Machining Feed Rate Research Articles

Double-pulsed wire electrochemical micro-machining of type-304 stainless steel

Traditional wire electrochemical micro-machining (WEMM) of type-304 stainless steel using dilute hydrochloric acid (HCl) generates a certain amount of insoluble electrolysis product that adheres onto the wire. As the machining process continues, a blackened layer is generated on the wire that hampers the machining process. Herein, a double-pulsed WEMM (DP-WEMM) method is proposed to eliminate this blackened layer, effectively so as indicated by experimental results. An optimal negative voltage is determined as −0.3 V. The slot profile and machining stability obtained with DP-WEMM are considerably better than those with traditional WEMM. For the same machining parameters and feed rate, traditional WEMM with dilute HCl manages a 1.8-mm-long slot until short circuit occurs. By contrast, DP-WEMM is terminated manually after a 5.0-mm-long slot is obtained, there having been no short circuit.

The Study of Variational Feed Rate in 4-Axis Machining of Blades

As a core part of aerospace, space, and steam turbine plants, blades are generally machined via 5-axis linkage processing to satisfy the high precision requirements of the rigorous surface. To save costs in blade machining, many small- and medium-sized enterprises often combine standard 3-axis computer numeric control machines with the automatic indexing turntable. The traditional 4-axis machining method adopts a constant feed rate, which causes overcutting near the leading and trailing edges of the blade because of the rapid changes in tool orientation. To solve this problem, we propose a speed optimization method that utilizes variational speed to ensure that the decomposition velocity and acceleration of each axis do not exceed the allowable values. First, we guarantee the correct tool lead angle. Second, a corrected speed model is established to obtain the component speed of each axis and to determine the constraint conditions of maximum and accelerated speed. Third, a 4-axis post processor for blade processing is developed using Java advanced language combined with the optimization algorithm. The cutting experiment reveals that our proposed speed optimization method effectively controls the precision of the surface profile and overcomes the overcut phenomenon that often occurs in traditional 4-axis machining.

Three-axis CNC machining feedrate scheduling based on the feedrate restricted interval identification with sliding arc tube

In the computer numerical control (CNC) machining for free form surfaces, the time-optimized and smooth feedrate profile plays an essential role in the high-speed and high-precision machining. For the traditional feedrate scheduling method (e.g., the “bang-bang” control method), there may be many fluctuations in the planned feedrate profile, especially in region of large curvature, which results in poor quality of machining surface. To address this issue, a novel concept called sliding arc tube (SAT) is proposed in this paper, from which the trajectory is partitioned as feedrate restricted intervals (FRIs) determining the target feedrate and the positions of tool acceleration and deceleration on the tool path. The SAT is built based on the local geometric information of tool paths. As the SAT is constructed in the tube-shaping process and then sliding on the tool path and finally blocked by it, the breaking point for generating the FRI is found on the trajectory curve. For the proposed FRI identification method, it is computational efficient and it can be implemented in the real-time manner in the CNC controller. Results from both simulation and real machining experiments validate that, with the proposed SAT, the FRIs can be precisely and efficiently identified for the given trajectory curve, the frequent acceleration and deceleration of machine tool is alleviated, and the machining quality can be improved in this way.

Numerical Modelling and Optimization of Dry Orthogonal Turning of Al6061 T6 Alloy

In this paper, the influence of machining parameters, Cutting Speed, Feed Rate, and Depth of cut, on surface finish during dry orthogonal turning of Al 6061 – T6 alloy, is studied using the response surface methodology (RSM). This paper proposes a unique way to predict the surface finish in turning, using the effective plastic strain (PEEQ) values obtained from the simulations. A comprehensive finite element model was proposed to predict the surface finish accurately, by correlating the variance of the PEEQ. The Johnson-Cook damage model is used to define the damage criteria and Johnson-Cook material model is used to explain the material constitutive behavior. A dynamic, explicit method is used along with the Adaptive Lagrangian-Eulerian (ALE) method to predict material flow accurately. The influence of machining parameters was studied by assuming Central Composite Design (CCD). The output response, PEEQ, was fitted into analytical quadratic polynomial models using regression analysis, which shows that feed rate was the most dominant factor for PEEQ than the other parameters considered in this study. Using the individual desirability function method, the objective, optimal setting of the machining parameters was obtained for better surface finish.

Numerical Modelling and Optimization of Surface Finish during Peripheral Milling of AISI 4340 Steel using RSM

The effect of machining parameters, Cutting Speed, Feed Rate, and Depth of cut, on surface finish during peripheral milling of AISI 4340 steel, studied using response surface methodology. This paper suggests a distinctive way to calculate the surface finish, using the variance of effective plastic strain values obtained from the numerical model. The Johnson-Cook damage and material models are used in the numerical model along with the ALE. The variance of PEEQ was optimized using ANOVA, which shows that cutting speed was the most dominant factor. The optimal settings of the machining parameters was obtained for better surface finish.\\

A METHOD OF REAL-TIME NURBS INTERPOLATION WITH CONFINED CHORD ERROR FOR CNC SYSTEMS

This paper presents a method of real-time CNC interpolation for free-form NURBS curves. The interpolation algorithm is based on second order Taylor’s expansion with the principle part being a formula for updating the parametric value u after each sampling period. With the updated value of u, a new interpolated point is calculated based on the DeBoor’s algorithm. In this paper, an efficient method of limiting chord error introduced by the interpolation algorithm is also presented with the basic idea of reducing machining feedrate at positions with a radius of curvature smaller than a critical value.

Contribution of machining to the fatigue behaviour of metal matrix composites (MMCs) of varying reinforcement size

The high cycle constant stress amplitude fatigue performance of metal matrix composite (MMC) components machined by a milling process was investigated in this study as a function of machining speed, feed rate and reinforcement particle size. The presence of reinforcement and particle size were found to be the most influential factors that affected the fatigue life. In contrast to this, the effect of feed and speed on tool-particle interaction, strain hardening and heat generation during milling of MMCs were balanced in such a way that the contributions of feed and speed on fatigue life were negligible. The interactions of different parameters contributed significantly to the fatigue life which indicated that the modelling of fatigue life based on these three parameters was relatively complex. The fatigue life of the machined MMC samples increased with decreasing particle size and increasing feed. However, the fatigue life was not influenced by speed variation. The presence of smaller or no particles induced a complete separation of failed samples, in contrast to that of specimens containing larger reinforcing particles where crack growth was arrested or deflected by the reinforcing particles.

Implementing Thermomechanical Properties of 22MnB5 Steel during Hot Single-Point Incremental Forming

The strategy in manufacturing hardened parts used in car bodies is to tailor the mechanical properties. This is done by combining together a high-strength region and a high-toughness region to ensure the crash performance required. Other successive secondary operations such as trimming, joining and welding can be improved as a result of the tailoring process. In this work, the mechanical properties of 22MnB5 alloy sheet material produced by single-point incremental forming have been tailored. For this purpose, the sheets were locally heated by induction during the forming process and subsequently cooled. The sheet temperature was controlled by the CNC milling machine feed rate and induction power. As a result, the produced tailored parts consist of three different regions: ductile, transition and hardened regions. The Vickers hardness values were 583 HV1 and 175 HV1 for the hardened and ductile regions, respectively. The proposed application allows forming and quenching at the same time without transfer and to reduce the process time.

The Effect of Cooling Strategies and Machining Feed Rate on the Corrosion Behavior and Wettability of AZ31 Alloy for Biomedical Applications

In this work, the corrosion rate of the AZ31 magnesium alloy in physiological environment was improved by optimized machining process parameters. Cryogenic turning was exploited to obtain a featureless layer in the machined sub-surface, while the feed rate was modified to reduce the aspect ratio of the feed marks characteristic of the turning operation, achieving a decrease of the alloy wettability. The obtained results showed that the aforementioned combined aspects acted as an efficient strategy to enhance the AZ31 poor corrosion behavior, which represents the major obstacle of its effective application in the biomedical field.

What are the Driving Factors Influencing the Size Distribution of Airborne Synthetic Clay Particles Emitted from a Jet Milling Process?

In the field of workplace air quality, measuring and analyzing the size distribution of airborne particles to identify their sources and apportion their contribution has become widely accepted, however, the driving factors that influence this parameter, particularly for nanoparticles (< 100 nm), have not been thoroughly determined. Identification of driving factors, and in turn, general trends in size distribution of emitted particles would facilitate the prediction of nanoparticles’ emission behavior and significantly contribute to their exposure assessment. In this study, a comprehensive analysis of the particle number size distribution data, with a particular focus on the ultrafine size range of synthetic clay particles emitted from a jet milling machine was conducted using the multi-lognormal fitting method. The results showed relatively high contribution of nanoparticles to the emissions in many of the tested cases, and also, that both surface treatment and feed rate of the machine are significant factors influencing the size distribution of the emitted particles of this size. In particular, applying surface treatments and increasing the machine feed rate have the similar effect of reducing the size of the particles, however, no general trend was found in variations of size distribution across different surface treatments and feed rates. The findings of our study demonstrate that for this process and other activities, where no general trend is found in the size distribution of the emitted airborne particles due to dissimilar effects of the driving factors, each case must be treated separately in terms of workplace exposure assessment and regulations.

Machining Parameters Optimization of Titanium Alloy using Response Surface Methodology and Particle Swarm Optimization under Minimum-Quantity Lubrication Environment

The present paper depicts an application of response surface methodology (RSM) and particle swarm optimization (PSO) technique for optimizing the machining factors in turning of titanium (Grade-II) alloy using cubic boron nitride insert tool under minimum quantity lubricant (MQL) environment. The three machining factors, i.e., cutting speed (Vc), feed rate (f) and side cutting edge angle (approach angle π), are designed as three factors by using RSM design, which is withal subject to several constraints including tangential force (Fc), tool wear (VBmax), surface roughness (Ra) and tool-chip contact length (L). The multiple regression technique was used to establish the interaction between input parameters and given responses. Moreover, the results have been presented and optimized process parameters are acquired through multi-response optimization via desirability function as well as the PSO technique. The lower values of Vc (200 m/min), f (0.10 mm/rev) and higher values of ϕ (90°) are the optimum machining factors for minimizing the aforementioned responses. It was also observed that the selected responses predicated on PSO are much closer as that of the values acquired in view of the desirability function approach. Henceforth, PSO has the potential to cull appropriate machining factors while turning titanium (Grade-II) alloys under MQL conditions.

A real-time and look-ahead interpolation methodology with dynamic B-spline transition scheme for CNC machining of short line segments

Tool path is presented as continuous small line segments in some existing NC machining programs. To achieve high machining speed and smooth machining quality, the tool path needs to be processed. This study presents a real-time and look-ahead interpolation methodology with dynamic B-spline transition scheme for short line segments machining. In the methodology, transition curve is adjusted to avoid intersection and keep high machining speed. Firstly, the unit length of every B-spline transition curve is calculated depending on tool path and NC system requirements; then, the maximum allowable velocity of the curve which is called threshold velocity can be got. Secondly, transition curve is determined according to the unit length and two consecutive threshold velocities, and time optimization function makes the transition curve take less machining time. Thirdly, the 7-phase velocity planning algorithm and static look-ahead algorithm are adopted to generate smooth machining feedrate and fine machining quality. Lastly, the curve interpolation is performed on the processed tool path. The simulations and experiments demonstrated that the proposed algorithm is able to achieve high machining speed and generate fine machining quality.

Analysis and optimisation of machinability behaviour of CFRP composites using fuzzy logic

Purpose– The purpose of this paper is to analyse and optimise the machinability behaviour of Carbon Fibre Reinforced Polymer (CFRP) composites with multiple performance characteristics using the Taguchi method with fuzzy logic.Design/methodology/approach– A multi-response performance index (MRPI) was used for optimisation. The machining parameters,viz., tool geometry (helix angle of the endmill cutter), spindle speed, feed rate and depth of cut, were optimised with consideration of multiple performance characteristics,viz., machining force and material removal rate.Findings– The results from confirmation runs indicated that the determined optimal combination of machining parameters improved the performance of the machining process.Originality/value– The machinability behaviour of CFRP composites during milling of CFRP composites using Taguchi method with fuzzy logic has not been previously analysed.

Experimental study of machinability in mill-grinding of SiCp/Al composites

An attempt was made to investigate the machinability of SiCp/Al composites based on the experimental study using mill-grinding processing method. The experiments were carried out on a high-speed CNC machining center using integrated abrasive cutting tool. The effects of combined machining parameters, e g, cutting speed (vs), feed rate (vf), and depth of cut (ap), with the same change of material removal rate (MRR) on the mill-grinding force and surface roughness (Ra) were investigated. The formation mechanism of typical machined surface defects was analyzed by SEM. The experimental results reveal that with the same change of material removal rate, lower mill-grinding force values can be gained by increasing depth of cut and feed rate simultaneously at higher cutting speed. With the same change of MRR value, lower surface roughness values can be gained by increasing the feed rate at higher cutting speed, rather than just increasing the depth of cut, or increasing the feed rate and depth of cut simultaneously. The machined surface of SiCp/Al composites reveals typical defects which can influence surface integrity.

Chatter Investigation in Titanium Milling

&lt;span&gt;&lt;p align="LEFT"&gt;&lt;span&gt;&lt;span style="font-family: Times New Roman;" face="Times New Roman"&gt;Titanium and its alloys have been experiencing extensive development over the past few decades. They have found wide applications in the aerospace, biomedical and automotive industries owing to their good strength-to-weight ratio and high corrosion resistance. Machining performance is often limited by chatter vibrations at the tool-workpiece interface. Chatter is an abnormal tool behaviour which is one of the most critical problems in the machining process and must be avoided to improve the dimensional accuracy and surface quality of the finished product. This research aims at investigating chatter trends in the end milling process and to identify machine parameters that have effects on chatter during machining. The machine parameters investigated include axial feed rate, spindle revolute speed and depth of cut. In this research, experimental data was collected using sensors to analyze the existence of chatter vibrations on each processing condition. This research showed that the combination of the machine parameters, feed rate and spindle speed within certain proportions has an influence on machine vibrations during end milling and if not managed properly, may lead to chatter. &lt;/span&gt;&lt;/span&gt;&lt;/p&gt; &lt;p align="LEFT"&gt;&lt;/p&gt;

A force controlled grinding-milling technique for quartz-glass micromachining

This paper presents a novel approach to the micromachining of quartz glass using an intellectualized grinding-milling technique to overcome the difficulties in machining hard-brittle materials. A bench-type linear 3-axis CNC machine tool providing grinding-milling at depths of several nanometers is constructed to realize ductile-regime material removal during quartz-glass milling. Finite element analysis (FEA) is conducted on the deformation and resonant frequency of the developed machine tool. A micro-tipped grinding-tool made of boron-doped polycrystalline composite diamond (BD-PCD) and designed with a double-negative back rake angle (DN-BRA) to create compressive stress grinding-milling is proposed and employed. To sense the force at which grinding-milling is conducted and provide real-time feedback on the milling tool's feed-rate, load-cells are devised on 3 axes. Using an appropriate grinding-milling technique in combination with proper feedback to control the machining feed-rate, quartz glass is machined layer-by-layer under a ductile regime. A miniature 3-step-shaped pyramid made of quartz glass of 0.3mm in height and of Ra0.66μm surface roughness with very little brittle fracturing is achieved. The optimum grinding depth, milling speed and corresponding grinding-milling force are 1μm, 50–70m/min, and 0.4N, respectively. A comprehensive examination of the quantitative and qualitative properties of the BD-PCD tool was undertaken. Experimental confirmation of the proposed approach is presented. Additionally, the following aspects are discussed in detail: the spark erosion rate of the machined diamond tool, milling feed-rate, grinding depth, graphitization of diamond, and tool wear.

A Review Paper on Effects of Drilling on Glass Fiber Reinforced Plastic

Drilling is an important process for making and assembling components made from Glass Fiber Reinforced Plastic (GFRP). Various processes like conventional drilling, vibration assisted drilling and ultrasonic assisted drilling have been attempted in order to maintain the integrity of the material and obtain the necessary accuracy in drilling of GFRP. This paper attempts to review the influence of machining parameter on the delamination damage of GFRP during drilling. In conventional machining feed rate, tool material and cutting speed are the most influential factor on the delamination hence machining at higher speed, harder tool material and lower feed rate have lesser delamination of the GFRP. Vibration assisted drilling and Ultrasonic assisted drilling have lesser thrust and hence lesser delamination compared to conventional drilling, which indicates that both vibration assisted drilling and Ultrasonic assisted drilling are more appropriate for drilling of GFRP.

An Approach for Continuous Small Line Blocks High Speed Machining of Embedded Systems

A key issue of the machining for the small line block is to improve the machining feedrate while keeping the machining precision and satisfying the acceleration constraints. In this paper, a new approach for continuous small line blocks high speed machining is proposed to avoid the impact of Computer Numerical Control (CNC) equipments caused by acceleration gust. This approach uses the small line flag to distinguish whether the path is small line block. While the paths are continuous small line blocks, this approach can automatically adjust the number of look-ahead segments, and predigest the velocity calculation method of the connection point. We first define what a path is small line block. Then we analyze the restrictions for velocity linking of adjacent processing paths, and propose the approach for continuous small line blocks machining. Finally we design a simulation experiment on 30 points processing of the spline track. The result of the simulation shows that this algorithm can obviously shorten the processing time and make control system more harmonious in high speed machining.

MODIFICATION OF A LOCAL MACHINE THRESHING UNIT FOR THRESHING SUN FLOWER

The objective of the present study is to test and evaluate the performance of Mabrouk type threshing machine for threshing sunflower heads (variety of vidok) after modification of the threshing drum and the cleaning unit. The machine performance was evaluated in terms of threshing efficiency, percentage of un-threshed seeds, percentage of seed losses, seeds purity, fan losses and losses behind sieves. The experimental work was carried out to investigate the effects of some engineering parameters of the machine threshing and cleaning units included threshing drum speeds of 300, 400, 500 and 600 rpm (10.99, 14.65, 18.31 and 22.78 m/s) ,heads feeding rates of 300, 450, 600 and 750 kg/h, air velocity of 3.5, 4.5, and 5.5 m/s. suction fan, and sieve tilt angles of 2, 5 and 8 degree. The obtained results indicated that, considering the lower percentage of un-threshed and broken seeds and the higher threshing efficiency with acceptable machine capacity, the machine feed rate of 600 kg/h. and drum speed of 400 rpm is recommended for threshing sunflower heads. Meanwhile, considering both seed purity and total seed losses, it canbe said that the air velocity of 4.5 m/sec with sieves tilt angle of 5 degree recorded proper seed purity of 98.5 % with total seed losses of 0.42 %.

Experimental study of the dry facing of magnesium pieces based on the surface roughness

This paper shows an experimental study of dry face turning carried out on UNS M11917 magnesium pieces. The work is focused on repair and maintenance operations which are generally carried out under cutting conditions of low performance. The main goal is to determine if such type of operations can be reached successfully by dry machining, the most drastic and sustainable cooling technique that exists, and, if so, what factor or factors among the involved ones in the machining (spindle speed, feed rate and tool coating) and their possible interactions are more influential in the quality of surface finish. To achieve this objective, a sustainable methodology that combines Taguchi design of experiment (DOE) and the analysis of variance (ANOVA) method are considered. The main result is the establishment of a model for estimating the expected surface roughness, in terms of average roughness, Ra, that allows selecting the best combination of cutting conditions and type of tool to obtain pieces within a certain range of surface roughness. The principal conclusion is that the dry machining technique can be used in the face turning repair and maintenance operations of pieces of magnesium producing a very good quality of the surface roughness and reducing costs and environmental impact.