Abstract:

Objective In conventional spinning process, colored yarns are prepared by blending different colored fibers through the process of fiber blending, grabbing, and drawing, but the process does not support online regulation, real-time control, and accurate digital adjustment of the yarn color. Inspired by color inkjet printing, the purpose of the paper is to investigate how to build a multi-channel computer numerical control (CNC) spinning system for making colored yarns of a full color phase. To this end, using the Newton's three primary-color principle and through digital blending of the six primary colored fibers of red (R), yellow (Y), green (G), cyan (C), blue (B), and magenta (M), the color hue of the forming yarn can be changed from 0 to 360°, enabling the spinning of colored yarns of full color phase.

Method The mechanism of controlling the mixing ratios of colored fibers by CNC spinning was combined with the full color phase mixing model of with six primary colored fibers, and the "multi-channel drafting ratios - colored fiber mixing ratios-colors of yarns" synergistic regulation mechanism was established. Based on the six primary colored fibers of red, yellow, green, blue, cyan and magenta, a full color phase mixing model with 60 grid points and a hue control of 0-360° was built. The spinning process parameters were designed based on the grid point number and a total of 60 different colored yarns and their fabrics in six color systems, consisting of R-Y, Y-G, G-C, C-B, B-M, and M-R, were fabricated.

Results According to the fiber mixing ratio in the above model, 60 colored fabrics were obtained (Fig. 6). The color variation regularity was consistent with the regularity of mixing ratios of the six primary colored fibers, and also has consistency with the color distribution regularity of the full color phase grid mixing model. The colored yarns were measured and analyzed for appearance and mechanical properties such as yarn unevenness, surface hairiness and tensile strength. In terms of evenness, the coefficient of variation (CV) varied with the mixing ratios, with a minimum of 12.40%, a maximum of 16.50%, and an average of 14.15% (Tab. 4). Its corresponding unevenness (U) also varied with the mixing ratios, with a minimum of 9.23%, a maximum of 12.73% and an average of 10.68%. Among them, the number of thick parts and thin parts was less than 220, and the number of neps varied from 50 to 95, with a mean value of 72. Regarding the surface hairiness, the number of 3 mm hairiness ranged from 46 to 64 (Tab. 5). Among the hairiness of 1-3 mm, the samples with mixing ratios of 10∶0 and 5∶5 had relatively small numbers of hairiness, while those with mixing ratios of 9∶1 and 1∶9 had more hairiness. With respect to the tensile strength, the minimum breaking strength was 442.70 cN and the maximum was 527.70 cN, and the minimum elongation was 5.72% and the maximum was 6.58% (Tab. 6). Among them, the strength CV value ranged from 1.75% to 3.74%, with an average of 2.91%, and the elongation CV value ranged from 1.46% to 6.13%, with an average of 3.78%.

Conclusion The research results proved that the mixing ratios of colored fibers in the forming yarns can be adjusted based on the regulation of the multi-channel drafting ratios by using the multi-channel CNC spinning platform, and furthermore, the color of the forming yarns can be controlled. By building a full color phase gridded mixing model through the six primary colors of R, Y, G, C, B and M, the color mixing of full color phase can be realized in the range of 0°-360° according to the six color system gridded color mixing of R-Y, Y-G, G-C, C-B, B-M and M-R. by combining the regulation mechanism of multi-channel CNC spinning with the full color phase mixing model, 60 different colors of yarns distributed in six color systems of R-Y, Y-G, G-C, C-B, B-M and M-R were prepared, which realized the spinning of colored yarns of full color phase. It is proved that the process of the spinning of colored yarn of full color phase is feasible by testing the color, appearance and mechanical properties of the forming yarn, and the indexes of the yarns are substantially in line with the second level of the standard GB/T 398—2018 "cotton gray yarn".

Key words: colored spun yarn, color mixing model, computer numerical control spinning, spinning machine, color mixing of full color phase