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Welding is arguably the most complex manufacturing process and is frequently the least understood. A surprising number of companies spend millions of dollars to automate assembly while ignoring the welding process. Manual welding is still the best process for many assemblies. However, many assemblers are implementing automated welding systems to increase quality, productivity and profitability.
Welding automation can be broken down into two basic categories: semiautomatic and fully automatic. In semiautomatic welding, an operator manually loads the parts into the welding fixture. A weld controller then keeps the welding process, motion of the torch, and stillness of the parts to preset parameters. After the weld is completed, the operator removes the completed assembly and the process begins again.
In fully automatic welding, a custom machine, or series of machines, loads the workpiece, indexes the part or torch into position, accomplishes the weld, monitors the quality of the joint and unloads the finished product. Additional "part in place" and final product quality checks may also be designed into the machine if necessary. Depending on the operation, a machine operator may be necessary.
Not every welding operation is a good candidate for automated welding. Applications will benefit most from automation if the quality or function of the weld is critical; if repetitive welds must be made on identical parts; or if the parts have accumulated significant value prior to welding. Excellent candidates for automation include batteries, capacitor cans, solenoids, sensors, transducers, metal bellows, relay enclosures, light bulb elements, fuel filters, thermos flasks, medical components, nuclear devices, pipe fittings, transformer cores, valve elements and airbag components. Companies that assemble limited quantities of products requiring accurate or critical welds may benefit from a semiautomatic system, but would probably not need fully automated systems.
Benefits of Automated WeldingAutomated welding systems offer four main advantages: improved weld quality, increased output, decreased scrap and decreased variable labor costs.
Weld quality consists of two factors: weld integrity and repeatability. Automated welding systems ensure weld integrity through electronic weld process controllers. Combining mechanized torch and part motions with electronic recall of welding parameters results in a higher quality weld than can be accomplished manually. This offers instantaneous quality control. Furthermore, because a weld is made only once, defects are readily visible and detectable. Humans tend to "smooth over" a mistake with the torch, hiding lack of penetration or a possibly flawed weld. In some cases, leak testing and vision systems can be integrated into fully automated systems to provide additional quality control.
Repeatability is a function of the quality of the weld process controller and of the engineering of the machine motions. Mechanized welding provides repeatable input parameters for more repeatable output. Assuming the controller is functioning properly, the question becomes: Can the mechanisms of the machine position the parts or the torch within the specified tolerances for welding? The answer to this question will attest to the quality of system purchased.
Semiautomatic and fully automatic systems increase output by eliminating the human factor from the welding process. Production weld speeds are set at a percentage of maximum by the machine, not by an operator. With minimal setup time and higher weld speeds, a mechanized welding system can easily outpace a skilled manual welder.
Automating the torch or part motions, and part placement, reduces the possibility of human error. A weld takes place only when all requirements are satisfied. With manual welding, reject welds often increase when welders become fatigued. Depending on the value of the parts when they arrive at the welding station, the cost savings in scrap alone may justify the purchase of an automated welding system. Automation should also be considered when assemblers need to minimize the risk of shipping a bad part to a customer.
Reliance on human welders can dramatically increase a manufacturer’s labor costs. When planning for labor costs, manufacturers must consider the time that welders spend producing assemblies.
Typically, a semiautomatic system has at least twice the output of a skilled welder. A fully automatic system can be built with twin welding positioners on an automated shuttle. Such a system can load and unload parts at one station while welding occurs at the other. In this way, a fully automatic system can run at four Arial the pace of semiautomatic system, or eight Arial the pace of a skilled welder.
Lost opportunity costs are also significant. If a skilled welder fails to report to work, the company’s variable costs skyrocket. Eight hours of production time is lost. Availability of skilled labor for manual welding may also pose a challenge. Conversely, general machine operators are more readily available and more affordable than skilled labor.
All That Glitters...Despite all the benefits, welding system automation is accompanied by some drawbacks. Although the drawbacks can be controlled, they should be recognized from the onset of an automated welding project.
Automated welding systems require a higher initial investment than manual systems. A modern manual welding power supply costs less than $5,000; semiautomatic systems often start around $30,000. Companies considering fully automated welding systems should budget $175,000 to $250,000 for a turnkey system.
Flexibility is also an issue. The flexibility of a machine has an inverse relationship with the degree of automation. While a manual welder can easily move from one part to the next, specialized welding equipment and systems can only satisfy a dedicated niche in the manufacturing process. Flexibility of performance is exchanged for accurate, repeatable and precise welds.
When shifting from labor-intensive to capital-intensive processes, companies must adopt and rigorously follow preventive maintenance programs. Relying on one machine to do the work of eight welders is like placing all of one’s eggs into one basket. While the gains in productivity and profitability can be outstanding, an effective preventive maintenance program must be followed to minimize the risk of costly downtime. Depending on the complexity of the system, a maintenance program should include cleaning and lubricating the machine, calibrating the controls and power supply, and replacing consumables.
Implementing an automated welding system requires a longer lead time for reaching full-scale production. If a company needs to begin welding parts immediately, manual machines may be purchased and implemented in a matter of days or hours. Semiautomatic machines can take 4 to 8 weeks to deliver. Fully automatic systems commonly have lead Arial of at least 20 weeks. The long-term benefits of automated welding systems often outweigh the initial costs of these lead Arial. As a result, delivery Arial should be considered in the planning process.
Before investing large sums in automation, assemblers should consider product life cycle. Most products follow a predictable pattern of introduction, growth, maturity and decline. Assemblers would be ill-advised to sink cash into automating the assembly of an eight-track tape player. On the other hand, the demand for airbag elements and automotive emission sensors will probably remain strong for years.
Deciding to AutomateWith quality and productivity as buzzwords, and customers demanding superior products, implementing an automated welding system may determine whether a company remains competitive. To avoid pitfalls along the way, assemblers need to establish a strategy and follow it closely.
First, assemblers should determine the exact objectives of the project. What specifically needs to be improved, accelerated or changed through automated welding? The following questions can help assemblers sort this out:
- Does the function of the part depend on a high-quality weld? What are the ramifications if the end customer receives or uses a defective part?
- What level of automated welding system will the production system justify?
- What metals are involved? Do they lend themselves to automation?
- How is the joining process currently being done? What is unsatisfactory about it?
- What budget is available for the welding portion of the project?
Before purchasing any system, assemblers should ask the supplier to provide sample welds using standard production parts. Material weldability, joint edge quality and fit-up are crucial to the success of a welding application. Welding sample parts can confirm parameters, such as the quality of the base materials, and part tolerances and fit-up. Sample welds will also display the weld quality possible with an automated system and generate approximate weld speeds to estimate system output.