Theoretical Surface Roughness Research Articles

Theoretical models for surface roughness in turning considering inclination and rake angles

New analytical four-parameter models for surface roughness are proposed based on the feed rate, nose radius as well as the inclination and rake angles. These models were derived to determine the maximum peak-to-valley roughness Rt and arithmetic average roughness Ra using homogeneous transformation matrices and are verified by digital simulation. The model for Rt was used to study two sequential effects of introducing the inclination and rake angles. The Rt and Ra values obtained from the four-parameter models and the existing two-parameter models, based on nose radius and feed rate, were compared. The comparison shows maximum percentage differences of 8.18% and 10.98% in Rt and Ra, respectively. The results demonstrate that the inclination and rake angles can influence the surface roughness by affecting the tool-workpiece contact geometry. The proposed four-parameter model can be employed for a more accurate theoretical surface roughness evaluation compared to the existing two-parameter models.

Prediction of surface topography in precision hard machining based on modelling of the generation mechanisms resulting from a variable feed rate

The paper presents an original contribution to the prediction of surface topography produced by precision hard turning operations using CBN cutting tools and the variable feed rate of 0.025–0.075 mm/rev. The differences between theoretical and real surface roughness parameters Rz and Sz are quantified in terms of springback effect, additional smoothing of irregularities and side flow effect. The primary experimental study includes measurements of 2D and 3D surface roughness parameters using contact profilometer. Correspondingly, cutting forces were measured using a piezoelectric dynamometer, and based on this data, specific corresponding values of ploughing energy and friction coefficient were determined. It was found that the measured value of maximum height of the surface Sz differs from the theoretical value mainly due to elastic recovery of the machined surface and the smoothing effect at the lower feeds and the elastic recovery and the side flow effect at the higher feeds employed. An empirical model for the prediction of the Sz value in function of the feed rate is derived. The prediction accuracy can be improved by advanced numerical modelling of surface generation mechanisms and associated distortions.

Comparison of Theoretical and Real Surface Roughness in Case of Ball-End Milling

In case of free form surface milling the quality of the manufacturing is described by the accuracy of the shape and the surface roughness. The 3D surface finishing milling by ball-end milling cutter is one of the most often used machining technologies. In case of ball-end milling the surface roughness can be described theoretically based on the tool diameter and the density of the tool path, but the experience shows than other parameters have effect on the surface roughness. In the article the effect of the different cutting parameters, like feed (fz), depth of cut (ap) and width of cut (ae), is presented in case of plane surface, and the surface roughness is compared with the theoretical roughness, and an estimation method is presented.

Precision machining of high aspect-ratio rotational part with wire electro discharge machining

Precision and micro rotational parts are widely used in various industries, such as micro probes for medical instruments, contact pins for micro assembly applications, micro electrodes for micro Electrical discharge machining (μ-EDM) or micro Electro-chemical discharge machining (μ-ECDM). In this research, a uniform annular area layer by layer feeding strategy was proposed to fabricate high aspect ratio, small radii rotational components on a conventional Wire electrical discharge machining (WEDM) machine equipped with an auxiliary spindle. The uniform annular area layer by layer feeding strategy consisted of the roughing and finishing stages. First, the theoretical Material removal rate (MRR) and radial infeed rate for each layer were determined for the roughing stage, and the theoretical surface roughness, Rz in the finishing stage was researched. Then, a series of optimization experiments were conducted to investigate the influence of the parameters on MRR and the machined surface roughness. A group of pin electrodes were machined by applying this feed strategy with the optimized parameters, and the minimum diameter of the pin electrodes was 40 μm with an aspect-ratio of 60. Finally, micro electrodes for an injection nozzle were achieved with this novel process and a qualified injection nozzle for powder metallurgy was fabricated with the machined micro electrodes.

Surface roughness of two-frequency elliptical vibration texturing (TFEVT) method for micro-dimple pattern process

This study presents a two-frequency elliptical vibration texturing (TFEVT) method that adds elliptical vibration cutting (EVC) to a conventional texturing (CT) method. The TFEVT method improves the surface roughness compared to the CT method during a micro-dimple texturing process. Kinematic analysis and a theoretical surface roughness model are presented based on the effect of the tool edge radius. The effect of this radius cannot be neglected since it is nearly equal to the undeformed chip thickness at the micro scale. The replication of the tool edge radius profile, the effect of the material spring back, and the residual error were also considered in the surface roughness model. The surface roughness of a micro-dimple also includes the replication of the tool edge radius profile, which can be determined by using a replication technique. The deflection of material spring back is formulated according to the value of the minimum principal stress in the tertiary deformation zone between the flank face and the machined surface, and the plastic strain value is determined based on elasto-plastic deformation theory. Experimental and simulation results were compared to validate the surface roughness model.

The equal theoretical surface roughness grinding method for gear generating grinding

A new approach is developed in this paper to predict the three-dimensional gear surface topography in the process of gear generating grinding, and a parametric equation is derived to describe the trajectory on the tooth surface of gear left by each ideal sphere grain. To determine the final three-dimensional gear surface topography generated by thousands of single abrasive grain with randomly distributed locations and protrusion heights, an algorithm for geometrical analysis is developed to systematically process the gear surface profile. There are two steps for this method: the first step is to map the cutting path to the tooth profile in each generating stroke, and the second stage is to combine these generated surface topographies together and trim them in an appropriate manner to create a whole tooth surface. The simulation results show that the surface roughness is increasing monotonously along the tooth profile direction, which is confirmed by the experiment. In order to get uniform surface roughness, a non-uniform generation method is introduced by dividing the entire arc length into isometric n segments. With the use of this method, the surface roughness in each part is essentially equal. Besides, the surface roughness improves about 16.3 % when the machining time is the same, and the reduction of machining time is 42.8 % when the surface roughness of addendum is equal.

Evaluation for tool flank wear and its influences on surface roughness in ultra-precision raster fly cutting

The occurrence of tool flank wear certainly affects the machined surface roughness in ultra-precision machining. The in-process evaluation of tool flank wear and its effects on machined surface roughness is significant, since it helps to find tool flank wear timely and reduce tool wear effect on surface roughness by further actions. However, little attention has been paid to the evaluation of tool flank wear and its effects on machined surface roughness in ultra-precision raster fly-cutting (UPRFC) process especially by using cutting chips. In the present research, evaluation of tool flank wear and its effects on surface roughness is conducted in UPRFC by examination of cutting chip morphologies. Based on the relations between chip morphologies and tool flank wear, a mathematical model was established to identify the width of flank wear land and the theoretical surface roughness under tool flank wear effects. Theoretical and experimental results show that: (1) Tool flank wear occurrence causes the formation of shutter-like structure rather than feather-like structure at the tool entry of cutting chips. (2) Cutting chips are truncated where chip thickness is comparable to the width of wear land. (3) The smooth tool flank wear increase the tool nose radius and therefore reduce the surface toughness theoretically.

Surface Roughness Prediction in Face Milling by Special Tools

The ability to plan the surface roughness in case of machining by rotational tools is introduced in the paper by the help of a formerly developed calculation method. This method utilizes the theoretical surface roughness indexes which were calculated in advance for the prediction of the expected surface roughness parameters. An experimental milling head is considered for the theoretical and experimental investigations, which can contain different insert geometries. The paper describes two distinct cases: in the first case, the face milling is performed by two identical cutting inserts, while in the second one, two different insert are applied simultaneously. Results of the carried-out experiments are also presented for the validation of the theoretical calculations.

A New Method for Copper Spherical Surface Lathing with High Speed Steel Cutting Tool

On the basis of uneven copper surface roughness during lathering in common CNC lather, analyze the cutting ways of copper spherical surface and the cutting layer different from cylindrical surface lathing. The cutting direction of cylindrical surface lathing is constant, and its cutting layer is too. However, the direction of spherical surface lathing varies along the tangent of its cutting point continually, and the working cutting edge angle and the working minor cutting edge angle of the cutting tool vary too, so the theoretical surface roughness is affected. The cutting layer of spherical surface lathing varies continually, so does the cutting depth of its every cutting point. Through analysis and experiments, prove that cutting force variety is caused by the gradient variety of cutting depth, which leads to increase of the surface rough and its unevenness. Based on the research result, design some new cutting path to improve the surface roughness of copper spherical surface lathing, and obtain good effect.

Machinability Evaluation of Inclined Planetary Motion Milling System for Difficult-to-Cut Materials

CFRP and Titanium alloy, which are known as difficult-to-cut materials have been widely used as structural material in aviation industries. The orbital drilling is one of an effective drilling technique for the industries. However this technique has some disadvantages such as increase of cutting force due to cutting with tool center point, inertial vibration generated by revolution and high installation cost. In order to improve the disadvantages, we have invented a new drilling technique which is called inclined planetary motion milling. The inclined planetary motion milling and the planetary mechanism drilling has two axes of cutting tool rotation axis and revolution axis. Cutting tool rotation axis of the orbital drilling is moved parallel to the revolution axis in eccentric. On the other hand, in the case of the inclined planetary motion milling, eccentric of the cutting tool rotation axis is realized by inclination of a few degrees from the revolution axis. Therefore, the movement of eccentric mechanism can be reduced by comparison with the orbital drilling because inclined angle is smaller than eccentricity of the cutting tool tip. As a result, eccentric mechanism can be downsized and inertial vibration is reduced. In the study, a geometrical cutting model of inclined planetary motion milling was set up. The theoretical surface roughness of the inside of drilled holes by use of two types cutting tool geometry were calculated based on the model. And cutting experiments using the new prototype for CFRP were carried out in order to evaluate the effect on machinability with change of cutting point atmosphere. In addition, optimal cutting condition was derived according to cutting experiments for titanium alloys utilizing the orthogonal array.

Fundamental Turning Characteristics of Inconel 718 by Applying Ultrasonic Elliptical Vibration on the Base Plane

Inconel 718, a nickel-based superalloy, exhibits desirable properties over a wide temperature range, and it is widely used in industry. However, Inconel 718 is typically difficult to cut because of its strong work hardening, high temperature tensile strength, and shear strength. To improve the machinability of Inconel 718, this study proposes ultrasonic turning by applying elliptical vibration to the base plane. The principle and features of the ultrasonic elliptical vibration are discussed in detail. Experiments were conducted on a commercial ultrasonic cutting unit installed onto a commercial numerical control (NC) lathe; the cutting forces were found to be lower in the new method than in conventional turning (CT). Microchip particles were observed on both chip and work surface in CT but were almost absent on the surfaces prepared by ultrasonic elliptical vibration assisted turning (UEVT). Furthermore, the cutting tool used in CT developed built-up edge (BUE), and its flank wear became heavier; in contrast, negligible BUE and less flank wear were found on the cutting tool used in UEVT. The theoretical surface roughness of UEVT was calculated and it agreed much well with the measured surface roughness.

Theoretical Surface Roughness Model in High Speed Face Milling

High speed milling is a newly developed advanced manufacturing technology. Surface integrity is an important object of machined parts. Surface roughness is mostly used to evaluate to the surface integrity. A theoretical surface roughness model for high face milling was established. The influence of cutting parameters on the surface roughness is analyzed. The surface roughness decreases when the cutter radius increases, total number of tooth and rotation angular speed, while it increases with the feeding velocity. The high speed face milling can get a smooth surface and it can replace the grinding with higher efficiency.

Physical Origins of High Normal Field Mobility Degradation in Ge p- and n-MOSFETs With GeO x /Ge MOS Interfaces Fabricated by Plasma Postoxidation

Mechanisms of the mobility degradation in high normal field (or Ns) in Ge pand n-metal-oxide-semiconductor field-effect transistors (MOSFETs) with plasma postoxidation GeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /Ge MOS interfaces: 1) carrier trapping due to surface states; 2) surface roughness scattering; and 3) electron transfer into the Δ valleys with the high effective mass, have been systematically investigated. It is confirmed that the existence of surface states inside the valence band and the conduction band of Ge results in over estimation of the mobile inversion carrier concentration and the rapid reduction of the effective mobility. It is also found that the Hall hole and electron mobility in high N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> region agree well with the theoretical surface roughness limited mobility, indicating that the high N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> mobility in Ge MOSFETs are still significantly limited by surface roughness scattering. On the other hand, any evidence of the carrier repopulation into the subband with low mobility has not been experimentally identified in both Ge pand n-MOSFETs yet.

Problems During Milling and Roughness Registration of Free-form Surfaces

Finishing machining of free-form surfaces is usually performed using ball mills. Constant rotational speed n and feed rate per wedge in axis of the mill fz are applied most often for the whole surface. It causes long machining time and theoretical machined surface roughness Rzt heterogeneity. In the paper we propose a milling method with variable parameters n and fz which gives greater productivity and more homogenous roughness of free-form surfaces. Based on roughness parameter measurement of the samples, many problems have been enumerated: necessity of the surface curvature pre-filtering from primary profile, necessity of 2D roughness assessment in two perpendicular directions, requirement for a high vertical measurement range and special long tips in contact profilometers most often, roughness variability and necessity of milling technology knowledge, to find a region with maximal roughness.

Digital Object Memory Integration into Indirect Surface Roughness Measurement in Turning

The paper investigates in-process signal usage in turning for indirect surface roughness measurement. Based on theoretical surface roughness value and in-process signal, a model is proposed for surface roughness evaluation. Time surface roughness and in-process signal surface roughness correlation based analysis is performed to characterize tool wear component behavior among others. Influencing parameters are grouped based on their behavior in time. Moreover, Digital Object Memory based solution and algorithm is proposed to automate indirect surface roughness measurement process.

Comparison of Theoretical and Real Surface Roughness in Face Milling with Octagonal and Circular Inserts

Various modeling techniques have applied by researchers to predict values of surface roughness parameters in different metal cutting processes. Some examples of these methods are briefly introduced. After this an analytical model and investigation method are presented which were used to make predictions of the expected values of surface roughness parameters. Cutting experiments were performed to obtain real roughness data and to validate the proposed and realised model by face milling of 42CrMo4 specimens with two different insert shapes. Conditions and results of these experimental investigations are presented in the subsequent part of the paper, and finally the determined approximation relations are introduced that can be used to calculate the expected roughness values from theoretical data.

Research on rotary surface topography by orthogonal turn-milling

As a new technology in manufacturing, turn-milling broadens the application ranges of mechanical processing, wherein both cutting tool and workpiece are given a rotary motion simultaneously. The objective of the present work is to study workpiece surface topography during orthogonal turn-milling process. This study begins with two mathematical models, which describe theoretical surface roughness and topography of rotationally symmetrical workpiece. The models are built with the establishment of locus function according to orthogonal turn-milling principle. Then based on these models, the influence law of surface topography affected by various cutting parameters is found by some simulation methods. The law also matches with orthogonal turn-milling surface roughness and topography experiments. By analyzing the experimental results, some parameter selection criteria during orthogonal turn-milling processing are also proposed qualitatively and quantitatively. The comparison between the simulation and experimental results shows that a better surface quality and tiny oil storage structure can be obtained if the cutting parameters are chosen in reason. This conclusion provides a theoretical foundation and reference for the orthogonal turn-milling mechanism research.

Vector modeling of robotic helical milling hole movement and theoretical analysis on roughness of hole surface

To avoid the machine problems of excessive axial force, complex process flow and frequent tool changing during robotic drilling holes, a new hole-making technology (i.e., helical milling hole) was introduced for designing a new robotic helical milling hole system, which could further improve robotic hole-making ability in airplane digital assembly. After analysis on the characteristics of helical milling hole, advantages and limitations of two typical robotic helical milling hole systems were summarized. Then, vector model of helical milling hole movement was built on vector analysis method. Finally, surface roughness calculation formula was deduced according to the movement principle of helical milling hole, then the influence of main technological parameters on surface roughness was analyzed. Analysis shows that theoretical surface roughness of hole becomes poor with the increase of tool speed ratio and revolution radius. Meanwhile, the roughness decreases according to the increase of tool teeth number. The research contributes greatly to the construction of roughness prediction model in helical milling hole.

Prediction of surface roughness due to spinning in the incremental tube forming process

Incremental tube forming (ITF) is a new process allowing a flexible manufacturing of 2D and 3D bent tubes with load-optimized cross sections by means of the combination of the procedures spinning and bending. The aim of this paper is to acquire an in-depth process understanding concerning the surface roughness. This paper focuses on the spinning process operation of the ITF process. The influence of the spinning roll geometry and the process parameters on the theoretical surface roughness is studied in detail. Crest height h and roughness average parameter Ra are formulated as function of process parameters and spinning roll geometry. Also, a fishbone diagram with the parameters influencing the tube surface characteristics is provided. Experiments are performed to quantify the divergences of the equations. The theoretical approach can be used to understand the incremental tube forming process in more detail.

Optimal selection of machining parameters for fast tool servo diamond turning

Ultraprecision machined components with micro-structured surfaces in micrometer or nanometer range have gained wide applications especially in optical industry. A technique called fast tool servo (FTS) diamond turning is superior in fabricating precision and complicated micro-structured surfaces with wavelength above tens of microns. However, in order to obtain optimal machined surface quality, the machining parameters need to be selected carefully. In this paper, optimal selection of the machining parameters, including spindle speed, sampling number, feedrate and tool geometry, for fabricating micro-structured surfaces by FTS diamond turning is presented. A simulation system is developed to select feedrate and tool geometry by computing the theoretical surface roughness, spindle speed, and sampling number based on the FTS dynamics and the motion controller capability. Experiments have been carried out to show the effect of the machining parameters. In addition, machining of typical micro-structured surfaces with machining parameters selected by the presented approach proves the effectiveness of the proposed optimal machining parameters selection method and the designed FTS diamond turning machine.