Slot Milling Research Articles

A comparative study on the cutting force coefficient identification between trochoidal and slot milling

Cutting force modeling is of great importance to understanding the mechanistic behavior of the milling process. Through the understanding of cutting forces the potential for process improvement by way of tool life, surface finish, dimensional accuracy and machining time is opened. The basis for establishing cutting force models lies in the method of gathering cutting force coefficients, of which literature has two main approaches, both of which occur under full engagement: linear-direction slotting cuts. The geometry of the uncut chip has a strong dependency on the toolpath, particularly for trochoidal milling techniques, where the chips do not exhibit the repeating and somewhat invariant thickness profile that occurs in slotting. Gathering cutting force coefficients for trochoidal milling remains largely unexplored and is the focus of this paper, particularly to establish an understanding of cutting parameters and coefficient values among different toolpath techniques. It was found that matching the tool feed and speed between trochoidal and slotting toolpaths produces large differences, which are reduced when using slotting parameters based on trochoidal milling chip geometry conditions, with the closest agreement resulting from matching the maximum chip thicknesses. Furthermore, the method of gathering coefficients produces similar results between single and double flute trochoidal, which are both less than the coefficients resulting from slotting tests.

Milling of Fir-Tree Slots in Allvac 718 plus

For the machining of profiled grooves in turbine discs made out of nickel based alloys, broaching is still state of the art. However, the broaching process entails some disadvantages like high costs and long delivery times for the machine tools and the broaches in combination with inflexibility with regard to the groove geometry and machining task. An alternative to the broaching process is the integration of the profile slotting on a 5-axis milling center. This paper deals with an approach for machining a fir-tree slot via different milling process chains. The two roughing strategies, ceramic side milling and carbide end milling, are depicted with regard to tool wear and the economy. The finished fir-tree slot will be evaluated in terms of dimensional stability. In addition, the possibility of finish broaching on a five-axis machine tool is shown.

Tool wear prediction in end milling of Ti-6Al-4V through Kalman filter based fusion of texture features and cutting forces

The current trend of Industry 4.0 development requires an integration of the process sensing technologies with the cloud computing network to design the cyber-physical systems which can seamlessly transfer data between the connected devices. This will pave a way for real-time process monitoring as well as the control of the process by the use of decision-making algorithms. The current paper explores the opportunities with this regard in the area of tool wear prediction in end milling of Ti-6Al-4V alloy at various operating conditions. A series of slot milling passes were made at various parameter combinations of feed, speed, and depth of cut until the flank wear on tool crosses the failure criterion. The cutting force data acquired in the process with the dynamometer and the texture features from the image of the milled surface are used to build a model for predicting the flank wear through the Kalman filter approach. The fusion model built using the Kalman filter methodology achieves a good accuracy in predicting the flank wear on the tool. The model is highly accurate in predicting the wear as the tool approaches the failure threshold. Thus the model can enable the decision control module to trigger a tool change signal and improve the overall productivity of the process.

Analyzing the performance of self-developed cermet micro end mills in machining of TC4 alloy micro-grooves

A Ti(C7N3)-based cermet micro end mills with a diameter of 0.5 mm has been developed and its cutting edge radius is ranging from 1.63 to 2.08 μm. The micro-cutting performance of cermet micro end mills has been evaluated by comparing their performance with commercial coated WC micro end mills (MXH230, NS Company, Japan) in dry slot milling of TC4 alloy. Tool damage, micro-milling forces, and surface quality of micro-grooves were analyzed exhaustively. It showed that the main wear mechanisms of cermet and coated WC micro-mills were dominated by micro chipping and adhesive wear. And flank wear and the tool coating failure were also found on coated WC micro end mills. The Peak-to-Valley (P-to-V) feed, normal and axial forces using cermet and coated WC micro-mills had a zig-zag pattern of increase with cutting distance. Micro-grooves milled by cermet micro end mills could achieve a higher surface quality with Ra around 92.6 nm and relatively smaller top burr compared with that manufactured by coated WC micro end mills during the whole machining, which was quite difference with the wrong combination of ceramic cutting tool and titanium alloys in macro machining. These results indicated that cermet micro end mills having 0.5 mm diameter were more suitable for micro-milling TC4 alloy than commercial coated WC micro end mills, indicated that the material of Ti(C7N3)-based cermet can be used to commercially fabricate micro end mills to machine TC4 alloy.

Neural Network Based Modelling of Time Optimal Interpolation of Non-linear Trajectory

Non linear curve fitting for execution of milling operation on Computer Numerical Control machining is always challenging. This paper focuses on fitting nonlinear curve and generation of time optimal trajectory to perform slot milling operation using NX CAM. Virtual simulation of trajectory is tested with various experimentation conditions and executed using Siemens 828D controller. Simulation and actual experimentation result is then compared with Multilayered Perceptron based Neural Network and optimum cutting parameters for time optimal trajectory is calculated.

An investigation on the cutting force of milling Inconel 718

Inconel alloy has been widely used in industry but is difficult to machine due to its rapid change in cutting force during machining. This paper investigated the cutting force for milling Inconel 718 as conventional force model is unable to handle the above situation. Theorectical force model is first reviewed and two-phase experiments of slot milling based on dry cutting are designed to measure the cutting force and the specific cutting force. Experiments in phase I are designed based on Taguchi method with spindle speed, feedrate per cutting edge and depth of cut as experimental parameters. The results showed that the first two parameters play more important roles in the cutting force. A phase II exhaust experiments is designed with spindle speed set from 400 to 800 rpm while the feedrate per cutting edge is set from 0.04 to 0.08 mm/tooth. The results are concluded as the following. (i) There exists a strong size effect in milling Inconel 718 as the cutting force changed with the chip thickness. Specific cutting force is larger at small thickness of cut and become smaller when the thickness increases. (ii) A 2ndorder non-linear cutting force model, which takes spindle speed N and feedrate fzinto account, for milling Inconel 718 is derived from the measured data and represented as Ft(N, fz)= (13910 -3.1N - 109900fz - 0.0028N2 +23.9Nfz+434500fz2) xapxh. The derived force model compensates the inaccuracy of conventional force model.

Limits to simplified calculation of uncut chip thickness in milling

Modelling of forces and temperatures for mechanical cutting processes is mainly based on the prevailing local uncut chip geometry. In this context, most researchers use a simplified equation for calculating the uncut chip thickness in milling processes, which neglects the tool movement in feed direction and simplifies the chip thickness. The simplified equation can be easily evaluated, but also adds errors to the calculation results. These errors are typically neglected without knowledge of their exact size. However, the resulting error is dependent on the cutting parameters like cutting speed, tool feed and radial tool engagement and can be very large. In order to quantify the resulting error for different cutting conditions, a novel approach for a more precise calculation of the uncut chip thickness is presented in this paper. Using this new calculation model the uncut chip thickness is determined for industrial relevant cutting parameters and tool dimensions in the first step. The second step includes the direct comparison of the calculated values to the simplified calculation. In this way, the resulting error is illustrated for different cutting situations, mainly focusing on full slot milling and the contact area, where the workpiece surface is generated. As a result, limits for the application of the simplified engagement calculation are presented. In case the limits are exceeded, a more complex and more accurate calculation of the uncut chip thickness has to be used.

3D Eulerian Finite Element Modelling of End Milling

In this article, a 3-dimensional Eulerian finite element method (FEM) model is introduced for simulation of end milling processes based on Abaqus/Explicit. Through the Coupled Eulerian Lagrangian (CEL) approach in model formulation, the chip formation process does not rely on the degradation of material or continuous remeshing algorithms to achieve chip separation. The process under investigation is the slot milling of Al6061-T6. A linear motion of the workpiece is adopted as a simplification of the trochoidal motion of the end mill. The workpiece is given a sinusoidal profile to achieve a varying uncut chip thickness in the cutting process. With a stationary tool and a confined region of mesh refinement, the computational cost of the model can be minimized. The model demonstrates good accuracy in cutting force predictions. The prediction error of the resultant cutting forces can be controlled within 12%. The proposed model also gives accurate predictions in terms of the morphology of chips. The excessive curling of chips in the early stages of chip formation can be predicted in the simulation process. The information obtained from the FEM model will provide more insights into the interactions between the cutting tool and the workpiece.

Tool wear performance and surface integrity studies for milling DD5 Ni-based single crystal superalloy

Based on the results of slot milling experiments on the DD5 Ni-based single crystal superalloy (001) crystal plane along the [110] crystal direction, in this paper, efforts were devoted to investigate the tool wear process, wear mechanism and failure modes of the physical vapor deposition (PVD)-AlTiN and TiAlN coated tools under dry milling and water-based minimum quantity lubrication (MQL) conditions. The scanning electron microscope (SEM) morphological observation and energy dispersive X-ray spectroscopy (EDX) elements analysis methods were adopted. Moreover, under the water-based MQL condition, the surface integrity such as surface roughness, dimensional and shape accuracy, microhardness and microstructure alteration were researched. The results demonstrated that the tool edge severe adhesion with the work material, induced by the high Al content in the PVD-AlTiN coating caused the catastrophic tool tip fracture. In contrast, the PVD-TiAlN tool displayed a steady and uniform minor flank wear, even though the material peeling and slight chipping also occurred in the final stage. In addition, due to the high effective cooling and lubricating actions of the water-based MQL method, the PVD-TiAlN coated tool demonstrated intact tip geometry; consequently it could be repaired and reused even if the failure criterion was attained. Moreover, as the accumulative milling length and the tool wear increased, all indicators of the surface integrity forehand were deteriorated.

A study on the effect of feed rate and cutting speed on surface roughness and material removal rate of mild steel

In any machining process, achieving a good surface quality and maximization of material removal rate are absolute importance. This paper provides an insight to the effect of feed rate and cutting speed on NOVIANO and conventional cutting tool in term of surface roughness and Material Removal Rate (MRR). The output of the machining during slot milling of Mild Steel with 17 HRC were measured. Mitutoyo surface tester were used to measure average mean surface roughness (Ra) of the slot milling surface. For the MRR measurement, mathematical formula was used to calculate and evaluate the different weight of workpiece before and after milling. The result shows that, when the feed rate and cutting speed increase, better surface roughness and MRR will be occur. However, the comparison between both cutting tools found that the NOVIANO cutting tool produce much better result than conventional cutting tool where surface roughness and MRR is 13.97% and 51.62%.

Development of cutting force prediction model for vibration-assisted slot milling of carbon fiber reinforced polymers

Carbon fiber reinforced polymers (CFRP) have got rapidly increased applications in aerospace/aircraft and other fields due to their attractive properties of high specific strength/stiffness, high corrosion resistance, and low thermal expansion. These materials have also some challenging properties like heterogeneity, anisotropy, and low heat dissipation. Due to these properties, the issues of excessive cutting forces and machining damages (delamination, fiber pull-out, surface/subsurface defects, etc.) are encountered in machining. The cutting forces are required to be minimized for qualified machining with reduced damages. In this research, a novel cutting force prediction model has been developed for vibration-assisted slot milling. The experimental machining has been carried out on CFRP-T700 composite material. The effective cutting time per vibration cycle and the force of friction have been expressed/calculated. The feasibility of vibration-assisted machining for CFRP composites has also been evaluated. The relationships of the axial and feed cutting forces with machining parameters were investigated. The results have shown the variations below 10% among experimental and corresponding simulation values (from the model) of cutting forces. However, the higher variations have been found in some experiments which are mainly due to heterogeneity, anisotropy, and some other properties of such materials. The developed cutting force model then validated through pilot experiments and found the same results. So, the developed cutting force model is robust and can be applied to predict cutting forces and optimization for vibration-assisted slot milling of CFRP composite materials at the industry level.

Development of cutting force prediction model for carbon fiber reinforced polymers based on rotary ultrasonic slot milling

ABSTRACTCarbon fiber reinforced polymers (CFRP) have got widely increased applications in aviation, defense and other industries due to their properties of high specific strength/stiffness, high corrosion resistance and low-thermal expansion. The issues like excessive cutting forces and machining damages are encountered in machining due to heterogeneity, anisotropy and low heat dissipation of these materials. The cutting forces are required to be predicted/minimized through modeling. In this article, the novel axial and feed cutting force model has been developed and validated through rotary ultrasonic slot milling of CFRP composites. The variations less than 10% have been found between the measured and corresponding simulated values of the cutting forces. However, some higher variations have also been observed in the few cases mainly due to heterogeneity and anisotropy of such material. The cutting depth is a significant parameter for axial and feed forces, while the feed rate is significant for the axial force. Both the forces decreased with the increase of spindle speed, while they increased with the increase of feed rate and cutting depth. The developed models have been found to be robust and can be applied to optimize the cutting forces for such materials at the industry level.

Studies on the effect of mill microstructure upon tool life during slot milling of Ti6Al4V alloy parts

Studies on the effect of mill microstructure upon tool life during slot milling of Ti6Al4V alloy parts

Milling performance optimization of DD5 Ni-based single-crystal superalloy

DD5 Ni-based single-crystal superalloy has presented a wide application prospect in aerospace, marine, nuclear reactor, and chemical industries due to its excellent comprehensive performances caused by the crystal boundary as the crack source complete elimination. However, because of the low thermal conductivity and strong adhesion characteristic, DD5 is difficult to machine and the research on this field is still blank. Therefore, the purpose of this paper is to investigate the material machining mechanism and optimize the milling performance. Based on the DD5 metallographic structure characteristics, the directional cutting method was proposed firstly. Then, considering the wear characteristic and failure mode of the tools with different coating materials, the milling tool proper selection was executed. Moreover, combining with the molecular dynamics (MD) simulation, slot milling experiments, and slip system theory, the best milling path was confirmed. In addition, considering the machining environmental sustainability, the milling performances acquired under the dry, minimal quantity lubrication (MQL) and water-based MQL conditions were evaluated and compared. Finally, in order to optimize the machining parameter sequence quantitatively and ascertain the milling and cooling interactive effect mechanism, response surface method (RSM), back-propagation artificial neural network (BP-ANN), genetic algorithm (GA), and uniform design experiments were all adopted. With the anticipation to improve environmental sustainability and milling performance simultaneously, the milling experiments on the DD5 (001) crystal plane along the [110] crystal direction under the water-based MQL technology with PVD-TiAlN-coated tools were conducted and the parameters of main spindle linear speed v c = 20 m/min, tool feed per tooth f = 8.97 μm, oil flow rate Q = 68.21 ml/h, the ratio of water and oil R = 0.94 and the air pressure P = 1.79 bar were used. Then, the better surface roughness Sa = 2.05 μm and the lower milling force F = 14.38 N can be acquired simultaneously based on the verification of the uniform design experiment results.

The Effect of Cutting Fluids and Cutting Speeds to The Vibrations of Milling CNC Machine

Vibration that occur in machining process is forced vibration. This vibration caused by external force excitation. External force that cause vibration in machining process is cutting force. This research was aims to determine the effect of cutting fluids and cutting speeds to vibration in milling process. The specimens were made using a cutting process type face milling, profile milling, pocket milling, and slot milling. Cutting speeds was variated at 62.83 m/min; 110 m/min; 157.14 m/min; 188.5 m/min. Vibration testing was done using the accelerometer sensor. Vibration response taken is the amplitude. The results show any type of cutting process has a different amplitude. Face milling has the smallest amplitude while slot milling has the biggest one. At cutting speeds parameter, the faster of cutting speeds the smaller of the amplitude. The use of cutting fluids can reduce the friction value between cutting tool and workpiece so that the cutting force will decrease. The use of cutting fluids causing the smaller the cutting force. The increase of the cutting force will cause greater vibration

Experimental study on effects of fiber cutting angle in milling of high-strength unidirectional carbon fiber–reinforced polymer laminates

It is still a challenge to machine high-strength carbon fiber–reinforced polymer with high quality due to its poor machinability. Fiber direction is the critical factor. This article aims to investigate the effects of fiber cutting angle in milling of high-strength unidirectional carbon fiber–reinforced polymer laminates with regard to milling forces, machined surface morphology and surface roughness. The edge trimming and slot milling tests were conducted. The largest radial and tangential forces were observed on 135° fiber cutting angle followed by 90° while the smallest milling forces were observed on 45° fiber cutting angle. Totally, four basic material fracture mechanisms, that is, fiber–matrix debonding, bending-induced fiber fracture, shear-induced fiber fracture and compression-induced fiber fracture, were observed by the analysis of fracture morphology for a single fiber. The four basic material fracture mechanisms dominate the material fracture behavior during the cutting of carbon fiber–reinforced polymer. Besides, it is indicated that surface roughness of the machined surfaces is highly related to the type of the surface defects. Surface cavities caused by fiber–matrix debonding and bending-induced fiber fractures on 45° fiber cutting angle were observed to be the main factors leading to the decline of surface finish in milling of carbon fiber–reinforced polymer laminates.

The cutting force and defect analysis in milling of carbon fiber-reinforced polymer (CFRP) composite

Carbon fiber-reinforced polymer (CFRP) composite parts are usually made as near-net shape in aerospace and astronautic industry. However, mechanical machining such as milling is often required for part finishing in order to meet the dimensional accuracy before assembly. The milling process is vulnerable to damage like fiber breakage and pullout, and delamination. The cutting force is generally recognized as an indicator of machinability for milling of CFRP. In this study, slot milling of unidirectional CFRP was conducted with different cutting orientations and conditions. The patterns of cutting force and resulting defects along with the inherent mechanism are investigated. A mechanistic milling force model is proposed in which the specific cutting energies are modeled and calibrated considering the instantaneous chip thickness, fiber cutting angle, and cutting speed. The model is applicable to force prediction in milling both unidirectional CFRP and multi-directional CFRP.

To characterize and optimize the surface quality attributes in slot milling operation

Burr formation and surface roughness are crucial surface quality attributes that vary widely according to machining conditions used. Inappropriate selection of cutting parameters may lead to tremendous non-desirable expenses and poor product quality. This becomes more apparent in slot milling operation that has a complex burr formation mechanism, and it is associated with multiple burrs with non-uniform dimensions appearing in the machined part edges. Therefore, as the first objective of this study, experimental characterization of governing cutting parameters on surface quality attributes, including exit burr size as well average surface roughness (R a ), is presented. Based on experimental observations, each aforementioned surface quality attribute is affected by different cutting parameters, and in fact, no systematic relationship can be formulated between them and the cutting parameters used. Therefore, advanced strategies are demanded for adequate selection of cutting parameters and reduction in the needs of deburring and surface treatment operations. Except the works reported by the authors, very limited studies are available on advanced optimization approaches for simultaneous minimization of surface quality attributes in slot milling operations. This can be considered as the second objective of this work. To that end, desirability function, D i (x), was used as the proposed approach to evaluate the possibility of simultaneous minimization of aforementioned surface quality attributes, despite the low control ability of each response. Using this approach, the optimum and near to optimum setting levels of cutting parameters were defined by means of surface quality improvement and the adequacy of the proposed optimum cutting conditions was reconfirmed through verification tests. The presented results in principle can be very useful in practice by local and international automotive industries dealing with similar family of materials.

Cycle Time and Cost Reduction of Ball Turning Operation of Cardan Shaft

The previous productivity of CNC used for ball turning was comparatively lesser which caused the use ofrunning load on next operation that is Slot milling and thereby reducing its Overall Equipment Efficiency(OEE). Here we found the scope of improvisation in order to reduce the cycle time to increase theproductivity. Previously insert of 0.8 mm radius was used which was later replaced by insert of 1.2 mmradius and also the number of strokes required to turn the ball were reduced to 2 from 3 reducing the cycletime from 30 seconds to 21 seconds.

Modelling of energy demand from computer numerical control (CNC) toolpaths

It is important to accurately model the total electrical energy requirements in order to compare and select the least energy consumption toolpath in a manufacturing process. To enable this goal in this study, a feed axes energy demand model (which incorporates the weights of feed axes, machine vice, and workpiece) proposed in previous work by the authors was integrated and used to refine the energy consumption models for machine tools to analytically estimate the power and processing time, and hence energy required to execute a CNC toolpath. Furthermore, an algorithm for establishing energy prediction software with regards to numerical control (NC) codes was developed based on the proposed energy consumption model. The NC-code based analytical model and energy prediction software were both validated by undertaking slot milling of a 2D half bottle toolpath. Results show that shorter linear path lengths (i.e. G01) and circular path segments (i.e. G02 and G03 codes) were highly energy intensive. This is because for short length segments, the maximum feedrate may not be reached due to constraints imposed by acceleration and deceleration; the weights carried take a higher share of the load, and therefore increase the inertia effects on the drive. Thus, energy intensity in machining could be significantly reduced by selecting toolpaths with longer linear path segments. The knowledge obtained in this study would enable machining engineers to predict the electrical energy for toolpaths and hence enable selection of toolpaths for reduction of electrical energy demand in machining.