For each of the curves in Figure 6-17, after the pulse parameters are determined, there is always an optimal workpiece thickness value that corresponds to the maximum value of the cutting speed of molybdenum cutting wire. When the workpiece thickness is at the optimum value, the pulse discharge efficiency is the highest, the workpiece thickness is too small or too large, and the cutting speed is reduced. When the workpiece is thin, the clearance discharge machining area is small, and the speed is limited by a thousand tracks. This results in a large carrier waveform, low average current, low effective output power, and low cutting speed.
As the thickness of the workpiece increases, the cutting speed of molybdenum wire increases. When the proper value is reached, the cutting speed reaches the maximum. At this time, the discharge efficiency is the highest. When the workpiece thickness is increased, the cutting speed is reduced. Because the thickness is too large, the output of the electrolytic corrosion product deteriorates, the processing stability deteriorates, and the pulse utilization rate is low, resulting in a decrease in the cutting speed for molybdenum wire. Comparing the two curves in (1) and (2) in Figure 6-17, the curve (2) keeps the pulse peak current not
As a result, the pulse width increases to twice the side of the curve (l), the cutting speed increases, and the optimum workpiece thickness increases. Pulse Width Increasing the discharge energy can increase the cutting speed and cutting thickness. The pulse widths of curve (I) and curve (3) are the same, the pulse peak current increases from 6A to 12 A, the cutting speed of curve (3) and the optimum workpiece thickness both increase, and the effect is more obvious than the curve (2). Increase the peak current of the pulse, increase the discharge energy, increase the discharge gap, and at the same time enhance the explosive force of the pulse discharge.
These factors are favorable to the discharge of the electro-corrosion products, can improve the processing stability, and increase the cutting speed of molybdenum wire. Thickness increases. While increasing the pulse width and peak current of the pulse, the peak current of the curve (4) increases to 12A, the pulse width increases to 48μ.s; the peak current of the curve (5) increases to 24A, and the pulse width increases. To 24 μs, the pulse discharge energy of curve (4) and curve (5) is approximately the same. From the curves in Fig. 6-17, it can be seen that with the increase of the peak current of the pulse, the cutting speed increases, the peak point of the curve shifts to the right, and the thickness of the workpiece capable of stable line cutting increases; the increase of the pulse width can also increase the cutting Speed and cutting thickness using molybdenum cutting wire, but not as effective as increasing the peak current of the pulse. Increasing the pulse width can increase the discharge energy address and facilitate the improvement of cutting speed and cutting thickness. After the pulse peak current is determined, the pulse width is selected according to the processing conditions.
The pulse interval is also an important factor influencing the molybdenum wire -cutting work of workpieces with a large thickness. The effect of the pulse interval can be studied through simulation experiments. The pulse width t; 48μs, the pulse peak current i=20A, varies at different thicknesses. The pulse interval gives different cutting speeds. Table 6-6 shows the simulation results.
From the data in Table 6-6, it can be seen that when cutting large thickness workpieces, after the pulse peak current and pulse width are determined, appropriately reducing the pulse interval can increase the pulse discharge frequency and increase the cutting speed. However, as the pulse interval decreases, processing stability deteriorates. This is due to the reduction in the pulse frequency during large-thickness molybdenum wire cutting, which results in insufficient output of the electro-erosion product from the discharge gap, which may cause the accumulation of electro-corrosion products and affect the stability of the process.
Through simulation experiments, it can be seen that increasing the pulse peak current can increase the discharge gap and improve the flow state of the working fluid in the kerf. It can help solve the main problem of large-thickness line cutting processing. One is the chip removal problem, which makes the molybdenum wire cutting speed and cutting thickness increase. . At the same time, the pulse width can be appropriately increased and the pulse interval can be reduced to increase the cutting speed, but it must be within a suitable range to ensure the stability of the processing process.