Profile wire measurement in process
Until recently, measuring systems used to determine the surface quality of products in-line during the process were almost exclusively deployed for process control. Process variables were measured, compared with target values and the settings of the production plant were optimized with the deviations determined.
For Industry 4.0 applications, this is often no longer sufficient. The quality of production processes should not only be regulated, but also analysed and documented.
As a manufacturer of rolling mills, Fuhr faces challenges from increasing demands on the finished wire's geometric precision. Accuracies of Class 6 according to ISO 386 are almost standard. This implies a permissible deviation of ±0.003mm for small profile wires with a nominal diameter of up to 3mm. If a process capability (Cp or Cpk) is also required, a spread of only ±0.0015mm remains in production.
In order to ensure that these requirements are met in daily production, the wire must be continuously measured while exiting the rolling mill, and the roll positions must be adjusted fully automatically. In multi-stage rolling processes it is necessary to measure and calibrate straight after the pre-rolling stages. Therefore, modern high-speed rolling mills made by Fuhr are equipped with several measuring systems.
Conventional laser shadow measurement systems, as typically used in the drawing of round wires, have not proven to be successful in profiling lines: a slight tilting of the wire changes the size of the shadow, and laser systems cannot be used permanently in the wet area of the pre-rolling stages.
Fuhr therefore relies on tactile measuring systems, in which the wire is scanned with diamond-studded, high-resolution displacement measuring systems. Alternatively, instead of diamond styli, stylus rollers adapted to the wire geometry are available. Fuhr uses these systems in new machines, but also supplies them for existing and third-party plants.
To meet requirements for data analysis and quality documentation, Fuhr's F-MAS data acquisition and evaluation system is available as an option for the tactile measuring systems; it can also be retrofitted to existing digital or analog measuring systems.
With F-MAS, two wire dimensions (eg width and thickness of a rectangular profile) are measured with a measuring frequency of 1,000 Hz. The data is shown in diagrams, statistical values are calculated, and frequency distributions are displayed. Reports are generated and raw data is exported. Data export to standard data analysis software is possible via an OPC UA interface.