Abstract
This paper describes a measurement method for the quality control of cylinders for printing machines based on roll-to-roll presses. If the surface finishing of the cylinders is not adequate, the printing is unacceptable, and the defective cylinders must be reworked. The performed quality check of the cylinder surface roughness by means of contact methods was unable to identify the cylinder defects, and acceptance of the manufactured cylinders before integration was demanded to the visual inspection performed by trained operators. In this work a contactless measurement method based on the eddy current displacement sensor was proposed and validated as a tool for quality check as an alternative to optical roughness measurements. A test bench for the characterization of printer cylinders was designed and manufactured, allowing for the validation of the proposed method on different batches of cylinders and the identification of a threshold to guide the acceptance of tested cylinders prior to mounting on the roll-to-roll press.
Highlights
Paper and tissue printing machines based on roll-to-roll presses are commonly used in the food and beverage or packing industries
Value registered during the testing of the batches. Comparing the latter value with the threshold value related to the detectability of the method, it can be noted that the risk of considering defective good cylinders as only being a consequence of it can be noted that the risk of considering defective good cylinders as only being a consequence of the randomness of the bearings’ noise or of the measurement chain lies well below a meaningful probability
A measuring system based on an eddy current displacement sensor was developed for the quality check of the surface of cylinders used in flexographic roll-to-roll printing machines
Summary
Paper and tissue printing machines based on roll-to-roll presses are commonly used in the food and beverage or packing industries. Among all the checks performed before the integration of the cylinders in flexographic printing machines, the cylinders’ surface finishing is assessed This step is of primary importance for the good quality of the prints, since any defect on the surface of the tested item (the anvil cylinder used in the direct printing process) would result in defective final prints. The surface roughness testing, based on the stylus probe measurement method, was demonstrated to not be sufficient to assure acceptable printing. The measured Ra averages the two conditions and is not sensitive to the presence of the defects on the cylinder surface This result allows for an understanding of why, beside the acceptance based on roughness measurements, the evaluation of the compliance of the tested cylinders is demanded to trained operators who judge the risk of failure in final prints based on their experience even though they cannot quantify the defect.
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