COVID-19 Face Masks as a Long-Term Source of Microplastics in Recycled Urban Green Waste

Following the outbreak of the COVID-19 pandemic in March 2020, many governments recommended or mandated the wearing of fitted face masks to limit the transmission of the SARS-CoV-2 virus via aerosols. Concomitant with the extensive use of non-sterile, surgical-type single-use face masks (SUM) was an increase of such masks, either lost or discarded, in various environmental settings. With their low tensile strength, the spunbond and melt-blown fabrics of the SUM are prone to shredding into small pieces when impacted by lawn cutting equipment. Observations highlight the absence of smaller pieces, which are either wind-dispersed or collected by the mower’s leaf catcher and disposed together with the green waste and then enter the municipal waste stream. As proof-of-concept, experiments using a domestic lawn-mower with different height settings and different grass heights, show that 75% of all pieces of SUM fabric caught in the catcher belonged to sizes below 10 mm2, which under the influence of UV light will decay into microfibers. The implications of SUM generated microplastics are discussed.

IMPROVING THE EFFICIENCY OF FINISHING MILLING OF CONCAVE SURFACES ON SMALL-SIZED CNC MACHINES

Pазвитие систем ЧПУ современного полногабаритного металлорежущего оборудования дало возможность корректировать режимы резания, например, величину рабочей подачи непосредственно в процессе обработки. Однако на производстве имеется значительная часть деталей, которые по своим габаритам экономически невыгодно обрабатывать на дорогостоящих крупных станках, имеющих мощную систему ЧПУ. Поэтому на предприятиях все большее применение получают относительно недорогие малогабаритные металлорежущие станки. Технологические возможности такого оборудования позволяют обрабатывать не только цветные металлы и сплавы, но и стали. Особенностью управления таким оборудованием является использование упрощенных систем ЧПУ, установленных на персональных компьютерах, которые не имеют возможности выполнять арифметические операции, и это становится препятствием для повышения производительности обработки сложных поверхностей. В то же время из-за своей простоты и низкой стоимости эти системы становятся все более востребованными. Предлагается повысить производительность обработки поверхностей сложной пространственной формы на основе расчета движения инструмента САПР системой путем преобразования реальной траектории в набор симметричных отрезков с известными координатами. Этот метод позволяет при заданной точности обработки установить значения параметров режима резания, близкие к оптимальным, исключить аварийные ситуации, связанные с выходом из строя инструмента при работе с переменной глубиной резания, сформированной после черновой обработки, и повысить производительность на 15-20% The development of CNC systems of modern full-sized metal-cutting equipment made it possible to adjust cutting modes, for example, the value of the working feed, directly during processing. However, there is a significant number of the parts in production that, according to their dimensions, are economically unprofitable to process on expensive large machines with a powerful CNC system. Therefore, relatively inexpensive small-sized metal-cutting machines are becoming increasingly used in enterprises. The technological capabilities of such equipment allow processing not only non-ferrous metals and alloys but also steels. A feature of the control of such equipment is the use of simplified CNC systems installed on personal computers that are not able to perform arithmetic operations and this becomes an obstacle to improving the productivity of processing complex surfaces. At the same time, due to their simplicity and low cost, these systems are becoming more and more popular. In the article, we proposed to increase the productivity of processing surfaces of complex spatial shape on such machines based on the calculation of the CAD tool movement by the system by converting the real trajectory into a set of symmetrical segments with known coordinates. This method allows you, with a given processing accuracy, to set the values of the cutting mode parameters close to the optimal ones, to eliminate emergencies associated with tool failure when working with a variable cutting depth formed after roughing and to increase productivity by 15-20%

Food-Grade Biorefinery Processing of Macroalgae at Scale: Considerations, Observations and Recommendations

Using brown seaweed kelp species Saccharina latissima and Laminaria digitata as feedstocks, a set of pilot-scale macroalgae processing batches were conducted (50–200 kg per batch) for the production of a range of food-grade liquid and solid fractions. The aim of this communication is to relay a number of lessons learnt during this period in combination with previous relevant observations and considerations for others who are intending to process macroalgae at scale. The novelty of this paper is thus to form a bridge between academic findings and practical know-how. Considerations covers material diversity; abiotic and biotic impact and variation; and supply chain considerations. Observations covers milling and cutting; equipment requirements; and acids including their effects on heavy metals, especially lead. Recommendations summarises key points from this pilot-scale and previous work. These include: harvest seasonality, water quality and proximity to processing facilities; minimising contaminants within the macroalgae such as stones and shells; considering equipment composition and volume for all steps and processes including final product quality; acid choice and its effects on both the equipment used and the metals bioaccumulated within the macroalgae.

Experimental study of mild steel cutting process by using the plasma arc method

Purpose: In this study, plasma arc cutting (PAC) is an industrial process widely used for cutting various away types of metals in several operating conditions. Design/methodology/approach: It is carried out a systematic or an authoritative inquiry to discover and examine the fact, the plasma cutting process is to establish the accuracy and the quality of the cut in this current paper assessed a good away to better the cutting process. Findings: It found that the effect of parameters on the cutting quality than on the results performed to accomplish by statistical analysis. Research limitations/implications: The objective of the present work paper is to achieve cutting parameters, thus the quality of the cutting process depends upon the plasma gas pressure, scanning speed, cutting power, and cutting height. Practical implications: The product of the plasma cutting process experimentally has been the quality of the cutting equipment that was installed to monitor kerf width quality by exam the edge roughness, kerf width, and the size of the heat-affected zone (HAZ). Originality/value: The results reveal that were technically possessed of including all the relevant characteristics, then a quality control for the cutting and describe the consequence of the process parameters.

Simulation and Experimental Study on Hydraulic Sandblasting Cutting in Uncontrolled Blowout Well

In this paper, the pre-mixed type high pressure hydraulic sandblasting before portable nozzle structure optimized design calculation of cutting equipment, hydraulic sandblasting cutting using high-speed sand fluid jet to finish cutting operation, to improve the work efficiency of the device, this paper adopts the method of computational fluid dynamics, using the business software, numerical simulation of different nozzle type, nozzle length and Angle of the cone Angle of nozzle, the internal flow field of comparative analysis and calculation results, and to test the performance of the different nozzle, it is concluded that the cone shape nozzle structure is better, and working parameters of the type sprayer experiment, with the help of mathematical software to deal with the experimental data, the theoretical formulae of cutting depth, cutting target distance, transverse velocity and jet pressure were obtained, which provided a basis for the development of nozzle with high cutting efficiency and proved the accuracy and reliability of simulation results.

Determining optimal laser-beam cutting equipment investment through a robust optimization modeling approach

The acquisition of Advanced Manufacturing Technologies (AMT), such as high-power fiber or CO2 laser cutting equipment, generally involves high investment levels. Its payback period is usually more extended, and there is a moderate-to-high risk involved in adopting these technologies. In this work, we present a robust model that optimizes equipment investing decisions, considers the process’s technical constraint and finds an optimal production plan based on the available machinery. We propose a linear investment model based on historical demand information and take physical process parameters for a LASER cutting equipment, such as cutting speed and gas consumption. The model is then transformed into a robust optimization model which considers demand uncertainty. Second, we determine the optimal production plan based on the results of the robust optimization model and assuming that demand follows a normal distribution. As a case study, we decided on the investment and productive plan for a company that offers Laser-Beam Cutting (LBC) services. The case study validates the effectiveness of the proposed model and proves the robustness of the solution. For this specific application of the model, results showed that the optimal robust solution could increase the company’s expected profits by 6.4%.

ISIM Own Contributions on Non-Conventional Abrasive Waterjet Cutting Technologies

Modern materials cutting operations are traditionally part of the research priorities and also in the production activities of ISIM Timișoara. In the last decade, within the institute, a special emphasis was placed on the development of the abrasive water jet cutting process as well as on implementing the research results obtained into industrial activities. The paper presents own achievements and contributions of ISIM to the development of the abrasive water jet cutting process in the following directions: cutting technologies for materials with different characteristics, innovative new patentable solutions regarding the cutting process respectively important modules in the composition of the water jet cutting equipment, ways to recycle used abrasive waste, solutions to streamline the process. The proposed solutions have been verified with good results in industrial applications, or have been proposed for analysis and development together with specialists in the field from important research units.

TECHNOLOGICAL FEATURES OF MANUFACTURING COMPLEX PARTS OF THE MECHANICAL PART OF OPTICAL DEVICES AT MACHINING CENTERS

The article defines the concept of "technological features". Examples of technological features of modern manufacturing by cutting complex parts of the mechanical part of optical devices are considered and analyzed. The examples contain fragments of manufacturing parts only on CNC machines of the "machining center" type. This type of metal-cutting equipment is accepted as the main one in the conditions of automation of processing by cutting metal products. The necessity of systematization of the features of manufacturing products in optical and assembly technology is stated. Attention is drawn to the practical and theoretical significance of this work.

Technological prerequisites for the energy efficiency increase of the engine cylinder bore processing

An example of the rationalization of the current technology for manufacturing a cylinder of a small-sized diesel engine at PA “TULAMASHZAVOD” from a cast iron is given. It is shown that lowpower obsolete equipment leads to an increase in the number of technological operations and equipment used. However, even if all the generally accepted technological recommendations are followed, only 80% of the parts meet the requirements for the required parameters of accuracy and quality of the cylinder bore surface. Studies have found that the main reasons for insufficient quality are the presence of residual stresses in the casting, which cannot be removed during artificial aging, as well as insufficient accuracy and rigidity of metal cutting equipment at turning and boring operations. The use of more powerful and accurate modern equipment is theoretically and experimentally justified, which, due to increased refinement, allows reducing the number of machining operations. Replacement of artificial thermal aging by natural, combined with the replacement of shaft furnaces for heat treatment of workpieces with chamber furnaces of lower power and higher capacity, reduce energy consumption for the manufacturing by almost 4 times.

CONSTRUCTION OF A REGRESSION MODEL OF THERMAL RESISTANCE OF A CONTACT PSEUDO MEDIUM

The operating experience of metal-cutting machines made it possible to develop reasonable recommendations for the permissible limit values of temperature for the main subsystems of the machine, which determine the accuracy of processing. However, the decrease in the seriality of the manufactured metal-cutting equipment and the constant improvement of its designs require the development of models that are the basis of engineering techniques that allow at the design stage to predict the thermal picture of the main machine units that affect the processing accuracy. In connection with a significant number of factors influencing the formation of contact thermal resistance, and the difference in the weight of their action, it is proposed to use a pseudolayer (pseudo-medium), consisting of areas of actual contact and cavities filled with air or oil, for their comprehensive consideration in the thermal model of joining parts. To determine the significant factors that dominate the contact thermal resistance, a number of one-factor experiments were carried out. To develop a regression model of temperature change in the contact zone, a PFE of type 24 was performed. The results obtained were verified by the Cochran, Student and Fisher criteria.