During electric discharge machining process there are start and stop intervals known as ON time and OFF time. The machining is performed during the pulse ON time when in the gap between work piece and electrode the voltage is applied. Alternatively the time during which no voltage is applied is the pulse off time. A greater value of On time is selected to obtain a long duration of electric discharge to increase the material removal rate but also leads to poor surface finish. During the pulse off time re-ionization of dielectric occurs and it is also essential to avoid any short circuit leading to wire breakages.
2.1.2 Peak current and gap voltage
In WEDM, the most important machining parameter is the peak current. Measured in unit of amperage it is basically the amount of power used in WEDM. Peak current is the preset level reached by the increasing current during each pulse on-time. In both processes, die sinking and wire-EDM, the surface area of cut governs the maximum amount of amperage. In roughing operations and in cavities or details with large surface areas, a higher amperage is used.
The supply voltage to be placed on the gap is expressed as the gap voltage or open circuit voltage. The electric discharge energy is directly proportional to this value i.e. greater the gap voltage value greater is the electric discharge energy. Moreover gap voltage and peak current are also dependent and peak current increases with the increase in gap voltage. In some WEDM machines machining voltage is shown by both of these factors.
2.1.3 Servo voltage and servo feed rate:
Fig.2. Feed rate and gap size (Roger Kern, 2008)
For controlling the advances and retracts of the wire a servo voltage is used. Depending on the state of machining b...
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... Only a few scientific works have been dealing with cutting by wires with a diameter below 50µm.The wire materials are brass coated steel wire and tungsten having high tensile strength and melting temperatures. According to Klocke, F. et al. typical ultra-thin wire diameters are 20, 25, 30 and 50µm which can be used to produce micro parts with wire EDM.
3. Literature Review
Dharmendra et al [4] found out the main parameters which are average cutting speed and surface roughness which affect the different machining criteria. They studied the trend of variation of these important machining criteria with four control factors which has been studied simultaneously to establish the trend of variation.
Bijendra Diwakar et al [] analyzed that metal removal rate is most affected by pulse frequency as and predicted optimal parameter setting with the help of Taguchi’s approach.
Before a metal piece or metal alloy can be used in any given application, whether it is a construction project or anything else, it might be necessary to cut the material to the right shape and size. One may need to cut metal into pieces of different sizes and shapes according to the end use.
For a point, we have the popular clip-point design. This allows for great precision and control as well as great slicing and piercing ability.
But the grain size ranges between 3 μm to 6 μm, 3 μm to 8 μm and 4 μm to 9 μm for 4 mm, 6 mm and 8 mm plates respectively. Higher polygon pin face edges approach circular pin, this vanishes the pulse formation in stirring. This leads to distorted grains due to decrease in dynamic area or lack of sweeping between tool and material. Whereas a low number of polygon pin face edges generates higher dynamic area. This shows the coarse grains relatively. The grain size ranges between 5 μm to 7 μm, 6 μm to 8 μm and 7 μm to 9 μm for 4 mm, 6 mm and 8 mm plates
This depends on the type of electrode that is being used. In some ESPs the discharge electrodes are tubes rather than plates in which case they are washed by a water stream. In case of the electrodes being plates, rapping is used to remove the dust layer on the electrode. It is a process in which dust particles are dislodged from the electrodes by sending mechanical impulses or vibrations through the electrodes which causes the dust layer to fall off as sheets and thus avoiding any re-entrainment. The removal of the layer is carried out when the thickness of the layer is between 0.3-0.5 in. The intensity and frequency of rapping depends upon the particle concentration in the flue
]. Some alloying elements sometimes added to impart special characteristics to brass. Lead, which is insoluble in copper alloys, used to improve machinability of leaded brass. However, Pb and Bi or other elements that are used to improve the machinability often deteriorate the low and high temperature ductility of brass [11]. The content of Pb element is varies between 2.5 and 3.5 %, which make the machining processes at high speed and good surface [12]. The solubility of lead in copper alloys is very low therefore, it is found in microstructure as dispersed globules all over the material. These globules lead act as a lubricant decreasing the friction coefficient between the tools and the materials by creating discontinuities of chip fragmentation. Therefore, it makes reducing in cutting force and then, the tools wear rate is minimized [13]. Different alloying elements help to improving the machinability are usually added to brass. The most common element using in this situation is lead, which improving the machinability with
Fabrication at the factory utilizes a mix of robotics and manual labor to produce the body of the V-Rod. Robots that are designed to cut pipe are capable of completing a single operation within 3 seconds. Other fabrication robots utilize 1800 watt lasers that can perform cutting operations at the rate of 100 inches per minute. Where robotics can be used to perform high speed cutting and welding operations, skilled workers are a...
Milling offers the advantages of being highly precise and having much smoother surface finish (surface roughness of easily around 1 µm ) compared to powder bed fusion additive manufacturing (layer thickness in the range of 20 µm and above; surface roughness of 15 µm and above ). Flat surfaces and sharp corners can be obtained with CNC milling. Similarly, features such as threads and holes are more accurately created through
The program consists of precise instructions about the methodology of manufacture as well as movements. For example, what tool is to be used, at what speed, at what feed and to move from which point to which point in what path. Since the program is the controlling point for product manufacture, the machine becomes versatile and can be used for any part. All the functions of a NC machine tool are therefore controlled electronically, hydraulically or pneumatically. In NC machine tools, one or more of the following functions may be automatic.bhk
It is thus a thermal erosion process. The sparks are created in a dielectric liquid, generally water or oil, between the work piece and an electrode, which can be considered as the cutting tool. There is no mechanical contact between the electrodes during the whole process. Since erosion produced by electrical discharges, both electrode and work piece have to be electrically conductive. Thus, the machining process consists in successively removing small volumes of work piece material, molten or vaporized during a discharge. The volume removed by a single spark is small, in the range of 10-6-10-4 mm3 but this basic process is repeated typically 10,000 times per
The change in direction of current is facilitated by the split ring commutator. The brushes remain stationary, but they are in contact with the armature at the commutator, which rotates with the armature such that at every 180° of rotation, the current in the armature is reversed.
There are number of methods to fabricate MEMS like silicon surface micromachining, silicon bulk machining, electro discharge machining, LIGA (in German, Lithographie, Galvanoformung(Electro Plating), Abformung(Injection Moulding)) .Only silicon surface micromachining is discussed here.
Abrasive Jet Machining (AJM) is the removal of material from a work piece by the application of a high speed stream of abrasive particles carried in gas medium from a nozzle. The AJM process is different from conventional sand blasting by the way that the abrasive is much finer and the process parameters and cutting action are both carefully regulated. The process is used chiefly to cut intricate shapes in hard and brittle materials which are sensitive to heat and have a tendency to chip easily. The process is also used for drilling, de-burring and cleaning operations. AJM is fundamentally free from chatter and vibration problems due to absence of physical tool. The cutting action is cool because the carrier gas itself serves as a coolant and takes away the heat.
The U.S. power tools market is divided into three segments: Consumer (home use buyers), Professional-Tradesmen (P-T) (contractors who purchase their own tools), and Industrial (procuring professional buying in large quantities for industrial usage). The P-T segment is the one experiencing the largest growth potential.
In general, any machine part can be produced by one of various manufacturing methods such as forging, machining, casting and welding. Determination of the manufacturing methods depends on production costs of the alternatives for individual parts. Friction welding which is an alternative welding method, is widely used in production of machine parts having different cross-section or diameter in order to decrease manufacturing costs and the main advantage of friction welding methods is to reduce defects existing during