Research of Durability of Braille Formed in Paper.
Certain studies, e.g. a simulation of a Braille image longevity evaluation process by developing a digital control system of the conformity of parameters of Braille symbols with the representation of a model of factors affecting the quality of Braille in their active usage by the blind , are known. Furthermore, the influence of a superficial topography and friction on human perception is studied, because there is a presumption that superficial geometric peculiarities play an important role in perception , friction coefficients are analysed, analysis or study methods are suggested, wherein different types of surfaces may be correlated with friction and tactile response [3-7]. Moreover, there are studies on friction force of a finger with and without artificial sweat, friction coefficients of the humanoid finger on the acrylic, paper surface with/without the artificial sweat . It is obvious that aforementioned and many other studies provide a capability to comprehend processes that occur during a human finger movement on a certain material , as well as demonstrate how to qualitatively measure, for example, the force of friction.
Another line of research includes modes of material processing for the purpose of obtaining relief images, i. e. Braille, or studying processes that take place in the material, where on a Braille is applied [10, 11].
However, the aforementioned studies do not answer the following question: how long will the Braille possess properties sufficient for being perceived by people with visual impairment? There is an obvious supposition that, during the friction process of a finger on a paper surface, where on a Braille is applied, (at least) lowering the height of a Braille dot will be evident. Our experiments carried out earlier demonstrate that such an effect is present .
The aim of the studies is to determine how the Braille applied onto ordinary paper by a Braille embosser will wear, and how the height of a Braille dot will change depending on the load (during storage in pallets, stacking, etc.).
In the present article, studies of the process of the change of height of a Braille dot taking into account factors that imitate not only the reading process but also factors that usually occur during use, storage and shipment of Braille have been expanded.
2. Experiment equipment and method
The Braille for the research was produced by a Braille embosser Index Braille Everest V2. Was used paper Volume Gloss: 80 g/[m.sup.2], 90 g/[m.sup.2], 105 g/[m.sup.2], 115 g/[m.sup.2], 130 g/[m.sup.2], 150 g/[m.sup.2], 170 g/[m.sup.2], 200 g/[m.sup.2], 250 g/[m.sup.2] (Table 1). Before being embossed, all samples were covered by a laminating film, 24, 27, 50, 75 microns, on the "reading" side (Table 2, Fig. 2).
Coating with a laminating film aimed at two things. The first aim was: during the application of a Braille with a Braille embosser, not infrequently "breaks" occur (Fig. 1). These "breaks" obviously are poorly tactilely perceived, and a laminating film aids in eliminating this issue. Secondly, this operation also contributes to a longer service life, due to the paper not being affected by sweat, dirt, etc.
Apart from the laminating film, a page with Braille was also coated with a layer of acrylic paint (the reverse side) (Fig. 2).
For the purpose of the research of the wear of a Braille, an original device was manufactured: a working tool - a leather cylinder, 1.5 cm in diameter, that moved on a sample in segments, one line of Braille each. The height of a Braille dot was measured every 500 cycles. The pressure was 1.0 N.
The following paper samples were employed for the research: 115, 130, 150 g/m (2). As an option, 80, 90, 105, 170, 200, 250 g/[m.sup.2] were also used, but 80, 90, 105 g/[m.sup.2] presented as a poor choice, because paper breaks, even under lamination, had a poor appearance, it is non-aesthetic, and 200, 250 g/[m.sup.2]--small height with lamination of 50 or 75 microns.
Small loads were left on an element of the script, and its settlement was examined with periodical contactless measurements of its height. The device FAG BRAI (3) Braille Dot Checker was employed for the study of the change in height of a Braille dots.
3. Results and discussion
The dependence of Braille dot diameter from paper grammage and thickness of a laminating film is presented in Figs. 3 and 4.
If the paper grammage is higher Braille dot diameter increases (see Fig. 3). Braille dot diameter also depends on the thickness of laminating film. If there is no film, the largest Braille dot diameter is obtained. When the laminating film is of a higher thickness, the Braille dot diameter is lower.
Fig. 4 and Table 3 show that in presence of 90 g/[m.sup.2] () and higher paper grammage and the absence of laminating film, Braille dot is at its maximum height.
Braille dot attrition research disclosed its dependency on attrition cycles. Braille dot height reduction's dependence on the layer of laminating film and acrylic ink has also been researched. The results are delivered in Figs. 5-9. As it might be seen from Fig. 5, covering samples with acrylic ink affects their resistance to attrition. In cases without acrylic ink, Braille dot height decreased at greater extend. Respectively, when samples were covered with a layer of acrylic ink, Braille dot height was higher by 30-50 %.
The results presented in Fig. 6 disclose that Braille dot height reduction increased under higher number of wear cycles. This tendency is especially obvious from 2000 cycles; when paper grammage is lower, Braille dot height reduction slows down.
Fig. 7 shows that the higher paper grammage, the smaller reduction of Braille dot height. Respectively, the higher paper grammage, the smaller number of cycles is needed to obtain Braille dot height stability.
Using a laminating film of 50 and 75 [micro]m, when the number of attrition cycles is from 2000, Braille dot height reduction does not change (Figs. 8 and 9).
Braille dot height changes under different loads (0.1 N, 0.2 N, 0.5 N, 1.0 N) and times of effect are presented in Figs. 10-12.
It might be noticed that when Braille is made on a paper with grammages 115 g/[m.sup.2], 130 g/[m.sup.2],150 g/[m.sup.2] and covered with different layers of a laminating film, Braille dot height decreased under short-term (up to 30 min) loads of 1.0 N or 0.5 N (Fig. 10-12). When samples are affected longer time period (up to 24 hours) with a load of 0.1 N, Braille dot height changes no more than 0.05 mm and with a load of 0.2 N mm it changes 0.09 mm.
Strengthening by a polymer layer after producing a Braille by a Braille embosser has a positive effect on a wear resistance, due to the height after 500 cycles (e.g. for 115 g/[m.sup.2] paper) without strengthening being lowered by 58 microns, and with strengthening by 48 microns. It is corresponding 29 and 19 microns for 130 g/[m.sup.2] paper. After 2500 cycles, these same numbers are 122 microns without strengthening and 101 microns with strengthening for 115 g/[m.sup.2] paper.
On the other hand, one of the conclusions of the analysis is the following: a strengthened structure demonstrates an equivalent drop of height after 3000 cycles, as a non-strengthened one after 2000 cycles, i. e. a positive effect is present.
Unacceptable changes (more than 50 microns) of a Braille dot height for 115 g/[m.sup.2] paper with a strengthening polymer layer and laminated films occur even with a short-time load (less than 30 min) weighting 1.0 N or 10.5 N in all samples without exception. For other samples (with loads weighting 0.1 N and 0.2 N. For laminating films from the whole thickness range), even with a long-term load, a height changes not exceeding 0.09 microns is observed.
Analogous conclusions may be formulated regarding all types of paper (130 g/[m.sup.2], 150 g/[m.sup.2]) and laminating films.
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Volodymir MAYIK (*), Taras DUDOK (**), Edmundas KIBIRKSTIS (***), Ingrida VENYTE (****)
(*) Ukrainian Academy of Printing, Pidholosko 19, 79020 Lvov, Ukraine, E-mail: firstname.lastname@example.org
(**) Ukrainian Academy of Printing, Pidholosko 19, 79020 Lvov, Ukraine, E-mail: email@example.com
(***) Kaunas University of Technology, Studenty 56, 51424 Kaunas, Lithuania, E-mail: firstname.lastname@example.org
(****) Kaunas University of Technology, Studenty 56, 51424 Kaunas, Lithuania, E-mail: email@example.com
Received June 18, 2018
Accepted January 15, 2019
cross ref http://dx.doi.Org/10.5755/j01.mech.25.1.20985
Table 1 Technical characteristics of coated paper Volume Gloss (Cezex) Grammage, g/m2 Thickness, [micro]m Density, g/[cm.sup.3] Opacity, % 80 65 0.81 89 90 73 0.81 91 105 82 0.82 93 115 96 0.83 95 130 107 0.83 95 150 130 0.87 96 170 150 0.88 97 200 180 0.90 98 250 255 1.02 98 Grammage, g/m2 Brightness (ISO), % Roughness, [micro]m Gloss, % 80 87 1.4 65 90 87 1.4 65 105 88 1.2 65 115 88 1.2 65 130 88 1.2 65 150 88 1.4 6 170 88 1.5 65 200 88 1.5 65 250 91 1.6 70 Table 2 Technical characteristics of films Product name Main characteristics Glossy film Cosmo Thickness - 24 [micro]m; Type--Gloss, 90%; Structure: biaxially oriented polypropylene (BOPP) based, clear and both side treated thermal laminating film. Matted film Cosmo Thickness - 27 [micro]m; Type--Matt, 70-75%; Structure: biaxially oriented polypropylene (BOPP) based, one side matte and both side treated thermal laminating film. Hot Melt Gloss Thickness - 50 [micro]m; Type--Gloss; Structure: polyethylene terephthalate (PET) based. Royal Sovereign Thickness - 75 [micro]m; Type--Gloss; Structure: polyethylene terephthalate (PET), low density polyethylene (LDPE), ethylene vinyl acetate (EVA). Table 3 The height of the Braille dot (mm) formed on different paper grammage and strengthening Grammage, Without Laminating Laminating g/[m.sup.2] laminating film 24 [micro]m film 50 [micro]m film 80 0.246 0.314 0.267 90 0.339 0.301 0.270 105 0.348 0.277 0.263 115 0.344 0.289 0.264 130 0.364 0.313 0.278 150 0.360 0.283 0.289 170 0.326 0.331 0.243 200 0.342 0.273 0.183 250 0.361 0.303 0.205 Grammage, Laminating g/[m.sup.2] film 75 [micro]m 80 0.258 90 0.258 105 0.249 115 0.255 130 0.241 150 0.248 170 0.236 200 0.198 250 --
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|Author:||Mayik, Volodymir; Dudok, Taras; Kibirkstis, Edmundas; Venyte, Ingrida|
|Date:||Jan 1, 2019|
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