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Heavy metal automation

Making light work of heavy fabrication welding

Cobots like the Motoman HC10DTP that feature hand-guided programming, an ISO standard tool flange and electrical connections for a plug-and-play approach facilitate easy deployment of a robot system.

Key to overcoming common heavy fabrication obstacles, today’s advanced technologies work in sync to enable highly flexible environments that effectively address general market fluctuations, supply chain challenges, skilled labor shortages, on-time customer demands and more. While there is not a “one size fits all” approach, manufacturers are modernizing current production spaces via highly flexible robots and other advanced technologies.

Fulfilling lean manufacturing initiatives, takt time requirements and more, manufacturers are realizing the benefits of adding robots to current production spaces.

Industrial robots and workcells

Streamlined industrial robots with contoured arms are ideal for reaching into tight spaces and workpieces in high-density factory layouts. Increasingly popular, extended-reach arm models are improving accessibility on long weld seams and large weldments. Likewise, features from power supply manufacturers are allowing faster welding at higher deposition rates.

Robots compliment these power supply advantages in multiple ways. Digital interfaces enable easy programming. Optimized feeder mounting areas reduce equipment interference. Single power and control cables simplify setup, and modular robot harness designs help to improve diagnostics and maintenance. All of which facilitate greater efficiency for heavy fabrication.

Similarly, throughput goals for large parts are being met head-on via robotic welding workcells. Many large parts can be successfully welded in a single pre-engineered system that features four (or more) 6-axis arc welding robots, while extremely large and uniquely shaped parts do well with customized workcells.

Widely used in ArcWorld welding workcells, Yaskawa’s Ferris wheel positioners feature MotoMount technology, which allows them to be lagged directly to the floor and eliminates the need for precision alignment for faster tool changeover.

Options for customized systems range from placing a single long-reach welding robot onto a horizontal servo-driven transporter to installing a vertical elevator servo-track (with a robot and peripherals) to increase overall reach. Overhead gantries can also be fitted with servo tracks for greater work envelopes. While the approach taken obviously depends on part specifications and application requirements, enabling efficient part rotation and optimal weld accessibility is vital.

Collaborative robots

Highly advantageous for high-mix, low-volume batch runs, flexible collaborative robots (cobots) with precision hand-guided teaching enable the creation of longer, continuous weld seams on a variety of parts. Easily positioned in front of large, heavy workpieces or placed in booths normally reserved for manual welders for supplemental welding, cobots with built-in safety-rated power and force limiting (PFL) help to create hyper-productive work spaces. Not only does the ability to safely move a robot up to a large or unwieldy part bolster production, it also allows other process, such as conventional welding or grinding, to occur simultaneously on oversized parts.

Robust power supplies

Fabricators frequently combine a headstock with a tailstock to support long part spans or to accommodate peripheral weld tools.

Manufacturers looking to meet high deposition rates can garner success via multiple tools. Growing in popularity, the use of metal-cored wire for MIG welding in fixed and semi-automatic robotic welding applications is increasing torch travel speeds for greater efficiency and facilitating stable wire transfer with higher deposition rates for ideal joint integrity. This is easily achieved with robust weld torches, such as Miller’s Hercules that can preheat specially formulated metal core filler metals designed to work in tandem for tackling heavy fabrication tasks.

Aside from maximizing productivity by combining select wire with innovative power source waveforms, manufacturers are also adding simplicity to the overall process. For example, Lincoln Electric’s HyperFill dual-wire process allows operators to make larger welds at faster speeds with greater ease. This MIG welding method utilizes two smaller diameter wires to produce a larger weld droplet and arc cone, generating a large weld puddle that is easier to control.

By only using a single power source, feeder, gun liner and contact tip with a familiar robot pendant interface, this promising method offers the potential to increase usable deposition rates up to 50 percent over traditional single-wire processes.

Heavy positioner technology

Regardless of part size, producing high quality welds is dependent on part positioning and weld access. Providing the stability and rotation needed, heavy payload capacity positioners help optimize these aspects, as well as cycle time and the number of welded inches per minute.

Seam tracking is ideal for large weldments with long or curved seams; it enables the robot to trace a weld pattern in real time after the arc has been established.

Headstock/tailstocks: While single-axis positioners can be mounted as a headstock on the floor or tabletop for simple and small part welds, fabricators frequently combine a headstock with a tailstock to support long part spans or accommodate peripheral weld tools. Because of its ability to spin freely and support large, heavy loads, the tailstock is especially appealing to fabricators looking to weld parts up to 7 m long, such as tower trussing, trailer parts or agriculture equipment.

More recently, manufacturers are moving from traditional hard-mount systems to scalable mounting systems to gain even greater flexibility on the shop floor. Traditionally, the alignment of a headstock and tailstock is achieved on a common base with the guidance of a laser-accurate leveling procedure – as misaligned headstock/tailstocks or headstock/headstocks can cause significant damage to the part and tooling.

A substantial reduction of positioner life can also occur. To avoid this, decision makers are implementing an innovative fixture mounting system called MotoMount that allows headstock/tailstocks to be directly lagged to the floor. Compliant bearings on both the head and tailstock allow two degrees of freedom, reducing stress on the positioner and subsequent tooling, as well as improving overall repeatability.

Ferris wheel: Ideal for medium to large parts from 2 m to 5 m long, this two-station positioner design allows the ideal programming of robot height and the quick yet comfortable loading and unloading of heavy parts with tooling while the robot is working. Two headstock/tailstocks help to facilitate this, while shot wedges steady the load, optimizing weld quality and the inches per minute rate.

When needed, heavy castings on either side of the positioner offer ample space and strength to mount additional robots for processing extremely large, tubular or boxy weldments. Highly efficient, Ferris wheel positioners are an attractive, space-saving option for manufacturers concerned about measuring production value per square inch while optimizing cycle time.

Skyhooks: Allowing for a vast number of part positions, 2-axis skyhook positioners typically offer 180 degrees of freedom on the tilt axis and 360 degrees on the rotate axis, with some options providing 360 degrees of freedom from both axes. Extremely capable, this option is well-suited for manipulating heavy parts, such as construction equipment frames, in confined spaces.

Drop-center: Offering a higher payload capacity than a single-column skyhook, a drop-center positioner enables the welding of very heavy parts that require complex manipulation during the weld cycle. Adding an extra axis to a headstock/tailstock positioner, this 2-axis design makes it possible to position the part for “flat in position” welds.

Ideal for large, contoured parts, the coordinated motion of all automated components is typically achievable through the robot controller. For example, Yaskawa AR-Series welding robots utilize the YRC1000 controller that provides multiple robot control with coordinated motion between devices for up to eight robots and multiple positioners, allowing configurations to smoothly operate from a single teach pendant.

For collaborative applications, cobots do not currently offer external axes compatibility for PFL part positioning, so tasks requiring the use of specific positioners for coordinated motion should be mitigated by fencing, light curtains or other means.

Trending technologies

To visually confirm a robotic workcell configuration and test it for reach and cycle time studies with motion before it is installed on the shop floor, the utilization of offline programming (OLP) software from a PC-based virtual environment is highly suggested. Offering key features like collision detection, path planning, conveyor tracking and CAM Path, OLP platforms provide a fairly accurate 3-D representation that visually demonstrates how a robot will move along the programmed path.

Overall, the flexibility provided by OLP software offers many perks and enables a higher mix of jobs with a simple transition from one job to the next. OLP allows the programming of detailed jobs with less robot downtime. Similarly, larger companies with multiple locations or workcells may be able to reduce programming time and inconsistencies by distributing the programmed job from a central, controlled source.

Other effective options for heavy fabrication continue to evolve and grow as well.

• Common user interfaces. For both industrial and cobots, easy-to-use pendant applications, like the Universal Weldcom Interface, are enabling greater robot usage. These common user interfaces enable full utilization of the advanced capabilities of any brand of digital welding power supply for arc welding tasks, and they also allow the setting of all weld parameters and special features directly from a teach pendant.

Through-the-arc seam tracking. Ideal for large weldments with long or curved seams, and some variation from part to part, a through-the-arc seam tracker, such as ComArc, enables a robot to trace a weld position in real time after the arc is established. This simple method measures the arc characteristics of a weave pattern to determine variations between the robot’s taught path and desired path. Intuitive software compensates for workpieces or workholding fixture inaccuracies, providing the utmost in weld quality and productivity.

• Computer vision with machine learning. For the robotic welding of heavier parts, the combined use of camera sensors and artificial intelligence software are helping to determine part shape and weld seam locations. Machine learning solutions, such as the one offered via Path Robotics, are especially advantageous as many are compatible with the multi-pass welding process that is often needed for heavier parts.

Easily adaptable for different geometries and weld joint configurations of different parts, Path Robotic’s technology independently recognizes what can be welded before determining exactly how to weld. It also provides a quality assurance analysis on performance. Frequently used for fabricating specialty automotive components, solutions like this complement the industry shift toward no-code programming for high-mix, low-volume production.

High-performance yet more affordable robots with intuitive features will continue to empower manufacturers to take the robot leap. Moreover, the right mix of robots and advanced technologies can greatly enhance welding operations for extremely large parts. Decision makers looking to make light work of heavy fabrication via robotic automation should reach out to a knowledgeable robot supplier or system integrator to gain helpful insights on how to successfully navigate down a path toward rapid ROI.

Yaskawa America Inc.

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