ON ONE ASPECT OF SUSTAINABLE MANUFACTURING Power Consumption vs Productivity

The paper presents one aspect of the analysis of energy consumption and productivity of the manufacturing operation. As an example of the operation, the operation of turning with a single-blade tool was taken. Sustainable development in its general concept implies sustainable materials, sustainable design, and sustainable manufacturing. This paper presents an analysis of one important part of sustainable manufacturing, and that is energy saving. The experimental study was conducted as follows. In laboratory conditions, an experimental-mathematical regression model of the relationship between cutting force and processing conditions was defined. Machining experiments were performed under ECO-friendly conditions with technology known as MQCL (Minimum Quantity Cooling Lubrication) machining. The obtained mathematical model was used to calculate the energy consumption and the workpiece material removal rate (MRR, productivity). The results of the analysis showed that there is a lot of space for optimization of machining conditions from the aspect of power consumption, with mandatory calculation and other machining costs, above all, the cost of tools and machine tools. In this regard, recommendations for analysis with the aim of power saving are given.


INTRODUCTION
To achieve the concept of sustainable manufacturing, which is a very complex problem, it is necessary to consider three integral levels of interaction, namely: products, processes, and systems [1,2], Figure 1.There is no universal or generally accepted definition of sustainable manufacturing in the literature and practice [1].However, it must be said that there are many insufficient attempts, including a partially integrated approach.Almost all of these attempts are flawed because they mainly deal only with products and processes, but do not emphasize the interconnectedness between the three constituent elements involved in manufacturing (products, processes, and systems).In line with the basic concept, sustainable manufacturing offers a new way of producing functionally sustainable products using sustainable technologies and advanced manufacturing methods.This is only possible if product design, production, supply chain design and management, and logistics at the manufacturing enterprise level can be understood, developed, and managed in an integrated way.The interaction between the levels of the elements shown in Figure 1 gives the desired sustainable goal.JST&M 2(2022) 2, 1-8 Figure 1.Integrated elements of sustainable manufacturing [1] In terms of products (Figure 1), a new 6R approach (i.e.re-duce, re-design, re-use, recover, re-manufacture, and re-cycle) has been established instead of the 3R Regarding the process (Figure 1), the reduction of energy consumption, hazards, and toxic waste is achieved by using an optimized technological process.This technological process is associated with an efficient process planning methodology, with the use of an efficient supply chain system that takes into account all stages of the life cycle (i.e.premanufacturing, manufacturing, u,se and post-use) ensures an effective sustainable system [5].The expectations of a sustainable manufacturing process are concluded as follows [3,4,5]:  Energy consumption reduction  Waste elimination/reduction  Product durability improvement  Health hazards and toxic dispersion elimination  Higher quality of manufacturing  Recycling, reuse, and remanufacturing enhancement  Development of renewable energy resources.On the other hand, the analysis of each of the elements shown in Figure 1 should be approached from a comprehensive point of view.In this paper, special attention is put to the process.The manufacturing process observed in a cybernetic way can be represented in the way that Figure 2 shows.The clear position of the so-called internal factors can be seen, among which are the cutting forces.This is especially important from the aspect of energy saving or energy consumption reduction to achieving sustainable manufacturing.So, technologically speaking, there are large reserves in the segment of energy consumption.In this paper, the example of a turning operation shows how energy can be saved.Previously, the relationship between the cutting forces and the elements of the cutting regime was experimentally modeled, and later this mathematical model was used for the analysis and calculation of energy/power consumption.

EXPERIMENTAL SETUP
Turning is one of the most widely applied production technologies in industrial practice [6].As with any other production technology by removing workpiece material, the presence of cutting forces is bound to take place.Greater magnitudes of the resulting cutting force in production processes cause higher wear of cutting tools, higher probability of tool breakage, higher cutting temperature, as well as lower quality of the machined surface and dimensional accuracy of the machined product [7].Since all of the aforementioned are important factors from the aspects of both productivity and costs, finding ways to predict the magnitude of the resulting cutting force for a given machining condition is of paramount importance.One way to obtain a reliable mathematical model describing the relationship between cutting forces and machining conditions is the experimental method.This is meant the conduct of experiments, and the use of appropriate statistical methodologies, primarily regression analysis and analysis of variance.The experiment has been performed at the Laboratory for Metal Cutting and Machine Tools, at the Faculty of Mechanical Engineering, University of Zenica.The experiments were conducted under ECOfriendly conditions, so-called MQCL (Minimum Quantity Cooling Lubrication) machining.
Figure 3 shows the experimental setting of the turning operation.Cooling and lubricating media is an aerosol that represents water droplets with such an oil film carried by a stream of compressed air.This aerosol is not harmful to the environment at all, it is composed of water and vegetable oil.The following volume ratio was used in the experiment: 0.9 liters per hour of water and 30 ml per hour of oil.Aerosol production (atomization) is done in a nozzle that directs it to the cutting zone.The conventionally operated lathe is a Potisje PA501M model.The cutting tool used in all of the experimental runs was Mitsubishi SNMG120408-MA inserts.The material of the workpiece is steel C45 (EN).The magnitude of the resulting cutting force was calculated based on measurements of the cutting force components, which were performed using a Kistler dynamometer 5070 type.The three most important machining conditions were selected for the factors: cutting speed, v, (or, rpmin of the workpiece), feed, f (mmpr,) and depth of cut, d (mm).
Factor levels with natural and coded values are shown in Table 1 Figure 4 shows the measurement results of the cutting force components for experimental runs 2 and 7.  (8) The metal cutting process is a process that has the following physical and production characteristics from a power consumption and productivity point of view.The crosssection of the chip is the product of the feed, f, mmprev, and the depth of cut, d, mm, and is equal to A = f  d, mm 2 .The product of this area and the cutting speed v, mpmin, gives the material.Analysis of power consumption and productivity of the cutting process in terms

𝐹 = 46 7 )
Figure5clearly shows, that the feed, f, depth of cut, d, and their induction significantly affect the overall cutting force.All other factors can be excluded from the model(7) so that it can finally be written by equation (8).

Figure 5 .Figure 6 .
Figure 5. Main Effects Plot for the magnitude of the overall cutting force F

Table 1 .
. Factor levels with natural and coded values

Table 2 .
Plan-matrix of experiment and measurement results Figure 4. Measurement results of the cutting force components for experimental runs 2 and 7 (

Table 2 )
The task of experimental research is to determine the mathematical model of the function of the dependence of the overall cutting force on the number of revolutions, n, feed, f, and depth of cut, d.If a mathematical form is assumed as:∅ =  +  •  +  •  +  •  +  •   +  •   +  •   +  •    , (2)