## 1 State of the Art  
Over the last decade, the use of the aluminum alloys in the manufacturing industry has grown due to the fact that these alloys have an extraordinary ability to combine their two properties: low weight and strength in a single material. Given this, it is imperative to assume knowledge of the machinability properties of these materials when it is desired to provide information for use in industry and by researchers. The aim is to offer the possibility to process these materials by making the best decisions in this regard. In the automotive industry, aluminum is already well known due to its wide range of applicability [1]. In the aerospace industry, in the 1930s, the most frequently approached aluminum classes were mainly 2 xxx, 7 xxx and 6 xxx [2; 3]. The preference felt in this regard in the automotive and aerospace industries is justified by the high strength of these materials against to their low weight but also the fact that they often bring a degree of profitability in the sense that they can replace steel and cast iron in parts manufacturing. Due to the low weight of aluminum, the impact on the environment is also reduced. The supporting argument of this claim is the low energy consumption [3]. Other areas in which aluminum alloys find their applicability, concern the construction area; of course, the electrical, electromechanical, electronic and packaging industries. Aluminum alloys are also used with great success in the manufacture of nanostructures where their property of high mechanical strength and thermal stability is required. A good example of this is the 6061-T6 aluminum alloy [1]. Compared to steels, aluminum alloys have a third of their density and modulus of elasticity, but also a much higher thermal and electrical conductivity, as well as high corrosion resistance, high coefficient of friction, etc. [1]. According to [PERSON] [4] and [PERSON] [5], aluminum is widely used in the manufacture of motor vehicle parts during turns, because it is lightweight. It is desirable to produce high quality surface products as soon as possible. The surface roughness of mechanical components plays a major role in the relationship between industrial production and cost. Surface roughness usually depends on the cutting parameters, such as: cutting speed, feed rate and cutting depth [6; 7]. Proper selection of the control factors is particularly important for the manufacture of surface components and high strength in a short time. With the processing in recent years, much has been done to improve the quality and efficiency of the product. Many aspects of research have yet to be explored. [PERSON] tested different models to get the best machining parameters for aluminum 6061 [8]. Studies have shown that shaft speed, strength and nose radii have very good surface quality impact. [PERSON] [9] uses control factors such as cutting speed, feed rate and cutting depth to optimize surface roughness when machining Al 6351-T6 alloy with uncoated carbide tools. The Taguchi technique is used to optimize the process parameters and the reinforcement test has been identified to determine the main factors affecting the surface roughness. This test shows that cutting speed has a greater impact on surface roughness. The effect of cutting parameters (spindle speed, feed rate, and cutting depth) on surface roughness and tool wear is investigated by [PERSON] when turning 6061 aluminum alloys [10]. Many regression models were developed for responses and the adequacy of the developed models was tested at 95% confidence interval using variance analysis (ANOVA) method. [PERSON] [11] studied the parameters that influence the roughness during the machining of Al 6061 on CNC lathes. The Taguchi and ANOVA methods were used to study the experimental results. According to his study, the result is that the feed and the speed levels are the most important parameters.