Ultrasonic Machining USM Process Parameters and Factors Affecting Ultrasonic Machining Rate
Process variable and their effect on the ultrasonic machining
The machining rate and accuracy of USM depend on many factors. Diagram shows some of the factors that affect the USM.USM Machining Rate
The cutting rate in USM depends on1. Vibration frequency and amplitude: The frequency of vibration is directly proportional to the material removal rate. The increase in frequency increase the number blows by the tool per second and cut more material from surface. For many materials, the material removal rate is proportional to the square of amplitude of vibration.
2. Static load on tool: The material removal rate increase with the static load on tool up to a maximum value. Beyond this point, the material removal decreases with the increasing static load.
3. Abrasive material, size: The characteristics of abrasive like size, shape hardness, etc. are effects its cutting efficiency. The increase in grain size increases the material removal rate till grain size equal to the amplitude of vibration. Beyond this, the increase in grain size decreases the cutting rate.
4. Slurry composition and property
The composition of slurry, the concentration of abrasive particle in slurry and viscosity of slurry effects the material removal rate. The abrasive grit worn out rapidly, so periodic replacement of slurry is required. Since the viscosity of slurry dampens the oscillation of grits, the material removal rate decreases as the viscosity increases.
5. Workpiece material and machining area and shape: the material removal rate depends on the characteristics of workpiece material like hardness, brittleness, etc. The shape depth of cut required also effects machining rate.
USM Machining accuracy and surface finish
1. Grain material and size: The abrasive material should be at least hard as the workpiece material, it should not erode itself during ultrasonic machining. The smaller the grain size smoother the surface obtained, but it reduces material removal rate.2. Tool material: The tool wear must be minimum. Unpredictable tool wear cause dimensional inaccuracy.
3. Abrasive slurry: The slurry should possess good wetting ability, high thermal conductivity, anticorrosive properties etc. The slurry must be recirculated so that it carries away debris readily from machining zone and a cooling system must be there to cool slurry. Otherwise, it ruins the machined surface.