in the weld zone, they can implement the appropriate welding parameter changes to limit the need for rework and reduce the cost associated with scrapped parts.
Over the years, it’s become quite apparent that the most effective way to monitor the welding process in real time is to use a camera. But all weld cameras are not created equal.
Traditional camera-based monitoring systems don’t offer the image quality operators require to efficiently see the weld pool and make necessary adjustments. While monitoring a weld pool with an inferior weld camera, operators simply do the best with what they have, and when they can’t properly monitor the puddle, that can add to the cost of scrap and rework.
Fortunately, better options are available today that offer higher contrast images of open arc welding, which has traditionally been a harsh environment for weld cameras. The best option is a camera that can see the bright light of a weld arc as well as the darker areas around the arc, such as the parent material, the weld seam and the weld pool.
Xiris Automation Inc., a company with 25 years experience in design and production of software, electronics, mechanical and optical products for machine vision, has developed a line of cameras for open arc welding that can do just that.
Seeing is believing
The weld pool and its surrounding environment offer telltale signs that clue in an operator in to the quality of the weld – or lack thereof.
A Xiris white paper relays the “strong correlation between weld pool width and the degree of penetration in tungsten inert gas (TIG) welding. In addition, weld pool width, volume and position are important in determining the surface profile of the weld and the likelihood of imperfections such as lack of fusion and penetration.”
In order to get great results, each welding process has specific parameters that must be followed. Furthermore, conditions need to be highly consistent and alignment is a requirement. Alignment at the weld seam and weld tip are specifically important for tube mills as are material inputs, such as weld wire or gas being fed at ideal speeds.
When the operator is able to see all the elements of the environment around a weld, they can more effectively control the manufacturing tolerances of upstream operations that significantly affect the quality of the welding operations, such as profile cutting and edge preparation, variations in the shielding gas and accuracy of assembly.
Wide Dynamic Range (WDR) weld cameras are extremely beneficial in an open arc welding environment. The concept of using a camera to monitor welding processes is not new, however. The traditional approach has been to use standard cameras (non-WDR) with the addition of special filters and/or digitization software techniques to achieve an improved image of the weld.
The traditional approach, despite the filter and software intervening to create a better image, does not allow for reliable evaluations of the welding process because the camera over or under exposes some portions of the welding environment.
For example, a weld tip might be as much as 10 million times brighter (or greater than 140-dB signal-to-noise ratio) than the background metal area around it. To image this is a great challenge as most cameras today are capable of only 50 to 60 dB (about 1,000:1 dynamic range of brightness). On a side note, the human eye is able to see about 1,000,000:1 range, but on the dark end of the scale, which is why eye protection is needed when looking at welding.
Image content, therefore, gets lost in the harsh and varied welding environment, limiting the ability of the operator to maximize the performance of the welding process. According to the Xiris white paper, the viewing camera should incorporate an electronic means to create a WDR image right in the camera sensor, removing unnecessary light wavelengths and pixel saturation to be able to clearly see the detail of the weld tip as well as its darker environment.
When fabricators use the best WDR weld cameras, they gain more clarity, which provides numerous advantages, including improved productivity and quality and health and safety benefits. Features found on a higher end WDR weld camera include:
- WDR sensor technology with range 140+ dB for superior images
- Integrated lighting/focus/cooling
- Ability to provide image processing
- Ability to provide image zoom
- Window de-dusting and spatter protection
- Rugged enclosure for harsh welding environments
- Ability to record and playback video
Operators looking for more details in their welding process are finding it with WDR cameras. Tube and pipe fabricators gain a full range of optical configurations with the cameras. Whether it’s a large tank manufacturer or a small precision assembly application, WDR cameras have proven their value.