Efficient control with the CENTERWAVE 6000
At the production of plastic pipes with large diameters and wall thicknesses, the product quality as well as the optimization of material costs are of the highest priority. Norms and standards define the minimum and maximum permissible diameters and wall thicknesses of the required pipe dimension. These specifications require a consequent use of measuring and control systems as early as possible in the production process in order to avoid unnecessary scraps and thus, resulting costs.
The CENTERWAVE 6000 measures online over the complete circumference the inner and outer diameter, the ovality and wall thickness as well as the inner profile of plastic pipes. The millimeter waves based system does not require any coupling media, is not influenced by temperature or the plastic material and does not need any calibration. Therefore, the system is predestined for a hot measurement and control as well as for final quality control at the end of the line.
For hot measurement, the CENTERWAVE 6000 is installed in the extrusion line after the vacuum tank. Assuming that the vacuum tank has a length of 9 m (29.5 ft) and that pipes with an outer diameter of 400 mm (15.7”) SDR 17 are transported at a line speed of 0.5 m/min (1.64 ft/min) on a 60 m (195.8 ft) long line, the CENTERWAVE 6000 already provides first measuring values after a dead time of 18 minutes instead of 120 minutes at an installation at the end of the line. The measuring values are used for a first control. The CENTERWAVE 6000 controls on average and minimum value.
In order to ensure that the minimum wall thickness will not be undershot, the system automatically adds a safety margin. Afterwards, the CENTERWAVE 6000 determines the standard deviation within the continuous measurements during the second dead time. By means of the standard deviation, a supplement factor is calculated which guarantees that, even at short-term variations, the minimal wall thickness is always reached. The supplement factor is automatically optimized by the continuous measurement and determined standard deviation. Already after the third dead time, meaning after 54 minutes in this example, the CENTERWAVE 6000 guarantees accurate measuring results due to the automatic control. Thus, a reference measurement at the end of the line is not required. Reproducible processes, the assurance of the highest pipe quality as well as a reduction of the scrap rate and involved time and cost savings are the results.