Arc Welding Robotics: The Welder's Guide to Automation Systems

This guide presents important aspects of arc welding robotics and automation systems to professional welders and fabricators. It covers the operation of welding robots in relation to welding automation systems, juxtaposes collaborative robots (cobots) to purpose-built robotic welding cells, assesses to what extent certain welding processes are viable for automation, offers vendor selection criteria, discusses most challenges pertaining to implementation, and outlines the factors that influence welding speed and the quality of welds. The purpose of the content is to provide welding professionals the knowledge needed to assess robotic welding systems, robotic arc welding systems, and welding solutions in order to improve the productivity and quality of welds, and increase the safety of workers in the fabrication process.

Understanding Robotic Welding Fundamentals

What does robotic welding mean and what does an arc welding robot do in welding automation?

Robotic welding means integrating welding power sources and robotics to automate repetitive welding processes in a variety of welding applications. Repeatability, speed, and quality of the welds are consistent, in all applications. An arc welding robot incorporates a multi-axis robot arm, a welding machine or welding power source, separate wire feeding and gas delivery systems for GMAW/MIG, and control software to coordinate the movement of the welding torch with respective welding parameters. The welding power source and wire feeder or electrode, which determines the rate of consumable deposition, are activated during welding. The robotic welding process commences when routed trajectories and weld parameters are programmed in the robot controller and weld. In order to execute the programmed path, the robot welder activates the welding power source. Furthermore, most advanced robotic welding systems have seam tracking sensors and vision systems with the ability to monitor and adjust to maintain consistent results with respect to the welding process. The majority of arc welding robots used in the automation of production lines are integrated with positioners, material handling, and weld cells to develop a complete system that is fully automated and requires consistent minimal human intervention to operate.

What steps are taken to convert an arc welding process into a robotic welding machine?

Converting an arc welding process into a robotic welding machine involves defining the parameters of the manual welding process and translating them into programmable setpoints for the robotic welding machine. Each welding power source has certain parameters that are adjustable and that can be linked to a welding robot. These parameters are the voltage, the current, the wire feed speed (for GMAW, also referred to as MIG or GMAW), whether the welding machine is in a pulsed or continuous mode for TIG, and the travel speed. The robotic welding cell is programmed (based on the design of the fixturing and the geometry of the weld joint) to ensure that the torch, (or electrode) is maintained at the specified distance to the workpiece, at the proper angle, and is moved at the required speed to achieve a specified level of heat and material deposition. The welding robot's seam tracking and adaptive control features allow for the welding of parts that are subject to defined tolerances while ensuring a high level of control and repeatability to provide the required weld quality and consistency for large production volumes. The integration of the robotic welding machine with specialized welding processes like laser or plasma welding focuses on crossing control for laser or plasma with the movement of the robot, while also managing the automation system for shield gas, focal position, and shield optics.

What are the main components of a welding robot and its power source?

Most welding robots have similar components that make a complete welding system. On the robot's arm and wrist are multiple joints and axes which give the robot a high range of dexterity. Each machine system has an associated robot controller that runs the motion program and a welding power source or machine that gives energy to the arc welding process. There are also robots which have Wire Feeders and torch assemblies for use with GMAW/MIG or For GTAW, there are also robots which use gas and consumables, and use sensors to both detect and monitor seams. To give robots the ability to optimally access large or awkward components, positioners and rotary tables are often integrated to locate the components. The welding power source can be purpose-built for robotic welding, offering embedded communication protocols and pulse waveforms tailored for automated deposition rates and arc stability. Many modern robotic welding machines and robotic arc welding systems have additional features to provide components for an integrated welding system, such as real-time data logging, automated adjustment of parameters, and factory automation system to modern fabrication systems.

How do weld cells and automation systems work together to get the same weld quality?

Weld cells and automation systems use mechanical (fixturing), process (control), and systems (integration) to achieve weld quality consistency. A weld cell contains the robot, welding machine, positioner, part fixtures, and safety enclosures. Fixture design within the cell focuses on one specific goal: the most repeatable part presentation; any variation, no matter how minute, will affect the perfomance of the weld process. The automation system captures real-time electrical and sensory data to monitor the Stability of the arc and rate of weld material deposition. The data is adjusted to keep the weld consistent. (i.e. welds and their composition) therefore, the data monitor will prevent the beading of weld material. The integrated system will statistically provide more deposit control, improved overall process compared to manual welding, will have a more consistent and stable arc. Integrated systems should be designed and commissioned properly, should provide consistent deposit control, improved overall process compared to manual welding.

Benefits of Robotic Welding Systems and Cobots

Why would someone want to invest in robotic welding systems and welding cobots?

Automation of welding processes using welding robots and welding cobots can augment or escalate output and can potentially alleviate the problem of not having sufficient quantity of appropriately skilled welders available in the job market. Repeating the same welding task many times will become the job of a robot or collaborative robot. Once the robot or cobot is in place, the welders can perform work of a greater value and or more skilled nature. Repetitive tasks can be completed with welding robots and welding cobots. Relied upon to perform high volume work load, welding robots will work more effectively and more efficiently than any human. Robotic welding systems are able to work at high duty cycle. Robotic welding systems can also ensure improvement of the weld quality. If the weld quality of the robotic welding system is constantly being improved, the amount of welding rework will also be decreased. Robotic welding systems are equipped with advanced informative welding technology. They also have the ability to monitor and adjust in real time to facilitate improvements of the welding process and to ensure improvements to the overall stability of the robotic welding process. New cobots are designed to embrace collaboration with a human welder. Because of this, the human welder will be freed up to focus on more high value welding tasks. New flexible automation and, more specifically, collaborative welding robots enable welding operators to focus on and perform more high value work since the cobot will be performing previously non automated welding tasks. Robotic welding solutions will ultimately allow the manufacturer to expand his output without the worry of having skilled welders perform the same task on the same weldments. Robotic systems will also ensure the manufacturer consistent welds and improved lead times. Robotic systems can replace non skilled welders. When utilized, robotic systems ensure reliable and consistent quality of welds. Robotic systems also add to the manufacturers ability to respond to changing market conditions, and they can be relied upon to respond to the changing market conditions.

What are the expected gains in productivity as a result of the automation of welding and the increases in deposition rates?

Welder automation provides measurable gains in productivity through increased deposition rates, faster cycle times, and higher operational uptime. Robotic welding provides greater travel speeds and more uniform arc conditions, which increases deposition rates for MIG/GMAW and other arc processes. When used in conjunction with a positioner, optimized torch path programming, and automated filler feeding, the robot positioner systems can operate in a way that increases their operational throughput. These systems can also be used in a way that increases their operational throughput. For most repetitive welding applications, throughput tends to increase at least two- to five-fold. These systems also provide additional improvements in productivity through the increases in the reduction of welding scrap, rework, and the predictability and improved scheduling of welding production. Purpose built robotic welding systems can be used to improve deposition rates and welding productivity for specific applications such as heavy structure shipbuilding or for high volume seam welding on production lines.

Collaborative Robots vs. Dedicated Robotic Welding Equipment

What are the considerations for picking collaborative robots (cobots) versus dedicated robotic welding equipment?

Consider the type of tasks, volume, cycle times, and payload to determine if a shop needs collaborative robots versus dedicated robotic welding equipment. For example, collaborative robots are great for low and medium volume production, and in flexible fabrication environments. Furthermore, for operations needing human-robot collaboration, or in cases where there are labor shortages, collaborative robots can be a good solution. Cobots are effective for less complex tasks and typically allow for lower payloads and smaller reach. This makes them useful for smaller volume welding, tack welding, and pre- or post-welding operations. For large repetitive tasks and environments with heavy-duty cycles (more than 100 cycles per shift), purpose-built robotic welding equipment is better. This makes them better suited for robotic welding in the shipbuilding, heavy fabrication, and automotive assembly industries, as they are designed for and can be equipped with advanced robotics to maintain consistent weld quality and productivity at high levels.

How do welding cobots assist with labor shortages and gaps in skilled welders?

Welding cobots assist with labor shortages and gaps in skilled welder availability by enabling less skilled operators to perform automated welding tasks and require less skilled programmers to simply demonstrate a weld to the cobot. This reduces the need for advanced programming and allows a current employee to shift to an operator or integrator role. Cobots also allow skilled welders to focus on advanced assemblies, quality checks and process improvements that need human expertise by automating welding on joints and other repetitive volume tasks. Finally, the collaborative nature of the cobots improves ergonomics and reduces operator fatigue and injuries, aiding in talent retention, and increasing productivity of the workforce in fabrication shops.

Welding Applications and Processes for Automation

Which welding applications and welding solutions are best suited for automation in metal fabrication?

Automation works best for welding applications that are highly repetitive and involve the same type of welding joining the same pieces together. Examples include butt, fillet, and groove welds in structural assembly, seam welding in assembly lines, and spot welding in metal sheets. Other examples are welding of pipes and tubes, and the welding of thick plates in the shipbuilding and construction industries. Most welding applications such as pipe and tube welding in ship manufacturing and construction are subject to automation. Automation of welding is mainly associated with MIG (GMAW) processes, since they have high deposition rates and are easier to feed wire. In contrast, automation of welding is more common in TIG (GTAW) processes when low heat input and precision are required. For applications that are high speed and low precision that are high in distortion, such as welding and plasma welding, Laser welding can be used. Once the right optics and safety equipment are incorporated, these welding techniques can be used for robotic welding. When deciding to automate a weld process, the most important factors to consider include the Return on Investment (ROI) for the automation, the expected production volume, the tolerances of the parts to be welded, and the ability to design fixtures to present the parts in a repeatable manner.

What criteria choose between MIG, TIG, or laser welding for automation?

Automation considerations for MIG, TIG, and laser welding include material, joint configuration, weld profile requirements, deposition rate, heat-affected zone, and automation cost. MIG (GMAW) is automated the most due to the high deposition requirements, and for MIG welding, a stable arc and high tolerance to joint fit-up are necessary. This makes it ideal for production welding, fabrication, and structural welding. For automation, TIG (GTAW) is used when welds demand high precision, great aesthetics, low spatter, and when working with thin stainless steel, or components of aerospace grade. However, TIG automation is generally more complex, with lower deposition rates. Fast and low-distortion laser welding and plasma welding are ideal for precision assemblies and thin materials, but require more investment and controlled environments. The dominant criteria is a comparison of welding deposition requirements versus the part throughput and the long-term cost savings from automation in relation to the integration and capital costs.

How are payload, part size, and fixture design relevant to the choice of a welding system?

The payload, part size, and fixture design are relevant to the choice of a welding system as they affect the type of robot, positioners to be used, and the design of the welding cell, respectively. The robot's payload impact is directly related to the weight of the torch and the end-of-arm tools. In addition to the tools that are used to mechanically handle the material and to add material to the weld, the robot also carries sensors. Therefore, larger payloads are associated with larger industrial robots that have greater torque and larger bases. The size and weight of the part also determines the reach of the robot and the need for external axes or positioners to move large workpieces in the cell. In addition, the design of the fixture impacts the welding process. A designer must have precision in order to achieve targets. In order to achieve consistent weld quality, the process should be designed to minimize the amount of variation. In order to design processes that are consistent, it is important to preserve fixtures. A well-designed fixture allows for simplification of loading and unloading, a reduction in cycle time, and the ability to place multiple welding stations in a single cell. Overall, this results in a system having a greater ability and optimal utilization.

What are the advantages of using a dedicated weld cell compared to a flexible robotic system for certain tasks?

Cells designed specifically for welding are optimal for fabrication activities of a high volume and repetitive nature while exhibiting a high level of consistency in part shape and fabrication cycle times. Examples include large volume production runs of identical parts, large volume seam welding, and high volume structural shipbuilding welding. These cells are designed to maximize welding efficiency and consistency by using custom built tools, custom built welding positioners, and custom programs for the welding robots. Flexible robotic systems are more advantageous for work cells, production lines employing a mix(model), and work cells that demand high levels of variability. This is because flexible robotic systems have the ability to be reprogrammed in a rapid fashion, employ modular welding equipment, and use flexible robotic systems in the collaborative mode to carry out a wider range of welding tasks. From an operational perspective, a decision for isolating a dedicated cell or adopting a flexible system is a function of the estimated volume of production, the expected variation in parts, and the operational focus of maximizing deposition and weld cell uptime versus minimizing production time across a broader range of variants.

Vendor Selection and System Evaluation

How do you select the best welding automation system, welding machine, and robotics vendor?

To select welding automation systems, welding machines, and robotics vendors, you need a solid comprehension of the production objectives, welding specifics, and the details of what the welding process integration. Assess vendors according to their knowledge and experience in robotic welding, compatibility of welding power sources with robotic controller(s), and proven ability to deliver complete (turnkey) weld cells and system(s) with positioners, and any/all of the applicable) material handling and automation system design. Ask for working demonstrations of the same or similar systems as yours, and review the relevant shipbuilding or automotive production line case study(s) and references to assess the system(s) support and references. Technical questions you ask vendors should address long-term system(s) support; system(s) scalability; and potential communication(s) and upgrades to support the addition of seam tracking, real-time monitoring, or other forms of programmable (robotic or mechanical) welding.

What questions should a welder ask about control, programming, and real-time monitoring?

A welder or production manager should ask vendors about the robot controller's programming environment, how simple it is to teach weld paths, and if the system has offline programming to reduce downtime. Also, ask about real-time monitoring, if data during the process is collected, and if the system has intelligent welding capabilities for adaptive control and weld traceability. Regarding the integration of the welding power source and the robot for synchronized start/stop commands, how does the system provide corrections for seam tracking or vision system adjustments, and does the automation system provide dashboards or alarms for the operator to take immediate action? Answers to these questions provide confidence that the welding system will provide the necessary control, visibility, and flexibility to ensure weld quality.

How important are service, training, and application support when evaluating welding solutions?

Service, training, and application support are very important when evaluating welding solutions because they are critical to system uptime, operator proficiency, and the overall success of your automation efforts. Comprehensive support from the vendor should include an initial start-up support, on-site training for welders and programmers, plans for preventive maintenance, and onsite troubleshooting to resolve issues. Application engineering support assists you to improve your welding parameters, fixture design, and cell layout to meet your production objectives and ensures that your welding process is stable in the presence of variations. Investing in vendor relations that have strong training and support reduces the chance of poor quality welds, increases operator confidence, and helps you achieve your robotic welding systems ultimate productivity goals.

What influence does equipping requirements and compatibility with other sources of power have with regards the selection processes?

When products integrate effortlessly with current power sources and make compatible use of other equipment, power sources, and wire feeders, positioners, etc, the investment is protected, and the ROI on the automation is expedited. It is vital to obtain whether there is any compatibility of communication, voltage and phase, and mechanical interfaces of the robot with the welding power source, and the auxiliary to the welding automation covenant. Also, compatibility is necessary to a modular functional extension of the other automation components weld routing, positioners, or cobots so that there is the flexibility to increase automation components while operational flexibility and controlling the quality of the weld.

Implementation Challenges and Solutions

What hurdles exist for the implementation of welding automation and what solutions can be proffered?

Design of fixtures for welding automation is complicated, process variability is an essential concern, technically accepting ROI is another predominant concern and is an essential integration of safety of welding automation. These hurdles can be overcome by enabling a detailed plan, a well-designed fixture with parts that have a tolerance that shall be limited to within the design of the fixture to reduce the variability, and with the incorporation of position-clamping of the parts, to guide the servos or cylinders to reduce misalignment of the parts. Training to rehabilitate the welders to become operators and programs of the robots is an enormous undertaking and will require designing safe systems to process both the industrial robot and the cellular robot and the ROI analysis must be extensive to include productivity increases, less work and the labor cost will be reduced. These analyses and subsequent adjustments can be made with the assistance of vendors and a trained integrator and will be automated systems for welding at some downtime.

How can weld shops ensure quality and handle variabilities after automating their processes?

The successful determination of variabilities after automation and ensuring quality of welds are both supported by automation processes of control and measurement. Real time monitoring of parameters such as drift, deposition, and torch position enables imediate corrective actions to be taken. Sensor calibration, maintenance of welding power sources and wire feeder devices, and inspection of their fixtures, as well as protective equipment are motivators for reducing wear. Using robotic arc welders, processes are documented and adjusted to reflect changes of the weld characteristics for raw materials. Continuous monitoring is often viewed as a means of supporting weld quality, and operators must be trained in the interpretation of data to ensure this.

What primary issues with safety, ROI, and change management do welders experience with automation?

The deployment of automated welding systems presents a number of issues that are related to safety, ROI, and change management. Safety must include of machine guarding and interlocks, with the need to train personnel in the safe use of both industrial and collaborative robots to avoid accidents. ROI evaluations must include the initial investment, the time to complete the job, the reallocation of labor, and the changes to both the quality and quantity of product produced. Communication and training are the primary means to change management. Employees must be retrained to provide maintenance and programming for the automated welding systems, and retraining and changes to their duties must be documented to ensure that talent is retained and valued. The successful elements in deployments are the technological, financial, and human factors that are incorporated to enable continuous use of welding automation.

How do you train operators and incorporate robotics into production processes?

The most effective method for training operators and integrating robotics into current production processes is a multi-step method that includes a combination of classroom instruction, practice sessions of a given set of skills in a non-production environment, and onto-the-job training in-the-wild live weld cell. You make sure that training begins with basic concepts around robotic operation and safety and basic knowledge of the construction of the welding power source and progresses up to teaching programming, teach pendants, and offline simulation tools. Some experienced welders might need to go through a training course for process engineering and cell operation. Knowledge about weld procedures and quality expectations needs to go through a process of knowledge transfer. When robotic workflow procedures for automating operator tasks, they do the process of mapping the workflow for each production step in order to find areas of optimal handling and staging to optimize the number of times the operator must load and unload and to reduce the number of times the production line is disrupted. Best practice mentoring and problem solving on the workflow is the best way to realize the maximum benefits of full process automation. Welding Robot Manufacturer — Industrial Robotic Welding Solution by Zhouxiang

Measuring Weld Quality and Productivity

How do you define success in terms of weld automation, weld quality and productivity?

Success in automation and welding technology is about measuring and continuous improvement of productive, quality and utilization the weld processand the system effectiveness and efficiency, in order to build a case for the stakeholder to justify their investments. The closure of the monitoring cycle starts with measuring deposition, cycle time of each component, the number of units that pass the test the first time without defects, the number of units that need corrective action, the effectiveness and efficiency of the system, and the time for the system to be fully operational. The monitoring of the system demand, health, stability and uniform delivery of the welding wire, current and voltage, and the arc of the welding machine is needed to maintain the operational efficiency of the welding process. The time needed to capture real time system operational data that shows the stability of the process and the process all factors that must be considered to define a measure of the health of the welding process. In the pre and post-measurement of the KPIs is the basis for successful automation of the welding process, measuring improvement of the productivity of the welding process, and the reduction of defects and the reduction in the cost of labor to demonstrate the ROI of the welding process to the stakeholder.

What are some KPIs for measuring workforce efficiency, volumetric efficiency and operating uptime?

The key performance indicators (KPIs) that measure welding productivity includes deposition rate (kg/hr and lb/hr), number of parts welded per shift, welding cycle time, welding uptime (%) and the mean time (in minutes) between failures (MTBF). Also, KPIs such as operator utilization, weld cell throughput, and planned production percentage (PPP) are useful for measuring overall system performance. Given the overall performance, combined KPIs help fabricators pinpoint the bottlenecks, scheduling and prioritization of some maintenance, thereby increasing productivity and sustaining the expected benefits of increased production capacity from the robotic welding cells.

How can the metrics for quality of the process be evaluated for quality of the arc welding robot?

To evaluate the quality metrics of an arc welding robot process, a combination of in-process/sensor and post-weld evaluation as well as statistical quality control are used. Real time weld metrics (current, voltage, and wire feed rate) also show process deviations that can increase the number of process defects; seam tracking deviations show defect locations and improve weld quality. Remaining defects are evaluated and measured using non-destructive weld testing, dimensional inspections and first pass yield (FPY) metrics. Automation of quality weld data, process control, and welding traceability reduce nonconformance and maintain and improve quality through defect identification, parameter adjustment and design modification (fixtures).