What is Ultrasonic Machining (USM) in Manufacturing Process: Working Principle, Equipment's, Process Parameter, MRR, Applications, Advantages, Dis-advantages

Introduction:

Ultrasonic Machining is a non-conventional cycle, where abrasives contained in a slurry are driven against the work by a device swaying at low abundancy (15-50 microns) and high recurrence (19-25 kHz).

Working Principle:

• Ultrasonic machining is a non-traditional machining process. Fig.1. briefly depicts the USM process.

• In general, this tool is pressed down with the power of feed, F. Between work tools and workpieces, the machining zone is flooded with hard hard particles in general in the form of water-based porridge.

• When the tool vibrates above the workpiece, the abrasive through particles act as indenters and indenting both work materials and tools.

Fig. Ultrasonic Machining (USM)

• Abrasive particles, because they are indentation, work material, will remove the same, especially if the material is fragile, due to cracking initiation, propagation, and fracture. Therefore, USM is mainly used for the machining of brittle materials.

Equipment of USM :

Ultrasonic Machining Consists of :

1. High Power Sine Wave Generator
2. Magneto-Strictive Transducer
3. Tool Holder
4. Tool

• High Power Sine Wave Generator:

High power sine wave generator: This unit converts, low recurrence (60 Hz) electrical capacity to high recurrence (20kHz) electrical force.

• Transducer: 

The high-frequency electrical signal is transmitted to the traducer which converts it into high-frequency low amplitude vibration. Basically, the transducer changes electrical energy to mechanical vibration. There are two kinds of transducers utilized

 1. Piezo Electric Transducer

 2.Magneto-Strictive Transducer

1.Piezo Electric Transducer :

These transducers produce a little electric flow when they are packed. Likewise, when the electric flow is gone through the gem, it extends. At the point when the current is taken out, the gem achieves its unique size and shape. Such transducers are accessible up to 900 Watts. Piezoelectric precious stones have a high transformation proficiency of 95%.

2.Magneto-Strictive Transducer :

These likewise change their length when exposed to the solid attractive field. These transducers are made of nickel, nickel combination sheets. Their change productivity is around 20-30%. Such transducers are accessible up to 2000 Watts. The most extreme change long that can be accomplished is around 25 microns.

• Tool holder / Horn: The device holder holds and interfaces the device to the transducer. It essentially sends the energy and now and again, enhances the sufficiency of vibration. Material of hardware ought to have great acoustic properties, high protection from exhaustion breaking. Due measures ought to be taken to stay away from ultrasonic welding between the transducer and apparatus holder. Normally utilized apparatus holders are Monel, titanium, tempered steel. Tool holders are more expensive, demand higher operating costs.

• Tool: Instruments are made of generally bendable materials like Brass, Stainless steel, or Mild steel so that Tool wear rate (TWR)can be limited. The value of the ratio of TWR and MRR depends on the kind of abrasive, work material, and tool materials.

• Process Parameter :

• The amplitude of vibration (ao): 15-50 μm
• Frequency of vibration (f): 19-25 kHz
• Feed force (F): related to tool dimensions
• Feed pressure (p)
• Abrasive size: 15 μm - 150 um
• Abrasive material: Al2O3, SiC, B4C, Boronsili Carbide, and Diamond
• Flow strength of work material.
• Flow strength of the tool material.
• The contact area of the tool: A
• The volume concentration of abrasive water slurry: C

Machining Characteristics:

 Following are the USM process criteria

1 Material removal rate

2. Geometrical accuracy

3. Surface finish

4. Out of roundness

The characteristics of the above process parameters on process criteria are as follows

Effect of amplitude (a) on MRR: 

• An increase in the amplitude of vibration increases MRR. To boost the sufficiency of vibration concentrator ought to work at a reverberation recurrence. In specific situations, this cutoff points additionally the greatest size of grating to be utilized.

Fig.Effect of Amplitude

Effect of Slurry, Tool, and Work Material:

• MRR increases with slurry concentration. Slurry saturation occurs at 30 to 40% abrasive/water mixture.

• Material Removal rate drops with increasing viscosity

• The pressing factor with which the slurry is taken care of into the cutting zone influences MRR. At times, MRR can be expanded even multiple times by providing the slurry at an expanded pressing factor.

• The shape of the tool affects the MRR. The narrower rectangular tool gives more MRR compared to the square cross-section. The tapered device gives twice MRR contrasted with the round and hollow apparatus.

• The weak conduct of the material is significant in deciding the MRR. Fragile material can be cut at higher rates than bendable materials.

Fig. Effect of slurry, Tool, Material

Applications of  USM:

• Utilized for machining hard and weak metallic compounds, semiconductors, glass, earthenware production, carbides, and so on 

• Utilized for machining round, square, sporadic formed openings and surface impressions. 

• Machining, wire drawing, punching, or small blanking dies.

Advantages of USM:

USM measure is non-warm, non-synthetic, makes no progressions in the microstructures, compound, or actual properties of the workpiece, and offers for all intents and purposes peaceful machined surfaces.

The main advantages are:

• Any materials can be machined paying little mind to their electrical conductivity.

• Especially suitable for machining of brittle materials.

• Machined parts by USM have a superior surface completion and higher primary respectability.

• USM does not produce thermal, electrical, and chemical abnormal surfaces.

Disadvantages of USM :

• USM has higher force utilization and lower material evacuation rates than conventional creation measures.

• Tool wears fast in USM.

• Machining area and depth are restraint in USM.