CNC

Mechanical Element of CNC Machine.

•Machine structure

•Guideways

•Ball screw

•Transmission elements -Couplings/Pulley

•Power chuck

•Auto Tool changer

•Auto pallet changer

Different Mechanical Elements Different Mechanical Elements

•Load carrying and supporting member of the machine

•Subjected to static and dynamic loads

•Structure should not deform or vibrate under the loads beyond limits

Machine Structure Machine Structure

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Machine structure

Safty and precaution

Flow arrangmentImpotanse of levellingHow lift the machine

Guideways are used to

•Control the direction of carriage or the table on which a workpiece/tool is held

•To absorb all static and dynamic forces

Guide Way Guide Way

Guideway Ball screw

Table / Carriage

Guide Way Guide Way

CNC machines use antifriction guideways to

•Reducing friction

•Improve smoothness of movement

•Reduce amount of wear

•Reduce heat generation

Rolling elements are used between moving and stationery elements of machine

Ex:Linear recirculating LM guides

Guide Way Guide Way

Anti friction Guide Way-Anti friction Guide Way-

LM bearingsLM bearings

Components which are in the force and motion transmission paths from drive motor to the slide

•Elements to convert rotary to linear motion

Ball screw ,Rack and pinion

•Torque transmitting elements

Timing belt pulley ,Gear box, Coupling

Mechanical Transmission SystemMechanical Transmission System

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Ball Screw

Recirculating Ball screwsRecirculating Ball screws

A ball screw is a mechanical device for translating rotational motion to linear motion. A threaded shaft provides a spiral raceway for ball bearings which act as a precision screw. As well as being able to apply or withstand high thrust loads they can do so with minimum internal friction. They are made to close tolerances and are therefore suitable for use in situations in which high precision is necessary. The ball assembly acts as the nut while the threaded shaft is the screw.

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Variable lead thread cuttingVariable lead thread cuttingFlexible Couplings Flexible Couplings

These couplings are used when the driver and driven shaft are coaxial

Flexibility built into the couplings compensate misalignment errors like radial,angular and axial

Variable lead thread cuttingVariable lead thread cuttingFlexible Couplings - Contd. Flexible Couplings - Contd.

Variable lead thread cuttingVariable lead thread cuttingTimer Belt and PulleyTimer Belt and Pulley

Endless toothed belts .Used when shafts are not coaxial

Advantages:

• Low cost

• Less noise

• No lubrication

• Less maintenance

• Higher efficiency

Set initial tension properly

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Electronics