Classic or fully automated technology lines?

In this paper we compared a classic technological lines and a fully automated line for the manufacturing of 100% cotton yarns. For this comparison we analyzed the complexity of classical and fully automated technological lines, the differences between the yarn structures, aspects related to the quality of textile yarns but also an analysis of production costs and benefits. The spinning mill is the first sector in the textile field, the sector in which the textile yarns are made. The quality of textile products, fabrics, knits, garments or technical articles are strictly dependent of the quality of textile yarns. The yarns are made of short fibres of cotton, wool, linen, hemp or other raw materials, with a great unevenness of the physical-mechanical characteristics, and the technological engineer must make a series of adjustments, settings of the machines so that the yarns made have a lower unevenness. This is the reason why the technological engineer must set the technological process so that the yarns are of adequate quality, have low production costs and deliver orders to the beneficiaries within the terms established by the commercial contracts concluded with them. In order to decrease the production costs, there were permanent concerns for the introduction of new automation elements, so that in the field of cotton spinning reached an extremely high level, right at the fully automated cotton spinning mill. Practical, on the technological line there are only two operators, one that supplies the technological line and one that transfers pallets with bobbins from the palletizing robot to the transport means. Practically the technological lines are composed of the same machines, but the automation elements on each machine and the aggregation systems between machines allow the almost complete elimination of the operators for service of machines. Given the complexity of the technological lines and the difference between the human resources for the two technological lines, in the first step we made a comparative calculation of the costs for the salaries of the operators and the taxes that an employer must pay. Then we made a comparative calculation of energy consumption. The comparative analysis was done for a cotton spinning mill with a production of 4000 t/year, classical yarn, 100% cotton yarn, with average fineness Nm40, made on ring spinning machines. Finally, we made a comparative study of the investment effort and the amortization of the investments made, amortizations which is reflected in the total costs and then in the delivery price of the yarns to the beneficiaries.


Introduction
Industrial automation has evolved in the last decennium as a propulsive power in all production systems and exert an extensive function in industrial and manufacturing area. [1] ModTech 2020 IOP Conf. Series: Materials Science and Engineering 916 (2020) 012006 IOP Publishing doi:10.1088/1757-899X/916/1/012006 2 Thus, in most area of textile manufacturing, automation represent a leading key to quality enhancement and competitive costs. There are several reasons that sustain the benefits of automation in the textile industry. Some of the major assets achieved through automation include: augmented production at lower cost, enhanced quality, minimized energy consumption, reduced environmental impact, removal of human error, easy identification of faults and improved customer satisfaction. [2] The processing of cotton and cotton-type fibers requires the following conditions: proper choice of raw materials according to the destination of textile products; optimization of the technological parameters for all equipment comprised in the technological flow; continuous control of the processing process.
Increasing demands for the characteristics and quality of textile products imposes changes in technology and equipment construction, which have led to increased labour productivity and economic efficiency.

Analysis of technological flows
As specified in the introduction, aim of this work consist in a comparison between the classic flow, a carded system, and an automated flow. The technological line for the classic flow is represented in figure 1.  From the point of view of manufacturing technology, the classical technology line is quite expensive due to several semi-finished products, which lead to more disruption of the technological flow. Thus, a quality control at several points, between operations, after several machines is needed. So automation of the technological line would be beneficial, but an analysis of this costs have to be also performed. Figure 3 represents the structure of the classic yarn produced on both a conventional and an automated line. Differences may occur due to the intervention of robots for breaking elimination in the ringspinning frame. [14] Yarn faults arising from the breaking elimination in the case of operator interventions may be assigned to lower classes of defects (faults). Through adjustments on the winding machines these faults can be removed, but instead others of the higher classes appear. In the structure of the classic yarn, the fibers have a random position. Besides, the number of fibers in the cross-section and their radial positions is also variable. Moreover, for a mathematical analysis, we can approximate that fibers describe helical trajectories, after a right cylindrical screw.

Analysis of the yarn structure and destination
Taking into consideration the fiber arrange in the yarn structure, it is obvious that most fibers contribute with their own breaking load to the yarn breaking load.
The presence of short fibers, with different lengths in the area of 10-40 mm, with a rather large non-uniformity of the length of the fibers, exert an influence upon the irregularity of the yarn fineness. Thus, this fineness irregularity generates irregularity of the burst load along the yarn. [15] 4. Analysis / Evaluation of production costs For the evaluation of production costs, two technological lines, classical and fully automated and aggregated, were taken into consideration. These lines, designed for 100% cotton fibers processing, produce yarns with average fineness Tt=25 tex (Nm 40) and a total production of 4000 tons/year. The assortment range of yarns is as presented in Our proposal concerning the automation of the classical technological line refers to 12 automation elements, namely: automatic cans change at cards; carousel for the transportation cans between cards and draw frame first passage; automatic cans change at draw frame 1; carousel for the transportation of cans between draw frame first passage and draw frame second passage; automatic cans change at draw frame second passage; carousel for cans transportation between draw frames and roving frames; automatic doffer at the roving frame; carousel transportation of roving bobbins towards ring spinning machines; robots for repair ends down at the ring spinning machines; automatic doffer at ring spinning machines; carousel transportation of cops towards winding machines; equipment for the packaging bobbins yarn boxes. For the comparative analysis of production costs we took into consideration only: a. raw material costs; b. costs due to human resource, wages and social tasks; c. costs caused by energy consumption; d. amortization costs as a consequence of the investment effort. Preceding the evaluation, the parameters of the preliminary spinning plan were calculated aiming to establish the kinematic and technological parameters required to obtain yarns with a quality according to the standards. Additional, at the end of the preliminary spinning plan, the calculation part envisages the theoretical production for all equipment contained in the technological flow along with the performance of the machines and the practical production. By means of the technological losses, the necessary of semi-finished products was determined for each technological phase, followed by calculus of machine number in order to establish a correlation of production capacities, table 2.
All these are components of the final spinning plan that furnish us information about the quantities of raw materials and semi-finished products and the number of machines for each technological phase. For this evaluation, the calculation of the needed human resource was performed according to the number of machines and their service standards.
The number of employees for each technological phase, men (M), and women (W), required for the three production shifts is specified in table 3, for classic technology, and table 4, for the automated technology. These values include also personnel reserves for medical leave situation and holyday. There are differences in the number of workers, the classic approach requires 315 workers whilst the automated one needs only 152 workers, less with 163 workers compared to the classic line. Generally, in Romania, the basic salary of workers in the textile industry has the lowest value in the economy compared to other industries.
According to HG 935/2019 [17], the minimum gross salary from 1st January 2020 is 2230 RON/month. As a result of the pressure exert by the trade unions and the very low unemployment rate, less than 2%, wages have been increased. To these wage costs are added also costs with social contribution allowances. Therefore, for the companies this implies a minimum labor cost of 3280 RON/month for each worker.
This amount includes, therefore, both staff remuneration and social burdens supported by the employee and the enterprise. Due to the difference of 163 workers, for the version with classic line, the company has a financial effort of 6.415 mil RON / month higher compared to the automated IOP Conf. Series: Materials Science and Engineering 916 (2020) 012006 IOP Publishing doi:10.1088/1757-899X/916/1/012006 6 technology. Related to the total annual production, this results in a higher production cost of 1.6 RON/kg.

4.3.Costs caused by energy consumption;
The accomplishment of this analysis requires the values of installed power for each type of machine and the total yields, CUM. The total yield, CUM, was calculated with the equation (1): where: CTU -the coefficient of useful time, the partial yield, which is dependent on the pauses imposed by equipment service and accidental repairs; CUF -machine efficiency in operation, the partial yield, which depends on pauses imposed by planned repairs: current repairs 1, RC1, current repairs 2, RC2, and capital repairs, RK. Table 5 displays the values for the installed power, according to the machine's technical books, and for the total yields CUM.

Amortization costs as a result of the investment effort
Starting from the FOB prices of the machines, including also transportation costs and customs duties, an investment effort of 33.181720 million RON was necessary for the modernization of the technological flow, at an average course of 1 USD = 4.4 RON, table 6.