Accuracy Of Holes Research Articles

Effect of Composite Material Fixing on Hole Accuracy and Defects During Drilling

Effect of Composite Material Fixing on Hole Accuracy and Defects During Drilling

Influence of the Kinematic System on the Geometrical and Dimensional Accuracy of Holes in Drilling.

This article attempts to show how the kinematic system affects the geometrical and dimensional accuracy of through-holes in drilling. The hole cutting tests were performed using a universal turning center. The tool was a TiAlN-coated Ø 6 mm drill bit, while the workpiece was a C45 steel cylinder with a diameter of 30 mm and a length of 30 mm. Three kinematic systems were studied. The first consisted of a fixed workpiece and a rotating and linearly moving tool. In the second, the workpiece rotated, while the tool moved linearly. The third system comprised a rotating workpiece and a rotating and linearly moving tool, but they rotated in opposite directions. The geometrical and dimensional accuracy of the hole was assessed by analyzing the cylindricity, straightness, roundness, and diameter errors. The experiment was designed using the Taguchi orthogonal array method to determine the significance of the effects of the input parameters (cutting speed, feed per revolution, and type of kinematic system) on the accuracy errors. A multifactorial statistical analysis (ANOVA) was employed for this purpose. The study revealed that all the input parameters considered had a substantial influence on the hole quality in drilling.

Mechanism and feasibility study of low frequency vibration assisted drilling of a newly developed CFRP/Al co-cured material

CFRP/metal co-cured structure has been increasingly applied in the aerospace industry due to its outstanding mechanical properties of high specific strength and high stiffness. Compared with the stack structure, the co-cured material of which the metal was heavily wrapped by the CFRP prepregs has better interface performance due to the absence of interface gap, being helpful to improve the bonding strength with other parts. Hole making is an inevitable manufacturing process for the assembly of co-cured material while there still exists several challenges during the drilling operation. To be specific, the hole size with low accuracy and hole morphology with severe defects are the main concerns for the manufacturers, which can be mainly attributed to the tangled chips and high cutting temperatures. To solve the aforementioned problems, the low frequency vibration assisted drilling (LFVAD) operation was performed for the newly developed CFRP/Al co-cured material in the present work. The mechanism and feasibility of controlling the machining defects via LFVAD were theoretically and experimentally explored and the influence of vibration amplitude (VA) on the cutting responses was specially studied. The results show that LFVAD can reduce the average thrust forces and drilling temperatures compared to conventional drilling while the maximum thrust force shows larger magnitude with the elevation of VA, in which the VA of ∼30 μm presents the best one. Meanwhile, LFVAD can on the one hand reduce the scratch traces on the hole wall surface owing to its superior chip breakage effect and thereby improve the drilled hole accuracy, and on the other hand shrink the lower interface damage area due to the reduction of cutting temperatures. The obtained findings of the present work indicate that the proposed LFVAD method presents great superiority for the CFRP/Al co-cured material concerning the machining responses of higher hole accuracy and lower interface damage.

ТОЧНОСТЬ ОБРАБОТКИ ОТВЕРСТИЙ КОМБИНИРОВАННЫМ ИНСТРУМЕНТОМ

Cement, powder metallurgy and various large-sized equipment are used in the industry of building materials for grinding raw materials. During operation, such equipment is exposed to external influences, especially at the joints, which reduce the reliability of the units. This leads to the early replacement of wearing parts. Large components of grinding mills are connected by flanges. The flanges are fastened with bolts, some of which must be precision, since they take the load of the equipment and ensure the tightness of the connection. The holes for precision bolts, respectively, must be accurate and of high quality. A study of the processing of holes with a reamer is given. The cutting elements of the tool, in the form of multifaceted plates, are mechanically attached to the body, which makes it possible to quickly replace the plate in case of wear or breakage. Such an assembled combined cutting tool allows to perform countersinking and reaming in one operation and thereby reduce the processing time of one hole and, in general, all precision holes in the flanges of the mill being repaired. The dependence of the precision hole accuracy on the shape and spatial deviation from the cutting modes of processing when using a combined tool is derived. The dependence is established for processing using a portable device with a rising spindle, as the most used equipment for repairs. The presented dependence makes it possible to predict the accuracy of machining holes with a combined tool, taking into account the rigidity of the technological system and calculate the required reamer accuracy.

Parametric analysis of hole circularity for laser percussion drilling of carbon fibre reinforced plastic using Nd: YAG laser

Holes of diameter less than 1 mm has wide application of manufacturing sector. Laser beam can be conveniently used for creation of such hole in different materials. The Carbon Fiber Reinforced Composite (CFRP) is quickly replacing the conventional materials in most of the engineering applications. Therefore, a detail parametric study to analyse the influence of factors like laser current, laser interaction time, pressure of assist gas, workpiece thickness and incidence angle on the geometrical accuracy of hole in terms of hole circularity at top (HCT) has been explored by changing the individual contributing factors. Small holes (< 1mm) have been fabricated with Nd: YAG laser of millisecond pulse duration in CFRP workpiece of thickness 1mm, 3mm, and 5 mm. It was observed that hole circularity at top surface is highest for zero angle of incidence. The increase of laser current, interaction time, and pressure of assist gas increases the HCT when the laser direction is normal to the workpiece whereas it shows a decline trend when the angle of incidence of 10° and 20°g;. The increase of workpiece thickness reduces the HCT irrespective of angle of incidence.

Adjustment of Wire Vibrations in Order to Improve Geometric Accuracy and Surface Roughness at WEDM

Although WEDM is one of the most precise finishing technologies, deviations from the required geometric shapes and surface roughness occur in the production of parts with rotary surfaces. Even though these shortcomings have only a minimal impact on planar cuts, the production of circular profiles is a different problem. One of the factors causing this poor quality is the vibration of the wire electrode. With appropriate vibration adjustment, it would be possible to achieve significant improvements of the eroded area quality, both in terms of geometric accuracy and in terms of surface roughness. This would significantly increase quality, enabling WEDM technology to compete with other technologies in terms of economic efficiency. Therefore, the proposed solution aims to provide a partial adjustment to the wire tool electrode vibrations, based on their sensing by the means of acoustic emissions or a laser beam, with subsequent dynamic adjustment of the actual technological parameter values. This way, the given solution will increase the production accuracy of circular holes, increase productivity, and ultimately provide an overall increase in the economic efficiency of the WEDM process. The article also presents the scheme of a control algorithm for monitoring and subsequent adjustments of the vibrations of the wire tool electrode during the electroerosion process in order to minimize geometric deviations of circularity, cylindricity and roughness of the machined surface.

Drill-milling process and novel drill-milling tool for making a hole on carbon fiber–reinforced plastics

During carbon fiber–reinforced plastic (CFRP) hole-making, exit damages such as burrs and delamination frequently occur. Some hole-making technologies are invented to cater to the demands of the high hole quality for CFRP laminates. To adequately eliminate the process-induced damages, a novel dill-milling tool is designed, and a series of drill-milling experiments are conducted on CFRP by using this novel drill-milling tool. Theoretical and experimental analyses of the drill-milling process and the performance of the novel drill-milling have been conducted. The result indicates that compared with the drilling process, using the new drill-milling process, the burrs can be thoroughly removed and the delamination can be reduced significantly, even removed. The changes of the hole quality and the exit damages are different with the variations of the helical milling parameters. Therefore, by comprehensive consideration, proper helical milling parameters should be chosen adequately. Furthermore, in theory, the right-handed helix angles βy should be raised, which is favorable for improving the hole accuracy and reducing the exit damages.

Experimental Investigations Towards Hole Accuracy in Micro-drilling of Carbon Fibre Reinforced Polymer Material

Nowadays, Carbon Fibre Reinforced Polymer (CFRP) materials are extensively used as substitutes for metal parts in aircraft and automotive components since they are lighter in weight. However, mi-cro drilling CFRP materials during the assembly process poses various challenges such as low hole accuracy and delamination. Hence, an experiment has been executed to investigate the influence of micro drilling parameters towards hole accuracy. The spindle speed and feed rate are the machining parameters that have been considered in this experiment. Three different optimum parameters have been obtained from previous experiments, involving the spindle speed combinations of 8,000, 10,762 and 11,017 min-1 with a feed rate of 0.01 mm/rev. A drill bit with a diameter of 0.9 mm is used to drill approximately 300 holes. It has been revealed that the combination of the spindle speed of 11,017 min-1 and feed rate of 0.01 mm/rev produce high hole accuracy at the 2nd hole compared to the 300th hole due to the presence of uncut fibres at the 300th hole which have reduced the hole area. Hence, out-come of this research could provide the benefit to the industries in term of manufacturing time and materials expenditure.

MODELING AND OPTIMIZATION OF HOLE ACCURACY AND DRILLING TIME IN MAGNESIUM AZ31 PLATE

Owing to the advancement in the field of materials, different range of grades have been developed. The machinability examination of these newer grades must be carried out for future applications. One such newer grade of magnesium with AZ31 is deemed for study during the drilling process. The independent parameters considered are spindle speed (SS), feed rate (FR) and drill bit diameter (DBD). The dependent parameters considered are burr height (BH), burr thickness (BT), drilling time (DT) and surface roughness (SR). Improving hole accuracy is essential for manufacturing superior products, which is discussed in this work. At the same time, the machining time has also to be minimized to increase the production rate. With these objectives, the experimental investigation is made. Further, an analytical model for predicting the responses is developed; later, optimization is carried out to obtain the desired responses through the desirability function approach. The multi-objective optimization suggests the SS of 1100[Formula: see text]rpm, the FR of 0.198[Formula: see text]mm/rev., and the DBD of 6[Formula: see text]mm for reducing the entire dependent is reckoned.

Analysis of Solid Carbide Drilling Performance on AISI 316L Austenite Stainless Steel using MQL (Minimum Quantity Lubrication) using Peck Drilling Approach

Minimum Quantity Lubrication (MQL) minimizes refrigerants and lubricants mixed with air to foster environmental sustainability. Austenitic AISI 316L stainless steel is often used for the aviation, biomedical equipment and food appliances. However, low machinability of this material makes it difficult to cut resulting low hole surface quality. The objective of the study is to evaluate the drill performance of solid carbide tools while drilling AISI 316L austenite stainless steel and to study the effect of drilling parameters, cutting speed (Vc), feed rate (Fr) and drill geometry (point angle) on tool life, surface integrity and holes accuracy. Solid carbide drilling performance analysis on AISI 316L Austenite Stainless Steel using MQL was assessed in terms of tool life, surface roughness, and hole accuracy. Investigation for optimal conditions of cutting speed, feed rate and point of angle when drilling AISI 316L austenite stainless steel would obtain the optimum output indicates longer tool life, better surface roughness and adequate accuracy in high-speed machining conditions. This MQL oil-air flow is accurately measured and sent to the drill tool edge. The cutting speeds applied for the machining process are 100m / min, 130m / min and 150m / min. For feed rate parameters, the selected values are 0.05mm / rev, 0.1mm / rev and 0.15mm / rev. Rotational drill angles are 110 °, 120 ° and 130 °. The peck drilling investigation is performed on high-speed milling machines keenly will provide guidance to produce good and optimal machining settings of cutting speed, feed rate and angle point to others when they want to drill a hole.

Surface quality and geometric accuracy control of fuel nozzle single-pass honing

Fuel nozzle is a key part of aero-engines. Due to the particularity of fuel nozzle’s working environment, the high machining requirements for the surface quality and geometric accuracy of nozzle hole were put forward. The existing process is difficult to meet the machining requirements, so a new process is proposed, which is called the flexible single-pass honing. For the novel single-pass honing tool with diameter less than 1 mm, the laws are not very clear, so studies were carried out. Firstly, a novel cutting force model of single-pass honing was established, which explains the relationship between force and machining parameters. Based on the cutting force model, the influence laws of honing parameters on surface roughness, bore diameter, and shape accuracy were explored detailedly. Finally, according to the machining requirements of fuel nozzles, the honing process optimization was carried out, and the optimal parameters were obtained. Furthermore, precision control of surface quality and geometric accuracy for fuel nozzle single-pass honing was realized.

Effective detection of metal surface defects based on double-line laser ultrasonic with convolutional neural networks

The time–frequency analysis by smooth Pseudo-Wigner-Ville distribution (SPWVD) is utilized for the double-line laser ultrasonic signal processing, and the effective detection of the metal surface defect is achieved. The double-line source laser is adopted for achieving more defects information. The simulation model by using finite element method is established in a steel plate with three typical metal surface defects (i.e. crack, air hole and surface scratch) in detail. Besides, in order to improve the time resolution and frequency resolution of the signal, the SPWVD method is mainly used. In addition, the deep learning defect classification model based on VGG convolutional neural network (CNN) is set up, also, the data enhancement method is adopted to extend training data and improve the defects detection properties. The results show that, for different types of metal surface defects with sub-millimeter size, the classification accuracy of crack, air holes and scratch surface are 94.6%, 94% and 94.6%, respectively. The SPWVD and CNN algorithm for processing the laser ultrasonic signal and defects classification supplies a useful way to get the defect information, which is helpful for the ultrasonic signal processing and material evaluation.

Pose and shape error control in automated machining of fastener holes for composite/metal wing-box assembly

Composite/metal wing-boxes are hard to drill by the conventional drilling method. In this paper, an automated machine-tool-based machining system equipped with a multifunctional end-effector is developed for helical milling, as well as circular and ellipsoidal dimple drilling of composite/metal wing-boxes. The system constitution, the control system, and the application software of the machining system are demonstrated. In aircraft manufacturing, the out-of-tolerance pose and shape of fastener holes deteriorate an aircraft’s strength and fatigue performances. Thus, a multi-sensor information fusion and integration architecture is built for enhanced pose and shape accuracy of machined fastener holes. The relative pose error of the end-effector and an aerostructure is analyzed. A coarse-to-fine control method by the touch probe and LDSs is applied for controlling the error. The fastener holes’ shape errors are controlled through the elaborate structure design and multi-sensor-based closed-loop motion control of the end-effector. Experiments performed on the machining system show that the positioning errors, hole diameter errors, dimple depth errors, and ellipsoidal dimple shape can fulfill the wing-box assembly requirements.

A New Method for Detecting Compensation Hole Parameters of Automobile Brake Master Cylinder Based on Machine Vision

The machining accuracy of the compensation hole of the automobile brake master cylinder directly determines the safety of the automobile and the reliability of parking. How to detect the parameters of the compensation hole with high precision becomes a crucial issue. In this paper, by analyzing the principle of Hough transform detection technology and several optimization algorithms, a new method combining Zernike moment and improved gradient Hough transform is proposed to detect the circular hole parameters. The simulation experiment shows that the proposed algorithm satisfies 0.1 pixels in the coordinate detection of the center position, and the radius detection accuracy is 0.05 pixels, with fast detection speed and good robustness. Compared with the random Hough transform algorithm and the gradient Hough transform algorithm, the algorithm proposed in this paper has higher detection accuracy, faster detection speed, and better robustness, which meets the online detection accuracy requirements of the brake master cylinder compensation hole.

Centralized spectrum sensing based on covariance matrix decomposition and particle swarm clustering

As the essential technology of cognitive radio networks, numerous spectrum sensing approaches have been established to date. However, some spectrum sensing methods seem to fail in providing an effective signal feature and an accurate decision threshold, which affects the detection accuracy of the spectrum holes. In this article, to further ameliorate the recognition rate of the spectrum holes, a novel centralized spectrum sensing method based on covariance matrix decomposition and particle swarm clustering is presented. A novel signal feature vector is extracted by the IQ decomposition method and the Cholesky decomposition technique. Moreover, particle swarm clustering algorithm is trained to obtain a decision classifier, which can be used to identify whether the licensed spectrum is available or not. Additionally, two different application scenarios are considered here. Indeed, simulations examples are provided to demonstrate that the proposed algorithm can considerably ameliorate the sensing performance for centralized spectrum sensing.

Development of a Non-Parametric Robot Calibration Method to Improve Drilling Accuracy

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The drilling of large quantities of repetitive holes during the manufacture of large aerospace components is often considered a key limiting factor with regards to production efficiency. Whilst the desire within aerospace is to use relatively cheap six axis robot arms with drilling end effector units, their poor accuracy remains an obstacle. Robot calibration presents a way of improving robot accuracy such that aerospace drilling tolerances can be met, without permanently committing metrology equipment to an automation cell during production. Extensive research has been conducted into robot calibration by correcting the kinematic model, known as parametric calibration. This method is highly complex, and calibrates the robot across the entire working volume. This is often not required in industrial drilling applications, as drilling routines are often contained within a smaller volume of the robot reach. In this paper, a non-parametric method of robot calibration is proposed. This method involves calibrating within regions of the working volume where the robot pose is similar, and thus the effects of geometric errors in the kinematic model are roughly constant. By establishing the average positional error for each region, the accuracy can be locally improved by compensation through definition of the tool centre point. The proposed method can be completed without the use of kinematic models or complex mathematics, making it more suitable to industrial users. From experimental trials, a significant improvement in the positional accuracy of holes drilled using a standard six axis robot is reported, from 2 mm to 0.1 mm, well within the requirements of the majority of aerospace applications.&lt;/div&gt;&lt;/div&gt;

A Virtual Emotion Detection System With Maximum Cumulative Accuracy in Two-Way Enabled Multi Domain IoT Environment

In this letter, we introduce a multiplex cumulative virtual emotion detection system for two-way enabled multi domain IoT environment, which avoids detection holes in all IoT domains. Formally, we define a problem whose objective is to maximize cumulative accuracy of detection holes on condition that perpendicular barriers or horizontal barriers are constructed in every domain area. After presenting the defined problem with ILP formulation, we devise a novel scheme to solve the problem. Moreover, we evaluate the obtained results through extensive experiments.

Surface accuracy optimization of mechanical parts with multiple circular holes for additive manufacturing based on triangular fuzzy number

Surface accuracy directly affects the surface quality and performance of mechanical parts. Circular hole, especially spatial non-planar hole set is the typical feature and working surface of mechanical parts. Compared with traditional machining methods, additive manufacturing (AM) technology can decrease the surface accuracy errors of circular holes during fabrication. However, an accuracy error may still exist on the surface of circular holes fabricated by AM due to the influence of staircase effect. This study proposes a surface accuracy optimization approach for mechanical parts with multiple circular holes for AM based on triangular fuzzy number (TFN). First, the feature lines on the manifold mesh are extracted using the dihedral angle method and normal tensor voting to detect the circular holes. Second, the optimal AM part build orientation is determined using the genetic algorithm to optimize the surface accuracy of the circular holes by minimizing the weighted volumetric error of the part. Third, the corresponding weights of the circular holes are calculated with the TFN analytic hierarchy process in accordance with the surface accuracy requirements. Lastly, an improved adaptive slicing algorithm is utilized to reduce the entire build time while maintaining the forming surface accuracy of the circular holes using digital twins via virtual printing. The effectiveness of the proposed approach is experimentally validated using two mechanical models.

Ensuring accuracy in the electromechanical processing of parts holes with a high-temperature strip source

Тhe accuracy of the holes in the electro - mechanical processing with a high-temperature strip tool is achieved by the development of original tooling. The article presents technical solutions of tool and technological equipment to ensure the accuracy of holes in the implementation of processes of electromechanical processing with a high-temperature strip source. The results of measurements on cylindricality of the hole of the sleeve bearing of the upper head of the connecting rod of the Yaroslavl Engine Plant engine after volumetric electromechanical mandrel are presented, confirming the effectiveness of using the developed tooling.

Comparison of the geometric accuracy of holes made in CFRP/Ti laminate by drilling and helical milling

Laminates of carbon fibre reinforced polymer (CFRP) and titanium (Ti) alloy are used in aerospace applications and require holes for joining to other components, which can weaken them. In this study, to determine the influences of drilling and helical milling on the geometric accuracy of holes, holes were made in a CFRP/Ti-laminated structure by these two techniques, and variations in aperture and roundness at different positions were investigated. In two processes, apertures are larger in the middle and smaller at the ends, and most are larger than the apertures of standard holes (6 mm). With drilling, roundness is relatively high at hole entrances and exits. In helical milling, the maximum roundness occurs just underneath the hole entrance, while the minimum occurs at the exit. In the drilling of Ti alloy, the maximum aperture occurs at the entrance; however, with helical milling, the hole entrance aperture is smaller. The aperture at other positions is relatively small. During drilling, the maximum roundness occurs at hole entrances, while the minimum occurs just underneath and then increases with depth. Helical milling produces a relatively large roundness at hole entrances, with consistent variation in other positions. Generally, helical milling of a laminated structure produces better geometric accuracy in holes in the Ti alloy layer, better hole roundness in the CFRP layer, and smaller roundness in the transition zone. However, drilling achieves better aperture accuracy in CFRP and smaller aperture errors in the transition zone. These results will help to produce stronger CFRP/Ti-laminated structures.