Straightness measurement on the fly at a steel production line

Due to residual stress from hot rolling the straightness of longitudinally shaped products is often a problem in steel and aluminium manufacturing. MonoDAQ-SM is a measurement system that accurately measures straightness (flatness) of steel bars in two axes.

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Straightness measurement is done on the fly during the production process of cutting the rectangular steel bars. During the measurement the bars are also scanned with luminescence sensor to capture color marks made by the operator to mark the surface anomalies. Length of the specimen is also detected and checked.

The combination of MonoDAQ EtherCAT measurement modules and DEWESoft X3 data acquisition software allows us to acquire the data with precision and synchronization, analyze the results on the fly and communicate with the manipulator and production line PLC.

straightness flatness measurement

The system consists of the following MonoDAQ hardware:

  • 2x MonoDAQ-1xACC isolated analog measurement module (acquiring data from 2 laser distance sensors)
  • 2x MonoDAQ-4xDI isolated digital inputs (capturing data from digital color sensors and inductive end-position sensors and for communication with external PLC)
  • 1x MonoDAQ-4xDO isolated digital outputs (driving the stepper motor and communication with external PLC)

There is only a single data cable for EtherCAT protocol going from the cabinet to the moving trolley. The trolley carries sensors and MonoDAQ modules. It is moved with constant speed parallel to the specimen so that the sensors can longitudinally scan its surface.

Data from the sensors can be acquired at up to 40 kS/s sample rate and synchronized down to 1 microsecond thanks to the EtherCAT distributed clocks protocol.

DEWESoft advanced signal processing is used for filtering the data on the fly. Disturbances such as tiny scratches on the surface or machine vibration need to be filtered out for accurate distance measurement.

fir filter data acquisition system software dewesoft monodaq

To compensate for the angular offset of the specimen with respect to the linear sensor movement, the software fits a line to the acquired data and measures the deviation from that line as an unflatness.

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Measurement result is available moments after the specimen is scanned. Bi-directional scanning is done and results from both directions are compared. If the results from two directions are not within a specified tolerance, the measurement is repeated. To control the process flow DEWESoft Sequencer is utilized. Complex sequences are represented by simple block diagrams. The sequence also handles the user inputs from the touch screen, such as input of tolerance values.

The data can be recorded in the form of full data files for later in-depth analysis or in form of simple log files tracking the history of each specimen with timestamp.

The measurement system communicates continuously with the PLC to track the machine cycle. Robot sorts the specimen on two palettes to distinguish between “good” or “bad” pieces. The system can be switched on or off independently of the PLC, while the PLC adjusts its cycle to include or skip the measurement.

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Customer testimonial

MonoDAQ designed and built a high-quality system for measuring straightness of flat steel bars. They succeeded in creating a system that measures straightness along with the existing sawing operation and does not extend the work cycle, while giving results that are more accurate as the previous method of measurement and remove the need for an addotional quality check, saving a lot of time.

Marcel Jevšnik, mag. inž. str.
Technologist in Cold processing plant

Štore Steel d.o.o.