Orientation Of Workpiece Research Articles

Exploring the contribution of unconventional parameters on spark gap formation and its minimization during WEDM of layered composite

Cladded materials are heterogenous in nature and considered as difficult-to-cut especially via conventional machining operations. Gas and/or plasma cutting are common in practice to cut clad materials. However, these processes induce deeper heat-affected zones and provide very rough surface integrity. Wire electric discharge machining (WEDM) is a capable alternate yielding better cut quality. Formation of a significant spark gap between the cut surfaces is the iconic problem of WEDM which is addressed in this study. WEDM has been performed on stainless-clad steel with a focus on identifying the significant parameters affecting the amount of spark gap and its minimization in the final cut. Eight input control factors, namely workpiece orientation, thickness of individual layer, servo voltage, pulse on-time, wire diameter, wire feed, and pressure ratio, have been employed to investigate their effects on spark gap development. Experimentation has been performed according to L18 orthogonal array followed by comprehensive statistical analyses. ANOVA shows that wire diameter and pressure ratio are the two main influential parameters for spark gap having percentage contribution of 71% and 16%, respectively. Optimal settings of control variables are also achieved through S/N ratio analysis. Improvement of 23.4% towards spark gap reduction is realized.

An investigation of surface roughness and parametric optimization during wire electric discharge machining of cladded material

The development of cladded materials to augment the industrial requirements is grown because of having combination of properties in end use applications. However, the real challenge regarding the application of these materials is its machining with reasonable surface finish and accuracy owing to the heterogeneous nature. Therefore, oftenly, thermal cutting process like gas cutting and plasma arc cutting are used, but these processes not only offer poor surface quality but also necessitate additional finishing operations. Wire electric discharge machining (WEDM) process is a viable alternate but the roughness generated on the two surfaces is different as the said process is thermoelectric in nature and both layers of material have different thermoelectric properties. In the current research the cutting performance of WEDM of stainless clad steel has been evaluated with a focus not only to reduce the surface roughness of individual layer but also to minimize the difference as well. The influence of uncommon parameters, such as layer thickness of specific layer, workpiece orientation, pressure ratio, and wire diameter are primarily investigated. Wire diameter and workpiece orientation have proved to be the significant control factors affecting the surface roughness of both the layers, whereas pressure ratio affects the surface roughness of one layer (mild steel). Optimal settings of control factors have been developed using grey relational analysis. The results of confirmatory experiment validates the model as not only the surface roughness of both layers have been decreased, but also the difference comes to be minimal of only about 0.02 μm.

Investigation of wire electric discharge machining of stainless-clad steel for optimization of cutting speed

The use of cladded materials has grown up in manufacturing industry as it provides a blend of properties in end-use applications. However, the cutting of a cladded material is really considered as a challenging task owing to their heterogeneous nature; therefore, it is often subjected to thermal cutting processes like gas cutting or plasma arc cutting. But thermal cutting processes offer poor surface finish and require subsequent finishing operations. Wire electric discharge machining (WEDM) is a competent alternate in terms of surface finish, but this process offers relatively low cutting rates. In this research work, an attempt has been made to evaluate and optimize the cutting performance of WEDM for cutting stainless-clad steel in terms of cutting speed which is one of the most crucial considerations in manufacturing. In addition to the commonly studied WEDM parametric effects, the influence of workpiece orientation, layer thickness of individual layer, wire diameter, and pressure ratio of dielectric fluid on the cutting speed is mainly evaluated. Taguchi’s L18 orthogonal array has been used for experimental design. Optimal combinations of machining parameters to maximize the cutting speed are extracted through various statistical analyses, and it has been found that the proposed optimal set of parameters results into an improvement of about 20% in cutting speed in WEDM of stainless-clad steel. It has also been observed that the individual layer thickness of the cladded material plays a vital role in controlling the cutting speed of WEDM. The contribution of stainless steel layer thickness on cutting speed is found to be two times as compared to the contribution of mild steel layer.

Proposing a method for estimating the real micro profile of a milling tool

Manufacturing Engineering domain generally uses for creating virtual work piece profiles or tool representations descriptive parameters or simplified drawings. More recent and accurate methods such as the present study uses optical devices for obtaining virtual projections of work pieces/tools. This paper presents an experimental method applied in order to obtain the profile for a given cutting tool, which can offer in addition possibility to estimate the cutting tool wear, without using such built-in machine-tool device. The experimental values obtained are materialized by the accuracy which characterizes the accurate profile of the measured cutting tool. This fact can make a difference between a classical measurement method applied outside of machine tool sector and a new one provided by a device which offers the solution to measure a work piece directly on the machine tool, without modifying the actual work piece orientation conditions and at a low price.

CCT-based mode coupling chatter avoidance in robotic milling

Currently, large aerospace structures are machined using large multi-axis CNC machining centers. In comparison, milling with a multiple degree-of-freedom (dof) articulated robotic arm has several advantages due to its lower cost and versatility. The low stiffness of an articulated arm robot, however, gives rise to severe low frequency mode coupling chatter during machining. Previous studies have shown that such chatter can be suppressed by minimizing the angle between the average resultant cutting force direction and the direction of maximum principal stiffness of the robot. This approach limits the range of permissible robot motion, and therefore its flexibility of use. This paper presents a new method for avoiding mode coupling chatter in robotic milling using the Conservative Congruence Transformation (CCT) stiffness model, which does not require changing the tool feed direction or the workpiece orientation. Robotic milling experiments show that mode coupling chatter is significantly reduced when using this approach.

Real-time online monitoring of nanosecond pulsed laser scribing process utilizing spectrometer

This study proposes a novel configuration and algorithm to develop real-time online monitoring of an ultrafast scribing process utilizing a spectrometer. The target process was the ultrafast low energy scribing process performed by using a nanosecond laser. A new configuration in which the spectrometer probe incorporated into the scanner head unit and received the reflection light of microprocessing via a special monitoring adapter has been developed. The scan head adapter enables the scan head-based observation of a galvanometer and polygon scan head's working field. Typical applications include process monitoring or determination of a work piece's orientation during laser processing.

Method for optimization of the orientation and fixing system of workpiece for the construction of control devices

The development and evolution of technological equipment for machining, assembly and control ensure the modernization of manufacturing processes. Devices as subsystems of technological system in the general context of the development and diversification of machinery, tools, workpiece and drives are made in a variety of sizes and constructive variants that create difficulties in their structure and improvement. Part of the research in recent years presented in this paper have as major objectives the increase of accuracy, productivity and flexibility of orientation and fixing devices for control operations. To this end there have been developed a mathematical model, a new method of working and an algorithm for optimizing the construction of the orientation and fixing system of a new type of control device.

Effects of tool handle dimension and workpiece orientation and size on wrist ulnar/radial torque strength, usability and discomfort in a wrench task

The effects of tool handle dimension (three modified designs of wrenches with 30–50 mm diameter cylindrical handles and traditional design with rectangular cross-sectional (5 mm × 25 mm) handle), workpiece orientation (vertical/horizontal) and workpiece size (small/large) as well as user's hand size on wrist ulnar/radial (U/R) torque strength, usability and discomfort, and also the relationship between these variables were evaluated in a maximum torque task using wrenches. The highest and lowest levels of maximal wrist U/R torque strength were recorded for the 30 mm diameter handle and traditional wrench design, respectively. The prototype handle with 30 mm diameter, together with 40 mm diameter handle, was also better than other designs as they received higher usability ratings and caused less discomfort. The mean wrist torque strength exerted on a vertically oriented workpiece (in the sagittal plane) was 23.8% higher than that exerted on a horizontally oriented one (in the transverse plane). The user's hand size had no effect on torque exertions. The wrist torque strength and usability were negatively correlated with hand and finger discomfort ratings. The results are also discussed in terms of their implications for hand tool and workstation configuration in torque tasks involving wrenches.

Comparative study of the lubricating behavior between 12-in. copper disk and wafer during chemical mechanical polishing

In this study, a specially designed carrier with a one-zone pneumatic loading system that uses a thick copper disk as the workpiece was developed. Comparative studies of the fluid pressure and workpiece orientation between the disk and wafer carriers during chemical mechanical polishing were conducted. The results reveal that the copper disk leans down toward the leading edge and produces a negative-dominated (approximately 70%) fluid pressure, which differs from the multi-zone carrier but agrees with other studies in which the fluid pressure is measured from the disk side. Different balancing statuses and wedged gaps are formed in these two structures.

Role of crystal orientation on chemical mechanical polishing of single crystal copper

The material removal mechanism of single crystal copper in chemical mechanical polishing (CMP) has not been intensively investigated. And the role of crystal orientation in CMP of single crystal cooper is not quite clear yet. Quasi-continuum method was adopted in this paper to simulate the process of nano-particles grinding on single crystal copper in CMP process. Three different crystal orientations, i.e. x[100]y[001], x[001]y[110] and x[–211]y[111], were chosen for analysis. The atom displacement diagrams, stress distribution diagrams and load-displacement curves were obtained. After analyzing the deformation mechanism, residual stress of the work piece material and cutting force, results showed that, the crystal orientation of work piece has great influence on the deformation characteristics and surface quality of work piece during polishing. In the A(001)[100] orientation, the residual stress distribution after polishing is deeper, and the stress is larger than that in the B(110)[001] and C(111)[–211] orientations. And the average tangential cutting force in the A(001)[100] orientation is much larger than those in the other two crystal orientation. This research is helpful to revealing the material removal mechanism of CMP process.

Kinematic analysis and experimental investigation on vibratory finishing

Vibratory finishing has been widely used for surface polishing, burnishing, edge finishing, texturing, and cleaning with a wide variety of different media. Medium properties and their motions dominate material removal efficiency and surface treatment quality in the vibratory finishing process. In this study, medium kinematic model and movement simulation of vibratory finishing were developed. Medium motion simulation was verified through a digit video recorded by a high-speed camera. It was found that medium kinematic path line is a circular-feeding helical motion, which is determined by the angular velocity ratio between the rolling and feeding, the rotation direction, and vibratory finishing machine configuration. Material removal intensity model was further established based on the kinematic model in order to better understand the vibratory finishing process. The optimal fixing location and orientation of workpiece were obtained through the analysis of the kinematic model. Finishing experiments were further carried out for the Ti6Al4V test pieces which were fixed onto the wall of a vibratory bowl. The surface roughness, Ra values (with initial surface roughness of 1.50 μm), approached to 0.13 μm after processing time of 2.5 h and 0.10 μm after processing time of 6.0 h. Surface quality of finished test pieces has been significantly improved as compared with the existing method (i.e., loosed workpiece in the vibratory bowl), whereby the surface roughness, Ra values (with initial surface roughness of 1.50 μm), tapered off (saturated) to about 0.52 μm with the increase of processing time.

Determining the Optimum Parting Direction in Plastic Injection Molds Based on Minimizing Rough Machining Time during Mold Manufacturing

ABSTRACTThe versatility of plastic materials allows engineering components of very complex geometries and functionalities to be injection molded from them. Because the manufacturing cost of a mold increases with the complexity of the cavity, it is important to optimize the design of component and mold concurrently. In this study, a methodology for determining the optimum parting direction (PD) considering mold‐manufacturing factors such as tool accessibility and the amount of material to be removed is presented. The methodology starts with an accessibility analysis in which a three‐dimensional part is discretized, and candidate PDs are selected based on maximizing the accessible area, that is, the area that can be machined with a single workpiece orientation or setup. Then, the rough machining process is considered, and an optimum PD that minimizes the rough machining time for both the cavity and core plates is selected. The methodology is applied to four different automotive components: a mirror cover, an interior panel, a pillar, and a fender splash shield.

ANISOTROPY OF MECHANICAL PROPERTIES OF PRODUCTS MANUFACTURED USING SELECTIVE LASER MELTING OF POWDERED MATERIALS

The paper examines factors leading to anisotropy of properties in products manufactured using lasercusing, a technology consisting in selective laser melting of metal powdered materials. The results obtained when evaluating mechanical properties of specimens made of titanium alloys Ti–6Al–4V, VT6 and heat-resistant nickel alloy Inconel 718 in different directions are presented. The study covers the microstructure of compact specimens obtained using selective laser melting, and describes dependence of their mechanical properties on workpiece orientation with relation to the unit working platform. The study of Ti–6Al–4V microsections showed that the direction of the rectangular specimen grain structure matched the growth direction, whereas thin elements with a lattice structure were made with other thermal processes due to their smaller cross section. This affected crystallization conditions and microstructure being formed: grain directions and shapes changed depending on the lattice structure element inclination.

一方向CFRPのドリル加工における工具刃数と切削力特性

3 flutes twist drills have recently been used to metal cutting in terms of accuracy of drilled holes. The paper discusses the cutting processes of 2 and 3 flutes drills in drilling of uniaxial carbon fiber reinforced plastic (CFRP). The cutting force depends on the relative angle of the cutting direction with respect to the fiber orientation of workpiece. The changes in the cutting forces with the cutter rotation are analyzed in the cutting force measurement and the cutting simulation based on a force model, where the orthogonal cutting data for the simulation changes with the relative angle of the cutting direction to the fiber orientation. The averages and the periodical amplitudes in the cutting forces are discussed for drilling of 2 and 3 flutes tools. Large cyclic changes in thrust and torque appear in drilling with 2 flutes drill. X and Y components, in contrast, change periodically in drilling with 3 flutes drill.

Dynamic Behavior Study of Drill Bush Guide Plates from the Fixtures Structure

Fixtures are use to ensure the orientation and position of workpiece and cutting tools in machining systems. Drill bush guide / holder or are part of a specific category of elements and mechanisms, found in the fixtures structure: elements for size adjustment and guidance for cutting tools. These drill guide bush/ holder are used for guidance of drills, in order to ensure a certain position of the tool regarding the certain reference elements of the workpiece, or to increase the stiffness of drills, when the tool diameter is reduce, or when the surface of the machined workpiece is inclined. The drill bushes are placed in the fixture body, directly or through drill bush guide plates/ drill bush support plates. The characteristic feature of these bush plates is the console length. Sometimes, the bush guide plates can have large lengths that affect the dynamic stability. The bush guide plates are dynamically excited by the direct contact with the drill of the bush. If the natural frequency of vibration of the plate is equal or higher than the excitation frequency of the machining process, then the resonance phenomenon can appear.

GRAVITY–OPERATED IMPACT FEEDER DYNAMICS

This paper deals with the dynamics of rigid body that collide with a rigid surface; such motion with impact of bodies takes place in the gravity operated impact feeders. Feeders are mechanisms of the single- peace feeding for the forced moving of the oriented workpieces. In this work the vertical gravity-impact feeder for moving of the prismatic or plane details is presented. The parts move on inclined guiding plates, free fall and collide with the down plates, the impact phenomena may be used both for decreasing of velocity and for the orientation of the tracking workpieces (lateral reversing). System of equations of plane motion of detail, including stages of sliding on the slope guideway, free flight, impact and motion to the next guideway, are written down. System of equations is solved numerically with help of MathCAD program.

Effect of Workpiece Orientation, Lubrication and Media Geometry on the Effectiveness of Vibratory Finishing of Al6061

Vibratory Finishing is a commonly used process for deburring and polishing. The process effectiveness is difficult to quantify due to a nexus of variables relating to workpiece, media, compound and machine. In this paper, effect of orientation of rectangular Al6061 workpieces is considered with respect to the motion of ceramic media using water as lubricant. It is found that parallel orientation of workpiece to media motion and higher lubrication level lead to higher degree of sliding, thereby leading to smoother finish. Experiments with different ceramic media showed smoother finish with the geometry more susceptible to rounding. The aforesaid findings can be employed in applications requiring superpolished surfaces.

Optimal workpiece orientation to reduce the energy consumption of a milling process

Energy consumption in the manufacturing sector is becoming a very hot topic due to its significant ecological relevance, especially for energy intensive processes such as machining. Machining finds nowadays large application mainly due to its high performance, in terms of both surface finish and tolerances achievable; as an example this is the key technology in dies and molds production, largely used in the automotive and housewares sectors. Process optimization could be carried out using different strategies, as already proposed by many authors, such as by optimizing machining parameters or implementing alternative toolpath capable of reducing both machining time and energy consumption. Within this paper will be presented a novel approach that takes into account the product orientation within the working zone of the machine. Milling machines are usually non symmetric regarding the energy consumptions of the axes due to the different masses that have to be moved, hence product orientation could sensibly affect energy consumption in performing a toolpath. Optimizing product orientation has the advantage not to affect product quality and require no adjustment of machining parameters. An approach to model the machine power consumption and to optimize the workpiece orientation is presented together with the results of validation experiments.

Concentric hole drilling in multiple planes for experimental investigation of five-axis reconfigurable precision hybrid machine

A five-axis machining center integrates two mechanical models: a three-degree-of-freedom parallel platform and traditional computer numerical control X–Y table. There is a trend for machining centers to be reconfigurable precision hybrid machine tools (RHMTs) for the fabrication of complex and precision products. Most industrial robots have open kinematic chains and serially connected links. A parallel manipulator is a closed-chain mechanism with two platforms (a base and moving platform) connected together by at least two independent kinematic chains. A parallel machine tool has the advantages of high rigidity, high precision, low inertia, and a simple mechanism. It is not easy to correct the errors in a five-axis machine tool. This paper focuses on the initial calibration of the static state errors, which consist of the errors from the component part machining, work-piece orientation, and mechanism combination. In an RHMT mechanism, a three-axis motion platform primarily controls the Z, α, and β freedoms. A laser displacement meter is fixed on the Z axis and measures the error in relation to the central position of the moving and fixed platforms when the x-y table is moved. The inverse kinematics of this mechanism will be revised, and an improvement will be made in the attitude precision of the moving platform. Finally, this paper discusses an experiment involving the drilling of concentric holes in multiple planes using an RHMT, and examines the cutting results from a coordinate measuring machine.

Room Temperature Screw Form Rolling of AZ91D Magnesium Alloy through Processing by Extrusion-Torsion Simultaneous Working

Extrusion-torsion simultaneous processing is a very attractive technique for fabricating a rod-shape material with fine grain and random texture. We have proposed a new screw form rolling process combined with preliminary extrusion-torsion simultaneous working. Microstructure evolution and mechanical property change of AZ91D magnesium alloy during extrusion-torsion simultaneous processing was examined through microstructure observation, X-ray diffraction analysis and micro-Vickers hardness measurement. By the addition of torsion, the crystal orientation of AZ91D magnesium alloy workpiece was drastically changed from basal crystalline orientation to the random orientation. Crystal grain occurred through the dynamic recrystallization and tended to coarsen with an increase of extrusion-torsion temperature. Grain refinement under 2 um was achieved at the lowest extrusion-torsion temperature of 523 K. M8 gauge AZ91D magnesium alloy screw was successfully formed at room temperature using the extrusion-twisted workpiece preliminary solution treating at 678 K for 345.6 ks. It was found that the extrusion-torsion temperature of 678 K must be selected to fabricate the good screw without any defects.