Robotic welding systems can help manufacturing operations establish and maintain a high volume of production and increase quality, while also reducing costs. Robots provide consistency, accuracy and precision, and deliver faster performance that helps reduce overall cycle times. These benefits make automated welding an increasingly common option for manufacturing companies.                                      

The return on investment (ROI) a robotic welding system can provide is an important consideration for companies. Robotic welding typically offers a solid ROI, especially when companies undergo careful advanced study and planning. Numerous factors impact the return on investment, including the choice of filler metal used with a robotic welding system.        

While solid wire has been the industry standard for robotic welding for many years, metal-cored wire is an excellent alternative that can offer significant productivity and quality improvements in many applications, particularly in the manufacture of heavy equipment and automotive exhaust, chassis and wheels. 

The basics of metal-cored wire

All filler metals have unique characteristics, benefits, limitations and best applications. Metal-cored wire, on average, has a higher per-pound cost than other filler metals, including solid wire, but it also offers significant productivity and quality improvements as a return on that upfront investment.

Metal-cored wire consists of a metal sheath filled with metallic powders, alloys and arc stabilizers formulated to create distinct effects, providing higher impact strengths and controlling silicon deposits in the final weld. Metal-cored wire carries higher current densities than solid wire of the same diameter (at equivalent amperage settings), which allows for more weld metal to be placed in a joint in less time. Metal-cored wire excels in robotic welding applications, from mild to stainless to low alloy steel, in large part due to this increase in weld metal deposition rate.    

While it offers the greatest benefit in flat and horizontal positions, metal-cored wire also can be used in single or multi-pass welding in most positions, including vertical down and overhead welding using a standard CV (constant voltage) power source. It also can be used for vertical-up position welding, though short-circuit transfer or pulsed welding must be employed in those cases.

Productivity and quality among the benefits 

Metal-cored wire is known for several key attributes, including welds with little to no spatter; excellent gap bridging; reduced burn-through; wide penetration profile; faster travel speeds; higher deposition rates; and the ability to weld through light rust or mill scale.             

These qualities are advantageous in most welding applications, but they are especially beneficial in contributing to the increased throughput sought in robotic welding operations. For example, companies can increase overall productivity by minimizing non-value-added activities in the pre- and post-weld stages, which helps increase workflow and allows for labor resources to be dedicated elsewhere. The ability to spend more time on value-added activities in the welding operation adds to the overall productivity.                             

Consider some of the reasons why metal-cored wire increases productivity and reduces quality issues:

•    The broad, cone-shaped arc results in a wider penetration profile as compared to the more fingerlike penetration of solid wire. The cone-shaped arc creates a larger, more consistent bead profile that easily bridges gaps without burn-through.

•    Metal-cored wire uses the spray transfer process, which creates tiny filler metal droplets that deposit in the weld puddle and generate little to no spatter. 

•    Higher deposition rates and greater travel speeds — in some cases 20 to 30 percent faster — result from the wire’s construction.

•    These features also help minimize porosity and undercut in the final weld.

•    Stable arc initiation and minimal turbulence in the weld pool offered with metal-cored wire helps improve deposition efficiency.

Consider pre-weld, weld and post-weld activities

In robotic welding operations, there are common tasks that are typical to both pre-weld and post-weld areas. In pre-weld processes, common tasks include pre-cleaning of the base material, applying anti-spatter, tacking parts, and moving parts and positioning them in fixtures. In post-weld areas, common activities include removing spatter and/or slag, grinding welds prior to painting or coating and moving parts to final production areas. Using metal-cored wire can eliminate several of these steps in robotic welding applications. The benefits of this filler metal in the pre- and post-weld stages are where many of the cycle time improvements can be found.

Pre-weld benefits

Some pre-welding tasks in a robotic welding operation will always be necessary, such as part-tacking or loading parts into fixturing. However, using metal-cored wire can make it possible to reduce or eliminate some other pre-weld activities that add time to the process.                 

Since filler metal manufacturers formulate metal-cored wire with added alloys, arc stabilizers and deoxidizers, it can be used to weld through mill scale, reducing the need for grinding and sandblasting. Companies can also reduce preparation time and costs using metal-cored wire since there is no need to apply anti-spatter compounds before the parts are to be welded. Anti-spatter compounds are known to be messy and typically increase the need for cleaning the weld area.

Companies using robotic welding systems can reduce the time, labor and costs associated with these pre-weld activities by using metal-cored wire.

Post-weld benefits 

Improvements in post-weld activities offered with metal-cored wire provide some of the greatest opportunities for optimization in robotic welding applications. The wire can greatly reduce or eliminate the need for post-weld spatter cleanup and repair and/or rework stations.       

Eliminating these time-consuming post-weld activities can help companies increase the flow of completed parts to other stages of production, such as painting or coating, which helps improve overall productivity. The ability to focus labor and resources on other areas of the process also helps lower costs and can result in a faster return on investment stemming from higher productivity levels.

Other tips for maximizing the technology 

Using metal-cored wire in robotic welding applications can provide benefits in other parts of the process than just the pre-weld and post-weld phases.

While pairing metal-cored wire with a power source offering pulsing capabilities is the appropriate choice for out-of-position welding, that combination also offers benefits for in-position welding. It provides accurate and fast seam tracking, and the pulsing action can shorten the arc, making the weld puddle more manageable and lowering heat input into the part. Lower heat input helps minimize the risk of burn-through and distortion.

There are additional ways to enhance the benefits from metal-cored wire in robotic welding applications: selecting the right contact tip and choosing the most appropriate wire diameter. The wear on the contact tip in robotic welding is greater than in a semi-automatic welding application, since robots have the ability to weld more parts per hour. Because of this difference, heavy-contact tips and/or chrome zirconium tips are good choices to withstand the greater amount of welding wire passing through the tip. Reducing the frequency that tips must be changed also helps minimize equipment downtime for changeover, so more time can be spent welding.                

The diameter of wire being used in many robotic welding applications also can be increased in most cases. For example, increasing from a .045- to .052-inch diameter wire, or even up to a 1/16-inch diameter metal-cored wire, allows the robot to put a greater amount of weld metal in the joint.                                       

For optimal results, it is best to weld in the middle of the recommended operating range for each specific metal-cored wire. Doing so helps provide the best quality results and allows companies to gain the most out of metal-cored wire’s attributes.                        

In the end, robotic welding can offer productivity, quality and cost-saving benefits for companies. Pairing a robotic welding system with metal-cored wire can serve to enhance these results in many manufacturing applications and help support an even greater return on investment.