A Novel Technique for the Surface Texture Inspection of Electrical Discharge Machined Surfaces Using Vision System

Wire electrical discharge machining has appeared mainly in response to the need for detachment with sufficiently high accuracy of parts of plate-type workpieces. The improvements introduced later allowed the extension of this machining technology to obtain more complex ruled surfaces with increasingly high requirements regarding the quality of the machined surfaces and the productivity of the wire electrical discharge machining process. Therefore, it was normal for researchers to be interested in developing more and more in-depth investigations into the various aspects of wire electrical discharge machining. These studies focused first on improving the machining equipment, wire electrodes, and the devices used to position the clamping of a wire electrode and workpiece. A second objective pursued was determining the most suitable conditions for developing the machining process for certain proper situations. As output parameters, the machining productivity, the accuracy, and roughness of the machined surfaces, the wear of the wire electrode, and the changes generated in the surface layer obtained by machining were taken into account. There is a large number of scientific papers that have addressed issues related to wire electrical discharge machining. The authors aimed to reveal the aspects that characterize the process, phenomena, performances, and evolution trends specific to the wire electrical discharge machining processes, as they result from scientific works published mainly in the last two decades.

Download Full-text

Experimental Study on the Influence of Machining Conditions on the Quality of Electrical Discharge Machined Surfaces of aluminum alloy Al5052

Machines ◽

10.3390/machines8010012 ◽

2020 ◽

Vol 8 (1) ◽

pp. 12 ◽

Cited By ~ 7

Author(s):

Angelos P. Markopoulos ◽

Emmanouil-Lazaros Papazoglou ◽

Panagiotis Karmiris-Obratański

Keyword(s):

Aluminum Alloy ◽

Electrical Discharge ◽

Electrical Discharge Machining ◽

Removal Rate ◽

White Layer ◽

Machining Parameters ◽

Machining Processes ◽

Machining Conditions ◽

Pulse On Time ◽

Machined Surfaces

Although electrical discharge machining (EDM) is one of the first established non-conventional machining processes, it still finds many applications in the modern industry, due to its capability of machining any electrical conductive material in complex geometries with high dimensional accuracy. The current study presents an experimental investigation of ED machining aluminum alloy Al5052. A full-scale experimental work was carried out, with the pulse current and pulse-on time being the varying machining parameters. The polishing and etching of the perpendicular plane of the machined surfaces was followed by observations and measurements in optical microscope. The material removal rate (MRR), the surface roughness (SR), the average white layer thickness (AWLT), and the heat affected zone (HAZ) micro-hardness were calculated. Through znalysis of variance (ANOVA), conclusions were drawn about the influence of machining conditions on the EDM performances. Finally, semi empirical correlations of MRR and AWLT with the machining parameters were calculated and proposed.

Download Full-text

High-Speed Noncontact Profiling of Pavement Surface Texture and Its Significance

Journal of Tribology ◽

10.1115/1.3261237 ◽

1986 ◽

Vol 108 (3) ◽

pp. 455-461

Author(s):

J. C. Wambold ◽

J. J. Henry

Keyword(s):

Surface Texture ◽

High Speed ◽

Large Scale ◽

Vision System ◽

Small Scale ◽

Skid Resistance ◽

Texture Measurement ◽

Pavement Surface ◽

Texture Characteristics ◽

Regression Techniques

It is generally agreed that the friction between a tire and a wet pavement (skid resistance) is controlled by the surface texture characteristics. Therefore, by measuring the relevant parameters describing texture, or by measuring a physical process dependent on texture, regression techniques can be used to relate skid resistance to the chosen texture parameter or process. Two scales of texture are of particular importance: microtexture (small-scale asperities) and macrotexture (large-scale asperities). This paper describes work performed to: (1) review candidate macrotexture and microtexture measurement methods that can be made at highway speeds (at or about 64 km/h [40 mph]), which are presently used or have potential for use in pavement texture measurement; (2) design and build a prototype of the most promising method; and (3) evaluate the effects of pavement surface texture on skid resistance. A prototype noncontact vision system that makes texture measurements at highway speeds was developed, and several improvements were made to upgrade the system to provide an improved prototype. Both hardware and software enhancements have yielded a texture measurement system that can obtain pavement macrotexture data in a fast, efficient, and reliable way.

Download Full-text

Precision Machining of Nimonic C 263 Super AlloyUsing WEDM

Coatings ◽

10.3390/coatings10060590 ◽

2020 ◽

Vol 10 (6) ◽

pp. 590

Author(s):

Katerina Mouralova ◽

Libor Benes ◽

Josef Bednar ◽

Radim Zahradnicek ◽

Tomas Prokes ◽

...

Keyword(s):

Electrical Discharge ◽

Cutting Speed ◽

Machining Process ◽

Precision Machining ◽

Machining Accuracy ◽

Pulse On Time ◽

Pulse Off Time ◽

Super Alloy ◽

Machined Surfaces

Wire electrical discharge machining (WEDM) is an unconventional and very efficient technology for precision machining of the Nimonic C 263 super alloy, which is very widespread, especially in the energy, aerospace and automotive industries. Due to electrical discharge, defects in the form of cracks or burned cavities often occur on the machined surfaces, which negatively affect the correct functionality and service life of the manufactured components. To increase the efficiency of the machining of Nimonic C 263 using WEDM, in this study, extensive design of experiments was carried out, monitoring input factors in the form of machine parameters like Pulse off time, Gap voltage, Discharge current, Pulse on time and Wire feed, the output of which was comprehensive information about the behaviour of such machined surfaces, which allowed the optimization of the entire machining process. Thus, the optimization of the Cutting speed was performed in relation to the quality of the machined surface and the machining accuracy, as well as an analysis of the chemical composition of the machined surfaces and a detailed analysis of the lamella using a transmission electron microscope. A detailed study of the occurrence of surface or subsurface defects was also included. It was found that with the help of complex optimization tools, it is possible to significantly increase the efficiency of the machining of the Nimonic C 263 super alloy and achieve both financial savings in the form of shortened machine time and increasing the quality of machined surfaces.

Download Full-text

A Novel Approach to Quantifying Surface Roughness in Grinding

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.339.147 ◽

2007 ◽

Vol 339 ◽

pp. 147-151

Author(s):

Chun Hua Ju ◽

Yi Xie

Keyword(s):

Surface Roughness ◽

Standard Deviation ◽

Vision System ◽

Computer Control ◽

Mean Value ◽

Quality Characteristic ◽

Edge Image ◽

Gray Image ◽

Novel Approach ◽

Machined Surfaces

Surface roughness is an important quality characteristic in grinding. Measurement of surface roughness by means of mechanical stylus is widely done in metrology. In this paper, a new machine vision system has been utilized to quantify the surface roughness of machined surfaces (ground and milled). Compared with other measurement methods, it is accurate, quick and credible. This system is mounted on the grinding machine and automates the measurement process by using computer control to automatically position the CCD and capture digital images of machined surfaces between grinding cycles. It was proposed that the proportional formula was used in calibrating this system, and calibration precision meets application requirement. Not only the statistic character of gray image but also which of edge image were calculated out. These characters include the mean value of pixels (Mean), standard deviation (σ), maximal value (Max) and minimal value (Min), the number of pixels on the examine line(Count), etc. It was found out that the standard deviation value σ of the gray image could express the surface roughness most. The correlation between σ and Ra is established by interpolating σ value used Lagrange interpolation law, and the σ value is converted into Ra value through the calculation procedure finally.

Download Full-text

Enhancement in Microhardness of Free Machining Brass in Ball Burnishing

International Journal of Vehicle Structures and Systems ◽

10.4273/ijvss.12.2.13 ◽

2020 ◽

Vol 12 (2) ◽

Author(s):

Pavana Kumara ◽

G.K. Purohit

Keyword(s):

Plastic Deformation ◽

Response Surface Methodology ◽

Response Surface ◽

Process Parameters ◽

Surface Texture ◽

Ball Burnishing ◽

Abrasive Particles ◽

Metal Finishing ◽

Burnishing Process ◽

Machined Surfaces

The burnishing process is becoming an attractive way among post-machining, metal finishing techniques due to its excellent features. The burnishing process carried out with ball or roller, smooth out the protrusions due to the plastic deformation and increases the surface texture. This paper presents the results of three ball burnishing conditions carried out on cylindrical free machining brass components. Influence of abrasive particles (abrasive assisted burnishing, AAB) during burnishing is investigated and compared with the burnishing carried out without (plain burnishing, PB) and with-coolant (lubricated burnishing, LB) conditions. The response surface methodology (RSM) is used to optimize the microhardness in terms of four process parameters. Result obtained indicates that the microhardness of the pre-machined surfaces increases by 12-29 percent. The AAB results in 141.67 percent higher microhardness than the PB and 41 percent more than the LB condition.

Download Full-text