Making tip extraction for fume removal work for robotic welding applications
17 July 2017
By Mike Hattingh, RoboVent
What’s the best way to control weld fumes from robotic welding? Overhead hoods and full work cell enclosures have long been the standard solution. But new tip extraction technologies are now offering another alternative for many manufacturers who rely on robotic welding.
Overhead hoods are a straightforward solution for many robotic welding applications. Hoods keep toxic weld fumes out of the ambient facility air and make them easier to collect. They work well for smaller parts that are easily enclosed and do not require cranes to move.
However, larger parts, such as frames for large vehicles and heavy equipment, do not lend themselves to work cells enclosed with hoods. Hoods can also interfere with overhead cranes and other equipment. In these situations, robotic tip extraction offers a viable source capture alternative. Tip extraction’s advantages are making it an increasingly popular option even for applications that have traditionally been hooded. Here’s why.
How Tip Extraction Works. Robotic tip extraction works much like the fume guns used for manual welding, collecting weld fumes right at the source as they are generated. For robotic welding, this involves adding a flexible fume extraction hose to the robot arm.
|In robotic tip extraction, a flexible extraction hose is added directly to the robot arm. The extraction hose must be hooked up to a high-vacuum dust collector. Click to enlarge.|
The hose must be lightweight and flexible so that it is able to follow the movement of the robotic arm without impeding or obstructing its operations. The tip of the extractor is positioned just behind the weld torch head. A special bracket holds the extractor tip in position so that it can collect weld fumes without interfering with the robot’s motion.
|A bracket holds the extraction tip at the right distance and angle from the weld torch head. Click to enlarge.|
The extraction hose is hooked up to a high-vacuum (hi-vac) dust collector such as a model from the RoboVent FlexPro Series. The dust collector needs to have high vacuum power to convey the weld fumes through the hose. While hoods rely on relatively large diameter ductwork to connect to the dust collector, weld fumes for tip extraction are collected through a hose that may be just one-and-a-half to two inches in diameter. This creates higher static pressure for the dust collector to overcome, compared to conventional hoods and enclosures where high-volume, low-vacuum systems can be used.
The Advantages of Robotic Tip Extraction. Robotic tip extraction may be a less expensive alternative for some applications. Because fumes are collected right as they are generated, a much smaller volume of air needs to be moved to collect the weld fumes. While dust collector for a hooded application may need to move 4,000 to 6,000 cubic feet of air per minute (CFM), robotic tip extraction typically only requires 100-150 CFM for effective weld fume collection.
This translates into big savings in both equipment and energy consumption. A compact hi-vac dust collector with a 3-4 HP motor will provide sufficient extraction power for a robot equipped with a robotic tip extractor. The same robot under a hood may require a dust collector with a 10 or 15 HP motor to compensate for the higher volume of air to be moved. Smaller motors and lower CFM translate into lower equipment costs up front as well as lower energy and operating costs. Facilities will also save on expensive ductwork, which is required for hooded applications.
In addition to these savings, tip extraction enables facilities to use source capture for applications that cannot be easily hooded. This keeps weld fumes out of the ambient air, creating a healthier environment and reducing the need for expensive ambient air quality systems.
Facilities where space is at a premium may also benefit from ditching bulky hoods and equipping robotic welders with streamlined tip extractors instead. Tip extraction is often the best choice for plants producing large weldments that need crane access for material handling, prohibiting the use of a conventional overhead hood.
Where Robotic Tip Extraction Works Best—and Where it Doesn’t. Robotic tip extraction works best for MIG [metal inert gas] welding applications. In MIG welding, fumes can be efficiently extracted as welding takes place. A properly designed system can collect between 80% and 95% of weld fumes, depending on the exact application and the way the robot moves. This makes robotic tip extraction an excellent option for many robotic welding jobs in the automotive industry, especially those that cannot be hooded do to size constraints or overhead cranes and equipment.
However, it is not the right option for every application. The tip must be close to the source of weld fumes or smoke in order to collect them. Tip extraction does not work well for resistance welding, which can create a large number of sparks and leaves parts smoking long after the robot arm has moved on. It is also not the best choice when welding parts covered with a heavy oil coating, which can continue to produce smoke during the cooling process.
Other applications may be problematic because of the way the robotic arm needs to move during the welding process. Complicated motion paths, tight angles or deep recesses can make tip extraction challenging (though not always impossible).
Finally, it is not the best option if 100% capture of weld fumes is critical. This may be the case for applications that produce especially toxic fumes or in situations where even low levels of particulates could interfere with other processes. For these applications, a hooded enclosure with negative pressure to prevent leakage is probably the best option.
For many applications, robotic tip extraction can be paired with an ambient air filtration system for optimal air quality control. While the tip extractor picks up 80 to 90% or more of fumes as they are generated, the ambient system takes care of the remaining particulates as they rise away from the tip extraction zone. Pairing tip extraction with ambient filtration allows facilities to use a much smaller (and less expensive) ambient system than they would need if they were using ambient filtration alone.
Design Considerations for Robotic Tip Extraction. Robotic tip extraction is not a one-size-fits-all solution. The tip extractor must be customized for the robot it is fitted to. Improper fitting of the extractor hose and tip will significantly reduce the effectiveness and could interfere with robot arm movement.
At RoboVent, each tip extractor is manufactured specifically to the exact geometry of the weld torch. First, a 3D model is created of the robotic weld torch. Designers use CAD and 3D printing to create a hood that fits the weld torch like a glove. Once the part is fitted, the system engineer conducts a series of calibration tests to ensure that the mass of the hose and bracket do not disrupt the operation of the robot arm and weld torch. RoboVent has patents pending for two different styles of tip extraction hoods for use with robotic welding.
Tip extraction is not yet widely used for robotic welding in North America, but its popularity is growing. For auto manufacturers concerned about energy consumption and air quality control, it provides a practical and effective alternative to traditional hooded dust collection systems.
About the Author. Mike Hattingh is a Product Development Team Leader for RoboVent. He is responsible for investigation, evaluation and development of new air quality product concepts. RoboVent is a leading provider of ventilation and filtration systems for manufacturing facilities.