Automated Welding for Smaller Jobs
Digital communications allow connectivity between a system's components to make welding automation less complex and costly
By Christopher A. Bailey
General Manager - Automation Division
The Lincoln Electric Co.
Conventional wisdom has been that automated welding only made sense for longer runs of repetitive parts. Historically, the costs of fixturing and special workstations tended to create these limitations. New systems that combine easier programming and more flexible workholding, and cells that provide closer coordination between weld control, robotic motion, and workpiece positioning, promise to make all but the smallest jobs candidates for automation.
New digital technology links welding equipment and robotics to create easily programmable cells, enhancing the appeal of automated welding for smaller and more specialized applications. More flexible programming and finely tuned digital communications between welding power sources, robotic arms, and positioning equipment makes it possible to create a system that is productive for manufacturing operations of almost any size.
A company running different batches of 50 or 100 weldments now can gain many of the same benefits as one producing hundreds or even thousands of identical assemblies. Larger firms can also benefit by automating their shorter run or more-specialized production welding using a packaged pre-engineered system that is programmed to their changing needs. With strategic alliances between manufacturers of welding equipment, robotics and positioners, even custom cells are often within reach for small-lot applications.
In the past, manufacturers often looked at only their most complex parts as candidates for automation, and concluded the investment wasn't economically justifiable. Today, more-flexible systems minimize the need for dedicated fixturing, and make it less difficult to switch production from one part to another. The 80/20 rule frequently applies, as 80% of a company's production typically represents only 20% of its part sizes. New robotic welding cells make it easier to automate more of these simple, often-repetitive jobs, and to switch quickly from one to another.
The biggest reason to automate is that it makes economic sense. Robotic systems for short-to-medium-run applications are now more affordable than ever. With a lower investment and greater productivity improvements, the return on investment (ROI) is greater than with larger, individually designed welding lines.
Consistent quality is another reason to automate. The fewer uncontrolled variables in the process, the higher the quality of the welds and the more uniform they will be.
In contrast to custom fixtures, the flexible fixturing or workholding incorporated into the newest robotic cells makes it less complicated to switch back and forth between different products with little changeover time. This capability also increases productivity and improves ROI.
There's a shortage of trained welding operators. This situation creates an automation imperative in which it makes sense to transfer skills to the machine and automate as many repetitive tasks as possible. Even when an operator is involved, labor content is lower. In a robotic welding cell, handling and welding occur simultaneously in two zones. While the operator loads and unloads in one zone, the robot welds in the other.
Connectivity between the system's components is what makes welding automation different today than it was just a few years ago. New industrial communication networks now create a continuous loop for feedback and control of the entire process, from office computer to factory floor and back. Digital communications make these systems much faster than analog controls. They provide more throughput, and are more flexible as well. Moreover, parameters can be added without adding more wires. Real-time process evaluation and connectivity to the Internet makes it possible to monitor the process without hardwiring the components together, not only on the factory floor but remotely, in a control room, or even at a totally different location.
Equipment manufacturers that previously functioned independently are forming more strategic relationships. By pooling their individual knowledge, they can design products that work together as systems. When a company with welding expertise joins with a leading robotics manufacturer and a supplier of innovative positioning systems, the team can offer automated welding solutions that are more effective than if a user tried to assemble a workcell independently. Moreover, the manufacturers of complementary equipment are blurring the lines between their individual firms, and creating a new synergy as they cooperate on re-engineering each other's products to work together.
By bringing together the right combination of equipment, software, and communications technologies, manufacturers can create technologically advanced arc welding platforms that provide seamless integration and high-speed communication between welding equipment, PLCs, remote I/Os, networked computers, and everything from the plant floor to the office computer. With digital speed and accuracy, these systems control the welding process and equipment, while also providing constant feedback to optimize quality and productivity. Using continuous feedback to a PC, process evaluation now can be accomplished in real time, without having to install separate external monitors.
An example of this capability has been created by technology developed for our company's Nextweld program that provides seamless integration of Waveform Technology, digital communication, and welding-consumable technology. Because arc waveforms can be shaped electronically using software, equipment with waveform-control capabilities can deliver customized results for each application without the need to change electrical components. Customized waveforms can be created upon request, and they can be downloaded from the web for real-time delivery.
Computer software customizes welding-arc characteristics to match the task at hand. This flexibility allows a single machine to adapt to a range of welding applications with varying material specifications, weld positions, and strength/appearance requirements. Inverter power sources are capable of running on virtually any power supply with a high efficiency rating for energy and cost savings. Digital communications provides faster, more reliable transfer of large volumes of data than analog methods.
A digital communications protocol for the arc welding industry, ArcLink, was first introduced by our company at the 1997 American Welding Society (AWS) show. As an open protocol, it can be adopted and used by all companies in the welding industry, and will allow more and more system components to communicate effectively. Such a protocol governs the exchange of information between devices or modules in an arc-welding system, and simplifies both interconnectivity and communications.
Typical modules may include a power source, a control box, and wire drive. Peripheral equipment such as fume extractors and gas mixers also are included. Because a welding system is really just a collection of modules, a gateway module can provide links with other networks used in a company, including DeviceNet and Ethernet. With a standard protocol, system integrators will have greater flexibility in choosing welding equipment and peripherals, and far fewer compatibility issues. The modular nature of the protocol offers the integrator a variety of manufacturers and peripherals to choose from, and integrating them into the system will not require a custom design effort for each new system component.
When investigating automated welding solutions, it's important to check out the full range of capabilities available from potential suppliers. Some manufacturers can offer more depth than others in areas such as technical welding expertise, arc management, process refinements, spatter control, and final weld quality. The right combination of equipment for welding, robotics, and workholding or positioning will help optimize cycle times and repeatability.
Compare the available offerings with your present requirements, but also make sure the system you choose has the combination of capabilities and sophistication necessary to meet future challenges. The manufacturer's team can use your drawings or CAD files to build a detailed computer model of your part, and create a 3-D animation that will accurately depict the proposed automated production process. This simulation can provide several benefits, such as:
- Discover and eliminate bottlenecks, inefficiencies and safety issues,
- Analyze how operator performance could impact production and flow,
- Explore multiple part scheduling,
- Verify and/or correct process assumptions and timing issues,
- Examine alternate floor layouts to optimize space,
- Identify potential torch/part/tooling interference,
- Estimate and study cycle time options to increase product throughput.
A manufacturer's automation development team may even be able to help repurpose or upgrade your company's older robots for use in a new, more flexible system. In many cases, this approach can convert less productive, older machines into profitable assets.
This article was first published in the January 2006 edition of Manufacturing Engineering magazine.