HD LASr [strand] – The new method for smart strand guide aligning

Perfect manufacture and precise aligning of the continuous casting plant are crucial to achieve minimized mechanical strain on the strand and best slab quality. The first step is the precise aligning of the components segment and mold using the digital aligning assistants HD LASr [segment] and HD LASr [mold], the innovation tools for the segment and mold workshop that provide the best possible support of the casting strand.

After mounting the aligned components in the caster, the strand should be perfectly guided. But how to check the alignment state of the strand guide and how to attain an easy to use, reliable and exact strand guide measuring method? Nowadays you use perpendicular or long templates for aligning your strand guide – this can take long time in which you cannot produce and is complex in handling.

With the aim of making checking easier, more precise and reliable, HD LASr [strand] has been developed based on the well-proven 3D laser tracker measuring technology combined with intuitive software. HD LASr [strand] replaces the long and heavy templates and feeler gauges, imprecise perpendiculars and micrometer gauges with three simple and light measuring tools: laser tracker, reflector and reflector slide.

The handy reflector weighs no more than 120 g and is used to probe the parts to be measured. Due to its small size it easily fits in your pocket. A reflector slide weighing only 3 kg guides the reflector over the mold copper plates and along the rollers. With a weight of only 10 kg, the laser tracker is significantly lighter than a template and far more precise and reliable, with a volumetric accuracy of +/-0.015 mm +5 µm/m.

However, to date not everyone uses a laser tracker to align the strand guide. Why not? The answer lies most probably in its operation. It can only be used in combination with a software program.  The operators need intuitive software that is easy to use: one that is tailored to the measurements of the strand guide, offering an interpretation of the measurement, including an evaluation that is as direct and as automatic as possible.

Based on user interviews, we developed the HD LASr software in such a way that it guides the operator intuitively through the program. The touchable, graphical user interface provides more information and feedback to the operator.

A crucial aspect here is the fact that the strand guide setpoints are already stored in the software, so the operator does not have to trawl through drawings to find the right and matching values. The operator is perfectly guided through the measuring procedure and is always able to see at which step he is in the process at any given time. This means he can see, for example, what he has already measured and what still needs to be done to attain an optimal measurement. Plausibility checks are performed continuously to prevent errors and to enable fault-free operation.

The preparation for the conventional measuring incl. the dismantling of the mold by crane is very time-consuming. The one-dimensional distance measurement using a flexible wire or a long template and distance-measuring tools at discrete points bears a high failure potential, is imprecise and non-reproducible.

HD LASr [strand] just requires that the laser tracker is positioned on the mold and that the reflector slide together with the reflector hanging in a wire cable is lowered along the copper plate and the rollers; this is quickly done and simple. The laser tracks the reflector which is vertically moved on the reflector slide along the strand guide and thereby continuously measures; i. e. automatically scans the surface of the mold copper plate and the subsequent rollers.

The largest influence over the slab quality takes place in the top part of the strand guide. HD LASr [strand] focuses on the transitions from the mold to the first segments. With its high volumetric accuracy of ± 15 µm +5 µm/m, the laser tracker offers the most exact and reproducible measurement quality compared to other systems which give a general orientation only.

In addition, less crane work is needed and the measuring process is considerably easier, as the laborious slinging and attachment of the heavy templates and the demounting of the mold are not required. In addition, when it comes to reaching measuring positions that are difficult to access, e.g. in the segments, it becomes difficult: the template must be pressed vertically against the rollers and at the same time, a distance must be measured.

HD LASr [strand] offers increased occupational safety. No further intervention by operators is necessary. The quick and easy measuring with HD LASr [strand] takes place in casting pauses with little preparation time and without demounting caster parts. This saves precious time for producing - key advantages of HD LASr.

Typical measuring reports for strand guides using templates or perpendiculars are handwritten. A feeler gauge or micrometer gauge is used to measure the distance from the template or perpendicular to the copper plate or to the roller at a single measuring point, and the operator then takes the set point value from the drawing. He must now calculate the difference manually in order to obtain the roller setting value which is entered in the report.

This method implies a high error potential. Every operator has much influence on the correctness of the measurement, and mistakes can occur during the measurement, e.g. calculation errors, reading errors when measuring, errors when reading the set points in the drawing, or reports that are simply illegible.

All of these problems can be solved with HD LASr [strand] because it records the measuring information automatically, knows all set points, and automatically also displays all deviations from the nominal position. Reliable measuring reports (Figure 4) are available at any time, automatically generated, clear, legible, reliable and incorruptible. Within a short time, the operator holds the scan result in his hands and can initiate the necessary measures for re-aligning the strand guide with the optimum strand contact line and the correct roller gap.

Furthermore, HD LASr helps documenting the measuring work. But achieving a high-quality alignment is not the only important thing to do – it must also be documented and stored. Up to now measuring reports were often stored in paper form. This often made finding or analyzing measurement data quickly more difficult.

With HD LASr a clear and full overview of your digital measuring reports is always available. Even with a large number of measurements you can make a fast and intuitive search for your report, right down to a single measuring point. Color displays used to highlight the measuring progress allow information on the alignment quality to be obtained directly and help you to analyze your measurement data easily.