Papers by Keyword: Abrasive Machining

Abstract: Ceramic Matrix Composites (CMC) are becoming increasingly important in aeronautical and space applications due to their excellent mechanical properties and wear resistance at high temperatures. Abrasive processes are commonly used for CMC machining due to its high hardness. In this work, an experimental analysis of the influence of grinding parameters has been carried out. Namely, the effect of the variation of cutting speed and feed speed have been studied when grinding a Cf/SiC composite with diamond wheels. Forces were registered during the tests and workpiece quality was analyzed by means of optical techniques. Results show that higher feed rates increase normal force values, while higher cutting speeds lead to lower normal machining forces. Moreover, a relationship between grain aggressiveness and specific grinding energy was observed. Decreasing machining forces also helped to preserve surface integrity of the machined parts.

Abstract: Surface finishing of glass and ceramics flats is difficult to perform using already existing traditional processes because of the brittle nature of these materials. In order to make traditional processes be able to accommodate these materials, relatively expensive aiding devices and approaches are required. The newly developed magnetorheological (MR) fluid finishing offers a solution to this problem at a relatively low cost. Magnetorheological fluids have been used in mechanical engineering applications because of the rheological behavior they possess under a magnetic field which enables the manipulation and pressure of loose abrasives on the machined surfaces and perform cutting action. This paper describes the design and development of an MR fluid machine-tool for flat surface finishing. The design presented herewith includes the design of the mechanical aspects of the ball-end tool machine and its support structure for a three-axis motion system. The objective of this study is realized based on utilizing a magnetic field, magnetorheological fluid and CNC router design to perform flat surface finishing.

Abstract: In this paper new kinematics systems were studied for a single lapping process. In order to ensure the constant profile wear of the tool a standard kinematic system can be changed. Lapping is carried out by applying loose abrasive grains between two surfaces and causes a relative motion between them. The result is a finish of multi-directional lay. During process, the mechanism of surface formation are decisively affected by a pressure force, a process time and a motion type of grains. It has been proven, that providing the additional movements of the conditioning ring affects the profile wear of the lapping plate. First of all, the kinematics equations of the lapping process have been developed and the process has been simulated. A type of the abrasive particle trajectories in standard single-disk lapping depends on rotational speed ratio of a tool and a conditioning ring. In addition, two new kinematic systems were presented: with radial and secant movement of the conditioning ring. Finally, comparison and analysis of abrasive trajectories were carried out.

Abstract: New tools for flat grinding are the subject of the paper. Electroplated diamond tools with different grains - D64 and D107 - were used in a modified single-disc lapping machine configuration. The results from flat grinding, such as the material removal rate (MMR), surface roughness and plane-parallelism are presented in the paper. Apart from ceramic samples, the additional experiments were carried out on cemented carbide workpieces (H10S) with the use of a diamond electroplated tool (D64). SEM microscopic images of unworn and worn active tool surface are presented with abrasive grains worn by attrition and cavities in the nickel bond after the grains pull out.

Abstract: Previous studies on one-sided lapping allow to state that not only parameters of lapping elements (i.e. properties of workpiece, abrasive grains and lapping plate) impact on a lapping efficiency. Influential are also kinematics and dynamics of the process. It is crucial to control an average velocity of lapping (v), a distribution of tangential acceleration (at), a nominal pressure (p), a lapping time (t) and disposal of workpiece in separator.Based on kinematics equations and the tribological models, the dimensionless distribution of the material removal volume and the trajectories of abrasive grains cutting on the lap were numerically simulated. Obtained information about excessive wear on lapping plate was the starting point to work out non-standard, single-plate lapping systems.In this paper ideas of unconventional lapping systems were presented. After numerous simulations and careful analysis it was observed, that the most desirable system is radial lapping system. It was point out that other systems are not very different from the standard kinematic system. Generated trajectories of an abrasive grain were almost identical. What is more, effects of kinematical parameters on the trajectories, velocities and accelerations observed in radial lapping system are shown.

Abstract: For the deep-hole drilling is in closed or half-closed condition and the cutting situation can’t be controlled directly, it brings a big challenge to attain the machining precision. Deep-hole honing is an effective process method that can ensure the precision of size, geometry shape and surface quality. A new machining technologies of finishing honing on precision deep-hole are discussed. Two typical machining examples were illustrated, and the machining effection were also discussed. The key technology and chief feature of strong honing were analyzed through honing experiment of titanium alloy and PH stainless steel. The experiments indicate that strong honing is one effective method to solve the problem of precision deep-hole machining of difficult-to-cut materials and the honing tools which was used in the experiments have the feature of good rigidity, high cutting efficiency.

Abstract: New tools for flat grinding of ceramics (Al₂O₃) are presented in the paper. Electroplated CBN tools (B64 and B107) were used in a modified single-disc lapping machine configuration. The results from experiments, such as the material removal rate and surface roughness parameters are presented and analyzed. Numerical simulations, based on the model for the shape error and tool wear estimation in machining with flat lapping kinematics, are also presented. The tool life of electroplated tools can be extended by choosing appropriate parameter K related to the process kinematics.

Abstract: Vibration-assisted machining (VAM) combines small-amplitude vibration with different machining process to improve the process fabrication quality. It has been applied to a number of machining processes, such as turning, drilling, grinding and polishing. The emphasis on this literature is the vibration-assisted abrasive machining (VAAM), which involves with finishing and grinding processes where VAAM have been applied to hard metal, brittle material and complex geometries products like optical molds. This paper presents different vibrating units in VAAM from tool vibration to workpiece vibration, which also includes different vibrating paths from linear to ellipse. Typical hardware systems used to achieve these vibratory motions are described too.

Abstract: Abrasive machining is widely used as final machining process. It is still challenged to investigate the fundamental knowledge on the formation mechanism of groove and pile-up in single abrasive particle cutting. A 3D finite element analysis model to simulate single abrasive particle scratching on bearing steel (52100) workpiece with low cutting speed is proposed. An adaptive meshing technique is applied to handle large mesh deformation problem of the scratching process. The formation process of groove and pile-up for workpiece material is indentified qualitatively. The simulated results show that cutting speed has little effect on lateral profile. The height and area of pile-up increase with increase of depth of cut.

Abstract: Titanium is a metal material which has many excellent properties; it has been widely used in many fields. In this paper, plane abrasive machining is carried out for Titanium plate. The surface roughness and morphology of Ti-plate is compared after fixed and loose abrasive machining. The experiment proved that the drop magnitude of Ra in loose abrasives machining is great larger than that in fixed abrasive when grit size is nearly equal, and the improvement of surface defect such as some directional marks, deep scratch and bits in loose abrasives machining is rapider and quicker than that in fixed abrasives during same machining time. The results of experiments indicts that loose abrasive machining is better than fixed abrasive in reducing surface roughness and improving surface morphology, since the higher density of active abrasives and machining force uniformity.