Ahmed A. D. Sarhan

Interrelationships between cutting force variation and tool wear in end-milling

Wear of a cutting edge in end-milling is a complicated process that requires a reliable technique for in process monitoring and control of the cutter performance. This paper presents an approach to examine the effect of wear variation on the magnitude of the cutting force harmonics. This approach implies a cutting force based model of end mill wear using computer simulation as function of axial depth of cut, feed rate per tooth, specific cutting pressure of work material and instantaneous angle of rotation. The results were plotted at various cutting conditions in time and frequency domains. Cutting forces in end-milling were measured using highly sensitive strain gauge dynamometer which was calibrated in static and dynamic ranges. The tool wear was measured in an off-line manner and interrelationships of cutting force harmonics and tool wear magnitude were constructed and were found comparable with the computer simulation results. Hence a cutter wear monitoring strategy is constructed.

Fabrication and deformation behaviour of multilayer Al2O3/ Ti/TiO2 nanotube arrays

In this study, titanium thin films were deposited on alumina substrates by radio frequency (RF) magnetron sputtering. The mechanical properties of the Ti coatings were evaluated in terms of adhesion strength at various RF powers, temperatures, and substrate bias voltages. The coating conditions of 400W of RF power, 250°C, and a 75V substrate bias voltage produced the strongest coating adhesion, as obtained by the Taguchi optimisation method. TiO2 nanotube arrays were grown as a second layer on the Ti substrates using electrochemical anodisation at a constant potential of 20V and anodisation times of 15min, 45min, and 75min in a NH4F electrolyte solution (75 ethylene glycol: 25 water). The anodised titanium was annealed at 450°C and 650°C in a N2 gas furnace to obtain different phases of titania, anatase and rutile, respectively. The mechanical properties of the anodised layer were investigated by nanoindentation. The results indicate that Youngs modulus and hardness increased with annealing temperature to 650°C.

A Study on Surface Modification of Al7075-T6 Alloy against Fretting Fatigue Phenomenon

Aircraft engines, fuselage, automobile parts, and energy saving strategies in general have promoted the interest and research in the field of lightweight materials, typically on alloys based on aluminum. Aluminum alloy itself does not have suitable wear resistance; therefore, it is necessary to enhance surface properties for practical applications, particularly when aluminum is in contact with other parts. Fretting fatigue phenomenon occurs when two surfaces are in contact with each other and one or both parts are subjected to cyclic load. Fretting drastically decreases the fatigue life of materials. Therefore, investigating the fretting fatigue life of materials is an important subject. Applying surface modification methods is anticipated to be a supreme solution to gradually decreasing fretting damage. In this paper, the authors would like to review methods employed so far to diminish the effect of fretting on the fatigue life of Al7075-T6 alloy. The methods include deep rolling, shot peening, laser shock peening, and thin film hard coatings. The surface coatings techniques are comprising physical vapor deposition (PVD), hard anodizing, ion-beam-enhanced deposition (IBED), and nitriding.

Sensor-less force-reflecting macro–micro telemanipulation systems by piezoelectric actuators

This paper establishes a novel control strategy for a nonlinear bilateral macro-micro teleoperation system with time delay. Besides position and velocity signals, force signals are additionally utilized in the control scheme. This modification significantly improves the poor transparency during contact with the environment. To eliminate external force measurement, a force estimation algorithm is proposed for the master and slave robots. The closed loop stability of the nonlinear micro-micro teleoperation system with the proposed control scheme is investigated employing the Lyapunov theory. Consequently, the experimental results verify the efficiency of the new control scheme in free motion and during collision between the slave robot and the environment of slave robot with environment, and the efficiency of the force estimation algorithm.

Compensation Method of the Machine Tool Spindle Thermal Displacement for Accurate Monitoring of Cutting Forces

In this research work, the authors use displacement sensors in the spindle structure to monitor cutting forces for intelligent machining. However, the monitoring quality in the long term is a problem because sensor signals involve offset drift, which is mainly attributable to the thermal displacement of the spindle. To solve this problem, we attached thermal sensors in the machine and cooling system. The estimation of the spindle thermal displacement based on temperature data from these thermal sensors can provide more information for monitoring of cutting forces. For accurate monitoring of cutting forces, thermal displacement compensation scheme is proposed, and the monitoring tests of cutting forces in end milling operations are carried out as cases study. With thermal displacement compensation scheme implemented, the experimental result shows that the monitoring of small and medium scale cutting forces is possible, if cutting process is intermittent.

Experimental Study on Minimizing Edge Chipping in Glass Milling Operation Using an Internal CBN Grinding Tool

Glass is one of the most difficult materials to be machined due to its brittle nature and unique structure as frequent occurrence of fracture and edge chipping during machining has to be avoided. To minimize edge chipping of the machined glass, which is common when cutting materials harder than 50 HRC, adopting right parameters is required followed by additional effort and cost. This article presents experimentation in minimizing the edge chipping for glass milling operations using an internal cubic boron nitride grinding tool by optimizing the machining parameters. Taguchi optimization method is the most effective method to optimize the machining parameters, in which the most significant response variables affecting edge chipping could be identified. In glass milling operation, several machining parameters are considered to be significant in affecting edge chipping. These parameters include lubrication pressure and direction, feed rate, spindle speed, and depth of cut. The standard orthogonal array of L 16 (44) is used, while the signal-to-noise response analysis and analysis of variance methods are carried out to determine which parameters are statistically significant. Finally, confirmation tests are carried out to investigate the optimization improvements.

Multi-objective selection and structural optimization of the gantry in a gantry machine tool for improving static, dynamic, and weight and cost performance

In this investigation, the multi-objective selection and optimization of a gantry machine tool is achieved by analytic hierarchy process, multi-objective genetic algorithm, and Pareto-Edgeworth-Grierson–multi-criteria decision-making method. The objectives include maximum static deformation, the first four natural frequencies, mass, and fabrication cost of the gantry. Further structural optimization of the best configuration was accomplished using multi-objective genetic algorithm to improve all objectives except cost. The result of sensitivity analysis reveals the major contribution of columns of gantry with respect to the crossbeam’s contribution. After determining the most effective geometrical parameters using sensitivity analysis, multi-objective genetic algorithm was performed to obtain the Pareto-optimal solutions. In order to choose the final configuration, Pareto-Edgeworth-Grierson–multi-criteria decision-making was applied. The procedure outlined in this article could be used for selection and optimization of gantry as quantitative method as opposed to traditional qualitative method exploited in industrial application for design of gantry.

Optimizing the Machining Parameters in Glass Grinding Operation on the CNC Milling Machine for Best Surface Roughness

Glass is one of the most difficult materials to be machined due to its brittle nature and unique structure such that the fracture is often occurred during machining and the surface finish produced is often poor. CNC milling machine is possible to be used with several parameters making the machining process on the glass special compared to other machining process. However, the application of grinding process on the CNC milling machine would be an ideal solution in generating special products with good surface roughness. This paper studies how to optimize the different machining parameters in glass grinding operation on CNC machine seeking for best surface roughness. These parameters include the spindle speed, feed rate, depth of cut, lubrication mode, tool type, tool diameter and tool wear. To optimize these machining parameters in which the most significant parameters affecting the surface roughness can be identified, Taguchi optimization method is used with the orthogonal array of L8(26). However, to obtain the most optimum parameters for best surface roughness, the signal to noise (S/N) response analysis and Pareto analysis of variance (ANOVA) methods are implemented. Finally, the confirmation test is carried out to investigate the improvement of the optimization. The results showed an improvement of 8.91 % in the measured surface roughness.

Novel uses of SiO2 nanolubrication in end milling of medium carbon steel for higher compressive residual stress measured by high-energy X-ray diffraction data

Milling is a machining process that removes any desired material from the surface by using relative motion between a work piece and a rotating cutter where the cutting tool intermittently enters and leaves the work piece. The milling process operates in two modes, namely, conventional (up) mode and climb (down) mode. Both modes are known for their significant effects on surface integrity due to the entering movement of the cutting tool and the formation of the chips during cutting process. Use of flood lubrication can improve the residual stress and surface quality of the component. It controls the temperature in cutting zone, reduces the power required, washes away chips, and reduces friction between chips, tools, and workpieces. Moreover, it has a great effect on the environment too. Minimum quantity lubrication can be used as an alternative of lubrication for clean machining. With an addition of nanoparticles into the minimum quantity lubrication, it is expected to enhance the machining performance that meets the environmental friendly purposes. Residual stresses remain in a solid material in the absence of external loading or thermal gradients, which is sometimes undesirable. The presence of compressive residual stresses is beneficial, while the presence of tensile stresses is detrimental. In order to study the residual stress and its relation with the surface quality (after milling process), the effects of reduced oil consumption in minimum quantity lubrication and the addition of SiO2 nanoparticles in minimum quantity lubrication for clean machining are presented in this research. Results indicate that there is an improvement in residual stresses and surface quality especially during conventional (up) milling under minimum quantity lubrication and minimum quantity lubrication–SiO2 nanolubrication condition.

Continuous dynamic modelling of bimorph piezoelectric cantilevered actuators considering hysteresis effect and dynamic behaviour analysis

Bimorph Piezoelectric Cantilevered (BPC) actuators have been of increasing interest in micro-manipulation processes during recent years. Due to properties such as transverse vibration, the performance and manoeuvrability have considerably improved, compared with conventional longitudinal piezoelectric actuators. Therefore, dynamic modelling of such actuators has been the centre of attraction. For this purpose, a target point on the actuator, e.g. the cantilever end tip, is usually considered as the actuator output. One degree of freedom lumped and continuous type dynamic models have been considered in prior research works. These types of modelling lead to two significant issues. First, the effect of higher vibrational modes in the actuator output is disregarded. Second, a minimum phase dynamic system is achievable for all target points regardless of position. In this paper, these two issues will be analytically and experimentally investigated. To this end, a linear continuous dynamic model for a general BPC actuator is derived and discretized by attaining exact mode shapes. The Prandtl–Ishlinskii (PI) model is utilized to model and identify the non-linear hysteresis behaviour. In contrast to previous works, dynamic behaviour analysis elaborates on the effect of higher modes in the actuator output response. In addition, the possibility of non-minimum phase behaviour based on the location of the target point is investigated. Simulation studies and experimental results confirm the validity of the proposed dynamic model and its behaviour analysis.