5,640 research outputs found

    Optimization of 5-Axis milling processes based on the process models with application to airfoil machining

    Get PDF
    5-axis milling is widely used in machining of complex surfaces such as airfoils. Improper selection of machining parameters may cause low productivity and undesired results during machining. There are several constraints such as available power and torque, chatter stability, tool breakage etc. In order to respect such constraints proper machining parameters should be determined. In this paper, methodologies for improving 5-axis milling processes are presented. Selection of machining parameters is performed using process simulations. The developed methodologies are presented on an example airfoil

    A holistic integrated dynamic design and modelling approach applied to the development of ultraprecision micro-milling machines

    Get PDF
    Ultraprecision machines with small footprints or micro-machines are highly desirable for micro-manufacturing high-precision micro-mechanical components. However, the development of the machines is still at the nascent stage by working on an individual machine basis and hence lacks generic scientific approach and design guidelines. Using computer models to predict the dynamic performance of ultraprecision machine tools can help manufacturers substantially reduce the lead time and cost of developing new machines. Furthermore, the machine dynamic performance depends not only upon the mechanical structure and components but also the control system and electronic drives. This paper proposed a holistic integrated dynamic design and modelling approach, which supports analysis and optimization of the overall machine dynamic performance at the early design stage. Based on the proposed approach the modelling and simulation process on a novel 5-axis bench-top ultraprecision micro-milling machine tool – UltraMill – is presented. The modelling and simulation cover the dynamics of the machine structure, moving components, control system and the machining process, and are used to predict the overall machine performance of two typical configurations. Preliminary machining trials have been carried out and provided the evidence of the approach being helpful to assure the machine performing right at the first setup

    Replacement bearing for Rocketdyne SSME HPOTPs using alternate self-lubricating retainer materials

    Get PDF
    Research was conducted to develop replacement bearings for the Rocketdyne Space Shuttle main engine (SSME) high pressure oxidizer turbopumps (HPOTPs). The replacement bearings consisted of standard balls and races with a special Battelle Self-Lubricating Insert Configuration (BASIC) retainer. The BASIC retainer consists of a phosphor bronze housing with inserts consisting of a polytetrafluoretheylene (PTFE) and bronze compound. The PTFE contacts the balls and the land guiding surface on the outer race. A PTFE transfer film is formed on balls and races, which lubricates the critical interfaces. The BASIC retainer is a one-to-one replacement for the current Armalon retainer, but has superior lubricating properties and is stronger over the broad temperature range anticipated for the HPOTP bearings. As a part of the project 40 sets of balls and races (two sizes) and 52 BASIC retainers were shipped to NASA/MSFC

    Thermal Error Modelling of a CNC Machine Tool Feed Drive System using FEA Method

    Get PDF
    Recirculating ball screw systems are commonly used in machine tools and are one of the major heat sources which cause considerable thermal drift in CNC machine tools. Finite Element Analysis (FEA) method has been used successfully in the past to model the thermal characteristics of machine tools with promising results. Since FEA predictions are highly dependent on the efficacy of numerical parameters including the surrounding Boundary Conditions (BC), this study emphasises on an efficient modelling method to obtain optimised numerical parameters for acquiring a qualitative response from the feed drive system model. This study was performed on a medium size Vertical Machining Centre (VMC) feed drive system in which two parameter dentification methods have been employed; the general prediction method based on formulae provided by OEMs, and the energy balance method. The parameters obtained from both methods were applied to the FEA model of the machine feed drive system and validated against experimental results. Correlation with which was increased from 70 % to 80 % using the energy balance method

    Modelling the influence of machined surface roughness on the fatigue life of aluminium alloy

    Get PDF
    The influence of machined surface roughness on the fatigue life of 7010 aluminium alloy has been investigated. Four-point bending specimen have been machined according to various machining conditions and tested in fatigue. In order to explain the high dependence of SN curves on the surface roughness of the specimen, an approach based on the finite element analysis of measured surface topography is proposed. Surface grooves due to machining are supposed to generate stress concentrations that are so calculated. A model of fatigue life prediction is developed, using this definition of local Kt

    A CNC machine guiderail wear in-process monitoring system

    Get PDF
    This research investigates and establishes a system for monitoring the guiderail wear on medium size CNC machines. The system possesses the function of measuring the wear state on guiderails in an in-process way, which is more functional and efficient than the traditional method. In this research, two different types of sensors for monitoring each particular friction wear feature have been implemented. Calculations to complete designing of a physical experimental rig and the realisation of in-process monitoring are also discussed in detail. The first type sensor adopted in the experiment is the accelerometer, used for monitoring the vibration caused by the wear on bearings and the increasing roughness on the guiderail surface. The second sensor is the capacitance probe mounted on the table and against a straight edge, searching the deviation signal of the moving table while rolling on the guiderail surface with wear. The novelty of this thesis covering an in-process monitoring approach has been tested based on a physical experimental rig. The data calculation illustrates how the noise and other disturbances are filtered and data analysed to determine the state of wear. This system utilises an indirect solution to wear monitoring with less cost while delivering convincing reliability according to the experiment result. The thesis shows the possibility to acquire CNC machine guiderail wear data through an in-process monitoring system
    • …
    corecore