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The gas turbine, aerospace and nuclear industries are dependent upon nickel-based superalloys to enable these industries to continue to innovate. Without these materials the industries would fail to achieve new heights of efficiency as the strength and operating temperature requirements continue to climb. Nickel-based superalloys thrive in these el...
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... materials that have better machinability such as aluminums and steels, failure due to notch wear is less severe when compared to superalloys, due to their strength and toughness. Figure 6 captures this behavior occurring at an axial depth of cut of 5 mm with a feed rate of 0.3 mm/rev and a cutting speed of 50 m/min. The standard force increase of the Fy component is typically a 0.5% difference from peak to peak (pass to pass), however in the case of tool failure the difference approaches a 40% difference. ...
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... Trochoidal milling, which could fully cool and lubricate the workpiece and tool during processing to improve the machining efficiency and tool life, has been applied to rough machining the workpiece with poor cutting performance and paid more and more attention by the manufacturing industry. When cutting extremely hard materials such as super titanium alloy, trochoidal tool path has been a good milling strategy for improving the tool life with a corresponding reduction in machining time [7][8][9]. Cao et al. [10] applied cycloidal milling to the nickel alloy deep hole. Experiments show that compared with layer milling, cycloidal milling can not only shorten the processing time by 50 ~ 75%, but also prolong the tool life. ...
The machining time is mainly related to the tool path and the corresponding feed speed, while the trochoidal tool path depends on the trochoidal step and trochoidal radius. The material removal rate is periodically distributed along the tool path in trochoidal milling a hole. But more than half of tool paths do not cut material in trochoidal milling a hole, so a constant feed speed in milling a hole will limit the machining efficiency. In this paper, a trochoidal radius optimization approach is presented to improve the efficiency of trochoidal milling a hole, which considers the optimal feed speed. Firstly, the mathematical representation of the trochoidal radius is formulated by analyzing the generation principle of trochoidal path, so the trochoidal radius could be determined under the premise of the hole diameter, maximum uncut radial material, and the tool diameter are fixed. Furthermore, the trochoidal radius optimization model, which is based on the adjusted feed speed, is established with the goal of minimizing the machining time. Secondly, an adaptive feed speed scheduling strategy for trochoidal milling is proposed, which is constrained by stable material removal rate and adjusted by a cubic polynomial algorithm. Finally, taking a hole machining as an example, simulation and experimental results show that the efficiency of applying the trochoid milling method proposed has increased by 13.8% compared to traditional helix milling method.
... Pleta et al. measured the process performance using productivity and efficiency indices when trochoidal milling of Inconel 738 [35]. These indices were defined as the total material removed volume per unit of tool wear and the total material removal rate per unit of tool wear respectively. ...
This paper aims to study, analytically and experimentally, the effects of trochoidal milling parameters on the waviness and the surface roughness of P20 alloy steel slots. The considered process parameters in this paper are the axial depth of cut, trochoidal step, and feed rate, in addition to the slot width. A geometrical analytical model of the tool cutting edges imprints has been developed to explain the of waviness and surface roughness at the slot walls and bottom. Results of this model proved that increasing the slot width significantly reduces the slot walls waviness, while increasing the feed rate or the trochoidal step increases the waviness of the slot left and right walls respectively. The experimental results proved that the axial depth of cut has not a significant effect on the slot walls waviness, and the tool edges imprints have the greatest effect on the bottom surface roughness. The surface roughness of the slot bottom decreases from left to right. Moreover, increasing the feed rate significantly increased the bottom surface roughness by 25%, 29%, and 29% at the left wall, middle, and right wall of the machined slot, respectively. However, increasing the axial depth of cut, significantly increased the bottom surface roughness only at the left wall and the middle of the machined slot by 11% and 19%, respectively. Experimental and analytical results of waviness and surface roughness were in good agreements which verifies the potential of using the developed model to predict the slot surface texture during circular trochoidal milling.
... Trochoidal milling, which could fully cool and lubricate the workpiece and tool during processing to improve the machining efficiency and tool life, has been applied to rough machining the workpiece with poor cutting performance, and paid more and more attention by the manufacturing industry. When cutting extremely hard materials such as super titanium alloy, trochoidal tool path has been a good milling strategy for improving the tool life with a corresponding reduction in machining time [7,8,9] . Cao et al. [10] applied cycloidal milling to the nickel alloy deep hole. ...
The machining time is mainly related to the tool path and the corresponding feed speed, while the trochoidal tool path depends on the trochoidal step and trochoidal radius. The material removal rate is periodically distributed along the tool path in trochoidal milling a hole. But more than half of tool paths do not cut material in trochoidal milling a hole, so a constant feed speed in milling a hole will limit the machining efficiency. In this paper, a trochoidal radius optimization approach is presented to improve the efficiency of trochoidal milling a hole, which considering the optimal feed speed. Firstly, the mathematical representation of the trochoidal radius is formulated by analyzing the generation principle of trochoidal path, so the trochoidal radius could be determined under the premise of the hole diameter, maximum uncut radial material and the tool diameter are fixed. Furthermore, the trochoidal radius optimization model，which based on the adjusted feed speed, is established with the goal of minimizing the machining time. Secondly, an adaptive feed speed scheduling strategy for trochoidal milling is proposed, which is constrained by stable material removal rate and adjusted by a cubic polynomial algorithm. Finally, taking a hole machining as an example, simulation and experimental results show that the efficiency of applying the trochoid milling method proposed has increased by 13.8% compared to traditional helix milling method.
... In these fields, gas turbines, which are mainly made from different types of nickel and titan-based superalloys [5], are widely used. These superalloys are manufactured by turning [6], milling [7] and Wiper Grinding [8]. The parts of these turbines contain many slots, which can only be made by milling. ...
In this scientific study, the authors have dealt with the slot milling of nickel-based superalloys. These alloys are among the most difficult materials to machine and are widely used in aerospace and energy industries. Due to the properties of the material, slot milling is a particular problem because tool wear happens quickly, and tool breakages are common. When these superalloys are machined, very high temperatures occur in the cutting zone, which cannot leave due to the extremely poor thermal conductivity of the material and will therefore transfer to the edges of the cutting tool, causing it to anneal, break off and fail. So, the researchers initiated a new field of research: cryogenically-assisted machining. In this paper, the authors used two cooling methods, the conventional flood cooling and cryogenic cooling with liquid carbon-dioxide (LCO2). The effects of these cooling methods were tested focusing on the cutting forces, tool wear, chip morphology and surface roughness of the bottom of the slots. The aim was to determine the best cooling methods for these materials. Based on the results, it can be concluded that, LCO2 has a negative effect on cutting forces, tool life and surface roughness. It only has a positive effect on chip formation. It can be see that, the lubricating effect has a greater impact on tool life, tool load and surface roughness of the milled slots than cooling.
... In the literature, several studies have been reported that aim to improve the productivity of IN718-based products by employing various toolpath strategies [6][7][8], optimizing cutting parameters [9][10][11][12][13], and developing models for predicting tool wear evolution [14][15][16]. Pleta et al. [6] applied trochoidal (i.e., epicyclcoidal) milling in the machining of IN718 and analyzed the effect of varying machining parameters such as cutting speed, feed, and depth of cut on material removal rate per unit of tool wear and cutting force dynamic response. ...
... Pleta et al. [6] applied trochoidal (i.e., epicyclcoidal) milling in the machining of IN718 and analyzed the effect of varying machining parameters such as cutting speed, feed, and depth of cut on material removal rate per unit of tool wear and cutting force dynamic response. The results were compared with conventional milling, and it was concluded that trochoidal milling has better productivity when the tool change is also considered, and the cutting force increases from the beginning to the end of the cut at a stable rate [7]. Sui et al. [8] generated a toolpath that combines corner-loop milling and clothoid curve transition strategies to optimize both the cutting force and dynamic characteristics of a machine tool during the machining of titanium alloys. ...
Tool wear plays a decisive role in achieving the required surface quality and dimensional accuracy during the machining of Inconel 718-based products. The highly stochastic phenomenon of tool wear, particularly in later stages, results in difficulty in predicting the failure point of the tool. The present research work aims to study this late-stage wear of the tool by generating consistent wear conditions and thereby decoupling the late-stage wear from the wear history. To do so, a multi-axis grinding operation is employed to create artificial tool wear that replicates the topology of natural wear occurring in the process. In order to evaluate the imitating ability of the proposed methodology, microscopic images in different wear states of naturally and contrived worn tools were analyzed. The methodology was validated by comparing the resulting process forces measured during end milling with the natural and contrived worn tool for different path strategies. Finally, a qualitative FE-analysis was conducted, and specific force coefficients for worn tool segments were determined through simulation.
... In these fields, gas turbines are widely used, which are made from mainly titan and nickel-based superalloys. These materials are manufactured by turning [3], milling [4] and Wiper Grinding methods [5] if the geometry of the part allows. However, these turbines contain many slots, which can only be made by milling. ...
... Using a spatial cubic curve-based cyclic five-axis tool path, Li et al. [20] proposed an innovative method for improving material removal rate (MRR) during trochoid milling of cavities. In order to minimize the tool wear and cutting forces during the TR milling of an Inconel 718, Pleta et al. [21] investigated the effect of the machining parameters on the slot geometry and calculated cutting forces [22]. Utilizing the Taguchi method, the authors found that tool wear and increasing chip thickness increase the depth of the machining impacted zone. ...
The capabilities of the milling process stem from the appropriate regulation of its parameters, the adoption of efficient milling strategies and the use of cooling methods, especially during machining of hard-to-cut materials. In the present work, the effect of kinematic parameters and cooling methods during trochoidal end milling of Incoloy 800 is investigated. The results indicate that MQL cooling is rather efficient for milling of superalloys, compared to flood cooling and dry cutting and allows for sufficient increase in productivity, by giving the possibility to select higher feed and trochoidal stepover values. Moreover, although the morphology of the milled surface, which is dominated by peaks cannot be altered, surface quality can be considerably improved by the use of MQL cooling.
... The poor machining process performance of nickel-based high-temperature alloys under ordinary grinding conditions [7,8] is due to nickel-based alloys having a high yield strength, which consumes a large amount of energy during material removal; the low thermal conductivity of nickelbased alloys makes it easier for the large amount of heat generated during material removal to gather and form local high temperatures, resulting in burns or cracks on the surface of the machined workpiece, which ultimately leads to the poor surface quality of the machined workpiece and makes it difficult to meet the machining requirements [9,10]. According to the grinding characteristics of nickel-based alloys, scholars at home and abroad have mainly studied them in two aspects: first, developing high-precision grinding equipment and tools to improving the grinding force of the grinding wheel and the removal rate of the workpiece to obtain better surface finish quality; The second is to study the influence law of material characteristics, cooling characteristics, machine tool characteristics, grinding wheel parameters, dressing parameters, and grinding parameters on the grinding process characteristics of nickel-based alloy materials [11,12]. ...
The flow conditions of the grinding fluid during grinding are analyzed with regard to the problem of easy burns during surface profile grinding of difficult-to-machine materials, nickel-based high-temperature alloys. The CFD simulations were carried out to analyze the grinding fluid flow in the grinding zone during flat and circular profile grinding according to the gas–liquid two-phase flow VOF theory. Numerical simulations were performed using FLUENT software to analyze the pressure and volume fraction in the gas–liquid two-phase flow field under different parameters by changing the injection speed and injection position. The effects of different injection positions and injection speeds on the grinding fluid flow in the grinding zone were investigated. The study showed that the higher the injection speed of the grinding fluid, the higher the dynamic pressure of the grinding fluid on the workpiece surface and the higher the return flow rate on the grinding wheel surface; the lower the speed, the lower the dynamic pressure of the grinding fluid on the workpiece surface but the higher the return flow rate. At the same injection position, the volume fraction of grinding fluid flowing from the outlet first increases with increasing injection speed, and then tends to level off; at the same injection speed, the integral number of grinding fluid flowing from the outlet is greatest for the central injection. Thus, the optimal injection position and injection speed of grinding fluid are proposed. It provides an important reference for improving the quality of profile grinding and preventing the workpiece from being burned during grinding, and provides a basis for subsequent profile grinding tests on high-temperature alloys.
... Material is cut in the front-half path and the cutting heat is dissipated as the tool moves in the back-half path [12]. Therefore, in highspeed machining, trochoidal milling is increasingly used in slot milling and is also widely used in cutting hard materials, such as NiTi-based super alloy [13][14][15]. Suppose a cavity is delimited by two surfaces S 1 and S 2 , see Fig. 1(b). Our purpose is to determine trochoidal milling paths as well as the shape of a milling tool such that high precision milling is obtained. ...
... Otkur et al. [17] propose a comprehensive analytical model to analyze the tool-workpiece engagement and predict the cutting force. Pleta et al. [13] find that the engagement angle has the highest correspondence with the component perpendicular to the feeding direction of the cutting force. The relationship between the cutting force and the cutting depth in trochoidal milling is further analyzed in [18]. ...
A novel method for trochoidal flank milling of 3D cavities bounded by free-form surfaces is proposed. Existing 3D trochoidal milling methods use on-market milling tools whose shape is typically cylindrical or conical, and is therefore not well-suited for meeting fine milling tolerances required for finishing of benchmark free-form surfaces like blades or blisks. In contrast, our variational framework incorporates the shape of the tool into the optimization cycle and looks not only for the trochoidal milling paths, but also for the shape of the tool itself. High precision quality is ensured by firstly designing flank milling paths for the side surfaces that delimit the motion space, in which the trochoidal milling paths are further computed. Additionally, the material removal rate is maximized with the cutter-workpiece engagement being constrained under a given tolerance. Our framework also supports multi-layer approach that is necessary to handle deep cavities. The ability and efficacy of the proposed method are demonstrated by several industrial benchmarks, showing that our approach meets fine machining tolerances using only a few trochoidal paths.
... To decrease the processing time, the in and out paths are usually modified to shorten the milled area with a straight line (with initial and final tangential arches) at a higher feed [20]. ...
Trochoidal milling is a well-stablished machining strategy which still allows for the introduction of new approaches. This strategy can be applied to any kind of material, although it is usually associated to advanced materials, such as titanium and nickel alloys. This study is based on the adaptation of the feed speed of a milling tool with Ti-6Al-4V, so the chip width can be maintained constant without modifying the path geometry. A singularity in the experimental stage was to mill an Archimedes spiral groove instead of the conventional straight grooves. This made it possible to obtain a concave wall as well as a convex one and to optimize the amount of material used. The time efficiency compared to a constant feed, was slightly superior to 20%, reducing tool wear also. These techniques require milling machines with high mechanical and kinematic performance, as well as the absence of clearance between joints and a high acceleration capacity.
