Experimental studies of the quality of embossed characters of the Braille alphabet

The paper presents studies pertaining to the quality of embossed characters of the Braille alphabet used, among other applications, for tagging drug labels. The following parameters of embossed inscriptions were measured: height, diameter of the dots and surface roughness (18 samples with various combinations of their values). 48 blind individuals assessed the quality of the printed text. Statistical analysis proved that a text with dots having height of 0.9 millimeter, diameter of 1.6 millimeters and roughness Ra of about 1 micrometer to be the best. The samples had been made using two different methods of rapid prototyping: PolyJet and SLS. 3D printing is increasingly popular and the studies proved the usefulness of these methods for labeling with embossed inscriptions, due to the repeatability, durability and quality they ensure. The assessing group of blind individuals was comprised of 24 persons 14–17 years old and other 24 persons aged over 60 who were not proficient in reading Braille alphabet, This allows to conclude that a text featuring the above values of the parameters will be easy to read for the majority of blind persons.