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Modify tool offset value to ensure dimensional accuracy
According to stainless steel parts machining manufacturers, when the workpiece error exceeds the workpiece tolerance due to the first tool setting error or other reasons, and the processing requirements cannot be met, the workpiece can be modified to achieve the required size by modifying the tool compensation. The method to ensure the radial size is as follows:
Absolute coordinate input method
According to the principle of "large reduction, small increase", modify the tool compensation at 001～004. If the workpiece size is larger by 0.1mm when cutting the groove with the No. 2 cutting tool, and the tool compensation display at 002 is X3.8, you can enter X3.7 to reduce the No. 2 tool compensation.
Relative coordinate method
As in the above example, input U-0.1 at 002 cutter compensation, and the same effect can also be obtained.
The same is true for the cnc operating of the axial size. For example, if you use the No. 1 external tool to machine a certain shaft segment, and the size is longer than 0.1mm, you can enter W0.1 at the 001 tool offset.
Semi-finish machining eliminates the influence of screw gap to ensure dimensional accuracy
According to the analysis of stainless steel parts processing manufacturers, for most CNC machining, after a long period of use, due to the influence of the screw gap, the size of the processed workpiece often appears unstable. At this time, we can perform a semi-finishing process after roughing to eliminate the influence of screw clearance. For example, after rough machining the outer circle with No. 1 tool G71, you can input U0.3 at 001 tool compensation and call G70 fine turning once. After stopping the measurement, input U-0.3 at 001 tool compensation and call G70 fine turning again. . After this semi-finished turning, the influence of the screw gap is eliminated, and the stability of the dimensional accuracy is ensured.
After the CNC machine tool is produced by the manufacturer, the machine tool has been subjected to various requirements and inspections, and only after passing the inspection, can it leave the factory. Regarding medium and large CNC machine tools, because the machine tools are large in size and not convenient for transportation, they must be distinguished and transported to the user after they collapse before they can be used before they can be reassembled and debugged. As for small machine tools, the float level gauge does not need to crash the machine tool during transportation, so the installation, debugging and acceptance tasks of the machine tool are relatively simple.
After the machine is transported to the user, it can be put into operation formally after simple connection, adjustment of the machine level and trial cutting, and the things required are relatively simple. The following introduces the equipment, debugging and acceptance requirements of small CNC machine tools.
First, the initial installation content of imported CNC lathe processing machine tools includes: according to the requirements of the machine tool, select the appropriate position to place the machine tool; read the material of the machine tool to ensure the accurate use of the CNC machine tool.
2. Wire connection processed by imported CNC lathes: This part of the content is mainly the main power connection of the machine tool. Although the step of the magnetic cnc milling column level gauge is very simple, if this step is not done well, it will cause unnecessary troubles, or even Severe results will occur. Here are some considerations for power connection:
1. Confirm the input power voltage and frequency. The current voltage power supply in our country is: three-order AC 380V; single-phase 220V. Domestic machine tools generally use three-phase 380V, frequency 50Hz power supply, and some imported machine tools do not use three-order AC 380V, frequency 50Hz power supply, and these cnc bending machine tools are equipped with power transformers, and users can choose according to the requirements. The next step is to reflect on the up and down fluctuations of the power supply, whether the glass tube level gauge can meet the requirements of the machine tool, whether there is a large fluctuation in the vicinity of the machine tool that can affect the power supply, if the voltage fluctuation is too large or there is a large-scale equipment, a stabilizer should be installed , Because the power supply does not fluctuate and the electrical disturbance occurs, the machine tool will affect the invariance of the machine tool.
2. The phase sequence of the power supply processed by the imported CNC training is confirmed. When the phase sequence is wrong, there is a fuse that can blow the control unit. The method of reflecting the phase sequence is relatively simple. Use the phase sequence to connect to the following figure to measure, when the phase sequence table is in sequence When the hour hand is twisted, the phase sequence is accurate. Otherwise, the phase sequence is wrong. At this time, you only need to swap any two power cords in the UVW three-phase.
Aluminum is the most widely used and widely used metal material among non-ferrous metals, and its application range is still expanding. There are many kinds of aluminum products produced using aluminum, and there are more than 700,000 types according to statistics. Various industries such as construction and decoration, transportation, and aerospace have different needs. Today I will introduce to you the processing technology of stand casting and how to avoid processing deformation.
The advantages and characteristics of aluminum are as follows:
1. Low density. The density of aluminum is about 2.7g/cm3. Its density is only 1/3 of that of iron or copper.
2. High plasticity. Aluminum has good ductility and can be made into various products through pressure processing methods such as extrusion and stretching.
3. Corrosion resistance. Aluminum is a highly negatively charged metal. A protective oxide film will be formed on the surface under natural conditions or anodic oxidation, which has much better corrosion resistance than steel.
4. Easy to strengthen. The strength of pure aluminum is not high, but its strength can be improved after anodizing.
5. Easy surface treatment. Surface treatment can further improve or change the surface properties of aluminum. The aluminum anodizing process is quite mature and stable in operation, and has been widely used in the processing of aluminum reflector.
6. Good electrical conductivity and easy to recycle.
Aluminum product processing technology
Punching of aluminum products
1. Cold punch
Use material aluminum pellets. The extrusion machine and the mold are used for forming at one time, which is suitable for columnar products or product shapes that are difficult to achieve by the stretching process, such as oval, square, and rectangular products.
The tonnage of the machine used is related to the cross-sectional area of the product. The gap between the upper die punch and the lower die tungsten steel is the wall thickness of the product, and the vertical gap between the upper die punch and the lower die tungsten steel is the bottom dead center when the press is completed. It is the top thickness of the product.
Advantages: The mold manufacturing cycle is short, and the development cost is relatively low compared to the stretch mold.
Disadvantages: the production process is long, the product size fluctuates greatly in the process, and the labor cost is high.
2. Stretch
Use material aluminum skin. The continuous mold machine and mold are used for multiple deformations to meet the requirements of the shape, suitable for non-columnar bodies (products with curved aluminum materials). (Picture 5 machine, picture 6 mold, picture 7 product)
Advantages: The more complex and multiple-deformed products have stable dimensional control during the production process, and the product surface is smoother.
Disadvantages: high mold cost, relatively long development cycle, and high requirements for machine selection and accuracy.
Surface treatment of aluminum products
1. Sandblasting (shot blasting)
The process of using the impact of high-speed sand flow to clean and roughen the metal surface.
The surface treatment of aluminum parts in this method can make the surface of the workpiece obtain a certain degree of cleanliness and different roughness, and improve the mechanical properties of the workpiece surface, thus improving the fatigue resistance of the workpiece and increasing the gap between it and the coating. The adhesion force extends the durability of the coating film, and is also conducive to the leveling and decoration of the coating. We often see this process in various products of Apple.
2. Polishing
The use of mechanical, chemical or electrochemical effects to reduce the surface roughness of the workpiece to obtain a bright, smooth surface processing method. The polishing process is mainly divided into: mechanical polishing, chemical polishing, and electrolytic polishing. The aluminum parts can be close to the stainless steel mirror effect after mechanical polishing + electrolytic polishing. This process gives people a sense of high-end simplicity and a stylish future.
3. Drawing
Metal wire drawing is the CNC machining services process of repeatedly scraping aluminum plates out of lines with sandpaper. Wire drawing can be divided into straight wire drawing, chaotic wire drawing, swirling wire drawing, and thread drawing. The metal wire drawing process can clearly show every tiny wire mark, so that the metal matte shines with fine hair luster, and the product has a sense of fashion and technology.
4. Highlight cutting
The diamond knives are reinforced on the high-speed rotating (generally 20,000 rpm) spindle of the precision carving machine to cut the parts, and a local highlight area is generated on the surface of the product. The brightness of the cutting highlights is affected by the speed of the milling drill bit. The faster the drill speed, the brighter the cutting highlights, and vice versa, the darker and easier to produce knife marks. High-gloss and high-gloss cutting are particularly used in mobile phones, such as iphone5. In recent years, some high-end TV metal frames have adopted high-gloss milling technology, coupled with anodizing and drawing processes, making the TV as a whole full of fashion and technological sharpness.
5. Anodizing
Anodization refers to the electrochemical oxidation of sheet metals or alloys. Aluminum and its alloys form an oxide film on the aluminum product (anode) under the action of an external current under the corresponding electrolyte and specific process conditions. Anodizing can not only solve the defects of aluminum surface hardness, wear resistance, etc., but also extend the service life of aluminum and enhance its aesthetics. It has become an indispensable part of aluminum surface treatment and is currently the most widely used and very successful. Craft.
6. Two-color anode
Two-color anode refers to anodizing on a product and giving different colors to a specific area. The two-color anodizing process is rarely used in the TV industry because of the complex process and high cost; but the contrast between the two colors can better reflect the high-end and unique appearance of the product.
Process measures and operating skills to reduce aluminum processing deformation
There are many reasons for the deformation of aluminum parts, which are related to the material, the shape of the parts, and the production conditions. There are mainly the following aspects: deformation caused by internal stress of the blank, deformation caused by cutting force and cutting heat, and deformation caused by clamping force.
Process measures to reduce processing distortion
1. Reduce the internal stress of the gross culture
Natural or artificial aging and vibration treatment can partially eliminate the internal stress of the blank. Pre-processing is also an effective process method. For the blank with fat head and big ears, due to the large margin, the deformation after processing is also large. If the excess part of the blank is pre-processed and the margin of each part is reduced, not only can the processing deformation of the subsequent process be reduced, but also a part of the internal stress can be released after pre-processed for a period of time.
2. Improve the cutting ability of the tool
The material and geometric parameters of the tool have an important influence on the cutting force and cutting heat. The correct selection of the tool is very important to reduce the deformation of the parts.
(1) Reasonably choose the tool geometry parameters.
①The rake angle: Under the condition of maintaining the strength of the cutting edge, the rake angle should be appropriately selected to be larger. On the one hand, it can grind a sharp cutting edge, and on the other hand, it can reduce cutting deformation and smooth chip removal, thereby reducing cutting force and cutting temperature. Never use negative rake angle tools.
②Clear angle: The size of the relief angle has a direct effect on the wear of the flank surface and the quality of the machined surface. Cutting thickness is an important condition for selecting the relief angle. During rough milling, due to the large feed rate, heavy cutting load, and large heat generation, good heat dissipation conditions of the tool are required. Therefore, the clearance angle should be selected smaller. When finishing milling, the cutting edge is required to be sharp, to reduce the friction between the flank face and the machined surface, and to reduce the elastic deformation. Therefore, the relief angle should be selected larger.
③Helix angle: In order to make the milling smooth and reduce the milling force, the helix angle should be selected as large as possible.
④ Entering angle: Appropriately reducing the entering angle can improve the heat dissipation conditions and reduce the average temperature of the processing area.
(2) Improve the tool structure.
①Reduce the number of teeth of the milling cutter and increase the chip space. Due to the large plasticity of the aluminum material, the larger cutting deformation during processing, and a larger chip holding space, the bottom radius of the chip pocket should be larger and the number of teeth of the milling cutter should be smaller.
②Finely sharpen the teeth of the knife. The roughness value of the laser cutting edge of the cutter tooth should be less than Ra=0.4um. Before using a new knife, you should lightly grind the front and back of the teeth with a fine oil stone to eliminate the residual burrs and slight serrations when sharpening the teeth. In this way, not only the cutting heat can be reduced, but also the cutting deformation is relatively small.
③Strictly control the wear standard of the tool. After the tool is worn, the surface roughness value of the workpiece increases, the cutting temperature rises, and the deformation of the workpiece increases. Therefore, in addition to the selection of tool materials with good wear resistance, the tool wear standard should not be greater than 0.2mm, otherwise it is easy to produce built-up edge. When casting, the temperature of the workpiece should generally not exceed 100°C to prevent deformation.
3. Improve the clamping method of the workpiece
For thin-walled aluminum workpieces with poor rigidity, the following clamping methods can be used to reduce deformation:
①For thin-walled bushing parts, if a three-jaw self-centering chuck or spring chuck is used to clamp from the radial direction, once it is loosened after processing, the workpiece will inevitably be deformed. At this time, the method of pressing the axial end face with better rigidity should be used. Use the inner hole of the part to locate, make a self-made threaded mandrel, sleeve it into the inner hole of the part, and use a cover plate to press the end face on it, and then tighten it with a nut. When CNC machining the outer circle, clamping deformation can be avoided, so that satisfactory machining accuracy can be obtained.
②When processing thin-walled and thin-plate workpieces, it is best to use vacuum suction cups to obtain evenly distributed clamping force, and then process with a small amount of cutting, which can well prevent the deformation of the workpiece.
In addition, a packing method can also be used. In order to increase the process rigidity of thin-walled workpieces, medium can be filled inside the workpiece to reduce the deformation of the workpiece during clamping and cutting. For example, pour a urea melt containing 3% to 6% potassium nitrate into the workpiece, and after processing, immerse the workpiece in water or alcohol to dissolve the filler and pour it out.
4. Reasonable arrangement of procedures
During high-speed cutting, due to the large machining allowance and intermittent cutting, the milling process often produces vibration, which affects the machining accuracy and surface roughness. Therefore, the CNC high-speed machining process can generally be divided into: rough machining-semi-finish machining-clear corner machining-finishing and other processes. For parts with high precision requirements, it is sometimes necessary to perform secondary semi-finishing and then finishing. After rough machining, the parts can be cooled naturally to eliminate internal stress caused by rough machining and reduce deformation. The margin left after rough machining should be greater than the amount of deformation, generally 1 to 2 mm. During finishing, the finishing surface of the part should maintain a uniform machining allowance, generally 0.2-0.5mm is appropriate, so that the tool is in a stable state during the machining process, which can greatly reduce cutting deformation, obtain good surface machining quality, and ensure The accuracy of the product.
Operation skills to reduce processing distortion
In addition to the above-mentioned reasons, aluminum parts deform during processing. In actual operation, the operation method is also very important.
1. For parts with a large machining allowance, in order to have better heat dissipation conditions during the CNC machining process and avoid heat concentration, symmetrical machining should be used during machining. If there is a 90mm thick sheet that needs to be processed to 60mm, if one side is milled and the other side is milled immediately, and the final size is processed once, the flatness will reach 5mm; if repeated feed symmetrical processing is used, each side is processed twice The final size can guarantee a flatness of 0.3mm.
2. If there are multiple cavities on the plate part, it is not advisable to use the sequential processing method of one cavity one cavity during processing, which will easily cause uneven stress and deformation of the parts. Multi-layer processing is adopted, and each layer is processed to all cavities at the same time as much as possible, and then the next layer is processed to make the parts evenly stressed and reduce deformation.
3. Reduce cutting force and cutting heat by changing the cutting amount. Among the three elements of cutting amount, the amount of back-cutting has a great influence on cutting force. If the machining allowance is too large, the cutting force of a pass is too large, which will not only deform the parts, but also affect the rigidity of the machine tool spindle and reduce the durability of the tool. If you reduce the amount of knives back, the production efficiency will be greatly reduced. However, high-speed milling is used in CNC machining, which can overcome this problem. While reducing the amount of back-grabbing, as long as the feed is increased correspondingly and the speed of the machine tool is increased, the cutting force can be reduced while ensuring the processing efficiency.
4. The order of the knife should also be paid attention to. Rough machining emphasizes the improvement of machining efficiency and the pursuit of removal rate per unit time. Generally, up-cut milling can be used. That is, the excess material on the surface of the blank is removed at the fastest speed and the shortest time to basically form the geometric contour required for finishing. The emphasis of finishing is high precision and high quality, and down milling should be used. Because the cutting thickness of the cutter teeth gradually decreases from the maximum to zero during down milling, the degree of work hardening is greatly reduced, and at the same time the degree of deformation of the parts is reduced.
5. The deformation of thin-walled workpieces due to clamping during processing is difficult to avoid even for finishing. In order to reduce the deformation of the workpiece to the minimum, you can loosen the pressing piece before the finishing process reaches the final size, so that the workpiece can be restored to its original shape freely, and then slightly tighten it, whichever is the only way to clamp the workpiece (completely According to the feel), the ideal processing effect can be obtained in this way. In short, the point of action of the clamping force is best on the supporting surface, and the clamping force should act in the direction of good rigidity of the workpiece. Under the premise of ensuring that the workpiece does not loosen, the smaller the clamping force, the better.
6. When machining parts with cavities, try not to let the milling cutter plunge directly into the part like a drill bit, resulting in insufficient chip holding space of the milling cutter, unsmooth chip removal, and overheating, expansion and collapse of the part. Unfavorable phenomena such as knives and broken knives. First, drill the hole with a drill of the same size as the milling cutter or one size larger, and then mill it with the milling cutter. Alternatively, the CAM software can be used to produce the spiral cutting program.
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In the process of using the die-casting mold, we need to understand the reason why the temperature of the die-casting mold becomes higher, so what is the specific reason? Let's take a look together below.
Many accessories used by people in daily life are manufactured by die-casting molds, so this mold technology is in great demand in the market. In the shopping malls, due to the increase in demand, the development of Kaiping die-casting manufacturers has gradually expanded along with the economy. However, what is the result of the high surface temperature of the die-casting mold? Here is a brief introduction to the problem, hoping to bring help to those in need.
Casting standards will be affected: the surface temperature of the die-casting mold is closely related to the standard accuracy of the casting. If the surface temperature does not meet the requirements or the temperature spread is unreasonable, the casting will have poor standard accuracy due to uneven heating. The phenomenon appears. So from this perspective, the temperature issue must be paid attention to.
The appearance of the casting will be affected: the surface temperature of the die casting mold will definitely affect the appearance of the casting. If the temperature is unreasonable, it will simply cause severe deformation of the casting, such as unevenness and shrinkage. It is necessary to know that the impact of appearance will have a great impact on product sales, so the appearance quality of castings must be paid attention to.
Standard accuracy and appearance quality will be greatly affected, which is caused by the surface temperature of the die-casting mold, so people must control the surface temperature of the mold at any time during processing.
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Method to solve casting porosity
First analyze the reasons for the formation of stomata, and then take corresponding measures.
(1) Choose dry and clean alloy materials.
(2) Do not overheat or degas the melt under control.
(3) Reasonably choose the die casting process parameters, especially the injection speed. The starting point for speed-regulating high-speed machining.
(4) Sequential filling helps to discharge the cavity gas. Pouring I: 1, and the runner has sufficient length. It should be 50 ram, which is conducive to the smooth flow of alloy liquid and gas discharge.
The thickness and direction of I:1 can be changed, and overflow grooves and exhaust grooves are set at the holes. The sum of the cross-sectional area of the overflow product is not less than 60% of the sum of the cross-sectional area of the gate part, otherwise the slag discharge effect will be poor.
(5) Choose good performance paint and spray volume control.
Choose the right die casting machine
Die-casting machine is the key equipment for die-casting production, and its performance objectively determines the quality of die-casting parts. The correct choice of die-casting machine is essential to ensure product quality, improve production efficiency and reduce production costs. The performance of the die casting machine depends on two aspects.
Sufficient clamping force: to prevent the flow pressure of the molten metal from reaching high peaks, and to prevent flashing and flying materials.
Sufficient injection capacity: to ensure that the stand casting process will not cause overheating or a large amount of overflow of the mold, and at the same time ensure that the machine has enough capacity to transport enough molten metal and fill the cavity as required to accelerate the speed in a short time.
Design of Die Casting Mould Runner
Because the zinc alloy must fill the cavity in a short time, the design and manufacturing of the die-casting mold and its runner system are much higher than that of the plastic mold.
The runner system guides the metal solution to fill the cavity in some way. It plays an important role in the flow direction of the metal liquid, pressure transmission, filling time, exhaust conditions and mold temperature distribution.
It is also an important factor that determines the quality of die castings.
The design principle of the die-casting mold runner system should be summarized from the gooseneck to the gate to avoid sharp corners, and the runner surface should be smooth to reduce resistance and maintain the flow rate of the liquid zinc alloy.
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