Precision Machined Surfaces Research Articles

ROUNDNESS ERROR AND TOPOGRAPHY OF HARD TURNED SURFACES

Accuracy and topography are significant indicators of precision machined high-quality surfaces. Case hardened steel (16MnCr5) was analyzed to obtain information about the effects of technological data and the connections between the analyzed accuracy (roundness) and roughness parameters (Sa, Sz, Ssk, Sku). It was found that the feed rate has a significant influence on the roundness and the roughness parameters, and there are strong relationships between the roundness and these roughness parameter values: the correlation coefficients varied between 0.78 and 0.85.

Study on laser de-weight and dynamic balance technology of rotating machines

Abstract To solve the poor precision and low efficiency of manual grinding de-weight dynamic balance of turbopump rotor, the laser de-weight dynamic balance technology of rotating machines is adopted. Combined with the advantages of laser de-weight, such as, fast processing speed high machining precision and good machined surface quality, the smooth transition of the machined surface was realized by means of hierarchical machining. According to the characteristics of the turbopump rotor structure, the equivalent transformation model for laser de-weight turbopump rotor was built to convert the unbalance into laser processing parameters, which achieve the rapid and accurate de-weight of turbopump rotor. It focuses on solving the repeatedly loading and low accuracy of manual grinding dynamic balance. To verify the effectiveness of the proposed technique, laser de-weight experiments were carried out on two turbopump rotor test pieces. A dynamic balance test bench was set up to measure the rotor residual unbalance at 1800 r/min test speed, which is low dynamic balance. The results show that the machined surface transition was smooth, the residual unbalance was small and the machining efficiency was high. The effect of laser de-weight dynamic balance reached the expectation. It is an universal technology which is not limited to the dynamic balance of turbopump rotor, but also applicable to other rotating machinery..

Development of a Surface Roughness Evaluation Method from Light and Shade Composition using Deep Learning

Many companies agree on the need to introduce smart factories that promote low-cost, high-efficiency operation by applying IoT technologies to manufacturing plants. To assist in efficient manufacturing, this paper proposes a system for evaluating surface roughness through deep learning AI methods from the distribution of shade on the surface of an object. This is thought to greatly relieve the meticulous and tedious process of manual quality control for precision-machined surfaces and assist in the establishment of smart manufacturing industries. To demonstrate the usefulness of the developed technique, 305 samples of paper were categorized into three classes based on Ra threshold values, and images of paper were taken using a microscope camera. Luminance values, standard deviations, mean values, and image histograms were used to train custom-designed CNN+ LSTM composite neural networks. Completely new samples of non-training data were used for validation, which showed an accuracy of 85.185%. The proposed method can be economical, efficient, and fast compared to conventional surface roughness evaluation procedures. It can be easily integrated into an assembly line and automate quality assurance processes. This method could also prove useful in reducing labor costs and streamlining quality assurance processes due to its flexible adaptability.

Method for Determining Texture Parameters of Processed Precision Surfaces by Correlation

The article describes a new method for texture analysis of precision machined surfaces, which is based on the use of computer optics and an autocorrelation method for processing the obtained images of the textures of the studied microreliefs. The method is based on a probabilistic comparative assessment of the unknown texture of the studied microrelief with known textures of the reference microreliefs, for which the parameters of the microreliefs are predetermined according to the state standards of the Russian Federation.

Serotonin transporter allele polymorphism associated with the gut microbiome of adult rhesus monkeys

Morphological filters are E-system-type filters, which are complementary to M-system filters that are based on mathematical morphology. They are the superset of the early envelope filters but offer more tools and capabilities. This chapter first reviews the historical development of morphological filters along with the associated basic theories of morphological operations. The applications of morphological operation in the field of geometrical metrology are illustrated. The chapter then presents two advanced computational algorithms that allow morphological filters to be applied to free-form surfaces. The first algorithm is based on a computational geometry technique, that is, alpha shape theory, which can be further optimized by searching contact points and using the divide and conquer technique. The second algorithm removes the dependence of the alpha shape method on the Delaunay triangulation and recursively searches the contact points of the structuring element and the surface. In conclusion, this chapter will present and evaluate examples of applying morphological filters on precision-machined surfaces and additive manufactured surfaces.

Study on key factors influencing the surface generation in rotary ultrasonic grinding for hard and brittle materials

Rotary ultrasonic grinding (RUG) provides effective solutions for hard and brittle materials processing, but the surface generating mechanism is still unclear. This paper presented a fundamental research for surface forming in RUG processing hard and brittle materials. A new method is pointed out for surface morphology regulating and predicting in engineering ceramics machining. According to the kinematics analysis and fracture mechanics of brittle materials, the surface forming model is developed step by step. The grinding force and material removal rate are discussed for evaluated the RUG process. Depend on the mathematical models, the dynamic association between ultrasonic energy, grinding parameters and surface micro structure were revealed and presented. The surface topography can be simulated and regulated by ultrasonic energy control or grinding parameters adjustment. Micro structure design and high precision machined surface can be realized through theory calculation. Due to the fundamental analysis, a series of simulation and experiment were executed for verify the theory deduction. This model can be served as a fundamental principle for surface topography modification and machining efficiency improvement in RUG.

Study on the extraction and reconstruction of arbitrary frequency topography from precision machined surfaces

This article presents an extraction and reconstruction method for arbitrary two-dimensional and three-dimensional frequency features in precision machined surfaces. A combination of power spectrum density and continuous wavelet transform is used to analyze the potassium dihydrogen phosphate crystal surface topography. All frequencies involved in sampling area of measuring instrument are distinguished by power spectrum density method. Compared to discrete wavelet transform used to decompose frequency features, continuous wavelet transform method can extract and reconstruct two-dimensional profile and three-dimensional topography of arbitrary frequency features from original precision machined surfaces. Analysis results show that amplitude and distribution of different frequency features in two-dimensional profile or three-dimensional surface topography are fully restored by continuous wavelet transform. The effects of different factors in machining process on precision machined surface topography may be discovered. Furthermore, the extraction and reconstruction method is generally applicable for the analysis of all precision machined surfaces.

Influence of Process Parameters on Geometric Precision of Machined Surface after WEDM

Geometrical precision machined surface is generally understood as mainly precision shape, orientation, location and run-out. As a rule, it is measuring the appropriate deviations from the nominal surface. The geometric size of this deviation from the nominal surface can in practice affect the conventionally measured value for the dimension and the dimension whilst maintaining the required tolerance. Because the WEDM technology is among the most accurate technology, the small final geometric accuracy deviation has also a negative impact on the final quality of the machined surface. The paper aimed to describe errors geometrical precision of machined surface which occurs in wire electrical discharge machining (WEDM) and quantify their scope.

Effect of cutting fluid on precision machined surface integrity of heat-resistant stainless steel

The machined surface integrity of blades is of utmost importance in the power equipment manufacturing industry. Recently, many blade accidents have been attributable to the misuse of cutting fluids that were necessary in the actual machining of difficult-to-cut materials, but the effect of the cutting fluid on surface integrity and service performance has been persistently neglected. In this article, an investigation into the effect of cutting fluids on the surface quality of a typical blade material was undertaken, combined with properties of two universal cutting fluids. Element composition, surface morphology, residual stress and hardness of the machined surfaces were investigated. The results indicated that cutting fluids could not reduce cutting forces in precision machining. There were some places where local and irregular elemental Cr loss was incurred when machined with the additive Cl, and the depth of Cr loss was 1–2 µm. The machined surface under CF-206 was smooth, and the roughness of CF-210 was the highest. The tensile residual stresses of dry cutting were the highest, whereas those of CF-210 were the lowest. Surface work hardening under cutting fluids was higher, with depths of 20–30 µm. These results are significant for the control of precision machined surfaces and subsurfaces of blades with high integrity and service performance.

Study on the Influence of Roughness on the Detection for Mechanical Characteristics of the Machined Surface by Surface Acoustic Wave Dispersion Theory

The surface acoustic wave (SAW) technique is a precise and nondestructive method to detect the mechanical characteristics of the precision-machined surface. The paper is concerned with the effect of the roughness of the machined surface on the dispersion of surface acoustic waves propagating in the precision-machined surface which indicates mechanical characteristics of the machined surface. The finite element method (FEM) is employed by establishing a series of models with different roughness Ra value to analyze influences from different roughness Ra value on surface acoustic wave dispersion. The models are established by applying a combined method based on fractal theory and wavelet analysis. The simulation results showed that the roughness of machined surface will cause the dispersion of surface acoustic wave propagation, the effect varies with the different roughness Ra values. A critical Ra value influencing on the surface acoustic wave propagation exists. Accordingly, that the factor of roughness should be considered in advance or not, the situation can be determined through studying and determining the critical roughness Ra value above mentioned. Consequently, the study has the important meaning regarding the detection for mechanical characteristics of the machined surface.

On-Machine Surface Texture Measuring System Using Laser Speckle Pattern Analysis

Functional surfaces are expected technologies in various industries. However, the efficient generation of microscale surface structures is difficult because the process relies on precision surface texture assessments, which require long measuring times. An on-machine measuring system may solve this issue. In this study, a new on-machine surface texture measuring system based on laser speckle pattern analysis is proposed. The proposed system efficiently assesses various qualities of the surface texture, such as surface roughness, undulation of microscale surface structures, and anisotropy, from a laser speckle pattern obtained from the precision-machined surface. For precise measurements, disturbances caused by the machining system itself and the environment must be avoided. The laser speckle detection unit in the proposed system is supported by non-contact active vibration-isolation units, which reduce the transmission of ground vibrations. From the experimental results, the system indicated high repeatability in measurements and robustness against disturbances.

NEMA Type 7 Hazardous-Area Enclosures: Challenges and Best Practices for Installation and Maintenance

National electrical manufacturers association (NEMA) Type 7 explosion-proof enclosures are widely regarded for their robust construction and dependable operation. These enclosures are sustained without the additional safety systems required to ensure the operation of a purged and pressurized piece of equipment. Similarly, NEMA Type 7 enclosures are maintained without the costly component inventory that may be required to ensure maximum uptime of nonserviceable encapsulated equipment. NEMA Type 7 enclosures are generally constructed with cast aluminum or iron-based materials and are capable of withstanding numerous explosive events. They ensure hazardous-area safety by extinguishing flames through precision-machined surfaces and controlling structural deformation should an explosive event occur. However, if maintenance practices are not designed to ensure the integrity of the enclosure, repeated access to the internal equipment and oxidation of the critical surfaces may lead to the loss of the enclosure's explosion-proof protection.

Multi-dimensional assessment of nano/micro scale surface texture using laser speckle pattern analysis

Abstract Nano/micro scale surface structure on precision machined parts dominates the various product functions such as friction, wear resistance, corrosion, fatigue, and wetting. This paper presents a multi-dimensional surface texture assessment using laser speckle pattern analysis. From the observation result of laser speckle in precision machined surface, the probability density distribution of light intensity on laser speckle changes with the surface roughness. In addition, the autocorrelation function of speckle intensity distribution changes with the periodicity of micro surface structure. By analyzing the relation between surface texture and laser speckle pattern, characteristic parameters of laser speckle reflecting surface texture properties are identified; i.e. the mean light intensity, the deviation of the probability density distribution of light intensity, the autocorrelation length of intensity distribution, and the degree of dissimilarity between adjacent speckle patterns. The proposed parameters can evaluate the roughness, the period, and the degree of dissimilarity in periodic micro surface structure. Furthermore, the surface texture distribution and the anisotropy of micro surface structure can be assessed by detecting the variation of the proposed parameters. In consequence, the proposed method can quantitatively assess the nano/micro scale surface texture.

Multi-dimensional Assessment of Precision Machined Surface Texture Based on Laser Speckle Pattern Analysis

Surface texture of precision machined surfaces plays an important role in providing various functions to product surfaces. This paper presents a surface texture assessment method based on a laser speckle pattern analysis. Considered as simple light scattering phenomenon, laser speckle intensity can represent surface roughness. On the other hand, considered as diffraction phenomenon, the period of anisotropic pattern on a laser speckle is estimated to be inversely proportional to the period of micro structure. The proposed method evaluates multiple properties of surface texture from a laser speckle pattern, such as roughness, period, and degree of similarity in periodic micro surface structures. By investigating experimentally the relation between surface texture and laser speckle pattern of machined surfaces, several characteristic parameters of laser speckle, such as the mean intensity, the autocorrelation length of intensity distribution, and the degree of similarity between adjacent speckle patterns are proposed for evaluating surface texture properties. In addition, the anisotropy of micro surface structure is assessed by using the proposed parameters of laser speckle pattern.

The Mechanical Polishing Research on the Surface of WC-Co Cemented Carbide Based on ELID Grinding

In the paper, the ELID grinding is, first of all, adopted to pre-process the surface of WC-Co cemented carbide, obtaining the precision machined surface, Ra=18nm.Then the mechanical polishing process is implemented. When conducting mechanical polishing, the polishing liquid with W1 diamond grits is used to process the surface about 100 minutes after ELID grinding, aiming to achieve rapid removal. About 100 minutes again, the ultra-precision surface, Ra=4nm, is obtained, by the mechanical polishing ,using the polishing liquid with W0.5 diamond grits .Meanwhile, on the surface roughness effects of abrasive type, grain size, polishing liquid solvents, polishing pressure, polishing machining time and so on, are researched in-depth for the process of mechanical polishing.

Tool path planning for 5-axis flank milling of ruled surfaces considering CNC linear interpolation

This paper investigates tool path planning for 5-axis flank milling of ruled surfaces in consideration of CNC linear interpolation. Simulation analyses for machining error show insights into the tool motion that generates a precision machined surface. Contradicting to previous thoughts, the resultant tool path does not necessarily produce minimal machining error when the cutter contacts the rulings of a developable surface. This effect becomes more significant as the distance between two cutter locations is increased. An optimizing approach that adjusts the tool position locally may not produce minimal error as far as the entire surface is concerned. The optimal tool path computed by a global search scheme based on dynamic programming supports this argument. A flank milling experiment and CMM measurement further validate the findings of this work.

Focus on Laboratory Equipment

Focus on Laboratory Equipment

Scanning force microscope as a tool for studying optical surfaces

The scanning force microscope (SFM) is used to study the characteristics of optical surfaces, such as polished and precision-machined surfaces and thin-film structures. Previously unreported images of raised surface scratches and clumpiness on the surface of extremely smooth dielectric films are presented. The characteristics of SFM's that are important in studying optical surfaces are discussed. They include the effects of tip geometry, surface charging, particulate contamination, scanner artifacts, and instrument calibration.

Investigation of characteristic measures for the analysis and synthesis of precision-machined surfaces

Error prediction and control are key factors in precision machining. These factors rely on the development of formal approaches for analyzing and characterizing error sources in manufacturing. One such approach is the development of mathematical measures of precision, where precision, in this context, is defined as surface variations of manufactured part profiles. In this paper, we discuss a novel investigation of four mathematical measures. These four methods, namely the autocorrelation function, the Fourier spectrum, a fractal-wavelet representation, and the Karhunen-Loève expansion, are applied to surfaces produced from grinding processes. The first two methods provide a basis for the investigation, as they are commonly used in the literature for qualitative signal characterization of manufacturing surfaces. However, the fractal-wavelet method and Karhunen-Loève expansion have never been applied to the analysis and synthesis of surface variations. While other fractal methods have been used to characterize surface-finish variations, a wavelet formalism is a new approach, especially at the scales of both surface finish and tolerances. A combination of the first three techniques is shown to give a proper minimum set of characteristic precision measures for representing grinding surfaces. This combination is a clear contribution to the field of analysis of surface characteristics. It is also shown that the Karhunen-Loève technique is a novel alternative to represent surface errors. The existence of characteristic measures of surface precision should aid designers in choosing process and design parameters and in comparing the precision between competing machining processes.

Investigation of characteristic measures for the analysis and synthesis of precision-machined surfaces

Investigation of characteristic measures for the analysis and synthesis of precision-machined surfaces