Welding more than 16,000 parts per week is a big order for any company. But that was the situation Luitink Manufacturing Co. of Menomonee Falls, Wisconsin, faced after accepting a new project as a supplier of shock caps for the Ford Ranger light duty truck line. Using manual welding methods, this was an impossible task, but with the help of automation equipment Luitink was able to meet this challenge. Now the company is able to weld at a rate of two shock caps every 15 seconds.
"The speed and accuracy of the robots are incredible," says Mike Krajna, Process Improvement Manager for Luitink. "Since robotic welding is new to us, when we first started investigating the process we thought our operators would have to wait for the robots to do their job, but it is actually the other way around. We are able to meet our production requirements and will even increase our volume to 20,000 parts per week in the near future."
The robotic cell at this 110-year-old job shop and metal stamping company uses six plug welds to attach a .176" thick carbon steel, ring-shaped reinforcement bracket to the bottom half of .156" thick shock caps. The total circumference of the shock cap is 7 ½", while the size of the hole being plug welded is 5/16". Luitink, which manufactures both the shock caps and reinforcement parts, provides a value-added service of welding them together for its customer, a Ford Q1 Supplier.
According to Krajna, Luitink is very pleased with the robotic system purchased from The Lincoln Electric Company. "The quality of the welded parts is wonderful," states Krajna. "We check four parts each shift to make sure the robot is maintaining penetration and overall consistency of the weld and what we are finding is that there is very little variation. Because the robot produces minimal smoke and spatter, we don't have to do any grinding or clean up. We couldn't keep up with the required quantities any other way."
Prior to receiving the Ford shock cap project in August 1997, Luitink had never used robotics. But because of the large volume of shock caps required per week, the company felt that automation was the only option. Based on a recommendation, Luitink contacted Gayle Roofe of local distributor Bentley Welding Supply and Lincoln Electric's Milwaukee area representative, Rob Stinson.
"We were impressed with the presentation that Lincoln gave us," notes Ernie Muehlenberg, Maintenance Supervisor at Luitink. "We told them the type of parts we had to weld and with the help of a software program, they were able to simulate visually on the computer screen how the robot would be able to weld our parts. We felt comfortable with Lincoln right from the beginning."
In addition to providing a package that could weld within the parameters required for this job, Lincoln was able to deliver in the tight timeframe required. The initial time from project investigation to purchase of the cell was two weeks with an additional 10 weeks for delivery and installation.
"We built all the tooling and fixtures at our plant," comments Muehlenberg. "We then shipped them to Lincoln's Cleveland headquarters where the Automation engineers mounted the robots directly to our tables. They then programmed the robots to weld our plug welds."
Luitink's system includes two FANUC ArcMate robots with R-J2 controllers and two Lincoln Power Wave® 450 power sources and accompanying wire feeders. The robotic cell utilizes .045" diameter Lincoln L-50™ wire and a shielding gas mixture of 85 percent argon and 15 percent C02. Luitink's customer dictates most of the parameters.
The robots simultaneously weld two parts at one time. During the cycle, the robot arms move to the first fixture where two right shock caps are positioned. Once the right parts are welded, the robot arms move to the second fixture to weld the left parts that are positioned and waiting. In this way, there is no downtime, and when the process is complete, four parts are ready - two right parts and two left parts. Only one operator is needed to man the robotic cell.
Shock caps are then put through a gauge to check for height, burrs, weld build-up among other factors and if they pass the test, they are counted and dropped into a holding basket.
Luitink has a safety feature to the cell – a safety mat that will automatically shut the robots off if someone gets too close to them.
In addition, Luitink's robots have other features built-in. "After an established number of cycles, the robots will automatically move to a torch cleaning station where the nozzles are cleaned and antispatter spray is applied to the nozzles and torch tips," explains Muehlenberg. "We have also programmed in an automatic tip check and the robots recalibrate themselves automatically with the help of Lincoln's TorchMate program."
Another feature is a crash prevention program that will automatically stop the motion of the robots if one arm should happen to move the wrong way. In addition, sensors show if parts are loaded correctly onto the fixtures. By customer request, Luitink also programmed in a repeatability test so that after a certain number of cycles the robot arms will land on sensors that supply an accuracy report.
According to Muehlenberg, both the robots and the power sources are easy to program. "I admit that I have a hard time with computers, but programming is very easy with the hand-held teach pendant that walks you through set-up step by step."
Luitink believes the service that Lincoln has provided during all phases of the project has been outstanding. "Rob Stinson did a great job of helping to get us up and running in only two days after delivery. If we have a problem, we know we can call him and he will be right here. At one point we needed to have a minor repair to one of the power sources. Rob had another power source in our building three hours later," says Muehlenberg.
Luitink has also been impressed with the training offered by Lincoln Electric. "We were provided some hands-on training while the robots were being installed, but for more formal training we sent four employees including myself to Cleveland. The training program was outstanding. I had never even worked with robots before, and I left feeling confident that I can do any type of programming," notes Krajna.
The robots at Luitink run 52 weeks a year for 20 hours each day and require very little maintenance.
Not only is Luitink pleased, but its customer is as well. "We will definitely use Lincoln and FANUC the next time we put a cell together," says Muehlenberg.
Twelve plug welds in 15 seconds and high quality in addition... Luitink has met and even exceeded the challenge!