Understanding and Justifying a Process Change to Metal Cored Wires
Because they comprise only about four percent of the overall cost of a welding operation, filler metals are often perceived as a simple commodity. They demand a per unit cost and require ongoing stocking, which necessarily separates them from equipment acquisitions in terms of expenditures and financial justifications. Or does it?
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In today’s high-level manufacturing environment, companies continually seek ways to improve productivity and lowercosts in order to maintain their competitive edge. Often they look to new equipment technologies to achieve that edge, and rightly so. With all of the advances in power source technologies, there is often a fast return on investment in terms of productivity increases.However, there have also been significant advancements in filler metal technology, many of which can complement the advancements of newer equipment or even enhance older equipment.
In recent years, metal-cored wire has become an increasingly popular alternative to solid and flux cored wire for many companies. Metal-cored wire touts benefits such as reduced spatter, higher deposition rates, faster travel speeds and the ability to weld effectively through mill scale or rust. Yet with these benefits comes a slightly higher per unit cost. The question becomes: how can a company justify a process change to metal-cored wires?
Determine Your Baseline: Is There Potential for Improvement?
No company can justify additional expenditures or process changes without cause. As with equipment acquisitions, changing to metal-cored wire must offer a solution to certain problems: low productivity, high labor costs, a high volume of rework, or other factors affecting the quality of products and the overall profitability of the welding operation.
As such, a potential switch to metal-cored requires assessing the entire welding operation, looking not only to the weld cell, but also to the pre- and post-weld areas to determine the impact of the current filler metal on productivity and costs.
To establish a baseline against which to measure the potential for improvement, look first at the pre-weld area to determine activities that cause bottlenecks or slow downs in the beginning of the welding operation. Because the pre-weld area is often used for activities such as grinding mill scale, applying anti-spatter or degreasing materials, companies can incur additional labor costs here. These activities can also affect operations further downstream and add expenses to the overall operation.
If a pre-weld area exists, first quantify the amount of labor and time used for grinding or other such weld preparation and consider the cost of maintaining or replacing the equipment necessary for the activities. A welding distributor or equipment supplier can usually help in this assessment. If a company uses anti-spatter, the cost for purchasing it and the labor necessary for applying it and cleaning the pre-weld area should also be considered.
Also look at the weld cell and post-weld area of the operation. Measure the actual amount of arc-on time, how many parts can be welded in a given shift, the quality of the parts being produced and the welding parameters at which the operation is running.
In semi-automatic welding applications, review the impact of the welding cell on welding operators’ health. With certain filler metals, such as solid wire, operators often oscillate their MIG gun to create fillet welds and can suffer wrist problems as a result. In this case, companies should quantify the amount of worker compensation claims due to such injuries.
Consider the amount of rework necessary for each of the parts using the current filler metal. If there is a problem with undercut, lack of fusion or spatter, quantify the amount of labor and time necessary for reworking parts, grinding spatter and the number of parts that must be completely rejected.
Metal-cored Wire: What Do You Need to Know?
If after assessing the pre-, weld, and post-weld areas, companies find high labor costs, low productivity, bottlenecks or excessive rework, a process change could be beneficial. Research shows that metal-cored wire can minimize labor costs for pre- and post-weld activities and improve productivity in the weld cell by approximately 20 to 25 percent, but in many operations the improvements are even greater. There are several reasons for these improvements.
One, metal-cored wire can weld through mill scale and/or rust while still achieving a smooth weld bead. Two, at equivalent amperage settings, metal-cored wire effectively carries higher current densities than solid wire—compared to a solid wire’s entire cross sectional area conducting the current, the outer sheath of metal-cored wire does the job. This results in higher relative burn-off rates and translates into the potential for increased deposition rates, faster travel speeds and greater overall throughput.
When using metal-cored wire, it is also possible to increase wire diameter by one size over a solid wire, which allows companies to weld on a variety of material thicknesses and joints and standardize on a single wire diameter throughout the welding operation. In addition, metal-cored wire provides smaller molten metal droplet transfer to minimize spatter and provide a wide weld metal projection area for better bridging of part gaps.
Payback: How Can You Justify a Change? Looking at the features and benefits of metal-cored wire is one thing, but justifying a process change is quite another. To substantiate the higher per unit cost, companies need to consider how the benefits can translate into real paybacks.
A good first step is to establish key measurements against which to analyze potential improvements in the welding operation. For example, if a company can eliminate pre- and/or post-weld activities (including anti-spatter application or grinding) by using metal-cored wire, they should consider how much this might help them reduce labor costs or whether the labor could be reallocated to the weld cell to produce a higher volume of parts.
Other key measurements to consider are: reduced rework and lower warranty costs. Given that metal-cored wire bridges gaps more readily than solid wire, a process change could yield significant results in terms of reducing labor costs for part rework and/or material costs for rejected parts.
Additionally, companies should consider the possibility of higher productivity yielding higher quality parts. If a company can produce better parts faster with metal-cored wire, there may be a potential for lowering warranty costs (not to mention increasing customer satisfaction) and increasing the overall throughput of the operation.
Once each of these factors has been considered, it is important for companies to calculate the payback of each potential improvement. Doing so may require running a trial of the wire in a portion of the welding operation—local welding distributors or a filler metal manufacturer can assist with this process.
Final Considerations
No single piece of equipment or spool of wire will yield immediate results in a welding operation. For that reason, considering a process change to metal-cored wire is as much a matter of being productivity-minded as it is having a long-term vision for improvement. Remember, higher upfront costs can often give way to higher quality and productivity.