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    Hardware Components of CMM

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    kumar km
    The document summarizes the key hardware components of a coordinate measuring machine (CMM), including structural elements, bearing supports, drive systems, and displacement measurement systems. The structural elements support the workpiece and machine components and are made from materials like granite, steel, and aluminum for dimensional stability. Bearing systems like air bearings and hard contact bearings are selected based on load capacity and accuracy needs. Common drive systems include rack and pinion, belt, friction, lead screw, and linear motor systems, which are used to position the probe.

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    Hardware Components of CMM

    Uploaded by

    kumar km
    450 views14 pages
    The document summarizes the key hardware components of a coordinate measuring machine (CMM), including structural elements, bearing supports, drive systems, and displacement measurement systems. The structural elements support the workpiece and machine components and are made from materials like granite, steel, and aluminum for dimensional stability. Bearing systems like air bearings and hard contact bearings are selected based on load capacity and accuracy needs. Common drive systems include rack and pinion, belt, friction, lead screw, and linear motor systems, which are used to position the probe.

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    The document summarizes the key hardware components of a coordinate measuring machine (CMM), including structural elements, bearing supports, drive systems, and displacement measurement systems. The structural elements support the workpiece and machine components and are made from materials like granite, steel, and aluminum for dimensional stability. Bearing systems like air bearings and hard contact bearings are selected based on load capacity and accuracy needs. Common drive systems include rack and pinion, belt, friction, lead screw, and linear motor systems, which are used to position the probe.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    450 views14 pages

    Hardware Components of CMM

    Uploaded by

    kumar km
    The document summarizes the key hardware components of a coordinate measuring machine (CMM), including structural elements, bearing supports, drive systems, and displacement measurement systems. The structural elements support the workpiece and machine components and are made from materials like granite, steel, and aluminum for dimensional stability. Bearing systems like air bearings and hard contact bearings are selected based on load capacity and accuracy needs. Common drive systems include rack and pinion, belt, friction, lead screw, and linear motor systems, which are used to position the probe.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PPT, PDF, TXT or read online from Scribd
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    Hardware Components of CMM

    Structural elements Bearing supports Drive systems Displacement measurement systems Probe heads Control systems

    Structural Elements
    M/C base Table to support W/P M/C columns Slide ways Probe shaft

    Material Granite, Steel & Aluminium

    Ideal Properties of Structural Elements


    Dimensional stability Stress relieving techniques Infinite stiffness FEA & Hollow structures Weightlessness High damping capacity - Servo control system Low coefficient of thermal expansion Proper selection of material easy workability & lower cost High thermal conductivity

    Bearing Systems
    What are bearing systems? Part of structure & affect measuring accuracy Types of bearing systems Non-contact air bearing systems Hard contact bearings Design considerations Dynamic stiffness Load carrying capability Damping & frictional effects

    Air Bearings
    Air bearings utilize a thin film of pressurized air to provide a zero friction' load bearing interface between surfaces Being non-contact, air bearings avoid the traditional bearingrelated problems of friction, wear, and lubricant handling Distinct advantages in precision positioning and high speed applications

    Working of air bearings


    The fluid film of the bearing is achieved by supplying a flow of air through the bearing itself to the bearing surface (gap of 5mm) The design of the air bearing is such that, although the air constantly dissipates from the bearing site, the continual flow of pressurized air through the bearing is sufficient to support the working loads Air bearings are a natural choice for applications in coordinate measuring machines

    Hard contact bearings


    Used for higher loads (mainly foundries) Precision roller bearings Ball bearings Sliding guide ways

    Drive systems
    Used only to move the probe Natural frequency higher than that of machine structure Types of Drive systems Rack & Pinion Belt Friction Lead screw Linear motor

    Rack & Pinion


    Pinion-driver Rack-driven Preffered for Lengthy travel (Gantry) Form errors and Backlash limit accuracy Cost effective Used for rough positioning

    It consists of Belt fibre-reinforced notched or a metallic flat tape Multi-stage speed reducer Servo motor Offers a quiet transmission of power to the moving axes Acts as a low pass filter preventing motor oscillations Axes driven at high speed & accelerations Disadv-Elasticity-cannot be used for high-precision scanning operations

    Belt Drive

    Friction Drive
    Also called as capstan or traction drive It consists of
    Driving wheel - driven directly by a motor or speed reducer A flat or round bar A supporting back-up roller

    Constant preload is applied

    Adv of friction drive Simplicity in design Low friction force Minimum backlash High positioning accuracy Disadv of friction drive Low drive force capability Low stiffness & damping Minimum transmission gain

    Most common type Ball screws Transforms rotary motion to linear translational movement Adv Provide mechanical advantage Good dynamic stiffness Disadv Inability to disengage and reengage Noisy Subject to wear

    Lead screw drive

    Linear motor drive


    Direct drive It offer unusually high &virtually infinite stiffness Adv High acceleration (Gantry) Disadv No gear reduction mechanism Heat generation Cost is more

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