Change Of Cutting Depth Research Articles

Experimental study on rock drilling vibration of PDC bit in interbedded formations

Mastering the vibration characteristics of PDC bit, especially in interbedded formations, can help to explore reasonable bit failure control measures, achieve bit optimization and drilling optimization. This work used single rocks to construct different types of vertical and horizontal interbedded rocks with different interbedded properties, the experimental study obtained the bit vibration characteristics under single rock, sudden-changed rock, and alternating rock conditions. The vibration acceleration of a single rock is consistent with the rock strength. The acceleration increases with the increase of weight-on-bit and rotary speed, the influence of weight-on-bit is greater than that of rotary speed. The maximum amplitude of accelerations always occurs in the low frequency range of 0∼300 Hz, the difference between rocks is mainly reflected in the high frequency range greater than 400 Hz. When the drill bit suddenly crosses from soft rock to hard rock in the vertical interbedded formation, the acceleration increases rapidly, causing direct impact. When the drill bit suddenly crosses from hard rock to soft rock, the impact and acceleration attenuates slowly, which could cause fatigue damage to the drill bit and induce high-frequency vibration. The rapid and significant change in depth-of-cut is the fundamental reason for the impact generated when the bit crosses through the interlayer, and both the maximum and minimum depth-of-cut occur in the transition region. PDC bit alternately encountered soft and hard rocks in the horizontal interbedded formation, causing intensified vibration. The acceleration is consistent with rock difference. The influence of weight-on-bit on acceleration increases with the increase of rotary speed for horizontal interbedded formation with small rock differences. However, with the increase of weight-on-bit, the influence trend and degree of rotary speed on acceleration remain basically unchanged. The increase in weight-on-bit /rotary speed weakens the effect of rotary speed/ weight-on-bit on acceleration in horizontal interbedded formations with significant rock differences. The research results illustrate that the reason for the abnormal bit failure in interbedded formations is the frequent changes in depth of cut caused by rock mutation and alternation, and the resulting impact. This provides theoretical guidance for the implementation of effective measures such as reasonable cutter arrangement design, pertinent setting of auxiliary structures, and appropriate adjustment of drilling parameters.

Effect of grinding parameters and coolants on grindability of Ti grade 9 alloy

For many years, surface roughness has drawn considerable attention, and it is a crucial design element in a variety of circumstances, including components sensitive to fatigue stresses, precision fittings, fastener holes, and aesthetic demands. Grinding the is best conventional machining process to achieve a better surface finish on a given component. Titanium 3Al-2.5 V or Ti grade 9 alloy is primarily utilized in the biomedical, aerospace, and automotive sectors. But because of its low heat conductivity, high chemical reactivity and rapid work hardening, this alloy is known as a difficult-to-cut material. In grinding, the abrasives have low thermal conductivity and small chip sizes, which in turn more heat to being focused in the cutting zone. This heat harms the surface of the workpiece. Therefore, it's crucial to regulate the quantity of heat that the workpiece receives.In this context, this work examines the surface quality of the Titanium 3Al-2.5 V alloy following surface grinding with an Al2O3 wheel under various grinding settings, including surface roughness (Ra), microhardness and material removal rate (MRR) from the workpiece. Techniques for delivering coolant conventionally (flood coolant), dry and using MQL were used and grinding performance were evaluated. The findings demonstrated that the Ra varied from 0.32 to 0.594 µm and hardness on the machine surface varied from 61.7 to 72 HRC. The MRR varied from 0.09 to 0.42 g/minute for the changes in depth of cut, table feed and coolants. Overall, the MQL has produced a good surface finish, high MRR and moderate hardness on the workpiece.

Titanium Alloy Milling Using Abrasive Water Jet for Repair Application: Modifications in Surface Quality and Material Integrity Following Plain Water Jet Cleaning

Abrasive Water Jet (AWJ) machining has proven to be an effective and versatile technique for milling various kinds of materials, even with low machinability such as aerospace grade titanium alloy Ti6Al4V. Many studies have been performed in order to master this technology and produce geometrically accurate shapes. However, in the context of bonding repairs which require surfaces free from foreign bodies, AWJ machining presents a significant drawback in form of abrasive grit embedment. The goal of this present work is then to investigate the effect of a post-AWJ machining cleaning operation using Plain Water Jet process (PWJ – i.e. without abrasive particles) on the surface quality and material properties. For this, several characterization techniques were employed. It was concluded that the contamination has been reduced by 65% without noticeable changes in depth of cut and crater volume. The AWJ milling operation produced surface and subsurface hardening as well as biaxial compressive residual stress, mostly piloted by the jet pressure. PWJ cleaning reduced the depth of hardening without clear modification in surface hardness.

МОДЕЛИРОВАНИЕ ДИНАМИЧЕСКОГО ВОЗДЕЙСТВИЯ ИНСТРУМЕНТА И ЗАГОТОВКИ ПРИ КРУГЛОМ ШЛИФОВАНИИ В ПЛАВУЧИХ МАСТЕРСКИХ

The article analyzes the results of modeling dynamic processes during circular grinding of parts. Models are presented in the form of experimental dependences of the vibration amplitude on the grinding time; models of the process of interrelation of cutting forces and control actions; the obtained function of dynamic accuracy, which characterizes the trajectory of motion and relative oscillations of the grinding wheel and the part; models for assessing the influence of the value of an adjustable normal grinding force on the course of radial wear of a grinding wheel, volumetric productivity and basic grinding time, surface roughness of a part processed by wheels with different characteristics. Models of external cylindrical grinding in the form of a set of differential equations characterizing the dynamics of displacements of the centers of the wheel, workpiece and changes in the actual depth of cut are most acceptable for use in the implementation of stochastic observation and filtration procedures. They are taken as a basis for stabilizing the parameters of the technological system, taking into account the effects of equipment and the external environment (waves of the water surface) on the machine in floating workshops.

The effect of changes in depth of cut and cutting speed of CNC toolpaths on turning process performance

Abstract In this article, a novel approach to computer optimization of CNC toolpaths by adjustment of cutting speed vcand depth of cut apis presented. Available software works by the principle of adjusting feed rate on the basis of calculations and numerical simulation of the machining process. The authors wish to expand upon this approach by proposing toolpath optimization by altering two other basic process parameters. Intricacies and problems related totheadjustment of apand vcwere explained in the introductory part. Simulation of different variant of the same turning process with different parameter values were conducted to evaluate the effect of changes in depth of cut and cutting speed on process performance. Obtained results were investigated on the account of cutting force and tool life. The authors have found that depth of cut substantially affects cutting force, while the effect of cutting speed on it is minimal. An increase in both depth of cut and cutting speed affects tool life negatively, although the impact of cutting speed is much more severe. An increase in depth of cut allows for a more significant reduction of machining time, while affecting tool life less negatively. On the other hand, the adjustment of cutting speed helpsto reduce machining time without increasing cutting force component values and spindle load.

Machining process influence on the chip form and surface roughness by neuro-fuzzy technique

The main aim of the study was to analyze the influence of six machining parameters on the chip shape formation and surface roughness as well during turning of Steel 30CrNiMo8. Three components of cutting forces were used as inputs together with cutting speed, feed rate, and depth of cut. It is crucial for the engineers to use optimal machining parameters to get the best results or to high control of the machining process. Therefore, there is need to find the machining parameters for the optimal procedure of the machining process. Adaptive neuro-fuzzy inference system (ANFIS) was used to estimate the inputs influence on the chip shape formation and surface roughness. According to the results, the cutting force in direction of the depth of cut has the highest influence on the chip form. The testing error for the cutting force in direction of the depth of cut has testing error 0.2562. This cutting force determines the depth of cut. According to the results, the depth of cut has the highest influence on the surface roughness. Also the depth of cut has the highest influence on the surface roughness. The testing error for the cutting force in direction of the depth of cut has testing error 5.2753. Generally the depth of cut and the cutting force which provides the depth of cut are the most dominant factors for chip forms and surface roughness. Any small changes in depth of cut or in cutting force which provide the depth of cut could drastically affect the chip form or surface roughness of the working material.

Modelling metal cutting using modern ductile fracture mechanics: quantitative explanations for some longstanding problems

The assumption that negligible work is involved in the formation of new surfaces in the machining of ductile metals, is re-examined in the light of both current Finite Element Method (FEM) simulations of cutting and modern ductile fracture mechanics. The work associated with separation criteria in FEM models is shown to be in the kJ/m 2 range rather than the few J/m 2 of the surface energy (surface tension) employed by Shaw in his pioneering study of 1954 following which consideration of surface work has been omitted from analyses of metal cutting. The much greater values of surface specific work are not surprising in terms of ductile fracture mechanics where kJ/m 2 values of fracture toughness are typical of the ductile metals involved in machining studies. This paper shows that when even the simple Ernst–Merchant analysis is generalised to include significant surface work, many of the experimental observations for which traditional ‘plasticity and friction only’ analyses seem to have no quantitative explanation, are now given meaning. In particular, the primary shear plane angle φ becomes material-dependent. The experimental increase of φ up to a saturated level, as the uncut chip thickness is increased, is predicted. The positive intercepts found in plots of cutting force vs. depth of cut, and in plots of force resolved along the primary shear plane vs. area of shear plane, are shown to be measures of the specific surface work. It is demonstrated that neglect of these intercepts in cutting analyses is the reason why anomalously high values of shear yield stress are derived at those very small uncut chip thicknesses at which the so-called size effect becomes evident. The material toughness/strength ratio, combined with the depth of cut to form a non-dimensional parameter, is shown to control ductile cutting mechanics. The toughness/strength ratio of a given material will change with rate, temperature, and thermomechanical treatment and the influence of such changes, together with changes in depth of cut, on the character of machining is discussed. Strength or hardness alone is insufficient to describe machining. The failure of the Ernst–Merchant theory seems less to do with problems of uniqueness and the validity of minimum work, and more to do with the problem not being properly posed. The new analysis compares favourably and consistently with the wide body of experimental results available in the literature. Why considerable progress in the understanding of metal cutting has been achieved without reference to significant surface work is also discussed.

Control Enhancement of Cutting Force in CNC Turning Machines Based on a New MRAS

ABSTRACT Controlling the cutting force in machining is a challenging problem since the cutting dynamics varies significantly under normal operating conditions. In this paper, a linearized state-space model for a Computerized Numerical Control (CNC) turning machine is synthesized. A model reference adaptive control system (MRAS), which includes the cutting force as a controlled output and the feed rate as a control input, is implemented. The deterministic autoregressive moving average (DARMA) model with auxiliary input is introduced to cope with any disturbances of the system. The parameters of the DARMA model are obtained using the structure of a lattice adaptive control system. A minimum variance controller is designed to maintain the cutting force at a prescribed level by adjusting the feed rate. The robustness of the proposed controller copes with any changes in depth of cut and/or the cutting speed. These changes are embedded in the Iinearized model of the CNC machine and are considered as system paran1eters. Extensive computer simulations are made to prove the applicability of the proposed controller for controlling the cutting force over different operating conditions.

Optimal Preview Control of Cutting Force in CNC Turning Machines

In this paper, a new linearized state-space model for a Computerized Numerical Control (CNC) turning machine is synthesized. The linearization is implemented using a factorization method in which the feed is divided into two terms. The first term is the measurable part of the integer feed and the second is a fractional of feed, which will be calculated. An optimal preview controller for the CNC machine is implemented. A new error system technique is introduced into the control system to cure the adverse phenomena that is caused due to parameter uncertainties, un-mode led dynamics and disturbances. The disturbances comprise material properties, depth of cut and tool conditions while the un-modeled dynamics to dispense with the fractional feed. A preview feed-forward controller utilizing the desired cutting force is designed to improve the transient response of the CNC control system. The robustness of the proposed controller copes with any changes in depth of cut and/or cutting speed during the cutting process where they are embedded in the linearized model of the CNC machine and are considered as system parameters.