Spierings increases output with welding automation

Spierings, the Dutch builder of mobile cranes is facing a big challenge to increase production capacity, now that the demand for mobile tower cranes has increased dramatically, in the last few years. Automation of welding production is one of the keys how this manufacturer wants to increase output, as well as guarantee the high quality of its tower cranes. This is why Spierings has moved ahead rapidly with welding au¬tomation and, among other measures, entered into a cooperation with Valk Welding. "We see Valk Welding as a partner that can help us move forward to be prepared for the future," according to Operations Manager Gijs Delissen.

Spierings Mobile Cranes

Spierings offers the largest mobile tower crane in the market which can be assembled and operated by one person. Due to the strong recovery of the construction sector and expansion of market outside of the Netherlands, the demand for these tower cranes has risen rapidly in recent years. In addition, the introduction of the first hybrid tower crane is being planned, with which the manufacturer has the ambition to grow further into a global brand. As much as possible, all components, including the chassis, masts and booms, are manufactured in-house. The assembly and welding of the masts and booms takes up most space and increasing the throughput had to be achieved within the same space.

Accelerating knowledge acquisition regarding welding automation

Gijs Delissen: “Together with Valk Welding, we looked at the welding process where we could reduce handling and welding time. For the mast production line, a concept was developed consisting of a linear system for automation of the welding of the longitudinal seams, and a welding robot installation for the welding of the sub, end and head parts. Both complex installations had a delivery time of one year. We used that time to familiarize ourselves thoroughly with welding robotization. To this end, we purchased a welding robot for less complex parts. Consequently, we were able to take early measures in the upstream process to control the tolerances to align with the requirements of robot welding.”

Lead time longitudinal seam welding greatly reduced

Spierings already has been using a welding tractor to weld the longitudinal seams of the 8 different models of masts. Gijs Delissen: “By combining rotation and welding with multiple welding tractors in one set-up, we wanted to greatly reduce the cycle time of 10 hours. To achieve this, Valk Welding developed a new concept in which the mast segments are rotated and welded, so that the longitudinal seams can be automatically welded on both the inside and outside simultaneously. This has reduced the cycle time of this part of the process from 8.5 hours down to 2.5 hours."

Welding robot used for the final phase

Next, the sub, end and head parts are attached to the masts and welded on four sides by the larger welding robot system. For this purpose, the installation is equipped with a rotation system, driven by positioners. Gijs Delissen: “This is about complex welding performance, where the accessibility of the welding robot and the accuracy of the welding are crucial. A completed mast consists of three parts that must be able to slide exactly into each other, so there cannot even be a deviation of a millimeter. Partly because rotation of the mast has now been automated, the robot can now continue for several hours without to much human assistance. For us, this is a substantial gain in terms of time, welding quality and output. If we can weld a mast every day, we are doing well!"

“Together with Valk Welding, we looked at the welding process where we could reduce handling and welding time.

Gijs Delissen

Booms, next step

Together with Valk Welding and Spierings engineers, Delissen is now researching how the welding process of the booms can be automated as well. Gijs Delissen: “We may also have to look at how we can take into account handling of individual parts. An exciting process!"

Crane construction is at the forefront of high-strength steel applications

The use of high-strength steels plays an important role in achieving a weight advantage in crane construction. Spierings has been using high-strength steel since 1998 for the load bearing parts, mast, boom and tension rods. “When designing construction cranes, our goal is to be able to lift loads as high as possible within the permissible weight on the pavement of 12 metric tons per axle. Accordingly, in our designs the focus is always on where materials and weight can be reduced. Our model 1265, developed in 2003, is still very popular and is the largest mobile tower crane in the market. This tower crane has a reach of 60 m, a maximum lifting capacity of 10,000 kg and a maximum capacity at the tip of 1,700 kg. Without the use of high-strength steel, we would not have been able to build a tower crane with such capacity. Valk Welding is also our partner for the supply of welding wire for this high strength steel application, another benefit from Valk Welding as supplier. They can advice us not only for the complex robot welding system, but for the total application, including the welding process.” concludes Gijs Delissen.

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