In order to guarantee the efficiency of the milling operation, there are many factors to consider, such as the use of the correct milling tool, the correct diameter and the right number of teeth, as well as the correct speed, feed rate, axial depth of cut and radial cut width. However, there are many more important but often overlooked factors that guarantee the effectiveness of tool applications. Consider the five milling factors that determine productivity and profitability: principal declination, pitch, milling cutter position, milling cutter throughput and arc cutting technique.
Principal declination Different principal declination angles have a significant impact on the milling effect, if a 90° milling cutter is used as a face milling cutter, it is often just because it is easy to use, but its productivity or cost efficiency is not as good as the 45° milling cutter. Using 90° milling cutter face milling instead of 45° milling cutter reduces production efficiency by 30%, which in turn directly affects profitability. Mainly, the dominant declination angle affects the metal removal rate and tool life. In addition, because the main declination angle decreases, the chip thickness becomes thinner, which is why there is an opportunity to increase the feed rate to compensate. More and more machine shops are now using small depths of cut and high feed rates to increase productivity, often using milling cutters with small declination angles (e.g. 10°) or round insert concepts that achieve chip thinning. Compared to 45° face milling cutters, 10° face milling cutters have increased feed because the chips are thinner to almost one-sixth of 90° milling cutters. If this strategy results in a insufficient depth of penetration, a high feed rate can be used to compensate for the loss of efficiency. Large feed milling cutters with a main declination of 10° enable very high table feeds due to the thin chips formed. In addition, the large axial cutting force ensures spindle stability and limits vibration, making these milling cutters more suitable for long tool overhangs and/or unstable clamping applications. For 45° milling cutters, these are usually the first choice for face milling, because they have a good balance of radial cutting force and axial cutting force, and the eating tool is very smooth. The low vibration of these milling cutters makes them suitable for short-chip materials such as gray cast iron, which are prone to chipping at the end of the pass because the workpiece allowance is getting smaller and smaller. What are the main factors that influence successful milling? If a 90° milling cutter is used as a face milling cutter, it is often just because it is easy to use, but its productivity or cost efficiency is not as good as that of a 45° milling cutter. Large feed milling cutters with a main declination angle of 10° can also be used with very high table feeds due to the thin chips formed. The main application of the 90° milling cutter is shoulder milling. In this application, the radial force is mainly generated in the feed direction and is best suited for milling parts that are prone to vibration. In addition, the surface is not subjected to large axial pressure, which is very beneficial for structural parts or thin-walled parts with low milling strength. It must be noted that the 90° milling cutter cannot form thin chips, and the programmed feed rate per tooth for large cutting widths is equal to the actual maximum chip thickness. So, what about round blades? Round inserts are best suited for efficient, heavy-duty roughing and general milling.Round inserts are particularly suitable for machining titanium alloys and HRSA materials, but the results are not optimal when striving for excellent surface accuracy. This is because the main declination angle changes in the range of 0~90°, resulting in the cutting force changing with the arc cutting edge, so that the pressure also changes. Round blades are unique in that the chip thickness they form varies with depth of cut – the smaller the depth of cut, the thinner the chip. Therefore, if the depth of cut is small, the feed rate must be increased to ensure the appropriate chip thickness and improve production efficiency. Pitch By increasing the number of cutting edges, the table feed can be increased while maintaining the same cutting speed and feed per tooth (no large heat is emitted at the cutting edge). However, the denser the pitch, the smaller the chip evacuation space. In addition, increasing the number of inserts in the milling cutter has the disadvantage that if the rigidity of the clamping is not enough, it has a negative effect on vibration. The use of unequal pitch milling cutters optimizes the application, and it is also important to choose the correct pitch as it affects productivity, stability and power consumption. In general, there are three pitches of thin, dense and ultra-dense teeth. The number of inserts of the thinning milling cutter is small. Due to the small cutting force they transmit, they are the first choice for unstable processes. Full groove milling operations and long chip ISO N materials are the most suitable choice for thinning milling cutters. The number of inserts of the close-tooth milling cutter is medium, and it can be isometric or unequidistant design. They are the first choice for general roughing in stable conditions. The benefits also include efficient processing of all materials without worrying about chip space. In general, unequal milling cutters (thinning or close teeth) are best suited to break resonances and therefore have good stability. The number of inserts of the ultra-dense tooth milling cutter is large, and the inserts are evenly distributed. Ultra-tight tooth milling cutters are best suited for applications with small radial cutting widths, high feed rates (roughing and finishing) with short chip formation in ISO K material, roughing of ISO S material Due to the round insert, the chip load is evenly distributed. Milling cutter position The way the milling cutter cuts into the workpiece is important. At this point, the first thing to consider is how the chips are formed, as this seriously affects the tool life. The golden rule is that the chip changes from thick to thin (the thickness of the chip is the thinnest when the milling cutter cuts out the workpiece). This saves time and money and guarantees the stability of the process. In contrast, thick chips when the milling cutter cuts out the workpiece can cause the cutting edge to fail and the tool life to be shortened. Importantly, it is the milling cutter position that determines the chip formation. For example, in full-groove milling, after the milling cutter has completely cut into the workpiece, the resulting chip thickness is from thin to thin. Although the chips when the milling cutter cuts out the workpiece are thin, there are many problems with this method, because the heat cannot be expelled and can only enter the tool or the workpiece – not the chip, because there are no chips at all. When the milling cutter edge cuts into the workpiece, the cutting edge only rubs the material, not the shear material, which generates heat and vibration. However, by optimizing the milling cutter position, for example, the cutting width reaches 70% of the milling cutter diameter, this situation can be greatly improved, the effect is that the maximum chip thickness of 90% can be obtained when cutting, the stress on the blade is small, friction is reduced, climb milling, can also be reverse milled, the formation of thick to thin chips, good heat dissipation effect, less insert stress. What are the main factors that influence successful milling? This situation can be greatly improved by optimizing the milling cutter position, where the throughput reaches 70% of the milling cutter diameter. Note that the direction of the milling cutter into the workpiece must be correct. If it is not correct, even if the cutting width of the milling cutter reaches 70% of the diameter, it can form chips from thin to thick, and the tool life will be shortened and the cost will increase when cutting into the workpiece. Milling cutter eating volume and arc cutting technique When milling parts, it is recommended to keep the milling cutter in a knife-eating state at all times. Frequent cut-in and cut-out milling cutters shorten tool life. To solve this problem, the most important thing is the correct tool path and contact length. Continuous knife eating also needs to be reminded, that is, the sudden change in the direction of the knife when eating the knife continuously will make the blade bear stress and form thick chips when cutting out, so it is recommended to also use the arc cutting path at the corner of the workpiece. Straight feed results in poor surface finish and high noise. In order to alleviate this contradiction, in most cases the feed volume is reduced, but at the same time the production efficiency is reduced. A simple solution to this situation is to change the programming to clockwise arc cuts. With this smooth and continuous cut-in, tool life is extended and wear patterns are optimized. The milling cutter cuts out the chips with thin chips and low vibration. What are the main factors that influence successful milling? Continuously eat the knife and cut in a clockwise arc to ensure that the chips are thinner when retracting, reduce vibration and prolong the service life of the tool. When cutting into the workpiece, it is recommended to use the circular arc cutting technique, and when the milling cutter eats continuously, if you need to suddenly change the milling cutter feed direction, it is best to use the circular transition. These tips not only extend tool life by avoiding heavy stress on the insert, but also improve the surface finish of the part by thinning from thick to thin chips. Use arc cutting techniques, correct milling cutter positions and continuous tool eating to ensure a safe and efficient machining process. Dongguan ganzoo Prototype Manufacturing Co., Ltd. is a solution provider focusing on prototypes, high-precision parts, molds, on-demand manufacturing and other one-stop services. Is an expert in CNC machine equipment,Cnc Machining Parts,Custom Cnc Machining Aluminum Accessories,Parts Cnc Machining Service, if you are interested in our services or need any technical support, welcome to contact us Ms.Becky+8613006687216, we are happy to share our understanding of Plastic Injection Molding with you and provide solutions for your economical injection molding.
