3Q MACHINING is a top-quality CNC machining manufacturer in DONGGUAN, GUANGDONG, CHINA. We are working our best work for your custom plastic & metal machining parts from design drawing or sample to final shipment with fast delivery and low MOQ. We are using advanced technology and equipment to offer high precision for producing metal and plastic machining parts. In this article, we focus on some common problems and solutions of aluminum alloy parts processed by CNC wire cutting.
When machining aluminum alloy parts by CNC wire cutting, there are often problems such as serious wear of the feed block, short circuit, wire breakage, processing track distortion, and workpiece deformation, and some directly cause the processed product to be scrapped.
The problem of wire-cutting aluminum alloy parts easy to break
The reason why wire-cut aluminum alloy parts are easy to break
When wire cutting aluminum alloy parts, because the material is relatively soft, chip removal is difficult, and aluminum alloy is very easy to form a hard oxide film at high temperatures. A large amount of aluminum oxide or aluminum scraps is easy to stick to the molybdenum wire, making the molybdenum wire and the feed block Deep grooves will soon be ground at the contact area. Soft aluminum and hard abrasive grains are mixed together and stuffed in the groove. Once brought in, the groove will be squeezed to death, and the wire will be jammed.
Solution
- In view of the problem that the molybdenum wire is caught in the feed block and the molybdenum wire is clipped, adjust the position of the upper and lower wire frame feed blocks to prevent the worn grooves of the feed block from causing the clipped wire broken wire, resulting in low efficiency and machined surface Quality degradation and material waste.
- The thickness of the processed material is more than 40mm. Generally, the feed block is slightly rotated by an angle after 3 to 4 hours of processing, and then rotated by an angle after 8 hours of processing, the position of the feed block is adjusted once every 8 hours of processing to reduce wire breakage probability. The actual processing shows that this method greatly reduces the processing cost and improves the economic benefits. Note that the overvoltage of the feed block and the electrode wire is generally 0.5 to 1 mm. When there are cutting grooves at three points on one surface, rotate the feed block by 90º, and so on until there are cutting grooves on all four surfaces. Then put a shim of 1~2mm on the side close to the sampling line to adjust the position of the feed block to the left, which is equivalent to replacing the feed block with a new one, saving production costs.
- Of course, it must be noted that when the dimensional accuracy requirements of the workpiece are relatively high, the diameter of the molybdenum wire must be measured, and the compensation amount must be modified in time to ensure the dimensional accuracy requirements.
The problem of deformation of the workpiece
The cause of deformation of the workpiece
Due to the effects of uneven heating, internal structure phase transformation, force deformation, and other effects of workpiece blank manufacturing, cutting processing, and heat treatment, residual stresses are generated inside the workpiece, and the stress distribution is relatively balanced within a period of time without external influence. However, in the online cutting process, due to a large amount of cutting and cutting of the workpiece material, the stress distribution will be changed, and it will gradually become balanced with the passage of time, which will cause the workpiece to deform. This deformation phenomenon is more obvious for aluminum alloy parts.
Solution
- Stress relief before cutting
The parts are first heat-treated to eliminate the internal stress of the material before cutting so that there will be no large stress deformation during cutting to stabilize the size. Of course, different materials have different processing methods.
- Outer contour processing method
When the outer contour is processed, it is usually possible to cut in from the outside of the blank without punching and threading. This method is very easy to cause large deformation due to the release of the internal stress of the material after the blank is broken, resulting in a decrease in the machining accuracy of the parts. In order to avoid and reduce the occurrence of this kind of deformation, the method of punching wire holes can be used to maintain the closeness of the contour of the blank, which can minimize the stress and deformation during the processing.
- Adopt the secondary cutting method
For parts that require relatively high machining accuracy, it is best to use the secondary cutting method.
Aluminum alloy parts are easy to short-circuit when cutting and the problem of cutting track distortion
Analysis of the cause of the problem
- In daily processing, it is difficult to cut large-thickness workpieces. Due to the restriction of the erosion conditions of electrical discharge machining, the workpiece is thick to a certain extent, and there is not enough coolant to enter the workpiece. The electrical corrosion products in the gap cannot be eliminated normally, and the processing is very unstable. , Until there is a current without discharge short circuit occurs, this phenomenon is more likely to occur when cutting aluminum parts.
- Under normal circumstances, the WEDM machine tool has a short circuit protection function. Once a short circuit occurs, the machine tool table immediately stops moving and remains in place for processing. However, when machining aluminum parts, due to the lightweight, softness, and difficulty of chip removal, sometimes the discharge point is transferred from the processing area to the feed block after a short circuit, causing spark discharge between the feed block and the molybdenum wire. Therefore, despite the workpiece and the molybdenum wire, The electrode wires are in a short-circuit state, but the discharge state of the machine tool is normal. Therefore, the machine tool will not realize short-circuit protection due to the short circuit between the workpiece and the molybdenum wire. At this time, the machine tool is still cutting and processing according to the normal procedure, and the workpiece cannot be processed because there is no electrical discharge at the processing site. With normal shape and size, only molybdenum wire is used to pull grooves on the softer aluminum workpiece, which causes distortion of the cutting trajectory and causes the workpiece to be scrapped.
Solution
- The first is to optimize the process parameters and set different wire cutting parameters according to different thicknesses. Through many experiments, it is found that processing aluminum alloy materials can appropriately reduce the pulse width. This is because the pulse width is reduced, which reduces the discharge energy of a single pulse, and the discharge mark is also small, and the size and number of alumina particles can also be reduced, Effectively reduce the wear of the feed block. Relatively increasing the pulse gap is conducive to chip removal, reducing wire sticking, improving cutting stability, and improving the surface roughness of the workpiece. If the pulse gap is too small, the discharge products are too late to be eliminated, and the discharge gap is too late to deionize, which will make the processing unstable and easily cause wire breakage or distortion of the cutting track. If the set feed rate is lower than the actual possible erosion speed of the workpiece, the machining state will be open and the cutting speed will be slow. And because of the low melting point and vaporization point of aluminum alloy, the machining erosion amount of the same discharge energy is increased, so that the discharge gap is large. Due to the large discharge gap, the pulse voltage cannot penetrate the liquid medium between the electrodes in time, which greatly reduces the pulse utilization rate. At the same time, too large a distance between the electrodes will increase the electrode wire amplitude, make the processing unstable, and even cause wire breakage. . When the set feed speed is greater than the actual possible erosion speed of the workpiece (called over-tracking or over-feeding), it is easy to short-circuit during processing, and the actual feed and cutting speed will decrease instead, and the electro-erosion material of the aluminum material is not used. , Causing broken wires and short-circuit suffocation. Therefore, reasonably adjust the frequency conversion feed to achieve a better processing state. The entire variable frequency feed control circuit has multiple adjustment links, most of which are installed inside the machine tool control cabinet, and should not be changed. There is also an adjustment knob installed on the console operation panel. This knob can be set in the appropriate position according to the specific situation during processing to ensure stable reading of the ammeter and voltmeter, the molybdenum wire shakes little, and the processing is in the best tracking state.
- Choose an appropriate discharge gap according to the thickness of the workpiece. The discharge gap should not be too small, otherwise, it will easily cause a short circuit, which is not conducive to cooling and the discharge of electrical corrosion products; if the discharge gap is too large, it will affect the surface roughness and processing speed. When cutting workpieces with a large thickness, molybdenum wire with a large diameter and a large pulse width current should be used as much as possible to increase the discharge gap, enhance the effect of chip removal, and improve the stability of cutting.
- Keep the cleanliness of the coolant and replace it with a new coolant in time, and use a filter at the return port of the workbench to filter the impurities of the coolant, and then put a layer of sponge at the outlet of the coolant to absorb the coolant. The effect is very good. In order to improve the chip removal ability and prevent the processing path from being deformed, detergent and soap bar can also be added to the coolant, so that the washing performance becomes better, the chip removal ability is increased, and the chip removal state is improved. At the same time, it is necessary to rotate and adjust the position of the power supply block in time or replace it with a new one. Frequently clean the chip particles at the power supply block, maintain a good contact state between the molybdenum wire and the power supply block, and avoid the discharge phenomenon there. , It can effectively avoid the distortion of the cutting track and cause the workpiece to be scrapped.
The conclusion
Starting from the actual operation of the wire cutting process, it is analyzed that aluminum oxide particles are easily generated when processing aluminum parts, resulting in decreased conductivity, wear of the feed block, wire breakage, and short circuit, etc., which seriously affect the processing quality and efficiency. Summarizes the problems and solutions that often occur in practice. These methods and measures are practical and have good effects on improving the quality of wire cutting, reducing wire breakage, short-circuiting, and cutting track distortion of processed aluminum parts. Based on years of experience accumulated in processing, 3Q MACHINING has summarized the key technical issues in processing practice.
