Robots are helping companies become more competitive by reducing costs and cycle times, but they are increasing one vital shop function: maintenance.

Effective maintenance is critical to consistent performance of robotic systems, Tom Jaeger, engineering manager for research and development and new product development for Tregaskiss (www.tregaskiss.com), said. Tregaskiss manufactures MIG welding equipment and consumables, including robotic MIG welding guns.

“Seconds count in this industry, and a slow-down, stoppage, or weld re-work on a line or in a cell can result in costly downtime and lost production. The welding industry is very competitive and all manufacturers work diligently to maintain productivity and get a good return on their investment in their automation,” Jaeger said.

Maintaining robotic torches is important to avoid weld quality issues.

“Any challenges in your system will cause you quality issues, but the end result is the process itself and any issue with this affects the quality of the output,” Jaeger said.

As robotics have become more common and human interface with the torch less frequent, more companies have come to understand the importance of preventative maintenance programs that are designed to take care of issues before they start.

Jaeger said a production line could produce more than one bad part from a faulty system before any problem is noticed.

“If you have several hundred manufacturing cells – and we have customers that have as many as 750 welding robots with a single line consisting of 24 robots to 32 robots – you might have a challenge at the beginning of the line that goes unnoticed until there are six parts they have to pull off for rework, then restart production,” he said.

“We’ve seen some very bad examples due to lack of maintenance, from an hour’s to a day’s worth of production, affected that could have been prevented with a good preventive maintenance program,” Jaeger said.

Jaeger added that while large organizations generally have good preventive maintenance programs, he recommends that even smaller companies develop and put into place a good preventive maintenance program to ensure proper maintenance is done on a regular basis.

“Several years ago, you might have found that maintenance programs were sketchy, but today it’s more common to have them,” he said. Still, ongoing training and awareness initiatives that facilitate the implementation and execution of preventive maintenance programs are a consistent challenge.

Jaeger provided tips to develop a regular maintenance regimen that can help to avoid costly quality issues:

• Clean, tight connections
Cleaned and tight connections are very important to the efficient and productive operation of a welding cell.

Debris can cause a poor connection, so care should be taken to avoid fouling the internal and external connecting threads.

Both the diffuser and the contact tip should be checked to ensure that they create a complete electrical connection. The diffuser must be installed tightly to the gooseneck because a loose connection will result in excessive heat.

Also, grounding blocks must be clean and free to make good contact to help ensure good weld quality. Check that the welding power cable connections are tight, and that the weld process feedback cables are connected according to the manufacturer’s directions.

Excessive spatter build-up on all components of the system must be avoided.

“All this might seem simple but it’s operator awareness of how all components relate to each other, such as the diffuser and the contact tip, that provide optimum performance from the consumables,” Jaeger said.

• Wire Liners
It is important to understand how long it takes for the liner to become worn or to foul with the process, and to schedule replacements accordingly, Jaeger said.

“If the liner becomes full of debris or worn, it needs to be replaced to maintain minimal friction on the wire. It will take some analysis on the part of the manufacturer to determine how long a liner lasts. Then, key to a good preventive maintenance schedule is incorporating that information, and making sure that liner replacement regularly occurs before issues arise,” he said.

Additionally, the liner must be cut to the correct length. All torch manufacturers provide this specification.

Torches for robotic welding Demand for the specially designed torches that are used in robotic welding has increased with the increase in the applications of robots in manufacturing. Torches for robots are not just manual torches that are attached to a robot arm. Robotic torches are designed specifically to work in an automated environment, which by its nature is designed to reduce labor costs, cycle times and overall costs to manufacture. Robotic torches often include features that are designed specifically for automated operations, such as wire controls and emergency-stop capabilities that prevent damage to the robotic arm and the welding arm in the event of a collision. New generation of robot mounts that are connected to Estop circuitry, any collision activates a safety cut-off switch that provides a high margin of safety for both the robot and the welding torch that is attached, and to maintain the correct Tool Center Point (TCP) that is critical to quality welds and consistent automated processes, according to Abicor Binzel (www.abicorusa.com). Also, robots with collision detection software still require an accurate, repeatable torch mounting system. Applied Robotics (www.arobotics.com) has developed a collision sensor that it calls QuickSTOP to prevent the robot arm from crashing into the part it is welding. The company has two models of its collision sensor that are designed specifically for arc welding, laser and plasma cutting. The company said its collisions sensors are designed to avoid problems such as collision protection devices that do not hold the torch rigidly in normal operation and false reset signals that can compromise repeatability and weld quality. Applied Robotics said it developed its QuickSTOP’s collision sensor with a pneumatic chamber that incorporates a metal-to-metal seal to hold the unit rigid during the articulated robot motion. Air pressure to the unit can be adjusted to ensure correct breakaway resistance, and a pressure switch monitors that air pressure is present and that the QuickSTOP is reset in the proper position before resuming operation. Tom Jaeger, engineering manager for Tregaskiss (www.tregaskiss.com), said torch design is critical in robotic applications. “You should look at features that allow you to easily install and uninstall a torch in a short period of time,” he said. “The same goes for consumables. If the system is complex and you have to pull the entire system off to replace components or consumables, it requires a lot of time. System design should allow maintenance to be simple and as quick as possible,” Jaeger said. Abicor Binzel’s concurs: “Robotic gun design should take into account the need for automatic cleaning. An air line may be incorporated for blowing spatter out of the nozzle, and the internal nozzle structure should allow complete reamer cleaning up to the gas ports.”

“Improper liner length can be a big problem,” Jaeger said.

“A liner that is cut too short will pull back away from the seat in the diffuser and cause wear and drag on the wire. To avoid this problem, companies should provide their welding operators with proper training as part of the overall preventive maintenance program.”

• Proper Tools
When performing scheduled maintenance, always make sure to use the proper tools for the job.

“I can’t stress this enough. You can damage the equipment and it won’t perform as well if you use the wrong tools,” Jaeger said.

For example, diffusers should be installed with the proper adjustable or crescent wrench, and tips should be installed with the proper pair of pliers or welpers, or a specialized tip installation tool. Liners should be cut with proper side cutters because using anything else will create a large burr that can wear or drag on the wire.

• Wire feeder
Check the drive roll pressure to make sure there is no excess pressure.

Drive roll tension that is too tight can cause excessive wear on the drive roll and may deform the wire, both factors that can cause poor wire feeding and/or a wandering arc.

“On the other hand,” sai d Jaeger, “too loose of drive roll tension can cause the wire to slip and also affect feed-ability.”

Drive rolls do wear out, Jaeger noted, as do the wire guides, and they can cause the wire to skip or cause birdnesting. These components must be inspected visually for wear on a regular basis and replaced as needed.

• Wire conduit
This is also part of the system and these can get bound, creating friction. You need to look at it and do a wire pull check at least once a month, Jaeger advised.

“On a robot, the wire conduit often can extend the full length of a robotic cell, and if there are any points of friction along that path it can cause wire feeding issues,” he said.

“As part of a good preventive maintenance program, operators should release the drive roll pressure and pull on the wire. It should pull through easily. If it doesn’t, replace the conduit,” he added.

• De-reeler
Found within a welding drum cone, this component allows the wire to come off the spool smoothly.

Be sure the proper let-off mechanisms are in place and that the equipment you use is correctly installed. Also, check regularly to see if the de-reeler requires service, including the addition of lubricants.

“No matter how good preventive maintenance schedule you develop, it’s only as good as your ability and willingness to act on it,” Jaeger said.

“Many companies have very skilled people drawing the plans up for PM, but the challenge is adhering to the plans and training the operators to understand how all the elements of the system interact. They’ll be better suited to maintain the system, and be better at troubleshooting when there is a problem,” he added.

More maintenance is needed because there are more robots North American robotics companies saw orders to manufacturing companies rise 24 percent in 2007, reversing the declines of the previous year, according to the Robotics Industry Association (www.roboticsonline.com). The industry association estimates that 178,000 robots now work in U.S. factories, placing the United States second only to Japan in the overall use of robots and that includes the 15,856 robots valued at $1.07 billion that were ordered by North American manufacturing companies in 2007. Sales to companies outside North America put the 2007 total at 17,261 robots valued at $1.15 billion. “Most of the growth last year resulted from sales to automotive manufacturers and their suppliers,” Ake Lindqvist group vice president for Robotic Products and Automation for ABB Robotics and chairman of the Robotics Industry Association’s Statistics Committee, said. “In this market segment, which accounted for 64 percent of all orders, robot sales in North America rose 43 percent,” Lindqvist said. Automotive purchases of robots remain cyclical, but Robotics Industry Association members are used to that industry’s pattern, Jeffrey A. Burnstein, executive vice president of the Robotics Industry Association, said. The association’s data show that welding robots represent a sizeable chunk of orders in the automotive sector. Orders for spot welding robots increased 100 percent and arc welding robot purchases jumped 10 percent, according to the industry association. Spot welding robots represented 27 percent of new orders, while arc welding robots represented 17 percent of the new orders for 2007 and, together, these two welding processes represent 44 percent of the total new orders for robots for the auto industry.