A leading global manufacturer of longitudinally welded large-diameter pipes is optimizing its production processes with the new pipe bending press from Gaebener and can now produce a wide variety of special pipes with large dimensions and extreme diameter-to-wall thickness ratios.
The machine builder Graebener Maschinentechnik has been building customized machines for use in pipe mills for decades. The recently developed tube bending press is used for bending slotted tubes and half shells in the step bending process. The special feature of this custom-built press is its enormous flexibility, as it can be used to produce tubes of a wide range of dimensions: with outside diameters from 12″ to 48″ (up to 100″ for half shells), wall thicknesses from 12 to 75 mm and lengths between 6 and 13.2 m. What is unique above all is that the bending press can also be used to produce tubes with very small diameters and high wall thicknesses at the same time. Materials with high yield strengths, such as X80, X90 and X100, are processed without any problems. For such an enormous production spectrum, large-diameter pipe pavers normally require several lines.
Another economic plus point common to all Graebener tube bending presses is the increased stroke of the bending blade as well as its stable lateral guidance. The increased stroke ensures that the sword can be completely pulled out of the tube after the bending process is completed. This allows the remaining gap in the pipe to be closed directly in the machine using the sword itself. The stable lateral guide makes this process possible even for small, thick-walled tubes. An additional pipe closing press, as would be regularly used, is thus no longer necessary.
Consequently, the Graebener tube bending press allows both investment volumes to be reduced and production cycles to be shortened – the basis for an economical manufacturing process in the long term.
The bending press has a pressing force of 70,000 kN, which is achieved by six controlled hydraulic cylinders on the bending blade. Thanks to a special force distribution and control system, it can also be used to produce the small, thick-walled tubes. For six meter long pipes, for example, the press achieves a pressing force of an exceptional 52,000kN.
If pipe diameters of up to 100″ are to be produced, the press can be used to bend half shells which are later assembled into a pipe. A specially developed handling system ensures automated removal of the half shells after the bending process. In parallel, all process parameters are stored with the help of the Graebener BendPro automation system, so that the settings and travel paths for recurring products can be recalled at any time.
Faster production of different batches
On the one hand, large-diameter pipe producers must ensure high throughput with consistent quality. On the other hand, they are expected to respond flexibly and quickly to customer requirements, even for special dimensions and small batch sizes. Frequent mold changes, however, especially for small batches, cost time and money. All Graebener bending presses are therefore designed in such a way that the various pipe sizes in the standard dimension range can be produced flexibly and without changeover using only a single tool set. The changeover time for dimension-dependent tools is eliminated, thus helping to increase the efficiency of the bending process.
Limited heavy load route requires constructive rethinking
It was not only the customer’s requirements that demanded special design solutions. The new tube bending press was also a challenge for the special machine builder from a logistical point of view. Thus, due to the required output and the resulting design, weighing around 1,100 tons, the press was not only the largest and heaviest pipe bending press in Graebener’s history, it also required a special design of the crossheads. Since these far exceeded the maximum weight of the heavy-duty route, Graebener designed the structure so that the individual trusses could each be manufactured in two parts and welded together on site.
Graebener Maschinentechnik is a medium-sized, family-run mechanical engineering company with locations in Netphen (Germany), Houston (USA) and Shanghai (China) as well as various international representatives. Based on 100 years of experience in metal processing, the Siegerland-based company develops and implements customized special solutions worldwide for the core markets of automotive, hydroforming, large-diameter pipe production, shipbuilding, wind tower production, tank construction and renewable energies. The portfolio includes hydraulic forming lines, milling and bending machines, calibrating and straightening presses, and panel production lines. Graebener stands for holistic approaches to solutions. As a technology and plant partner, the company accompanies its customers along the entire process chain – from the initial idea, through comprehensive engineering (including hydraulics, control technology, and intelligent Industry 4.0 applications), to the customized new or modernized existing plant.