Advanced Roll Forming Technologies for Value-added Tubes & Pipes

Challenging Opportunities for rapidly Changing Market

Challenging Opportunities

It seems to be quite a long time ago that tubes and pipes were just dedicated to transport water and gas, supporting scaffolding or are being used as a bicycle frame, strong and lasting, but also heavy and sensitive to corrosion. Today they still do transport water and gas, support scaffolding and build-up bicycle frames. But they are no longer subject to corrosion, even under harsh ambient conditions. They have often more than 30% less weight than ordinary steel pipes. Used as automotive components they reduce fuel consumption and CO2 emissions.

In addition they incorporate many multiple functions and are produced by cost effective integrated processes. As a result there is almost no industrial or consumer product anymore today, which cannot be designed, better, lighter or cheaper by using value-added tubes and pipes. This trend certainly will continue for the next future. But there will be also some important changes. Some of them we already can see today. For sure we will see more competition - between materials (e.g. ultra-high strength steel grades, new aluminium alloys or carbon fibre reinforced plastic), between alternative processes (e.g. welding versus bonding) or by new companies entering the markets especially out of emerging countries. You also don't have to be a futurologist to know that customers will demand for more individual and faster changing products requiring highly flexible production processes without necessarily higher cost. In the last years Dreistern has contributed considerably to the development of such new processes like Laser welding of high-strength steel, integration of additional production processes like piercing, embossing or notching into tube manufacturing lines or production of completely new types of tubes such as multi-layer composite tubing. The article is explaining a few milestones of these developments. It also will allow for an insight into present Dreistern developments, which are targeting highly flexible processes with reduced capital investment for the cost effective production of small batch sizes.


Multi-Layer Pipe Production

Multilayer Pipes have remarkable physical properties. With the corrosion resistance of plastic pipes and pressure ratings of metal pipes it does not come as a surprise, that these pipes have conquered radiant heating and plumbing markets in the recent past. Dreistern supplied its first industrial production system in 1984. Since then production technology has evolved dramatically and Dreistern has supplied more than 60 systems all across the world. In the meantime markets have consolidated and settled, at least in Europe, and it seems that there is no current need for additional production capacity. As logic consequence manufacturers concentrate on reducing cost and are trying to load production schedules. As an equipment builder Dreistern is able to help with both issues. First, the biggest part of the total cost of tube manufacturing is made up by the cost for the base material itself. Today there is a number of possibilities to save as much as 5% of the overall cost by optimizing individual line components without the need of costly equipment. New ideas become even more interesting if, besides of saving money, they allow filling up order books. One direction of thought could be finding new additional uses for multilayer pipe. This process requires thinking outside the classic box of plumbing and radiant heating applications. New product uses usually also bring new requirements along with them. Production capabilities of today's equipment are limited to tubing with varying diameter and or wall thickness, which might not be able to satisfy new requirements. Tests at Dreistern with slightly modified equipment have proven that existing systems can also produce multilayer pipes with layers of copper or stainless steel in lieu of aluminum. Stainless steel looks exceptionally promising. These new "species" of multilayer pipe could become a low-cost version for ornamental or chemical tubing. In order to keep cost low the thickness of the stainless steel layer can be as small as only 100 Microns or even less. An inner or outer plastic tube supplies the necessary strength. Best of all, these new members to the family could still exhibit the advantages that have gained their older siblings a hefty market share within plumbing and radiant heating markets in the first place. Equipment builders like Dreistern are able to contribute their Know-How during product development. This could level some bumps in the road ahead to new products.


Flux Cored Wires Production

Flux cored wires are used as electrodes for gas-shielded arc welding. It allows for executing first class welds even by less skilled welding personnel, which is a demand coming out of many fast growing markets. Up to now such wires were not hermetically sealed allowing the ambient air moisture entering into the flux substance and impairing critical welding parameters. Dreistern together with Bühler-Würz, its partnering company in the field of cored wire technology, introduced Laser technology to avoid this disadvantage. The process design incorporates a specialized Dreistern Laser tube mill, which is producing a tube with an outer diameter of approx. 10 - 12 mm and a wall thickness of 2 mm. The tube mill is followed by the rolling reduction process of Bühler-Würz, which is providing the final wire with a diameter of only 1.3 mm. While the welding process is running at moderate 10 - 15 meter per minute, the reduction of the diameter is resulting in an enormous acceleration up to amazing 600 meters per minute of the final wire leaving the line and being coiled. This new process design is avoiding the need of intermediate annealing between the reduction steps. As a result energy cost and thus the total manufacturing cost can be reduced compared to conventional process design. The high demands to the weld seam quality due to the massive reduction of the tube diameter und the exceptional low diameter/thickness ration of only 5 - 6 requires both, an adapted forming and a suitable welding process. The Dreistern development demonstrated its capabilities by an outstanding low scrap rate of the first line being installed. But not only the forming and welding are requiring special technologies. Before closing and welding the open tube has to be filled with a precisely constant quantity of flux substance. This is done by one or more gravimetric dosing units, depending on the number of flux components. The units must be perfectly synchronized with the actual line speed. The competent engineering of complex production lines such as flux-cored wires is only possible by the cooperation of specialized partners with comprehensive know-how in their specific sector. The flux cored wire technology is an excellent example for this fact.


Multi-Purpose Production Lines

For a long time predicting future in the tube and pipe sector was almost limited to forecasting volumes and market shares for the different pipe dimensions, required steel grades and their cost. New applications for tubes und pipes in many industry sectors open up opportunities, but they increase the number of uncertainties about future requirements for pipe production too.

In addition high fluctuations in steel prices and new players out of emerging countries make forecasting to an increasingly difficult task. Some trend researcher even talk about a rising impossibility of predicting the future. Investing in new production equipment usually means to precisely define the requirements at the very beginning of investment planning. In order to cover future changes production manager tend to define larger ranges for their requirements. Equipment cost is rising as a consequence while still leaving the pipe producer with the risk to invest in the wrong equipment. One answer of tube mill suppliers was the development of flexible tube mills, which are capable to produce different sizes without the need of additional tooling. But this kind of flexibility is not an answer to the requirements of a number of new tube applications, which require the integration of additional process steps like forming complex shapes, piercing, bending, coating, etc. Integration of a high number of possibly necessary auxiliary processes is also not option, because it would excessively increase investment cost. A surprisingly new answer is given by Dreistern engineers. The concept is based on a highly modular machine base, which can incorporate almost any tube processing technology at any position of a tube production line. For a given production task only such processing units are temporally integrated into the line, which are needed for this task. The machine control is providing the same flexibility in incorporating additional functions my means of an easy extendable bus system. At first glance this concept might be too visionary. Not at all for Dreistern. The German machine builder already supplied the first machines, which are capable to produce standard tubing and complex shaped automotive parts within an integrated line concept close to this modular design.

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