Presented by

Debashish Bose

Reg no-1101298278

Branch-Mechanical

Roll No-14

Guided by

Jukti prasad padhy

Lecturer

Dept. Mech Engg.

Introduction Literature Review History Ultrasonic Waves Working Principle Mechanism Process Parameters Materials That Can Be Machined Various Work Sample CNC Ultrasonic Drilling Machine Limitations Applications Advantages Disadvantages Conclusion References

Ultrasonic drilling is a non-traditional, loose abrasive machining process.

In this the mirror image of a shaped tool can be created in hard, brittle materials.

Material removal is achieved by the direct and indirect hammering of abrasive particles against a workpiece.

Farrukh Makhdum, Luke T Jennings, Anish Roy and Vadim V Silberschmidt conducted experiments on commercially available samples of a carbon fibre-reinforced plastic at a feed rate of 16 mm/min. In this study, a thrust force reduction in excess of 60% is observed when compared to conventional drilling.

B. Azarhoushang, J. Akbari designed an ultrasonically vibrated tool holder and also investigated the ultrasonically assisted drilling of Inconel738-LC. The obtained results show that the application of ultrasonic vibration can improve the hole quality considerably up to 60%.

M Wiercigroch,Wojewoda and A.M.Kritsov conducted experiment on Ultrasonic percussive drilling with diamond-coated tools on rocks such as sandstone, limestone, granite and basalt, in order to investigate the applicability of this technique to downhole drilling. The studies showed that an introduction of high-frequency axial vibration significantly enhances drilling rates.

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NASA originally developed a prototype of the Uitrasonic Drilling Machine in 2000, which weighed in at 1.5 pounds, or .7 kilograms.

A second drill was developed to fit onto the Sojourner Rover, which had a drill head that weighed in at one pound alone, or .4 kilograms.

The Ultrasonic waves are sound waves of frequency higher than 20,000 Hz.

Ultrasonic waves can be generated using mechanical, electromagnetic and thermal energy sources.

They can be produced in gasses (including air), liquids and solids.

In the process of Ultrasonic drilling, material is removed by micro-chipping or erosion with abrasive particles.

The tool is oscillated by a piezoelectric transducer and an electric oscillator at a frequency of about 20 kHz.

The tool forces the abrasive grits, in the gap between the tool and the workpiece, to impact normally on the work surface, thereby machining the work surface.

During one strike, the tool moves down from its most upper position with a starting speed at zero, and speeds up to reach the maximum speed at the mean position.

Then the tool slows down its speed and eventually reaches zero again at the lowest position.

When the grit size is close to the mean position, the tool hits the grit with its full speed.

The smaller the grit size, lesser the momentum it receives from the tool.

As the tool continues to move downwards, the force acting on larger grits increases rapidly, therefore some of the grits may be fractured.

Eventually, the tool comes to the end of its strike and grits with size larger than the minimum gap will penetrate into the tool and work surface to different extents.

Piezoelectric Transducer

Piezoelectric transducers utilize crystals like quartz whose dimensions alter when being subjected to electrostatic fields.

The charge is directionally proportional to the applied voltage.

To obtain high amplitude vibrations the length of the crystal must be matched to the frequency of the generator which produces resonant conditions.

Abrasive Slurry

The abrasive slurry contains fine abrasive grains. The grains are usually boron carbide, aluminum oxide, or silicon carbide ranging in grain size from 100 for roughing to 1000 for finishing.

It is used to microchip or erode the work piece surface and it is also used to carry debris away from the cutting area.

Tool holder

The shape of the tool holder is cylindrical or conical, or a modified cone which helps in magnifying the tool tip vibrations.

In order to reduce the fatigue failures, it should be free from nicks, scratches and tool marks and polished smooth.

Tool

Tool material should be tough and ductile. Low carbon steels and stainless steels give good performance.

Tools are usually 25 mm long ; its size is equal to the hole size minus twice the size of abrasives.

Mass of tool should be minimum possible so that it does not absorb the ultrasonic energy.

Amplitude of vibration – 15 – 50 μm Frequency of vibration – 19 – 25 kHz Feed force – related to tool dimensions Feed pressure Abrasive size – 15 μm – 150 μm Abrasive material – Al2O3

- SiC- B4C - Diamond dust

Contact area of the tool Volume concentration of abrasive in water slurry

Hard materials like stainless steel, glass, ceramics, carbide, quartz and semi-conductors are machined by this process.

It has been efficiently applied to machine glass, ceramics, precision minerals stones, tungsten.

Brittle materials

1- The first picture on the left is a plastic sample that has inner grooves that are machined using Ultrasonic Drilling. 2- The Second picture (in the middle) is a plastic sample that has complex details on the surface 3- The third picture is a coin with the grooving done by Ultrasonic Drilling.

4-axis CNC drills holes as small as 0.010", multi-sided holes, multiple hole and slot patterns, and many other complicated, irregular shapes.

Works on hard, brittle materials such as ceramic and glass with precision to 0.0005".

Under ideal conditions, penetration rates of 5 mm/min can be obtained.

Specific material removal rate on brittle materials is 0.018 mm cubic/Joule.

Normal hole tolerances are 0.007 mm and a surface finish of 0.02 to 0.7 micro meters.

A nearly limitless number of feature shapes and cavities of varying depths can be machined with high quality and consistency.

Features ranging in size from 0.008" up to several inches are possible in small workpiece.

Machining, wire drawing, punching or small blanking dies.

Requires little power to operate.

Nearly zero torque is needed to operate the drill.

The drill is able to properly function at both extremely low and high temperatures.

Does not produce electric, thermal, chemical abnormal surface.

Can drill circular or non-circular holes in very hard materials

Difficult to drill much past an inch into very dense material.

Ultrasonic drilling provides very little tolerance surrounding the bit, henceforth no pathway is created for the cutting fluid.

Low Material Removal Rate.

High tool wear occurs.

USD has been shown to possess several advantages including reduced thrust force and torque.

Comparative experiments of the hole quality demonstrated up to 60% improvement in average surface roughness and circularity for the workpiecemachined.

USD leads to significant improvements on the hole oversize and surface finish.

The design of tool and transducer capacity plays an important role in providing a resonance state in USD to maximize the material removal rate.

Cutting forces in ultrasonically assisted drilling of carbon fibre-reinforced plastics by Farrukh Makhdum, Luke T Jennings, Anish Roy and Vadim V Silberschmidt.

Ultrasonic-assisted drilling of Inconel 738-Lc by B. Azarhoushang, J. Akbari.

Industrial Applications of Ultrasound-A Review II. Measurements, Tests, and Process Control Using Low-Intensity Ultrasound by Lawrence c. Lynnworth.

Assessment of ultrasonic drilling of C/SiC composite material by H. Hocheng, N.H. Tai and C.S. Liu.