As a result of the Axcess systems’ capabilities, operator training and weld procedure pre-qualification, the manufacturer experienced an immediate production increase after installing the 22 semi-automatic systems. The largest contributors to the increase were:

— An improvement of at least 35 percent in welding deposition rates. The company now averages 10.5 to 11 lbs. of weld metal deposited per hour.
— Completely eliminating the need to chip slag and greatly reduced grinding saves about one hour per day at each welding station.
— Reduced over-welding.
— The ability to control heat input and reduce time spent compensating for warping.

The ability to control weld size was significant. In any semi-automatic welding operation, preventing over-welding generally offers the big opportunities to increase productivity. For example, a 1/8-in. fillet weld requires a filler metal volume of 0.0078 cu. in. However, if the operator over-welds and creates a 3/16-in. fillet weld, the joint requires a weld metal volume of 0.175 cu. in., a 124-percent increase in weld metal volume.

Other productivity increases come from not chipping slag or cleaning spatter balls. Every station previously had an air-powered chipping hammer and several people just dedicated to cleaning parts. Now there is hardly any grinding done anywhere in the shop. The decibel level went down considerably, and the people who were cleaning parts are now welding parts.

Less heat
When welding the stainless used for the frames, the end customer provided an upper limit on joules per inch of weld. The heat limit ensures that the welded part will have appropriate mechanical properties, and it prevents carbide precipitation (carbide precipitation is the chief culprit of weld quality issues on stainless).

Experts consistently agree that the Accu-Pulse process provides more flexibility to control heat input compared to spray transfer or flux-cored welding. Pulsed MIG provided a perfect solution because it pulses between a high transition point and a low background current. Accu-Pulse users can adjust these and other variables to control heat input while maximizing deposition rates.

Less air time
In any robotic application, two of the biggest potential areas for improvement involve reducing “air time,” or the time the robot arm spends moving between welds, and optimizing torch angles (experts can often increase productivity by 10 to 15 percent through torch angle optimization alone).

At this manufacturer, the previous flux-cored wire robot programs had been written around additional movement points to control heat input. Some components were actually flipped (by an automated fixture) to weld on the opposite side of a part to address distortion issues caused by high heat input.

As part of shifting to the Accu-Pulse progress, the robot welding programs were completely rewritten. This would have been required anyway because the flux-cored process uses a drag technique where, with Accu-Pulse, the torch or gun gets pushed.

Reprogramming the robots did take longer than anticipated (about one month for 30 subassemblies). However, the company allowed for these difficulties by building up inventory as a contingency so as to never miss a customer deadline.

While upgrading the automated welding stations took a concentrated effort and significant capital investment, the rewards were worth it: air time was reduced by an average of 60 percent. Because Accu-Pulse lowers heat input, the robot can move shorter distances between welds in the same plane and the fixture does not need to rotate until a new side is ready for welding. As a result of these improvements, the manufacturer estimates that the payback time for its new Auto-Axcess systems will be less than one year.

Moving forward
In addition to the Accu-Pulse pulsed MIG processes, Axcess and Auto-Axcess systems can be upgraded with Miller’s optional Regulated Metal Deposition (RMD^™) program.

RMD provides the ability to weld thin material (1/8-in. or less) while controlling weld bead profile. RMD is a modified short circuit transfer process that offers improved gap filling, reduced spatter, lower heat input, minimized distortion, and the ability to weld with a larger-diameter wire on thin materials.

After testing the RMD program to weld thinner material with less warping, initial results indicate that they can spend less time straightening parts, which will increase further productivity. In addition, the RMD process will better enable the company to meet customer’s weld specifications.

For example, on one thinner component, the customer wanted a fillet weld with a 1/8-in. throat. Other MIG processes and a 0.035-in. solid wire would have struggled to achieve that. But, with RMD the company easily achieved 1/8-in. fillet welds.

Now, with the “multi-MIG” capabilities of Accu-Pulse and RMD, the type of projects the manufacturer can adapt to seem nearly endless.

Kevin Summers is the business development manager, robotics/automation, for Miller Electric Mfg. Co.