CASE BRONTO SKYLIFT
PRODUCTIVITY AND QUALITY IN ARC WELDING AND PLASMA CUTTING
Bronto Skylift uses robots for both arc welding and 3D plasma cutting. The pieces to be welded and cut are load-bearing steel structures of lifting platforms reaching as high as 112 metres. A lifting platform consists of a truck mounted frame and the attached telescopic boom system.
New products are constantly being designed. In order to start the manufacturing of new products quickly and very reliably, all work that slows down or compromises these goals must be eliminated.
Bronto Skylift purchased the Delfoi ARC software for offline programming of a welding robot and 3D plasma cutting robot. A single software is used to design the programs for both Yaskawa arc welding robot and plasma cutting robot. The products welded are oil tanks, outriggers and outrigger casings. The plasma cut components are booms and outrigger casings.
MORE MACHINE TIME
“The used capacity of the 3D plasma cutting robot was poor. Now that we introduced the offline software, its used capacity has improved and the cutting quality is extremely good. Earlier, the low cutting quality hindered the wider use of the cutting robot. Getting Delfoi ARC was definitely the right move. Now we can use the cutting robot more efficiently. This week for the first time I saw the cutting robot at work and the result was good – and to think of the many years it has been here!” says Production Director Markus Jaatinen about the software purchase. There are no dry runs with the plasma cutting robot, but the process is started immediately.
When asked why Bronto Skylift purchased an offline programming software, Production Manager Mika Heinäkallio replies briefly: “We wanted more machine time.” Programming the arc welding robot to weld an outrigger casing by teaching (online programming) used to take two or three days in two work shifts, up to a total of 45 hours. All this time, the robot was not used for production.
At the moment, offline programming takes approximately 22 hours, but it is done at a desk without having to stop the welding robot. The only downtime is when the program is implemented. The dry run lasts one work shift, i.e. ca. 7.5 hours. After this, the robot is ready to weld the new product. Approximately an additional 37 hours of robot capacity is available.
OFFLINE PROGRAMMING AT BRONTO SKYLIFT
Four professionals are using the software at Bronto Skylift. Most of the users have prior experience in programming the robot by teaching. Understanding the process and mastering robot programming also in production are of great importance in both offline programming and in checking the validity of the programs through simulation. The simulation models of both the arc welding robot and the plasma cutting robot are calibrated to the dimensional accuracy required by the process. Geometry errors are always caused by repositioning the pieces and the process itself, and they are compensated by using the welding torch or touch sensor on the robot. Welding programs always use crack search and monitoring functions. On the plasma cutting robot, the defects are compensated by searching with the touch sensor one boom side at a time.
Picture. From left to right: Mikko Blomster, Ville Katajisto, Jari Pahkala and Mikko Heinäkallio
Before production, a so-called dry run is done with the arc welding robot to check the program on the production robot one more time. This will take approximately one work shift. No dry run is done with the plasma cutting robot, but the 3D cutting starts immediately once the cutting program is transferred to production. In practice, this means that the offline programmed and in the simulation tested program is saved in the job queue on the robot controller.
The basis of programming are the 3D product models and fixtures designed with Siemens NX and read by the offline program in the so-called native, i.e. NX format. Delfoi ARC software is also used to make product weldability analyses. Simulation is of great help when ensuring in advance that the product is weldable, and products that cannot be welded by the robot are not sent to production. The programmers have added markings on robot axis positions in the robot simulation models; they help in collision detection. The work is done in collaboration with product designers. The users consider the software’s user interface easy and quick to use.
The quality of offline programmed programs is extremely good. In arc welding, there is no variation in wire length, typical in programming by teaching, but the wire remains at the desired distance from the welding point. Also the torch angle remains constant at the set value throughout the welding or cutting.
Quality control in welding will improve as new welding programs are made. The process values found to be valid are saved in the software’s welding database (WPS), and the model welds can be used any time equivalent joints are being programmed for new products.
BRONTO SKYLIFT LTD.
Bronto Skylift is the world’s leading manufacturer of truck mounted lifting platforms. The lifting equipment manufactured by the company is divided into two product categories based on their use: fire and rescue equipment and industrial equipment. Their product range includes approximately 50 models between with a range of 17 to 112 meters working height. In its 50 years of operation Bronto Skylift has delivered more than 6,700 devices to fire departments and companies in more than 120 countries worldwide. The company headquarters are in Tampere, Finland. The booms are manufactured in the plant in Pori, Finland. Bronto Skylift has subsidiaries in Sweden, Germany, Switzerland and the United States.
More information: Bronto Skylift