Ultrasonic Machining

Question 1

Ultrasonic Machining

Answer 1

Abrasive particles contained in a solution (slurry) are driven at high velocity against a workpiece by a vibrating form tool operating at high frequency

Question 2

Ultra Sonic Machining

Answer 2

• Electric energy is converted into mechanical energy usingthe principle of piezoelectricity
• A piezoelectric crystal (converter) expands and contractswhen electrically charged and converts (50Hz into 15-20kHz) electrical into mechanical energy
• Material removal is purely mechanical by abrasive particles in a fluid being driven against the workpiece

Question 3

What physical properties should the tools of USM exhibit?

Answer 3

Must be ductile but strong enough to resist fatigue

Question 4

What is the slurry mixed with?

Answer 4

Water and abrasives

Question 5

Ultrasonic Welding methods?

Answer 5

Moderate clamping pressure is applied between the partsto be joined

Sonotrode is coupled with an ultrasonic transducer transmitting high frequencies (15-75kHz; amplitude 0.015-0.15mm) generating an oscillatory motion

Oscillatory motion at the sonotrode tip is used in direction parallel to the contacting surfaces bonding them together

Combination of normal and vibratory forces result in shear stresses (plastic deformation) that achieve atomic bonding (diffusion and recrystallisation to fine grain structure)

Question 6

Name 3 characteristics of USW?

Answer 6

• Typically limited to short welds length (few cm) with a weld thickness <3mm
• Welding of dissimilar materials (also metals to non-metals)
• Typically used for softer materials (Aluminium, Copper) as harder workpiece materials may cause excessive tool wearon the sonotrode

Question 7

Application of USW?

Answer 7

• Electrical and electronics – splicing and terminating wires; welding of wires to a pad surface
• Assembly of metal sheet panels (e. g. Aluminium)
  Welding tubes to sheets in solar panels
• Joining different materials (e.g. electronic devices which have material combinations often impossible to do with a multi-shot injection moulding process)
• Sealing plastics for the food, toy and medical industry; no risk of contamination
  Sealing of explosives and reactive chemicals

Question 8

Variations of USM?

Answer 8

US Cleaning, US Cutting

Question 9

Advantages of USM?

Answer 9

Drilling of hard and brittle materials ~50m holes up to 10cm

Multiple holes simultaneously including non-round holes

No thermal distortion of HAZ

No chemical change to the microstructure

Safe – skin is impervious because of its ductility

Question 10

Limitations of USM?

Answer 10

Some erosion on sharp corners and edges

Some taper due to form tool wear

Chipping at exit end may require a backup plate at the bottom

High pitched noise due to secondary vibrations