2. Poor chip removal
A. Influence of processing depth
The smaller the discharge cross-sectional area and the deeper the machining depth, the more difficult it is to remove the chip. It is the key to improve the chip removal quality for the machining of this type of cavity. When it comes to EDM chip removal, there are two conventional methods at present, one is the flushing method, the other is the immersion method, and the flushing method is used in the immersion processing at the same time, so as to improve the fluidity of the liquid and strengthen the chip removal effect. In terms of machining accuracy and chip removal effect, the immersion method is much better than the simple flushing method. (see Figure) the chip removal mechanism of the immersion processing method is to use the high-speed movement of the spindle to cause the mold cavity to be in a high-pressure or vacuum state and cause the strong disturbance of the liquid to achieve the purpose of chip removal. Imported equipment is very suitable for this chip removal method due to the high running acceleration of the spindle, and the effect is very good. In the flush machining method, due to the uneven flow direction and pressure of the liquid flow, the chip removal may not be complete, and it is easy to form two discharges where the chip removal materials gather, which affects the accuracy of the cavity; Secondly, it is also easy to cause carbon deposition, so the immersion processing method should be used as far as possible when conditions permit.
B. Influence of processing position
It is not necessarily that the discharge stability of open EDM is higher than that of machining blind holes. Sometimes, machining only one surface is easier to cause the deterioration of machining stability than machining all peripheral surfaces at the same time. The reasons are as follows: EDM chip removal mainly depends on the disturbance of machining fluid, or scouring, or extrusion. The stronger the fluidity of the liquid, the more thorough the chip removal. When only one surface is processed, the up and down movement of the electrode can not cause the strong disturbance of the processing fluid. Moreover, if the up and down runout distance of the main shaft is relatively small, the electro-corrosion products can not leave the discharge gap, which is easy to cause the deterioration of processing stability and even carbon deposition. As shown in the figure.
In this case, if the machine tool has good performance and can realize three-axis linkage processing, it is best to adopt lateral servo processing, so that the electrode is slightly away from the processing surface for a certain distance when retreating, so that the electro-corrosion products can be washed away smoothly. If there are no conditions, try to increase the movement range of the main shaft and expose the machining surface to the machining fluid as much as possible, so as to eliminate the electric corrosion.
C. Effect of liquid flow treatment
In EDM, the liquid flow treatment is very important. The liquid flow direction should follow the direction of the generation of electro-corrosion products. For example, in the above example, if the liquid flow direction is not parallel to the discharge gap but perpendicular to the discharge gap, the discharge state may become worse. For example, when processing the above items, but the effect may not be very good by soaking, it is best to supplement it with flushing method.
D. Influence of electrode material quality
Of course, the quality of electrode material is also the main reason for abnormal processing. Generally speaking, the probability of quality problems of graphite material is higher than that of copper. The reason is that the manufacturing process of graphite is complex. In addition, it is a non-metallic material after all, and many characteristics are different from metal materials. The quality problems of graphite are generally manifested in loose material, easy slag falling, uneven discharge roughness, etc., but all these phenomena do not necessarily mean that it is the quality problem of graphite. Poor processing state and improper processing conditions will also cause these problems. We can only consider whether the material problem is solved after eliminating these possibilities. Dongyang carbon provides pure Nissan graphite with stable product quality and guaranteed service. Customers can rest assured to use the graphite products of various brands provided by our company.