Views: 94 Author: Site Editor Publish Time: 2019-06-12 Origin: Site
The recent development of modern hi-tech industries has given rise to the creation of a whole range of new materials. These include high strength, stainless and heat resistant steels and alloys, titanium, ceramics, composites, and other nonmetallic materials. These materials may not be suitable for traditional methods of machining due to the chipping or fracturing of the surface layer, or even the whole component, and results in a poor product quality.
Similarly, the creation of new materials often highlights some problems unsolvable in a framework of traditional technologies. In certain cases these problems are caused by the construction of the object and the requirements particular to it. As an example, in microelectronics, its often necessary to connect some components without heating them or adding any intermediate layers. This forbids the use of traditional methods such as soldering or welding.
Many of these and similar problems can be successfully solved using ultrasonic technologies. The USD (Ultrasonic Drilling Machine) uses a novel drive mechanism to transform the ultrasonic or vibrations of the tip of a horn into a sonic hammering of a drill bit through an intermediate freeflying mass.
The use of ultrasonic for machining processes of hard and brittle materials is known since early 1950s .The working process of an ultrasonic machine is performed by subjecting its tool to a combination of two motions. A driving motion is required to shape the w/p. A high frequency
(ultrasonic) vibration of specific direction, frequency and intensity is then superimposed. Ultrasonic machines belong to the general class of vibration machines, but they form a special group for the following reasons.
The first reason is determined by the peculiarities in the behavior of materials and media in an ultrasonic field. Among these peculiarities is the drastic change in elastic – plastic characteristics that include fragility, plasticity and viscosity. The second reason is due to the peculiarities in the construction of major parts of the machine. The main components are usually formed using vibrating bar systems consisting of heterogeneous sections and using waveguides. The tool-work piece interaction leads to a nonlinearity in the vibration system in its operating conditions.we have tried to consider the physical foundations of ultrasonic processes among which we are laying focus on the ultrasonic machining of brittle materials. The construction of the machine and its elements depends critically on the process being performed by the tool. Therefore the optimum parameters those are required for a specified set of operations are needed to be studied in order to produce required quality of machining within the permissible time and resources.
Ultrasonic machining is ideal for certain kinds of materials and applications. Brittle materials, particularly ceramics and glass, are typical candidates for ultrasonic machining. Ultrasonic machining is capable of machining complex, highly detailed shapes and can be machined to very close tolerances (±0.01 mm routinely) with properly designed machines and generators. Complex geometric shapes and 3-D contours can be machined with relative ease in brittle materials. Multiple holes, sometimes hundreds, can be drilled simultaneously into very hard materials with great accuracy.
Channels and holes ultrasonically machined in a polycrystalline silicon wafer.
Coining operations for materials like glass ,ceramics, etc.
Threading by appropriately rotating and translating the workpiece/tool.
Rotary ultrasonic machining uses an abrasive surfaced tool that is rotated and vibrated simultaneously. The combination of rotating and vibrating action of the tool makes rotary ultrasonic machining ideal for drilling holes and performing ultrasonic profile milling in ceramics and brittle engineered materials that are difficult to machine with traditional processes.
Ultrasonic machining can be used to form and redress graphite electrodes for electrical discharge machining. It is especially suited to the forming and redressing of intricately shaped and detailed configurations requiring sharp internal corners and excellent surface finishes.
It is particularly useful in microdrilling holes of upto 0.1 mm.