Research Part Surface Position Influence on Metal Removal and Steady-State Roughness During Vibro-Abrasive Processing

The paper is devoted to the study of part surface position and its influence on metal removal and steady-state rougness during vibro-abrasive processing. The article raises the differences between vibro-abrasive processing of external and internal part surfaces. Theoretical dependencies analysis for determination on part material removal and surface steady-state roughness is carried out. It is known that available theoretical dependencies do not take into account part surface position for material removal and the steady-state roughness calculation. Experimental researches to determine internal surface material removal with external surface isolation were carried out. The influence of part surface position on the steady-state roughness is investigated. Based on obtained experimental results, the dependence graphs of material removal and roughness on the processing time are constructed. The comparative analysis of the part surface position influence on material removal and the steady-state roughness during vibro-abrasive processing is carried out. The results showed that material removal volume from the internal surface more than from the external for short part length, however material removal volume from the external surfaces grows significantly in case of part length increasing, while from the internal surfaces is not significant. It is established that the internal surface steady-state roughness is ∼1.55 times higher than external surface steady-state roughness after processing in triangular prism 15×15, grit 16.

Influence of part surface preparation on the coating adhesion strength of during plasma spraying

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Volumetric adaptive slicing of manifold mesh for rapid prototyping based on relative volume error

Purpose Compared with cusp height and area deviation ratio, volume error (VE) caused by the layer height could represent the stair-case effect more comprehensively. The proposed relative volume error (RVE)-based adaptive slicing method takes VE rather than cusp height as slicing criteria, which can improve part surface quality for functionalized additive manufacturing. Design/methodology/approach This paper proposes a volumetric adaptive slicing method of manifold mesh for rapid prototyping based on RVE. The pre-height sequences of manifold mesh are first preset to reduce the SE by dividing the whole layer sequence into several parts. A breadth-first search-based algorithm has been developed to generate a solid voxelization to get VE. A new parameter RVE is proposed to evaluate the VE caused by the sequence of the layer positions. The RVE slicing is conducted by iteratively adjusting the layer height sequences under different constraint conditions. Findings Three manifold models are used to verify the proposed method. Compared with uniform slicing with 0.2 mm layer height, cusp height-based method and area deviation-based method, the standard deviations of RVE of all three models are improved under the proposed method. The surface roughness measured by the confocal laser scanning microscope proves that the proposed RVE method can greatly improve part surface quality by minimizing RVE. Originality/value This paper proposes an RVE-based method to balance the surface quality and print time. RVE could be calculated by voxelized parts with required accuracy at a very fast speed by parallel.

Analysis of Interferometer with Micro-Mirror on Beam Splitting Cube

The control of the shape of the optical part surface by the interference method has become an integral part of the process of their shaping. With a precisely focused interferometer interferometry allows obtaining an interference pattern similar to a topographic map of the error profile of the wave surface under investigation. The interferometer must form a map of the optical surface with high accuracy --- the permissible distortion of the interference fringe caused by an interferometer error should not exceed 0.1 of the distortion value caused by an error on the examined surface. The dependence of the interference pattern formation on the errors in the arrangement of the interferometer components, i.e., defocusing, was theoretically analyzed using Fourier transforms. The analysis was performed for an interferometer containing a laser illuminator, a concave spherical mirror with a central hole, coaxial to the illuminator, and a beamsplitting element in the form of a cube-prism with a semitransparent hypotenuse face. On the first flat face of the cube-prism, a microspherical concave mirror is made with the center located on the optical axis of the interferometer. A method for calculating the defocusing of a controlled spherical mirror and the corresponding wave aberration of the working wavefront is presented. An example of calculating the design parameters of the interferometer and the permissible defocusing of the controlled spherical mirror is given

Effects of residual stresses on the bending stiffness of shafts strengthened by enveloping de-formation

The aim was to study the effects of technological residual stresses on the bending stiffness of cylindrical parts of shafts and axes. Experiments were conducted for elongated cylindrical specimens made of steel grade 35 with a diameter of 30 mm using boring and turning methods. Specimens were annealed in a protective medium to remove initial residual stresses. Experiments were carried out using an Amsler laboratory hydraulic testing machine and VK8 grade hard-alloy matrices. The experiments showed that, for an extremely low degree of relative crimping of 0.1 to 0.5%, the size of the layer with tangential residual compression stresses gradually decreases. The stiffness of such cylindrical workpieces remains almost unchanged. An increase in relative crimping (from 0.5 to 1.2%) leads to a decrease in resi dual compression stresses on the part surface. The layer thickness with tangential residual compression stresses starts to increase. This leads to a decreased residual buckling and an increased bending stiffness. It was found that the degree of relative crimping has no effect on the variation of distribution depth of axial residual stresses. Optimal distribution of tangential residual compression stresses can be reached by increasing their depth. A linear relationship was found for relative crimping of 0.1 to 1.0%. The highest bending resistance was recorded for specimens strengthened by residual crimping of about 1.0%. By processing workpieces using enveloping deformation with crimping of 0.1% and loading them with a transverse force of 0.6 kN, bending distortion can be decreased and the strength of parts can be increased by 5 times. It was found that the bending stiffness of cylindrical shafts is greatly affected by residual compression stresses. The bedding depth of residual stresses has various effects on the stiffness of cylindrical parts. Thus, correct use of strengthening enveloping deformation can form a high-quality surface layer on parts with the pre-defined distribution of residual stresses.

The Prospects of Abrasive Treatment of Tough-To-Machine Materials

In current conditions, great attention is paid to the quality of parts, which is in many ways determined by finishing operations of mechanical treatment, with surface grinding being the most widespread. Grinding process efficiency, abrasive tool wear intensity, machined surface quality and other features of grinding process depend on properties of the environment, where the cutting process takes place. Forced changing of conditions of this environment is one of the ways to control and optimize the grinding process, which can be reached due to finding new technological decisions. One of the most promising directions to solve this problem is the process of face grinding with discontinuous grinding tool and supply of cooling fluid or air in the cutting zone directly. Carried analysis of features of face grinding has shown that heat density can be decreased by the usage by grooved wheels with vortex air cooling or by supply of cooling-lubricant technological fluid. Obtained dependences of temperature field of part surface during grinding establish the influence of the length of working shoulders and grooves, vortex tubes number, outflow rate, temperature and flow rate of cold vortex flow of air. These data provide conscious control over the process of discontinuous face grinding by changing wheel grain size and grinding speed.

Object Grasping Instructions to Support Robot by Laser Beam One Drag Operations

We propose a system in which users can intuitively instruct the robot gripper’s positions and attitudes simply by tracing the object’s grasp part surface with one stroke (one drag) of the laser beam. The proposed system makes use of the “real world clicker (RWC)” we have developed earlier, a system capable of obtaining with high accuracy the three-dimensional coordinate values of laser spots on a real object by mouse-operating the time-of-flight (TOF) laser sensor installed on the pan-tilt actuator. The grasping point is specified as the centroid of the grasp part’s plane region by the laser drag trajectory. The gripper attitude is specified by selecting the left and right drag modes that correspond to the PC mouse’s left and right click buttons. By doing so, we realize a grasping instruction interface where users can take into account various physical conditions for the objects, environments, and grippers. We experimentally evaluated the proposed system by measuring the grasping instruction time of multiple test subjects for various daily use items.

A New Conformal Cooling System for Plastic Collimators Based on the Use of Complex Geometries and Optimization of Temperature Profiles

The paper presents a new design of conformal cooling channels, for application in collimator-type optical plastic parts. The conformal channels that are presented exceed the thermal and dynamic performance of traditional and standard conformal channels, since they implement new sections of complex topology, capable of meeting the high geometric and functional specifications of the optical part, as well as the technological requirements of the additive manufacturing of the mold cavities. In order to evaluate the improvement and efficiency of the thermal performance of the solution presented, a transient numerical analysis of the cooling phase has been carried out, comparing the traditional cooling with the new geometry that is proposed. The evolution of the temperature profile versus the thickness of the part in the collimating core with greater thickness and temperature, has been evaluated in a transient mode. The analysis of the thermal profiles, the calculation of the integral mean ejection temperature at each time of the transient analysis, and the use of the Fourier formula, show great improvement in the cycle time in comparison with the traditional cooling. The application of the new conformal design reduces the manufacturing cycle time of the collimator part by 10 s, with this value being 13% of the total manufacturing cycle of the plastic part. As a further improvement, the use of the new cooling system reduces the amount of thickness in the collimator core, which is above the ejection temperature of the plastic material. The improvement in the thermal performance of the design of the parametric cooling channels that are presented not only has a significant reduction in the cycle time, but also improves the uniformity in the temperature map of the collimating part surface, the displacement field, and the stresses that are associated with the temperature gradient on the surface of the optical part.