Browse Topic: Milling
Impact testing utilizing instrumented hammers and accelerometers is a widely adopted technique in dynamic testing. The mass loading effect of the accelerometer alters the dynamic response of the test structure, leading to deviations between the measured frequency response functions (FRFs) and their true values. Furthermore, the effects on the FRFs are contingent upon the positioning of the accelerometer, thereby causing the measured FRFs between two points to fail to meet the principle of reciprocity. This paper investigates the compensation method for the mass of a single accelerometer in impact testing. Compensation formulas for both origin–FRF and cross–FRF are derived using the frequency domain substructure decoupling method. Numerical simulations on a cantilever beam and experimental tests with milling tools validate the proposed methodology. The compensation formulas for FRFs presented in this paper are expected to enhance the measurement accuracy of FRFs in modal testing of small structures, particularly relevant for lightweight components in aerospace, aircraft, and transportation systems, where precise dynamic characterization is critical.
The initial powder used for the manufacturing of NdFeB permanent magnets is usually prepared through rapid cooling, either by melt spinning or strip casting. The powders produced by these two methods are suitable for different applications: while melt-spun powder is a good initial material for bonded and hot-deformed magnets, strip-cast powder is normally used for sintered magnets. To investigate the suitability of using strip-cast powder to manufacture hot-deformed magnets, NdFeB powder prepared by strip casting was hot pressed (without particle alignment) and compared with melt-spun powder prepared under the same conditions (700 °C, 45 MPa, 90 min). Although the processing parameters are the same (pressed in the same mold), the magnetic properties of the magnets made from the two powders are significantly different. Surprisingly, the magnet made from the strip-cast powder (after ball milling) shows comparable magnetic properties to those of isotropic magnets, with coercivity (HcJ) of 1270 kA/m and remanence (Br) of 0.7 T, while that made from the melt-spun powder exhibits much lower properties: HcJ = 480 kA/m, Br = 0.5 T, although the melt-spun powder initially shows much better magnetic properties than the strip-cast powder. Possible reasons for such a difference in magnetic properties are discussed. It was shown that the particle size of the initial powder plays an important role in determining the final magnetic properties of the hot-pressed magnets.
With over 15,000 products, Boston Scientific is a market leader in pacemakers, defibrillators, monitoring equipment, spinal and brain stimulation, stents, catheters, and ablation devices. On one recent cardiac monitoring battery component, the company had an application running year-round on multiple mills, rectangular in shape, consisting of multiple milling operations per part, requiring an operator per mill at all times. Both Mill operations consist of multi-part fixtures as the process involved running Mill OP-1, light hand deburring and prepping the parts for Mill OP-2 fixture & process, following manual deburring step. The overall process was running around seven minutes per part.
As the aerospace industry moves toward determinate assembly and ever-tighter manufacturing tolerances, there is a need for automated, high-precision milling, trimming and drilling equipment that is specialized for aerospace applications. Precision countersinking is a common requirement for aircraft parts, but this is not a process that typical general-purpose milling machines are able to accommodate without the use of specialty tools such as depth-stop tool holders. To meet this need, Electroimpact has designed a 5-axis milling machine with high-speed clamping capability for countersink depth control. A custom trunnion and head with a quill and an additional clamp axis provide clamping functionality similar in speed and precision to a riveting machine, while maintaining the accuracy and features of a conventional machining center. An additional focus on design for pre-compensation accuracy has allowed the system to achieve post-compensation path and positioning tolerances that are competitive with premium milling machines. This combination of capabilities makes the system well suited for a variety of cutting and drilling processes for aircraft manufacture. This paper will describe the background and design process that led to the development of this system, and will provide details on its capabilities, specifications, and possible applications.
In the metal-cutting process, the condition of the cutting tool is critical. The tool condition is one of the factors that impact the surface finish. Monitoring the tool’s condition is necessary to ensure the quality of the end result and productivity. Because vibration signals have a strong relationship with tool state, vibration signals were captured in this investigation while milling mild steel specimens with carbide inserts in a vertical milling machine. Four tool conditions were considered in this study, namely, a good tool (G), a tool with nominal flank wear (FW), tool flaking on the rake face (FL), and tool breakage (B). Histogram features were extracted from the captured vibration signal. J48 algorithm is used to select relevant features, which are then fed into Support Vector Machine (SVM) and K-Nearest neighbourhood (KNN) algorithms. SVM and KNN classification abilities are compared. SVM classifies the tool condition with 88.75% accuracy, whereas KNN achieved the classification with 90% accuracy, suggesting that when it comes to monitoring tool conditions, KNN surpasses SVM.
This specification covers the equipment and process requirements for forming or straightening metal parts using Ultrasonically Activated Needle Peening.
Innovators at NASA Johnson Space Center have developed a cost-effective method to create fabric-based circuits and antennas by combining conventional embroidery with automated milling. The technology allows for higher surface conductivity, improved impedance control, expanded design and application potential, and greater choice of materials for optimized performance.
During aircraft wing assembly, machined fiberglass shims are often used between mating parts to compensate for inherent geometric variability due to manufacturing. At present, fiberglass shims for large aerospace structures, such as shims attached to wing ribs, are manufactured either manually or by precision machining, both of which pose a challenge due to tight tolerance requirements and wide geometric variations in the aircraft structures. Relative to articulated arm industrial robots, gantry-style computer numerical control (CNC) machines are costly, consume large footprints, and are inflexible in the application. Therefore, industrial robots are viewed as potential candidates to replace these gantry systems to facilitate metrology, shim machining, and permanent joining of aircraft structure, with all these processes taking place in the assembly process step. However, the accuracy of articulated arm robots is limited by errors in kinematic calibration, gear backlash, joint compliance, controller performance, and mechanical deformation of the robot structure during machining. Therefore, industrial robots are currently unable to meet the strict accuracy requirements for aerospace parts without error compensation methods. This article presents a control architecture that utilizes real-time closed-loop position feedback derived from a high-accuracy laser tracker to improve the machining accuracy of articulated arm industrial robots. In addition, the article evaluates the performance of two closed-loop control methodologies in robotic milling, namely, controlling for path error versus controlling for trajectory error. The control methodologies are tested in robotic milling of fiberglass coupons along a curvilinear (sinusoidal) path. In addition, the best control methodology is tested in robotic milling of fiberglass shims installed on the mating surfaces of a 3.5 m aluminum aircraft wing rib. The dimensional accuracies and surface finish of the machined features using the proposed control methodologies are shown to be within acceptable tolerances for machined fiberglass shims.
Due to the chemical stability and durability of industrial polymers, plastic waste does not easily degrade in landfills and is often burned, which produces carbon dioxide and other hazardous gases. In order to stop the growing flood of polymer waste and reduce carbon dioxide emissions, plastics have to be recycled or converted into new value-added products.
In this developing world, the need for lightweight and high strength materials is increasing in various industries. As a result of the above, the importance of natural fiber is also increasing to satisfy the industrial need. In manufacturing industries in order to assembly the engineering components the drilling is one of the important operations. The main objective of this research is to determine the mechanical properties and drilling efficiency of natural fiber composite. Sisal/flax as a natural fiber, the copper foil of thickness 0.025mm as structural reinforcement and epoxy resin as a matrix was used for making composite. The hand layup technique was used for the fabrication of the composite. Two different types of the composite were fabricated such as C1 (Sisal and flax fiber, embedded with punched copper foil (Ø5mm), 20mm apart and 90° to each other) and C2 (Sisal and flax fiber embedded with a punched copper foil of (Ø4mm), 20mm apart and 45° to each other). After the fabrication of composite, the test sample was cut and tested according to ASTM standard. The mechanical properties such as flexural, tensile and impact were determined. The CNC milling machine was used to test the drilling efficiency of the fabricated composite. In this research, it was found that the impact strength of C1 (1.23J) was better than C2 (1.03J), the flexural strength of C2 (49.99MPa) was better than C1 (26.57MPa) and tensile strength of C2 (16.4 MPa) was better than C1 (14.9MPa) specimen. The fabricated sandwich composite can be used in the fabrication car door panels, the dashboard of automobile vehicles.
In order to take advantage of the machining characteristics of magnesium it is useful to consider recommended tool design and angles. The geometry of the tool can have a large influence on the machining process. Tool geometry can be used to aid with chip flow and clearance, reduce excessive heat generation, reduce tool build up, enable greater feed rates to be employed and improved tool life. This paper presents a new approach for the optimization of Machining parameters on face Milling of ZE41 with multiple responses based on Taughi orthogonal array with VIKOR. Machining tests are carried out 12 mm diameter of insert having 1 flute under dry condition. In this study, Machining parameters namely cutting speed, feed and Depth of Cut and Tool Node radius are optimized with the considerations of multi responses such as surface roughness, Material Removal rate, Tool Wear and Trust Force. A VIKOR grade is obtained from the VIKOR analysis. Based on the VIKOR grade, optimum levels of parameters have been identified and significant contribution of parameters is determined by ANOVA. Confirmation test is conducted to validate the test result. Experimental results have shown that the responses in Machining process can be improved effectively through the VIKOR approach.
Peripheral grinding of the aluminum alloy EN AB-AlSi9Cu3(Fe) using a vitrified silicon carbide grinding wheel was investigated in this article. The effect of grinding parameters, namely, grinding speed, feed and depth of cut, and grinding condition, up-grinding or down-grinding, on resulting forces, grinding energy, and surface roughness were analyzed. A 22 × 32 full factorial design of experiments was performed. The ground surface morphology showed evidence of rubbing and plowing effects, and ductile material removal was the main mechanism. Within the analyzed process window, the minimum value of surface roughness was 0.28 μm. The experimental evaluation highlighted that forces and grinding energy are directly dependent on chip thickness, and this relationship was further explored as a function of depth of cut and feed per grain. Conversely, an inverse dependence was observed in the case of surface roughness. Empirical relationships for a reliable prediction of the grinding force and the specific grinding energy were defined. On the contrary, the surface roughness could not be fully modelled by the variation of the kinematic factors considered, and only a rough estimation was obtained. The results may be used for a more conscious setup of the grinding process on aluminum alloys, especially in the automotive field, where these are key materials.
The desired milling process with high material removal rate (MRR) and low surface roughness of the product can be achieved only if machining chatter is absent. Incorporating chatter into the optimal selection of the machining parameters leads to a complex problem. Therefore, the approach of selecting conservative intervals for the machining parameters is usually employed instead. In this paper, a practical approach is proposed to specify the optimal machining parameters (depth of cut and spindle speed) in order to maximize MRR and minimize forced vibrations by considering machining chatter. Firstly, the worst-case scenario-based optimization problem in terms of the surface quality is solved to find the critical time at which maximal amplitude vibrations occur. Then, the time dependency of the problem is eliminated. Secondly, the multi-objective optimization is conducted to achieve the Pareto Optimal Front (POF). The Stability Lobe Diagram (SLD) is obtained independently through well-established analytical methods. Optimal machining parameters on the obtained POF are mapped into the SLD to represent optimal results for the cases at which machining chatter is absent. Finally, these optimal results are sorted by the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) decision-making method and displayed on the combined POF-SLD diagram which can be used by the machining operator for determination of the process parameters. A case study is considered, illustrating the efficiency of the proposed method.
In 3D printing — also known as additive manufacturing — an object is built layer-by-layer, allowing for the creation of structures that would be impossible to manufacture by conventional subtractive methods such as etching or milling.
This specification covers a fluorocarbon (FKM) rubber stock in the form of molded test slabs.
The high demand of efficient large scale machining operations by concurrently decreasing operating time and costs has led to an increasing usage of industrial robots in contrast to large scaled machining centers. The main disadvantage of industrial robots used for machining processes is their poor absolute accuracy, caused by the serial construction, resilience of gearings and sensitivity for temperature changes. Additionally high process forces that occur during machining of CFRP structures in aerospace industry lead to significant path errors due to low structural stiffness of the robot kinematic. These errors cannot be detected by means of motor encoders. That is why calibration processes and internal control laws have no effect on errors caused by elastic deformation. In this research paper an approach for increasing the absolute accuracy of an industrial milling robot with help of a Laser Tracker system during machining tasks will be presented. To measure the position and orientation of the robot tool center point (TCP) a specific adapter is mounted on the milling spindle near the TCP to provide a 6DoF measurement. Via a real time interface pose data can be obtained in millisecond cycles and is used for calculating the current path errors of the robot. The implementation of an additional controller in the manufacturers CNC allows the correction of the programmed trajectory so that the machining path will match its specifications.
A dispatch from the coalfields of West Virginia describes the unique set of challenges faced by the Baja SAE team at West Virginia University Institute of Technology. WEST VIRGINIANS HAVE ALWAYS persevered in times of hardship. The state is currently in an economic depression, particularly in the southern coalfields region, a place where funding for a Baja team is scarce. But West Virginians have always had pride, determination, and gratitude for the things we have. That heart and grit is something that the SAE Baja team at West Virginia University Institute of Technology uses in the shop each and every day. WVU Tech is a school nestled deep in the Kanawha Valley, right in the heart of the coalfields. Of our 1,200 students, 25 are members of the WVU Tech chapter of SAE's Baja and Aero Design teams. The team faces new challenges as the end of the school year fast approaches. Our school will close its campus in Montgomery after 127 years and move to Beckley, W.Va.-about 40 miles to the southeast. Only one major school has ever moved campuses before. They did it in 10 years, while we will be doing it in two. We have already had to adapt our schedule around the move.
This specification covers a standard fluoroelastomer (FKM) rubber stock in the form of molded test slabs.
Items per page:
50
1 – 50 of 190