Cutting of Steel Profiles

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Fraunhofer SCAI developed innovative methods for reducing waste metal during the cutting process of profiles in cooperation with a manufacturer of hot-rolled steel profiles. On the one hand, the software calculates optimal sawing plans for day-to-day business according to the stored length and the customer order; which calculations take less than a minute. On the other hand, it computes production plans for cutting and storing based on the long-term customer orders expected. Hence, the best possible length for production is determined while simultaneously achieving a maximized utilization of material. Our algorithms result in an increased efficiency of several percentage points in the calculation of stored lengths and even the overall optimum in sawing plans.

After this project, SCAI has developed the software AutoBarSizer, which generates optimized layouts for the cutting of stock items, namely steel profiles (metal beams) and other bars and rods, into shorter pieces.

Cutting of Steel Profiles at a Glance

When producing hot-rolled steel profiles, steel ingots are first heated to 1250 °C in an energy-intensive process.
They are formed into long profiles and then cut into short custom profile sections in two stages.

The customers - e.g. manufacturers of utility vehicles, agricultural machinery, or fork trucks, but also building companies - normally order their individual steel profile in different lengths over several months or years. The profiles can be produced in advance and stored in line with the expected quantity to be ordered in the short term.

When cutting the steel profiles, waste metal occurs in the form of edge pieces (for technical reasons) and and left-over pieces resulting from the fact that a perfect partitioning of the original length is not possible in each specific case.

Optimization aims at the computation of the best sawing plans as well as initial and intermediate lengths in order to minimize waste. We have two sub-problems: first, a sawing plan must be found that uses only a small amount of material and also occupies only a few de-stacking stations at the same time. Secondly, it is essential for production planning to find the best possible initial and intermediate lengths that allow the customer orders to be fulfilled flexibly from storage with only little loss of material.

As humans cannot keep track of the millions of variants for choosing initial and intermediate lengths, we need intelligent optimization algorithms. From a mathematical point of view, the problem of length optimization belongs to the class of integer linear or quadratic optimization problems - depending on the use case and model. However it is too complex to be solved with standard software.

Cutting a steel profile in two steps: partitioning the initial lengths into intermediate lengths for storing and partitioning the intermediate lengths into custom lengths. The waste shaded in black is unavoidable (edge pieces, width of saw blades), whereas the waste shaded in red is a feasible target for minimization. Schematic diagram - not true to scale.

As the first step, initial and intermediate lengths were optimized for simple sawing plans. The software can compute several variants according to the maximum number of different initial and intermediate lengths allowed, which helps the planner to find a compromise between avoiding waste and organizational effort (e.g. for set-up).

By using the function "performance comparison", the amount of waste arising from previously fixed lengths can be computed. It is thereby possible to assess the saving of material for optimized lengths compared to conventional lengths, hence the economic and ecological benefit.

In 2012/13, the manufacturer's production line was enhanced and the software, which had been successfully used in practice, was re-engineered in order to take advantage of the wider technical capabilities.

The enhanced production line allows the realization of considerably more complex sawing plans. Thus, the adapted software can further improve efficiency compared to the former version. For orders in the range used normally in practice, the algorithms even guarantee the overall optimal solution. The computations for a single sawing plan are carried out in less than one minute so the software can perfectly well be used in day-to-day business.

While a special solution for an industrial customer was developed in this project, we offer the standard software AutoBarSizer for similar problems.  

The computer based optimization of length combinations for cutting profiles helps to avoid waste in the best possible way and can thus save considerable amounts of cost-intensive material. Production expenses are decreased without affecting the quality of product or service.

The economy of material can amount to ten percent compared to conventional approaches, depending on the individual use case. The software makes an important contribution especially for unsteady production volumes as there is no data available based on prior experience.

In addition, considerable amounts of energy can be saved - not only within the production process (heating, rolling, handling, melting down the waste), but already in the steps before (iron extraction, steel production, delivery).

In the long term, the aspect of increasing prices on raw materials and energy becomes more and more important. However, the saving of resources is not only a matter of economy but also of environmental protection.