Ultrasonic Machining Process Research Articles

Macromodel for Ultrasonic Machining of Titanium and its Alloys: Designed Experiments

Titanium and its alloys have many potential engineering applications. There has been a critical need for cost-effective machining processes for titanium and its alloys. Not much work hitherto has been reported on the machining of tough materials like titanium by the ultrasonic machining process. An approach to macromodelling of the material removal rate, the tool wear rate, and surface roughness during ultrasonic machining of titanium and its alloys has been proposed and applied. Relationships between material removal rate (MMR), tool wear rate (TWR), surface roughness (SR), and other controllable machining parameters have been deduced by using Taguchi technique L18 orthogonal arrays. The comparison with experimental results will also serve as future validation of the model.

Rotary ultrasonic machining of aluminium oxide ceramics: designed experiments

There is a crucial need of reliable and cost-effective manufacturing method for advanced ceramics because of the limitations of conventional processes. These materials are used in a large number of critical engineering applications due to its hardness, high wear resistance and thermal-chemical stability. In this point, Rotary Ultrasonic Machining (RUM) process appears as a recognised an efficient machining solution. RUM uses a superabrasive tool together with an axial vibrating motion in ultrasonic region (∼20 kHz). The tool also rotates and feeds against the workpiece producing beneficial effects such as reduction of cutting forces, improved surface roughness, less tool wear, higher MRR, etc. This paper presents the performance of Ultrasonic Machining (USM) of Aluminium Oxide using a design of experiments. The principles and real benefits of RUM process for this ceramic material are assessed.

Ultrasonic machining effects on the surface finish and strength of silicon carbide ceramics

Ultrasonic machining experimental investigation was conducted on Silicon Carbide (SiC) and 20% volume titanium diboride-silicon carbide (TiB 2 /SiC) composite. Rectangular 304 stainless steel tools were used with three different abrasive grit sizes of silicon carbide (SIC) and boron carbide (B 4 C) abrasives were used while all other machining parameters were kept constant. The effects of the different abrasive sizes and types on the workpiece materials in terms of material removal rate, surface integrity, and flexural strength are presented. The #220 grit size for both abrasive types yielded the best overall results. Although both materials responded well to the ultrasonic machining process, the TiB2/SiC composite exhibited the better surface roughness and characteristic bending strength.

화학적 초음파가공을 이용한 유리의 미세가공

An ultrasonic machining process has been known as efficient and economical means for precision machining of glass or ceramic materials. However, because of its complexity, the mechanism of the machining process is still not well understood. Therefore, it is hard to optimize the process parameters effectively. The conventional ultrasonic machining which uses the abrasive slurry only, furthermore, is time-consuming and gives the relatively rough surface. In order to increase the material removal rate and improve the integrity of the machined surface, we have introduced the novel ultrasonic machining technique, Chemical-assisted UltraSonic Machining(CUSM). The desktop-style micro ultrasonic machine has been developed and the z-axis feed is controlled by the constant load control algorithm. To obtain the chemical effects, the low concentration HF(hydroj1l1oric acid) solution, which erodes glass, added to alumina slurry. Through various experiments and comparison with conventional results, the superiority of CUSM is verified. MRR increases over 200%, the surface roughness is improved and the machining load decreases dramatically.br/

An Optimized Design of the Bearing in Machines for Ultrasonic Machining Processes

In high-power ultrasonic manufacturing processes, the design of the bearing of the components transmitting ultrasound is of particular importance, since the position of the nodal planes in the vibrating structure is altering as a consequence of changing coupling conditions during the process. A special bearing, which reduces the residual vibrations at the fixing ring by a system of several resonators, has been developed for the use in ultrasonic production processes, such as tube drawing and wire drawing but also drilling and welding. Since the transmitted longitudinal vibrations always involve radial components as well, the dynamic stiffness of the coupling on the interface between the components transferring energy and the components deleting vibration is very important. In the method described in this paper, an optimization of dynamic behavior is attained by stiffness-reduced coupling.

초음파에 의한 고 세장비 유리가공 특성

An ultrasonic machining process is efficient and economical means for precision machining of glass and ceramic materials. However, the mechanism of the process with respect to the crack initiation and propagation and the stress development in the ceramic workpiece subsurface arc still not well understood. In this research, we have investigated the basic mechanism of ultrasonic machining of ultrasonic machining of glass by the experimental approach. For this purpose, we designed and fabricated the desktop micro ultrasonic machine. The feed is controlled precisely by using the constant load control system. During machining experiments, the effects of abrasive characteristics and machining conditions on the surface roughness and the material removal rate are measured and compared.

Characterization of synthetic quartz crystals grown from cylindrical seeds produced by ultrasonic machining

The potential of ultrasonic machining is investigated as a tool to produce seed crystals for hydrothermal growth of synthetic quartz with required surface finish and unconventional geometries. For this purpose, cylindrical seeds with 5, 10 and 18 mm diameter were obtained along the optic axis of a Z-bar using a conventional ultrasonic machining process with abrasive particles ranging from 6 to 50 μm. The topography of seed surfaces was characterized by surface profilometry and scanning electron microscopy. Later, synthetic crystals were grown in a standardized hydrothermal growth condition using NaOH solution. The characterization of as-grown crystals was performed by double-crystal X-ray topography with Laue geometry. Based on X-ray topographic images, it was observed that the density of dislocations, nucleated at the early stage of the growth period, increases with increasing roughness of the seed-crystal surface.

Precision ultrasonic machining process: a case study of stress analysis of ceramic (Al 2O 3)

Recent study and development activity in the field of precision ultrasonic machining (USM) process has focused on the ceramic (Al 2O 3). This paper first analyzes the USM process, mechanism, dynamics, and trends. It then discusses, in detail, the USM process applications on the ceramic (Al 2O 3).

An experimental investigation of rotary ultrasonic face milling

Reliable and cost-effective machining of advanced ceramics is crucially important for them to be widely used in a number of critical engineering applications. The potential of Rotary Ultrasonic Machining (RUM) process has been recognized as one of the reliable and cost-effective machining methods for advanced ceramics and commercial machinery is available for the process. One limitation of the commercial RUM machines is that only circular holes can be efficiently machined. An approach to extend the RUM process to face milling of ceramics was proposed and the development of the experimental apparatus as well as the preliminary experimental results were published earlier in this journal. As a follow-up, this paper will present the results of an experimental investigation of the newly-developed Rotary Ultrasonic Face Milling (RUFM) process. In this investigation, a five-variable two-level fractional factorial design is used to conduct the experiments. The purpose of these experiments is to reveal the main effects as well as the interaction effects of the process parameters on the process outputs such as Material Removal Rate (MRR), cutting force, material removal mode and surface roughness.

Micro removal of ceramic material (Al 2O 3) in the precision ultrasonic machining

Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. However, the mechanics of the process with respect to crack initiation and propagation, and stress development in the ceramic workpiece subsurface are still not well understood. This article presents experimental simulation of the process mechanics in an attempt to analyze the material removal mechanism in machining of ceramic (Al 2O 3). It is found that low-impact force causes only structural disintegration and particle dislocation. The high-impact force contributes to cone cracks and subsequent crater damage.

Micro ultrasonic machining and its applications in MEMS

A combined machining method, micro ultrasonic machining (micro-USM), is proposed here for the fabrication of three-dimensional (3D) microstructures with high aspect ratios. Wire electro-discharge grinding (WEDG) and electro-discharge machining (EDM) are combined onto the USM machine to provide a capability of making co-axial microtools for USM and, thereafter, microholes as small as 15 μm in diameter and a variety of high-aspect-ratio microstructures on brittle materials have been achieved for the first time by optimizing the ultrasonic machining processes. The combination of WEDG, EDM and USM on a micro-USM machine also makes possible the construction of complete 3D micromachines within one total manufacturing process. With this method, a 3D micro center-pin bearing air turbine has been successfully developed. The design, fabrication and testing issues are described in this paper.

Dynamic Analysis of the Ultrasonic Machining Process

This paper presents a dynamic analysis of the ultrasonic machining process based on impact mechanics. Equations representing the dynamic contact force and stresses caused by the impinging of abrasive grits on the work, are obtained by solving the three-dimensional equations of motion. The factors affecting the material removal rate have been studied. It is found that the theoretical estimates obtained from the dynamic model are in good agreement with the experimental results.

Rotary ultrasonic machining for face milling of ceramics

Among the various material removal processes applicable to ceramic materials, rotary ultrasonic machining has the potential for high material removal rate while maintaining low machining pressure and resulting in less surface damage. The limitation of rotary ultrasonic machining is that only circular holes or cavities can be machined due to the rotary motion of the tool. Attempts have been made by other researchers to extend rotary ultrasonic machining process to machining flat surfaces or milling slots. However, these extensions either changed the material removal mechanisms or had some severe drawbacks. One of the reasons for this might be an insufficient understanding of the material removal mechanisms involved. In this paper, a new approach to extend rotary ultrasonic machining to face milling of ceramics is proposed, which keeps all the material removal mechanisms of rotary ultrasonic machining. The development of the experimental apparatus and the design of the cutting tool are described. Preliminary experimental results are presented and discussed.

Design of tool holders for ultrasonic machining using FEM

There have been many new materials introduced recently which are hard, brittle and difficult to machine. The need for machining these materials has led to the widespread use of several unconventional machining methods, one of which is ultrasonic machining (USM) or ultrasonic impact grinding. USM complements the other non-traditional machining techniques such as electrochemical machining (ECM), electrodischarge machining (EDM), laser-beam machining, electron-beam machining and plasma-arc machining. It has made possible an appreciable simplification of the technology of fabricating profile parts from hard and brittle materials such as graphite, ceramics, quartz, semi-conductors, jewel stones and hard sintered materials. With the advent of USM, it is now possible to make cavities of any profile in such materials. One very important part of the ultrasonic machine is the horn (also known as a concentrator or tool holder). This is a waveguide focussing device with a cross-sectional area which decreases from the input (transducer) end to the output (tool) end. It amplifies the input amplitude of vibration so that at the output end the amplitude is sufficiently large for machining. The purpose of this research is to investigate the design of efficient tool holders or horns for the ultrasonic machining process by employing the finite-element method (FEM) to analyse the pertinent design characteristics of the horn, comparing the results with those measured experimentally using horns fabricated in-house as well as those supplied by an ultrasonic-machine builder. The common practice of using empirical approximations to calculate the resonant length of the horn can be wasteful and time consuming, as the designed horn may not be tuned to the machine, thus rendering the horn less efficient. By using FEM to do a modal analysis to find the natural frequencies of the various modes of the horn, the resonant frequency of the horn can be obtained easily. In this way, the horn design can be varied quite conveniently so that a more exact resonant frequency, which matches that of the machine, can be obtained. FEM also helps to verify and fine-tune the horn designs based on empirical formulae. In addition, dynamic analysis can be carried out to determine the stress characteristics of the horn under operating conditions.

Ultrasonic machining: a case study

The ultrasonic machining process uses a nonabrasive form tool, called a sonotrode, attached to a transducer/booster combination which vibrates at a frequency of approximately 20,000 cycles per second. A machining action occurs as the sonotrode vibrates the free abrasive particles flowing throughout the machining gap and propels them against the workpieee material. The form tool itself does not abrade the workpieee; the vibrating tool excites the abrasive grains in the flushing fluid, causing them to gently and uniformly wear away the material, leaving a precise reverse form of the sonotrode shape (Figure 1).

Recent trends in practical applications of macrosonics

Macrosonics includes the area of technology where treatment by sound or ultrasound produces permanent and useful changes in the treated medium. To date, two types of application have achieved major importance as viable commercial techniques. These—cleaning and plastics welding—are still expanding in scope and importance. Recent progress has been mainly in the direction of a greater degree of automation and control. Apart from these two established areas there are several applications that have already been more‐or‐less fully developed but which, for one reason or another, have a much more limited scope. Examples are: ultrasonic machining, metal‐welding, tinning, and various metal deformation processes. A third category consists of applications and ideas that appear very promising but which have not yet been fully explored or developed. Examples are: some aspects of chemical processing and various gas‐load applications, including the production of aerosols (atomization). After briefly reviewing the latest progress in the established areas, this paper will concentrate on new ideas and applications that show signs of developing into valuable practical techniques.

On the effect of ambient pressure on the rate of removal in ultrasonic machining

A preliminary investigation into the effect of ambient pressure on the ultrasonic machining process indicates that under certain conditions the rate of workpiece removal can be significantly increased. Ultrasonic machining of glass and cemented carbide was performed and the increase in the rate of removal for glass was found to be much greater than for the carbide.

Some Experiments With a Shock-Excited Magnetostrictive Impact Transducer

The usual ultrasonic machining processes use transducers operating at resonance and with a sinusoidal motion of the tip. Magnetostrictive transducers can be designed, however, with excitation applied sequentially along their length at a rate equal to the velocity of sound in the material. In this case, a steadily increasing strain pulse is produced, which travels in the direction of excitation. The motion of the tip has a large amplitude, short rise time, and is almost nonringing. The displacement can reach a few mils and large forces are generated if the tip is held against a solid object. The amplitude of the output and the repetition rate can be precisely controlled. The transducer was studied for applications such as rivetting, metal forming, and rock drilling. Another important use for this transducer with its short duration nonringing output signal is as a transducer in nondestructive testing. Two 7-in. transducers and one 5-ft-long transducer were built. The 5-ft transducer was used for dimpling metal disks and in a rock drilling experiment.

Improving Ultrasonic Machining Rates—Some Feasibility Studies

Investigations are reported on the influence on removal rate of slurry liquid cavitation, low temperature, liquid metal, and stress corrosion embrittlement of the work material, tool vibration amplitude, grit size and method of application of slurry, and the influence of heat-treatment and applied stress conditions of the workpiece. From these studies it is postulated that there may be three basic mechanisms involved in the ultrasonic machining process—microchip removal and material displacement by plastic deformation, and particle removal by fracture.

Effect of Pressure between Tool Tip and Workpiece on the Rate of Ultrasonic Machining in Ketos Tool Steel

Data are presented for the ultrasonic machining rate in Ketos tool steel obtained by using rectangular tool tips having different perimeters and circular tool tips having different radii. It is shown that the pressure rather than the force maintained between the tool tip and the workpiece is pertinent in the ultrasonic machining process, and that the ratio C/A of the tool tip perimeter C to the tool tip area A is of importance. It is also shown that for rectangular and circular tool tips a critical machining rate V0 and a critical pressure P0 exists, the values of which are related to the ratio C/A by the two simple expressions V0 = 2ξνdM(C/A) and P0 = L(C/A), where 2ξ and ν are the peak to peak amplitude and the frequency of vibration respectively, d is the abrasive particle diameter, and M and L are parameters independent of 2ξ, ν, d, C or A. On the basis of the above two equations a phenomenological expression is derived which for circular and rectangular tool tips relates the machining rate in general to the pressure in general.