K-zell Metals Diversifies with Pre-Engineered Robotic Welding Cells; Achieves Faster Part Start-up, Increased Throughput, Production Efficiencies
At a time when manufacturers are looking for new ways to diversify and compete against global competition, K-zell Metals, Inc. of Phoenix has been proactive in anticipating changes in the market through process improvement. The specialty fabrication and contract manufacturing business was started in 1986 by Don Kammerzell, a metallurgical engineer with more than 40 years experience in steel fabrication.
“About ten years ago, we started getting involved in military work, and rapidly noticed that our business model was changing from being the traditional job shop into a contract manufacturing facility,” says Kammerzel. “As we looked at the work that was out there, we saw that there was a need for more precise assemblies in the work that we were doing. We found that if we combined a laser, CNC press brakes and a robotic welding cell, we could be much more competitive in the marketplace. The combined precision of the laser and CNC press brakes allowed us to fixture our parts properly, so robotic welding made a lot of sense.”
Through the addition of two Miller PerformArc™ pre-engineered robotic weld cells, K-zell was able to substantially increase productivity (by more than 20 percent), reduce set-up time and find new efficiencies in its welding processes — even on relatively short production runs. A modular design allowed each system to be quickly dropped into the flow of the shop floor, and features such as offline programming have helped the company quickly take on new work with minimal start-up time.
Implementing a Robotic Welding Solution
As Kammerzell puts it, “I’m really not afraid of too many metals.” K-zell’s global customer base requires the company to be well versed in everything from mild steels and HSLAs to stainless and aluminum — the company also does a sizable amount of work with silicon bronze. Much of the work put through its robotic cells is parts for military and commercial products, ranging from basic mild carbon steel to 4130 chrome-moly. Run sizes range as high as 4,000 to 5,000 parts. Precision is critical as many of the parts K-zell fabricates are sub-assemblies that must fit perfectly into larger structures. In selecting a robotic welding solution, K-zell needed a system suitable for varying run sizes that could be programmed quickly and efficiently, and could also handle varying thicknesses and types of alloys. The two PerformArc cells currently at work in the company’s plant are the PA 1100 FW and PA 550 HW with advanced 350-amp TAWERS™ robotic welding systems from Panasonic. (Miller and Panasonic Welding Systems Co., Ltd., entered into a strategic partnership in 2010 to form a new business unit within Miller — Miller Welding Automation — designed to deliver these products to market as a complete automated welding system).
“What we really found was that there was a cost advantage to selecting a pre-engineered system because it was already done,” says Kammerzell. “We didn’t need someone to go out and find all of the components and put it all together. And no matter what we looked at, this was the fastest way to get us in the business.”
Pre-engineered weld cells can be dropped into existing workflows and put into operation with much of the basic tooling your manual welders are already using. With three mechanical engineers on staff, K-zell builds all of its own quick-change tooling and fixtures, a feature that helps the company adjust to product runs of all sizes and quantities. Each cell features a fully welded frame and comes pre-wired and pre-assembled (the PA 1100 FW comes in three sections that can be joined with quick assembly and connection capabilities). The cell is completely integrated and can be easily relocated by disconnecting the utilities and moving it to a new location.
“One of the primary advantages to us was lead time,” says Kammerzell. “We were able to order it and knew that we were going to have it come in and sit on the floor and we could get going with it right away. We looked at the ease of programming and found that this system was much easier to program than the robotic cells we had looked at previously. And then we looked at the ability eventually to go to offline programming.”
According to Jim Benjamin, quality assurance manager and robotic welding supervisor, at K-zell Metals, the design of each cell also allows for nearly 100-percent robot run time. The positioners on both the PA 1100 FW (Ferris wheel style) and the PA550 HW (merry-go-round style) create a two-station weld cell.
“You have a man loading one part on one side while the robot is working on the other side,” he says. “It’s a continuous arc-on situation. As soon as the table flips out, I’m unloading and loading a new one into the robot, but it’s still working at the same time.”
Kammerzell says the design of the cell, with the work being done away from the flow of the shop floor, was an important factor.
“The work flows by the cell,” he says, “and it stops just for a moment and moves on. It’s less of an impediment; it’s more of a sidebar to the flow of work through the shop.”
Offline Programming Helps Move Parts to Production Faster
One of the key factors that allows K-zell to move parts into production faster is offline programming. Offline software — such as Miller’s Desktop Programming and Simulation (DTPS) software — allows the company to program its robot from a computer rather than on the robot itself, eliminating downtime. Upon completing all of the weld sequences, the system lets you to run the welding program as a simulation, where the software will detect possible collisions, identify areas where weld procedure angles could be difficult to achieve, and provide the time it would take for the cell to make a complete part. Only minimal touch-up is required in the cell with the teaching pendant once programmed.
“One of the things that we obtained with our Panasonic robots were the solid models of the robot cell itself, so that we were able to design our fixtures in SolidWorks,” says Kammerzell. “We can marry our robots, fixture tables and parts all in one model. And then using offline programming, we’re able to program the welds and make sure that the fixture will work before we get it down in the shop. And so we can build the virtual model of everything, run through it, make sure all the welds will fit, we can get gun access to it, and it’s made a huge difference in how fast we can get parts into the robot.”
“It’s a very streamlined application once it gets to the floor,” says Benjamin. “It’s a very quick turnaround. You don’t have to stop your current production load. You may have 100 parts to get out today, but tomorrow there might need to be a different part coming through that robot. So you can get a lot of work done prior to actually hitting the shop floor.”
Proven Improvements in Quality
The primary goals of a robotic system are to drive out variation, increase throughput, reduce the amount of non-value-added activities in the welding process and ensure the total quality of each part. For K-zell, considering where many of its products go to work, this is exceedingly critical.
“With the military work we’re doing, I really don’t have any desire to go to a war zone to fix a reject,” says Kammerzell. “We need to make sure the parts we produce are right initially. If we design the fixtures properly and do the welding correctly to where the part stays in the fixtures, they’re really self-checking. We know we have them dimensionally accurate because the fixtures were accurate. The parts, when they come out, are going to stay that way, and we eliminated an awful lot of our inspection time because we design in the inspection when we build the fixtures.”
Many robotic welding applications stumble because of inefficiencies in upstream processes that lead to incorrectly sized parts and poor fit-up. This awareness can actually be a benefit: if you are unable to consistently get the same result with a robot, there are adjustments that may need to be made upstream in the process.
“The robotic weld cell has forced my laser guys and my press brake guys to be more on their toes in getting work done right because they’re automatically checked every day,” says Kammerzell. “The parts have to be right because they have to fit in the fixtures. It builds in more quality to the process.”
Driving out that variation ultimately leads to reduced failures, rework, and scrap. If a part is done right the first time, productivity moves forward. If it has to be redone, that’s a step backwards. Being able to reduce factors such as spatter and distortion, and more accurately control weld parameters ensure the greatest quality.
“To reduce the spatter in a welding operation, whether it’s manual or robotic, you need to make sure you’ve got your parameters set right,” says Kammerzell. “It’s a lot easier with the robot, especially with some of our parts where we’re changing directions after an inch of weld and we’re doing some things that it’s very difficult for a man to repeat every time. That’s what the robot is designed for. We’ve been able to reduce the spatter in a number of areas much (more) than we were able to do it manually.”
That reduction in spatter helps reduce rework and also helps reduce costs in other downstream activities.
“The reduction of spatter really matters on the military parts we’re doing because most of the parts have a sophisticated coating system on them,” says Kammerzell. “You can’t have loose BBs rolling around. So the reduction in spatter reduces the cleanup time there, makes the coatings go on better, and so we have less cost in applying the coating.”
The more precise control over parameters afforded by a robotic weld has also helped reduce distortion and over-welding. Controlling over-welding not only improves part quality, but helps lower gas and consumable use related to laying down too much weld material.
“Distortion is a very significant issue to our customer because a lot of our parts are subassemblies that need to assemble into a finished product,” says Kammerzell. “If our dimensions are just a little bit off, we’ve got a problem there. Over-welding is really an issue in some of the parts. If you over-weld it, then you have to do too much grinding to get it back down to where the parts fit together. Reducing over-welding is a significant issue.”
Productivity Enhancements Justify Robotics
Overall, the system has led to a number of efficiencies, including ease of installation, the seamless integration into the shop workflow, simplified programming that doesn’t slow production, and a reduction in spatter, rework and scrap. As with any system, however, the bottom line is the ultimate judge of its total effectiveness: can you produce more products while meeting or exceeding your customers’ quality standards?
“What we found to be really competitive was that our fixed overheads, such as building rent, stayed the same, but the amount of throughput we were able to push through the robotic cells really lowered our costs,” says Kammerzell. “When we looked at doing the robots, the first cell we put in, we said ok: Lets plan on getting a 15 to 20 percent increase in productivity. We were able to do better than that when we did it, so we were able to reduce our customer’s buying price and reduce our costs down to where our profit margins were able to stay where we wanted them.”
And that, he says, translates into return on investment:
“We’ve definitely seen the ability of the robot to pay for itself. Because of the contracts we were able to find, they paid for themselves significantly faster than we anticipated… within two years.”
Water circulates through external components to the nozzle, keeping front-end consumables running cooler and lasting longer.
Sidebar: Torch and Consumables Offer Long Lasting Performance
The welding power source and the robot get much of the attention in a robotic welding cell, but there are great efficiencies to be found in the torch itself. K-zell uses Tregaskiss TOUGH GUN I.C.E™ Robotic MIG Guns in its PerformArc cells for high-amperage applications that require a water-cooled torch. I.C.E., or Integrated Cooling Enhancer, provides the durability of an air-cooled torch with the cooling features of a water-cooled torch: water circulates through external components to the nozzle, keeping front-end consumables running cooler and lasting longer. This torch, combined with the TOUGH LOCK™ Consumable System, has helped extend consumable life and performance.
“I’d say comparatively, the heavy duty tips last about 30 percent longer,” says Benjamin, “they are easy to swap out, and allow us to do heavier weldments at times.”
K-zell frequently changes the water-cooled torch out for an air-cooled TOUGH GUN MIG Gun and finds the interchangeability to be a key benefit.
“It gives us a wide range of applications that we can put on the same robot, same power source, and the same welding cell,” he adds. “It’s quick-change neck allows you to go anywhere from very thin gauge to very thick, heavy amperage welding.”
The torches are also easy to maintain and quickly bounce back from any collisions that may happen in the cell thanks to a handy neck alignment tool.
“The solid mount and the safety devices that come along with the torch actually reduce the amount of maintenance you have to do to the gun,” says Benjamin. “If you happen to have a crash, you detach the neck and throw it in an alignment fixture and you’re back up and running in just a few minutes. Your robot program doesn’t have to be tweaked or touched up, you just move right back into production.”