Trochoidal Milling Research Articles

Investigating the effect of nanobubble-based cutting fluid on tool wear and cutting forces in milling of Inconel 718

Machining of Nickel-Based Superalloys (NBSAs) is characterized by rapid work hardening, low thermal conductivity, and extreme abrasive behavior. Due to such characteristics of NBSAs, the machining of materials like Inconel 718 (IN718) results in extensive tool wear and high cutting forces. The present study employs nanobubble-based cutting fluid during machining of IN718 and investigates its effect on tool wear and cutting forces. The trochoidal milling experiments were conducted on an IN718 workpiece with nanobubble-based and normal cutting fluid at varying surface speeds. The evolution of tool flank wear area and peak resultant cutting force were recorded and compared to evaluate the effectiveness of nanobubble-based cutting fluid over normal cutting fluid. The results showed that nanobubble-based cutting fluid lowers the tool wear rate by enhancing heat dissipation and reducing abrasion wear. However, higher cutting forces were observed with nanobubble-based cutting fluid due to increase in hardness of the workpiece. Also, it is realized that using nanobubble-based cutting fluid can significantly improve the lifespan of the tool, leading to sustainable manufacturing.

Generation of cubic Hermite spline-based trochoidal milling toolpath by introducing a coefficient factor in machining curved slots

Trochoidal milling has become popular in high-speed milling due to its ability to reduce cutting force, enhance thermal dissipation, and prolong tool life. Among other toolpath patterns, the cubic Hermite spline offers significant advantages in generating trochoidal milling toolpath in machining complex and curved slots. However, determining those two different relation coefficients in the polynomial function of cubic Hermite spline remains complicated and empirical. This paper introduces a coefficient factor to simplify the determination process, which only requires the position and tangent vector parameters of each endpoint pair. The coefficient factor combines an instantaneous in-process slot width (IISW)-related width factor and a tangent vector direction-related direction factor. Two complex-curved slots are used to validate the performance of the proposed method. The results show that this method is straightforward and effective in generating trochoidal milling toolpaths for machining complex-curved slots while matching the slot geometry. Additionally, compared with a direct 5-axis trochoidal milling (one-step slotting strategy) in trochoidal milling of 3D slots on both serial and hybrid machining tools, a two-step slotting strategy (3-axis trochoidal milling and a successive 5-axis perpetual milling) is preferable in improving machining efficiency.

Trochoidal Milling Using Indexable Inserts

Solid carbide tools were chiefly used for trochoidal milling in the past. Together with SolidCAM and its iMachining software, Mapal has now shown the highly-efficient machining technology also offers advantages for milling with indexable inserts

A parameter-variant trochoidal-like tool path planning method for chatter-free and high-efficiency milling

Trochoidal milling is known for its advantages in machining difficult-to-machine materials as it facilitates chip removal and tool cooling. However, the conventional trochoidal tool path presents challenges such as lower machining efficiency and longer machining time due to its time-varying cutter-workpiece engagement angle and a high percentage of non-cutting tool paths. To address these issues, this paper introduces a parameter-variant trochoidal-like (PVTR) tool path planning method for chatter-free and high-efficiency milling. This method ensures a constant engagement angle for each tool path period by adjusting the trochoidal radius and step. Initially, the nonlinear equation for the PVTR toolpath is established. Then, a segmented recurrence method is proposed to plan tool paths based on the desired engagement angle. The impact of trochoidal tool path parameters on the engagement angle is analyzed and coupled this information with the milling stability model based on spindle speed and engagement angle to determine the desired engagement angle throughout the machining process. Finally, several experimental tests are carried out using the bull-nose end mill to validate the feasibility and effectiveness of the proposed method.

Process Stability Analysis during Trochoidal Milling of AZ91D Magnesium Alloy Using Different Toolholder Types

Trochoidal milling is one of the solutions for increasing the efficiency of machining processes. A decreased cutting tool’s arc of contact leads to a reduction in the generated cutting forces, thus improving process stability. Vibration is an inherent part of any machining process, affecting the accuracy and quality of the manufactured components, but it can also pose a danger to machine operators. Chatter is particularly detrimental, leaving characteristic marks on shaped surfaces and potentially leading to catastrophic tool damage. Therefore, it is important to ensure the stability of machining and also reduce vibration. The primary purpose of the conducted research is to evaluate the stability of the milling process of the AZ91D magnesium alloy performed through a trochoidal strategy. An additional objective is to establish the effect of the variation in machining parameters and toolholder types on milling stability. Three types of toolholders most commonly used in industry are used in the study. The basis of the investigation is the measurement of vibration displacement and acceleration analysed in the time domain. A spectral analysis of the signals is also performed based on Fast Fourier Transform, to identify signal components and detect the susceptibility to chatter occurrence. An important part of the study is also an attempt to use the Composite Multiscale Entropy as an indicator to determine the stability of the machining processes. Entropy does not exceed the values of 1.5 for cutting speed and 2.5 for feed per tooth, respectively. Vibration acceleration does not exceed (in most cases) the value of 20 m/s2 for the peak-to-peak parameter and the shrinkfit toolholder. For vibration displacement (peak-to-peak parameter), there are oscillations around the value of 0.9 mm for all kinds of toolholders.

A novel method for trochoidal milling tool path tailoring based on curvature variation

Trochoidal milling has gained popularity in high-speed milling owing to its ability to reduce cutting force, accelerate thermal dissipation, and increase tool life. Nevertheless, it has the drawbacks of poor cutting efficiency and longer machining time due to decreased cutter-workpiece engagement (CWE). This paper studied the tailoring of trochoidal milling tool path curves subjected to improve machining efficiency by controlling curvature variation while meeting predefined CWE angle criteria. The relationship between the instantaneous CWE angle and the curvature variation of the tool path curve was quantitatively established. Then, a negative exponential function-based governing function was introduced to regulate the curvature variation. Finally, the proposed method was experimentally validated via trochoidal milling of curved slots by evaluating machining efficiency and surface quality. The results showed that compared with the circular, elliptical, and polynomial tool path, the tailored tool path-related average CWE angle increased by 40.5 %, 17.9 %, and 6.3 %; while the machining efficiency improved by 25 %, 16 %, and 14 %, respectively. Although the surface quality (surface roughness varies within 5 % and flatness raised by 27 %) is worse than that of the other three tool path patterns, benefiting from the highly improved machining efficiency, it is still applicable in high-efficiency rough milling of components.

An optimization method of trochoidal radius for trochoidal milling hole based on the adaptive feed rate scheduling

An optimization method of trochoidal radius for trochoidal milling hole based on the adaptive feed rate scheduling

A non-singular five-axis trochoidal milling process method for 3D curved slots

A non-singular five-axis trochoidal milling process method for 3D curved slots

Analysis and development of elliptical tool path in trochoidal milling

Trochoidal milling has been developed to extend the cutting tool life as compared to conventional milling. It is widely used in the machining of slots and corners of molds and dies. There are several tool paths typically used in trochoidal milling such as true, circular, variable-feed, and variable-step trochoidal tool paths. However, these paths suffer from low material removal rates, low surface qualities, high CPU processing times, and/or the requirement of high-dynamic machine tools. Elliptical trochoidal tool path showed its capability to improve the material removal rate, but the expected low surface quality of the produced slot. In this paper, the elliptical tool path will be analyzed analytically and experimentally. The effect of elliptical tool path on material removal rate, cutting forces, walls waviness, and surface roughness have been investigated. A novel linear elliptical-based tool path has been proposed to enhance the elliptical tool path performance by improving both material removal rate and surface quality. A Performance index has been utilized to evaluate the performance of these processes. An analytical model for the local maximum chip thickness in elliptical tool path has been conducted to correlate this path with the cutting forces. The slot walls waviness has been modeled based on the cutting tool path geometry and validated experimentally with error less than 11%. The experimental results showed that the elliptical tool path improved the material removal rate by 11%, with a slight reduction in the maximum resultant cutting force by 3%. On the other hand, the walls waviness and surface roughness have been increased by 45% and 38% respectively as compared to the typical true trochoidal tool path. The introduction of linear paths at the elliptical path sides in the linear-elliptical tool path improved the performance index about 18 times by improving the material removal rate, waviness, and surface quality by 5%, 300%, and 74% respectively, without a significant effect on cutting forces. Therefore, the novel linear-elliptical paths are promising tool paths in increasing the performance of trochoidal milling due to the improved material removal rate, walls waviness, and surface quality, without a significant effect on cutting forces, which will improve the process machinability and cost-effectiveness.

Effects of process parameters on cutting forces, material removal rate, and specific energy in trochoidal milling

Trochoidal milling has been developed to enhance tool life during slot machining. It is characterized by reduced cutting forces, cutting temperature, and tool wear as compared to conventional milling processes. It is effective in machining difficult-to-cut materials, high-speed machining, and groove corners. However, this process has not been deeply investigated enough to discover its advantages and optimize its parameters. A full factorial design of 144 experiments has been applied in this paper to investigate extensively the effects of axial depth of cut, feed rate, and trochoidal step on material removal rate, cutting forces, and specific energy in trochoidal milling. Trochoidal step and axial depth of cut almost have the same contributions on cutting forces by 32% and 31% respectively, followed by feed rate by 25%. Feed rate, trochoidal step, and axial depth of cut influence the material removal rate by 37%, 30%, and by 19% respectively. The contributions of feed rate, trochoidal step, and axial depth of cut on relative specific energy are 57%, 24%, and 8% respectively. The increase of axial depth of cut increases the maximum resultant force till a threshold value, then it stabilizes. This behavior occurred due to the increase of the maximum engagement angle to a certain limit, then it does not increase any more. Both feed rate and trochoidal step linear affect maximum resultant force and material removal rate, while the relationships are non-linear for specific energy. It is recommended to machine slots in full depth with the highest possible trochoidal step and feed rate, considering the increase of tool wear and surface roughness. It is preferred to use a cutting tool of a large helix angle and small diameter to reduce the threshold axial depth of cut. Overall, this study is significant in characterizing, designing, and optimizing of trochoidal milling through experimental work.

Tool wear area estimation through in-process edge force coefficient in trochoidal milling of Inconel 718

The rapid wear and premature failure of the cutting tool are prone to happen due to increased forces during machining difficult-to-cut materials such as Inconel 718. The application of alternative toolpath such as trochoidal milling has significantly improved tool life and reduced the overall cycle time of the process. The wear pattern of the tool has a direct impact on the cutting forces, which increases with tool deterioration. The cutting forces in milling are modeled through the mechanistic force model and can be designated through a set of force coefficients, i.e. cutting and edge representing the shearing and ploughing phenomenon of metal removal. It has been established in the literature that tool wear has a considerable effect on the value of edge force coefficients. This paper aims to determine the in-process edge force coefficients for the trochoidal toolpath and correlates them with the corresponding flank wear area. The proposed correlation will further assist in predicting the level of flank wear area based on the force values in trochoidal milling.

A STUDY OF THE PHENOMENON BUE CREATION IN TROCHOIDAL MILLING

Aluminum alloy 6061-T6 is a commonly used material in various industries, including automotive parts manufacturing. However, its machining process can be challenging due to the occurrence of build-up edge (BUE) at the cutting edges. To address this issue, this research employed trochoidal milling to machine aluminum alloy 6061-T6 specimens, utilizing a small step over and a suitable depth of cut. The engagement of the tool during the machining process generates fluctuating forces, which consequently leads to fluctuations in temperature. This phenomenon is not only observed in trochoidal milling but also in conventional machining methods. The results indicate that the calculated maximum temperature (350°C) is lower than the aluminum's melting point (652°C). Moreover, the experimental results show minimal BUE formation on the cutting edge and an improved milling process.

Effects of Toolpath Parameters on Engagement Angle and Cutting Force in Ellipse-Based Trochoidal Milling of Titanium Alloy Ti-6Al-4V

Trochoidal milling is an efficient strategy for the rough machining of difficult-to-cut materials. The true trochoidal toolpath has C2 continuity and avoids sharp changes in engagement angle and cutting load, resulting in smooth machine tool movement. However, its total length is too long, and its engagement angle is uneven. These factors limit further improvements in the material removal rate. Based on the true trochoidal toolpath model, this paper develops an ellipse-based trochoidal toolpath generation method by introducing a compression ratio in the trochoidal step direction. The analytical model of engagement angle and the mechanistic model of the cutting force are proposed. A series of simulations and milling experiments were conducted to analyze the effects of toolpath parameters on the engagement angle and the cutting force. The results show that the compression ratio has the most significant effects. A compression ratio of 50% is optimal, using which the total toolpath length is reduced by 34.0%, and the variance of the engagement angle is reduced by 31.2% compared with that of the true trochoidal toolpath. The profile of the total cutting force corresponds to that of the engagement angle.

Investigation of conventional and ANN-based feed rate scheduling methods in trochoidal milling with cutting force and acceleration constraints

In CNC milling, the feed rate scheduling is a frequently used method to increase machining quality and efficiency. Among the benefits of feed rate scheduling, this paper focuses on controlling the tool load and optimizing the machining time. Although the advantages of feed rate scheduling are undeniable, some areas remain still to be addressed. In order to control the tool load, geometric methods are often used, which are based on keeping a specific parameter, such as chip thickness or material removal rate (MRR) constant. However, a high level of tool load control can only be provided if cutting force models or experimental-based techniques are used. Besides traditional methods, this paper presents an artificial neural network (ANN)-based feed rate scheduling method to keep the tool load constant, using data gained by preliminary cutting experiments. A case study demonstrates that a significantly higher level of tool load control can be achieved with this method as compared to the geometric models. Besides controlling the tool load, the present feed rate scheduling method also addresses the consideration of acceleration limits which is of great importance for practical uses. The application of feed rate scheduling in trochoidal milling is also discussed in detail in this paper. This area has not received enough attention, as due to the limited fluctuation of cutter engagement, the tool load was considered as well-controlled. However, experiments have shown that in the case of trochoidal milling, the introduction of feed rate scheduling can still further increase the machining efficiency. Using the developed ANN-based feed rate scheduling method, significant progress could be made as compared to conventional technologies in controlling the cutting force and optimizing the machining time. In the present case study, a reduction of 50% in machining time was achievable by adjusting the feed rate without increasing the peak value of cutting force.

A new trochoidal toolpath in milling operations

The milling is a widely used method in the manufacturing industry, especially in the production of complex engravings such as die&molds. Rough milling often requires a large material removal rate in a short time. This purpose also requires the selection and use of the best milling tool path. Today, trochoidal milling is receiving more attention than conventional milling, especially as it significantly increases tool life. In this study, a new toolpath model for trochoidal milling is suggested and this proposed toolpath model is examined in terms of cutting temperature, cutting force, surface quality, tool wear. In this new trochoidal toolpath model proposed for the milling method, the cutting force did not change much compared to the standard trochoidal tool path, but better surface quality and less tool wear were observed.

A double-NURBS approach to the generation of trochoidal tool path

Trochoidal milling becomes a popular strategy in high-speed rough milling, thanks to its advantages in lowering cutting force (and tool wear) and increasing tool life. However, it also suffers from the disadvantages of low cutting efficiency and prolonged machining time due to its reduced cutter-workpiece engagement in the cutting area and the idle tool path in the non-cutting area. In this paper, a new trochoidal tool path generation method is proposed based on a double-NURBS curve. Unlike traditional circular trochoidal tool path that combines circular and linear paths to approximate the trochoidal path, the double-NURBS tool path can truly represent a trochoidal path with C2 continuity throughout the entire tool path. In the front cutting area, the control points of the NURBS are modified to increase the cutter-workpiece engagement angles; in the rear non-active area, the NURBS curve is modified to shorten the non-cutting distance and the machining time. Degree elevation of the NURBS circle from 2 to 3 maintains C2 continuity to ensure the machining is smooth throughout all transitions. Cutting force simulations and pocket machining experiments are carried out to validate that the proposed double-NURBS approach deliver the expected result and performance.

High- performance manufacturing with trochoidal milling strategies

Along with technological progress, manufacturing processes have been constantly innovated, hoping to reduce manufacturing time, extend the useful life of tools and offer high quality finishes of the product, however, information on the product is scarce. Machined in 7075 - T6 aluminum, which, due to its mechanical properties, is more used for the manufacture of molds and dies than other materials. In this project, a high-performance machining is studied, improving cycle times by comparing trochoidal and conventional milling roughing strategies, without the use of coolants that can contaminate the chip allowing the recycling of material, these strategies are found in a large part of CAM software. The experimentation was carried out in a Hision CFV 1100 vertical machining center with Fanuc Oi MF control, supported by the Taguchi L18 methodology for the milling parameters and roughing strategy. 9 tests were carried out for each strategy with a 25 mm flat cutting tool with 4 high speed steel (HSS) lips based on the 3 levels of the milling parameters, in the range of 800 m / min to 1000 m / min, with a feed per tooth of 0.25 to 0.35 mm / tooth. The results obtained for both time and temperature have a behavior described by Mr. Salomón for high-speed machining (HSM), an ANOVA statistical analysis was carried out that determined that the trochoidal machining strategy presents a reduction in the 93.27% compared to the conventional machining strategy and a stable temperature of 25ºC in the cutting tool.

Influence of trochoidal milling parameters on tool load

In recent years, there has been an increasing interest in high-production technologies, including trochoidal milling. As it provides high productivity even when cutting difficult-to-machine materials, this method has high potential. The research is aimed the issue of the variation of trochoidal milling parameters on tool load. The trochoid pitch and the engagement angle are the process-defining parameters in trochoid milling and their appropriate adjustment can optimize the production process. The effect of trochoidal milling on surface quality has been demonstrated in previous research.

Bézier curve-based trochoidal tool path optimization using stochastic hill climbing algorithm

Trochoidal milling is a widely used technique in high-speed machining. In the recent period, several theoretical and experimental studies have been performed to analyze the cutting process in trochoidal milling of slot-like geometries. However, these works typically focused only on cycloid- and circular-shaped trochoidal strategies and did not consider the possibilities of path shape optimization. This is because optimizing the trochoidal tool path is a double challenge: (1) modelling of material removal process is necessary to satisfy the geometrical and technological conditions, and (2) the relationship between tool path shape and machining efficiency is highly complex; therefore, direct optimization solutions cannot be applied.This paper presents a new Bézier curve-based tool path modelling technique and a new stochastic hill climbing algorithm-based optimization method to increase the efficiency of trochoidal strategy. During the tool path shape optimization, the limiting factors of cutter engagement and path curvature radius were also considered to meet the criteria of high-speed machining. The simulation experiments proved that the machining efficiency could be increased significantly by optimizing the trochoidal tool path by up to 40%, compared to the traditional cycloid strategy. The cutting experiments verified that the tool load remained well controlled, and productivity could be improved without increasing the tool load. The paper also discusses the appropriate settings to ensure the best functioning of the stochastic hill climbing algorithm. The industrial application of the developed algorithm can result in significant cost, energy and time savings for manufacturers when machining slot-like geometries.

Monitoring the Performance of the Drive Mechanisms During CNC Milling

The article deals with a monitoring system designed for the needs of a specific production plant. Its primary purpose is to provide online information about ongoing production processes at monitored workplaces. The system will make it possible to monitor the usability of the machines and the load on individual machine elements to increase production efficiency and prevent machine breakdowns. Furthermore, it will allow to monitor the load on the tool and predict its wear in order to prevent irreversible damage and the production of scrap. To test the applicability of the system on a milling machine, a sample was designed, the elements of which were produced in two ways - HPC and trochoidal milling. With these methods of milling, different manifestations of the tool load were assumed. The experiments proved the functionality of the system. The method of transmission, recording and storage of data has proven to be fully functional. The additional results were knowledge of machine load during both milling methods.