Today, the number of workpieces is increasing, and the size of the workpiece is continuously shrinking. The trend toward miniaturization requires that the manufacturing process must undergo corresponding changes. This growing demand requires people to rethink how to use smaller diameter tools for more efficient machining. The smaller the diameter of the tool is, the higher the required spindle speed (rpm) is, but the spindle speed of most conventional machine tools is difficult to reach such a high speed. Even if it can be achieved, the spindle of the machine tool will continue to operate under the limit state and will withstand it. Big stress. Conventional CNC machining tools that use tools with a diameter of less than 0.5†(12.7 mm) at 10,000 rpm or less often result in unreasonable feed and costly tool damage.
Traditional machining methods usually use larger tools to process at lower speeds. In general, larger tools themselves are not designed to perform more complex machining. In order to use micro-tools for processing, conventional machine tools must operate at low speeds, and micro-tools are brittle and easily break. Because of the large mass of the larger tool, there is a certain rebound effect on the force of the chip; on the contrary, the smaller tool is easier to break due to the greater brittleness.
Poor chip removal is one of the main causes of tool damage. In fact, micro-tools damaged due to poor chip removal are more than micro-tools damaged by unreasonable cutting parameters. In order to minimize the possibility of tool damage, the chips must be quickly discharged from the cutting zone. Miniature tools require high spindle speeds during machining, and the spindle speed required for fast chip removal is even higher.
Definition of tool size and processing speed: “Micro tool†includes cutters and drills with a diameter of 0.250†(6.35 mm) or less. This small-diameter tool is indispensable for complex, fine machining and uses a high-speed spindle for optimal machining. There is no exact definition and absolute parameter for "high-speed cutting", but one available reference definition is that high-speed cutting can be called when the spindle speed is above 25000 r/min.
"Three elements" solution Three related factors that increase the efficiency of micro-tool processing include the optimization of micro-tool design, the use of low-viscosity coolant, and high-speed cutting technology.
(1) Design of a micro-tool A micro-tool obtained by simply scaling the geometric parameters of a large-diameter tool is often difficult to achieve efficient feeding and satisfactory machining accuracy. As the tool diameter decreases and the spindle speed increases, the tool requirements change. The conventional tool design using the machine blade is not suitable for the machining requirements of the micro tool. This is mainly because increasing the speed of the tool is not only limited to the reduction of the tool diameter. Increased rotational speeds require better tool balance and greater chip space to ensure smooth chip evacuation and prevent build-up. The use of micro-tools for efficient high-speed machining requires special optimization of the tool design. With the correct geometrical parameters of the microtool plus a high-speed spindle machine and reasonable cooling methods, it is possible to completely eliminate secondary machining for burr removal.
(2) Optimization of cooling method When a high-speed machining is performed with a micro-tool, a large amount of cutting heat is generated. Therefore, some measures need to be taken to cool the cooling. Although high-speed cutting has certain advantages in reducing the heat of cutting, high-speed cutting alone is not always sufficient to completely solve the cooling problem, so an effective cooling system is still required for some processes.
The cooling system eliminates cutting heat and also provides lubrication, allowing the tool to cut quickly on the workpiece surface. Trying to cut a piece of cold butter with a cool knife is difficult because the knife does not lubricate when it cuts across the surface of the butter. However, if the knife is heated, it can melt a little butter to provide lubrication for the knife, making it easy to cut the butter. The same principle is used for high-speed cutting with a tool. Miniature tools require a lubricant with a lower viscosity than water because of the need to allow the coolant to reach the cutting edge of a high-speed rotating tool. Dairy-based coolants have a higher viscosity than water-based coolants and are therefore not suitable as lubricants for high-speed machining of microtools.
The micro spray cooling system used in processing can use alcohol (ethanol) as a cooling liquid, which is ideal for cooling lubrication of non-ferrous metals and certain plastic materials. However, oil-based coolants are used when processing steel materials. The advantages of alcohol coolants do not apply to the processing of iron and steel materials because carbide cutting tools may cause momentary discharges on the steel surface if they are exposed to ethanol-based cooling. In the liquid, a relatively high dynamic potential may be generated.
Commonly used spray coolants are usually petroleum-based products. These coolants need to be properly recycled after use, resulting in additional costs. Since alcohol evaporates after use, it does not need to be processed or recycled. Although alcohol is flammable, its low volatile point makes it a very effective cooling lubricant for high-speed machining. Since alcohol is a natural compound, it is harmless to the environment, has no waste, and does not require cleaning, so it will not incur related costs. In addition, the use of alcohol as a cooling lubricant does not leave any grease on the workpiece, which can avoid the secondary operation of re-oil removal of the workpiece, and the cost of these processes are quite high.
(3) High-speed cutting technology The smaller the tool diameter, the higher the spindle speed required to effectively cut the workpiece. When using micro tools for milling, drilling, threading, and engraving and milling, high-frequency spindles with a rotational speed range of 6000 to 60000 r/min are ideal. High-speed cutting technology uses a high speed, small step, large feed processing strategy. Imagine moving your hand through a burning candle flame. If your hand moves slowly, the flame will have enough time to burn your hand; if your hand passes quickly, the flame will not burn your skin. The principle of high-speed cutting with a micro-tool is similar to this. When the tool is moved quickly, the heat of cutting is too late for the incoming workpiece and causes various problems.
During the cutting process, the tool continuously cuts the chips away from the workpiece. About 40% of the cutting heat generated is due to the frictional heat generated by each tool face and the chip, and about 20% is due to the deformation (bending) of the chip. Therefore, a total of about 60% of the cutting heat is derived from the inside of the chip. High-speed cutting technology attempts to use chips to remove most of the heat for cleaner cutting. The higher machining quality is based on good tool cooling, lower cutting forces and thus reduced machining vibrations.
The use of high spindle speeds reduces the chip load (depth cut) to 0.005†(0.13mm) or less, and such a small depth of cut can significantly reduce the cutting forces between the tool and the workpiece material. With less heat, it can reduce the tool deviation and can realize the machining of thin-walled workpieces.Because of these advantages, high-speed cutting can achieve better machining surface quality, lower cutting temperature, easy workpiece clamping, and machining accuracy. Higher.
Correct choice of processing machine Based on the dynamic characteristics of a machining tool that uses a micro-tool for high-speed cutting, the above-mentioned principle of high-speed cutting technology is completely achievable. Such machines are generally lighter in weight and therefore have a larger range of motion, better sensitivity, flexibility, versatility, and higher speeds. Conventional CNC machine tools are heavy, so their speed and maneuverability are difficult to achieve with light machine tools, but they can be machined with larger tools. Conventional CNC machine tools are a bit like SUVs (pickup trucks). Although they are powerful, they lack mobility or cannot be parked in tight spaces. The design and structure of the sports car make it not only fully horsepower, but also has a high level of controllability and agility. The CNC machine used for high-speed cutting of micro-tools is very similar to the characteristics of sports cars. Just as you can't install a spoiler and paint stripe on an SUV, and then expect it to fly like a sports car, you can't reload a high-speed spindle on a heavy, regular CNC machine and expect it to High-speed cutting using micro-tools can be efficiently completed.
When designing a machine tool, you can choose between two ideas. You can make a large, powerful machine that can use large spindles to drive large tools for machining. Driving large tools requires powerful power, which means that large motors of heavier mass must be used. On the other hand, you can also create a lightweight machine specifically for miniature tools. Machines designed for high-speed cutting with microtools require less cutting forces, so the design focus should be on speed and sensitivity without the need for large motor drives.
In order to make a plane fly, which wing is more important, the left or right? The answer is of course: to make the plane fly, the two wings are equally important and equally indispensable. Similarly, in order to realize high-speed machining of micro-tools, each of the three elements (micro-tool, cooling method, and high-speed cutting) is equally important. Without any of these links, it is impossible to achieve high efficiency and high reliability. Sex and highly flexible processing. On the contrary, if the three elements are perfectly combined together, a surprisingly high processing speed and a high level of processing quality can be achieved. Its processing advantages are not limited to this, it can also completely eliminate the subsequent secondary operations such as deburring and degreasing.
Processing example Here are two examples of high-speed machining using microtools on the Datron machine: 1 High-speed milling of 1/61" thick 6061 aluminum plates with a 1/4" (6.35mm) single-slot milling cutter at 45,000 rpm /min, using alcohol cooling, the machine feed rate is 250ipm; 2 Milling 1/8′′ thick 6061 aluminum plate with a 1/8′′ (3.175mm) small helical angle double groove high speed milling cutter (HSC+), the processing speed is 50000r/min, using alcohol cooling, machine feed rate is 200ipm.
For high-speed machining, there is some experience worth noting: 1 It should be avoided to add bushes on the spindle, because it will increase wear and damage, greatly shorten the life of the spindle; 2 using a smaller step and higher feed rate Machine tool; 3 fast moving tool, use chip to take away heat.
in conclusion To sum up, to complete the task perfectly, you must use the right tools. A golfer will not use the long stick to hit the ball on the grass, nor will he use a putter to kick the ball off the ball. Similarly, when replacing a high-speed spindle on a conventional CNC machine, it is difficult to expect it to meet the high standards required for high-speed cutting. Only the machines designed and manufactured specifically for the high-speed cutting of microtools can meet the stringent requirements of this process.
The advantages of high-speed cutting with micro-tools include: small cutting force, easy tool damage, low processing temperature, and good surface finish, eliminating subsequent deburring, oil removal, and tool vibration. The spindle speed of up to 60,000r/min enables the processing speed to be much faster than before, and at the same time, the workpiece processing quality is also improved.
Our Medical Chair Products is good in quality and competitive in price. We are manufacturer and supplier Medical Chair Products following your specific requirement. We are looking forward to your E-mail and establishing cooperative relationship with you! We would provide professional Laboratory Tester with good services for you!
Medical Chair
Medical Chair, Medical Chairs, Seating Equipment, Medical Lift Chairs
Ningbo Cland Medical Instruments Co., Ltd. , https://www.cland-med.com