Michael Checkley 17/12/2010. A Batako Advanced Manufacturing Technology Research Laboratory GERI. My background. PhD aims and objectives.

Transcription

1 Michael Checkley A Batako Advanced Manufacturing Technology Research Laboratory GERI My background. PhD aims and objectives. Equipment at AMTRel. Background to HEDG. Background to Vibration Assisted Grinding. Dominator creep feed grinding machine modifications. Design and anlaysis of a vibration fixture. 2 1

2 University of Liverpool -MEng Aerospace Engineering GPG Sales -CNC Router Programmer/Operator Kratos Analytical -Mechanical Design Engineer Triumph Actuator and Motion Control -Mechanical Design Engineer Knowsley Community College -Lecturer Mechanical Engineering and Workshop Practise Skills 3 Design, Analysis and modifications of Dominator creep feed grinding machine for vibration assisted grinding. Design and analysis of a single axis vibrating fixture to explore vibration assisted grinding. -Grinding forces. -Workpiece Surface finish -Workpiece surface temperature. Expand on the initial design to create a 2 axis vibrating fixture. -Random vibrations. -Synchronised motion. 4 2

3 Abwood HS-5025CP Dominator

4 VIPER-most efficient machine on the market secures just 200 Q Low material removal rate. High Specific Grinding Energy. Conventional Grinding (Malkin) 7 Strategy: Maximum removal rate consistent with cost, quality and power available. Removal rate based on available power High Removal Rates can be achieved in Deep Grinding with Low surface grinding energy either using: A low workspeed and a very deep cut or A high workspeed and a less deep cut Wide cuts increase surface grinding energy and are less suitable 8 4

5 In terms of energy, the Optimos wheel produced lower specific energy compared to electro- plated CBN wheel. HEDG Specific Grinding energy versus material removal rate 9 Ball screw version Low work speed Low thrust Bent screw 10 5

6 HEDG Machine Specification Motor Max. Speed Rotation Hydrostatic bearing 63kW 6000rpm Bi-directional Max. wheel diameter 500mm HEDG wheel diameter 450mm (141m/s) Workspeedup to 3.3 m/s Table stroke 805mm (max) Dresser Electric 19,000rpm Coolant delivery Darenth high pressure system Measurable parameters: Power Fluid pressure Force Flow rate Temperature 11 Data acquisition system monitors: Spindle power Grinding forces Table speed Temperatures Specific energy Predicts temperature High performance DAQ system: 20MS/s 4 channels 5MS/s/ch Data Acquisition system flowchart 12 6

7 Improved Coolant entry to wheel-workpiece interface. Improved surface finish. Lower grinding forces and workpiece temperature. Longer Wheel Life. Al 2 O 3 Wheel: CBN Wheel: Fine 250µm Fine 126µm Course 500µm Course 252µm 13 Description: Rigid cast Iron structure for base and motor carrier. Ball rail linear table. Ball screw drives on 3 axis. 14 7

8 Mounting Details Resting on a front V support guide and a rear flat support. Restrained only by gravity. Any lifting forces are transmitted directly to the ball screw assembly. 15 Description: Rigid 30mm thick aluminium base and top plate. Hardened runner blocks and guide rails. Linear motor. 7100N attractive force between primary and secondary part. Measurement system. 16 8

9 Mesh Details The resultant FEA model consists of: Nodes Elements Degrees of Freedom Grinding forces during HEDG 2000N load in the normal direction. 800N in the tangential direction. 17 Grinding Forces 2000N load in the normal direction. 800N load in the tangential direction. Linear Motor Force 7100N attractive force Maximum Stress: 54.38MPa Displacement: 0.01mm (Linear motor) Displacement: 1.6µm (Grinding) 18 9

10 Mode Frequency / Hz Mode Frequency / Hz Designed to hold 155 x 100 x 50 Nickel Alloy work pieces. Designed to hold 70 x 8 x 15 Nickel Alloy work pieces

11 2000N load in the normal direction. 800N in the tangential direction. Maximum Stress: 9.28MPa Maximum Displacement: 0.47µm 21 Previous work at AMTRel has already investigated the application of vibration in the X direction. New work will be investigated the effect of vibration in the Z direction. X - Direction Z - Direction 22 11

12 Piezo Actuator Small Size Light weight ~210g Large Force compared to size For high frequency excitation ~>1kHz Accurate/ well defined displacement Piezo Stack provides large displacement Electromagnetic Shaker Large Size Heavy ~12kg Low Force compared to size Low frequency excitation ~<1Khz Low force and displacement at higher frequency 23 Technical Data: Length: 139mm Diameter: 18mm Push/Pull Force: 2000N/300N Displacement: 120µm Electrical Capacitance: 370nF For this Actuator a frequency above 150Hz results in a reduction in displacement. This reduction becomes significant above 700Hz 24 12

13 Before polarization, PZT crystallites have symmetric cubic unit cells (fig 1). At temperatures below the Curie temperature, the lattice becomes deformed and asymmetric (fig 2). The unit cell exhibits spontaneous polarization, i.e. the individual crystallites are piezoelectric. However, because of the random distribution of the domain orientations in the ceramic material no macroscopic piezoelectric behaviour is observed. Permanent alignment can be forced using a strong electric field. This process is called poling. The ceramic now exhibits piezoelectric properties and will change dimensions when an electric potential is applied. 25 Electrical Capacitance: 370nF For this Actuator a reduction in maximum displacement begins at frequencies above 150Hz. This reduction becomes significant above ~200Hz 26 13

14 Manufacture of the bridge amplifier vibration fixture. Characterise the motion/vibration of the fixture. Vibration assisted grinding trials in the Z direction. Vibration assisted HEDG grinding trials using the dominator grinding machine. Develop the fixture into a 2 axis vibration fixture. Develop the control system for multi-axis vibration monitoring and control