6,589 research outputs found

    Surface roughness variation of thin wall milling, related to modal interactions

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    High-speed milling operations of thin walls are often limited by the so-called regenerative effect that causes poor surface finish. The aim of this paper is to examine the link between chatter instability and surface roughness evolution for thin wall milling. Firstly, the linear stability lobes theory for the thin wall milling optimisation was used. Then, in order to consider the modal interactions, an explicit numerical model was developed. The resulting nonlinear system of delay differential equations is solved by numerical integration. The model takes into account the coupling mode, the modal shape, the fact that the tool may leave the cut and the ploughing effect. Dedicated experiments are carried out in order to confirm this modelling. This paper presents surface roughness and chatter frequency measurements. The stability lobes are validated by thin wall milling. Finally, the modal behaviour and the mode coupling give a new interpretation of the complex surface finish deterioration often observed during thin wall milling

    Dynamic analysis of runout correction in milling

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    Tool runout and its effects is an important area of research within modelling, simulation, and control of milling forces. Tool runout causes tool cutting edges to experience uneven forces during milling. This fact also affects tool life and deteriorates workpiece surface quality. In this article a procedure, in order to diminish the effects of tool runout, is presented. The procedure is based on chip thickness modification by means of the fast correction of the tool feed rate. Dynamic feed rate modification is provided by superposing our own design of a fast feed system driven by a piezoelectric actuator to the conventional feed drive of the CNC machine tool. Previously, a model of the dynamic behaviour of the system was developed to analyze the influence of fast feed rate modification on cutting forces. The model incorporates the piezoelectric actuator response as well as the structural dynamics of the tool and the designed Fast Feed Drive System (FFDS). Simulated and experimental results presented in this paper show the effectiveness and benefits of this new tool runout correction procedure

    A novel haptic model and environment for maxillofacial surgical operation planning and manipulation

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    This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone

    Dynamic behavior analysis for a six axis industrial machining robot

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    The six axis robots are widely used in automotive industry for their good repeatability (as defined in the ISO92983) (painting, welding, mastic deposition, handling etc.). In the aerospace industry, robot starts to be used for complex applications such as drilling, riveting, fiber placement, NDT, etc. Given the positioning performance of serial robots, precision applications require usually external measurement device with complexes calibration procedure in order to reach the precision needed. New applications in the machining field of composite material (aerospace, naval, or wind turbine for example) intend to use off line programming of serial robot without the use of calibration or external measurement device. For those applications, the position, orientation and path trajectory precision of the tool center point of the robot are needed to generate the machining operation. This article presents the different conditions that currently limit the development of robots in robotic machining applications. We analyze the dynamical behavior of a robot KUKA KR240-2 (located at the University of Bordeaux 1) equipped with a HSM Spindle (42000 rpm, 18kW). This analysis is done in three stages. The first step is determining the self-excited frequencies of the robot structure for three different configurations of work. The second phase aims to analyze the dynamical vibration of the structure as the spindle is activated without cutting. The third stage consists of vibration analysis during a milling operation

    Dynamics analysis of 3 axis gantry type multipurpose CNC machine

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    The determination of the natural frequency and the resonance is important before the machine can be use. If the natural frequency is occur and the resonance will be occur also and it will make the damage to the machine when the machine is using. From this paper, modal analysis is used to determine the natural frequency. Modal analysis is a process whereby describe a structure in terms of its natural characteristics which are the frequency, damping and mode shape of its dynamic properties. From the experiment that was carrying out, the natural frequency is occur at 24Hz. From the result, when the machine is running with the speed of 50Hz or 100Hz, it doesn’t meet with the natural frequency which is 24Hz. From the experiment that was carrying out, it was shows that the machine can be use as user to milling process. Most machines produce low levels of vibration when designed properly. During operation, all machines are subjected to fatigue, wear, deformation, and foundation settlement. These effect cause an increase in the clearances between mating part, misalignments in shafts, initiation of cracks in parts, and unbalances in rotors. All leading to an increase in the level of vibration, which cause additional dynamic loads on bearings. As time progresses, the vibration level continue to increase, leading ultimately to the failure or breakdown of the machine. So, the maintenance is needed for all the time the machine is use

    Alternative experimental methods for machine tool dynamics identification: A review

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    An accurate machine dynamic characterization is essential to properly describe the dynamic response of the machine or predict its cutting stability. However, it has been demonstrated that current conventional dynamic characterization methods are often not reliable enough to be used as valuable input data. For this reason, alternative experimental methods to conventional dynamic characterization methods have been developed to increase the quality of the obtained data. These methods consider additional effects which influence the dynamic behavior of the machine and cannot be captured by standard methods. In this work, a review of the different machine tool dynamic identification methods is done, remarking the advantages and drawbacks of each method.The present work has been partially supported by the EU Horizon 2020 InterQ project (958357/H2020-EU.2.1.5.1.) and the CDTI CERVERA programme MIRAGED project (EXP-00,137,312/CER-20191001)

    DESIGN AND EVALUATION OF AN ELEVATED TEMPERATURE CUTTING FORCE DYNAMOMETER FOR HYBRID MANUFACTURING

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    Cutting force coefficients, workpiece dynamics, and uncut chip area all change as a function of temperature during machining processes at elevated temperatures. In a traditional milling process, these parameters are nearly constant. The bulk workpiece temperature remains well below the working limit of the material, generally near room temperature. However, workpiece temperatures in hybrid manufacturing, where additive deposition precedes machining, are spatially and temporally variable. A milling force model that does not incorporate temperature effects will generally overestimate the cutting force and workpiece dynamic stiffness and underestimate the chip area. Milling parameters that are stable at room temperature may be unstable at higher temperatures, leading to unexpected chatter and poor part quality. A cutting force dynamometer was designed, constructed, and tested to measure cutting force during milling with the workpiece heated to a constant bulk temperature of up to 500°C. The measured cutting forces were used to determine temperature dependent cutting force coefficients. These coefficients and workpiece dynamics were integrated into a time domain milling simulation to predict cutting force and stability under elevated temperature conditions. The outcome is improved modeling capabilities for hybrid manufacturing processes

    Precision Machining

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    The work included in this book focuses on precision machining and grinding processes, including milling, laser machining and polishing on various materials for high-end applications. These processes are in the forefront of contemporary technology, with significant industrial applications. Their importance is also made clear by the important works that are included in the research that is presented in the book. Some important aspects of these processes are investigated, and process parameters are optimized. This is performed in the presented works with significant experimental and modelling work, incorporating modern tools of analysis and measurements

    Additive manufacturing for lightweighting satellite platform

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    Lightweight structures with an internal lattice infill and a closed shell have received a lot of attention in the last 20 years for satellites, due to their improved stiffness, buckling strength, multifunctional design, and energy absorption. The geometrical freedom typical of Additive Manufacturing allows lighter, stiffer, and more effective structures to be designed for aerospace applications. The Laser Powder Bed Fusion technology, in particular, enables the fabrication of metal parts with complex geometries, altering the way the mechanical components are designed and manufactured. This study proposed a method to re-design the original satellite structures consisting of walls and ribs with an enclosed lattice design. The proposed new structures must comply with restricted requirements in terms of mechanical properties, dimensional accuracy, and weight. The most challenging is the first frequency request which the original satellite design, based on traditional fabrication, does not satisfy. To overcome this problem a particular framework was developed for locally thickening the critical zones of the lattice. The use of the new design permitted complying with the dynamic behavior and to obtain a weight saving maintaining the mechanical properties. The Additive Manufacturing fabrication of this primary structure demonstrated the feasibility of this new technology to satisfy challenging requests in the aerospace field
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