High-speed machining with small tools

As the variety of parts continues to increase and the size becomes smaller and smaller, the miniaturization of parts requires manufacturing to change processing strategies. In order to achieve more efficient processing, it is necessary to rethink the previous processing. The traditional machining method is to use large diameter tools at low cutting speeds. However, large-diameter tools cannot machine parts with complex shapes. In this way, machining with small tools becomes a natural choice. However, the use of small tools requires a high spindle speed, which is not possible with ordinary machine tools. Even if some machines can achieve very high spindle speeds, such as small tools with diameters less than 0.5' on ordinary machines, machining complex parts at 10,000 r/min will often increase the spindle temperature. Therefore, it is only possible to select a low feed rate machining, and it will also make the tool easy to wear, and in severe cases, the tool will be damaged.
Of course, in the cutting process, the chip can not be eliminated in time, which is also the main cause of tool breakage, which is much more than the wrong choice of cutting amount. In order to prevent damage to the tool, it is necessary to ensure that the chips are removed from the cutting zone in a timely and smooth manner. For machining with small tools, it is necessary to increase the cutting speed while taking care to remove the chips from the cutting zone as quickly as possible.
The definition of high-speed machining of small plow tools refers to the selection of tools with diameters less than 0.250, and fine machining of complex shapes on high-spindle speed machines. Although there is no fixed definition and absolutely correct cutting amount for high-speed machining, the spindle speed of the machine tool is generally required to be around 25000r/min. Small tool high-speed machining strategy uses small tools to perform high-speed machining at a spindle speed of up to 25000r/min. The following three main technical aspects must be mastered: (1) the intelligent design, manufacture and use of small tools; (2) low Selection and rational use of viscosity coolant, (3) Give full play to the role of high-speed processing technology. Smart design, manufacture and use of small tools Shrinking large-diameter tool geometries onto small tools can result in unacceptable feed rates and unsatisfactory surface roughness. Therefore, it is necessary to design and manufacture a small tool that can fully play its role in high-speed cutting. The optimized design of the tool geometry combined with the high-speed spindle and the optimal cooling can not only improve production efficiency, but also save Go to the subsequent process DOT such as burr. When using small tools for high cutting speed machining, it is also necessary to balance the small tools used. At the same time, pay attention to increase the chip space of the tool to facilitate the smooth elimination of the chips, to prevent the chips from being clogged or burnt in the tool. Selection and rational use of low-viscosity coolants High-speed machining with small tools generates a lot of heat, so measures must be taken to cool the parts quickly during processing. Of course, in high-speed cutting, the chips can be quickly removed from the cutting zone, but this is not enough. It is also necessary to select a suitable cooling lubricant to design an effective cooling system. In addition to reducing the cutting temperature, the coolant also has good lubrication, so the tool can quickly pass through the surface of the part. It is difficult to cut the butter quickly with a cutter, and if you choose to heat the cutter and then cut it, you can cut the butter quickly. This is because the cutter is heated, it will melt the butter at the incision quickly, and the melted butter also has a good lubricating effect on the cutter, making the cutter easy to move, so that the butter can be effectively cut. The same principle applies to high-speed cutting, where small tools require low-viscosity cooling of the lubricating fluid for cooling lubrication. This is because the low-viscosity cooling lubricant has a strong penetrating ability and it is easy to fill the coolant to the cutting edge of the cutter head. The commonly used emulsion as the coolant is much more viscous than the aqueous solution, so it is not suitable for high-speed cutting of small tools.
The micro-coolant injection system available for use in high-speed machining with small tools is recommended to use ethanol (commonly known as alcohol) as the coolant. It is an alcohol formed by fermenting sugar, which is most suitable for non-ferrous metals and some plastic materials. Used in high speed machining. However, ferrous metals also require the use of oil-based coolants. This is because the surface of the iron-based metal is cut, and it is easy to generate an electric spark and cause a fire.
The commonly used coolant is an oil-based coolant that requires service personnel to handle it at an additional cost. Ethanol can be automatically volatilized without the need for time-consuming processing such as filtration and waste, saving production costs. Although ethanol is flammable, the low melting point gives ethanol a strong cooling and lubricating effect. Because it is a natural chemical, there are no negative environmental impacts, no pollution, no waste and additional surcharges. In addition, as a cooling liquid, ethanol has the advantage of not remaining on the surface of the finished part, so there is no need to increase the costly and cleaning process of the expensive parts. Give full play to the role of high-speed machining technology High-speed machining with small tools requires the use of advanced machining tools. Ordinary machines that use only one high-speed spindle can not meet the high standards of high-efficiency machining. Only use advanced machine tools designed and manufactured for high speed machining. Use a small tool to mill on advanced machine tools, drilling and engraving, you need to select the highest spindle speed of 6000 ~ 6000r / min. This is because the use of small tools to perform high-speed machining at such high spindle speeds has the ability to reduce cutting forces, less tool breakage, high cutting temperatures, better part machining accuracy and surface roughness. Eliminate many advantages such as deburring, degreasing and small tool vibration.
In addition to selecting a high spindle speed and a small depth of cut, high-speed cutting is required while using a small tool for high-speed cutting. Cutting at high cutting speeds and high feed rates allows a large amount of heat generated during cutting to be transferred to the part and is carried away by the chips.
The cutting test proves that in metal cutting, 40% of the large amount of heat generated is generated by the friction between the tool and the part, and 20% of the heat is generated by the bending deformation occurring in the chip formation. Therefore, it can be said that about 60% of the heat remains in the chips. In high-speed cutting, it can eliminate a large amount of heat by rapid chip removal, which can greatly reduce the cutting temperature and avoid the disadvantages such as the size of the parts due to heat. Of course, to better ensure the quality of the part processing, it is also necessary to take effective cooling tools, reduce the cutting force and prevent vibration from occurring. With a small tool that can be machined at high spindle speeds, the chiP Ioad (tool feed per tooth) can also be reduced to less than 0.005'. Such a low chip load can greatly reduce the cutting force. The reduction of the cutting force will result in a very low cutting temperature and reduce the deformation of the tool, so that thin-walled parts can be processed to obtain a good surface roughness of the parts and improve the machining accuracy of the parts.
The use of small tools for high-speed machining must master the above three main technical aspects. These three main technical links are interrelated and important. Can not ignore and look at a certain aspect, in order to ensure high reliability processing state, to ensure that the cutting speed is maximized under the premise of obtaining high quality products, thereby improving production efficiency. Processing Examples The following are two production examples for high-speed machining using a small tool in a Datron milling machine.
One is to use a l/4' single-edged tool to mill a deep l/8' groove on the 6061 aluminum alloy part. The machine selects the operating conditions for the spindle speed of 45000r/mSEl250i/m feed rate, using ethanol coolant.
The other is to use a 1/8' small helix angle double-edge milling cutter on a wide l/8' 6061 aluminum alloy sheet with a spindle speed of 50000r/m, a feed rate of 200i/m and cooling with ethanol. Perform high speed face milling.
In the two processing examples, excellent processing results have been achieved due to the following processing rules:
(1) Ensure that the spindle temperature is not increased during processing, otherwise the tool will wear quickly and reduce the service life of the tool;
(2) Select high cutting speed, high feed rate and small depth of cut processing;
(3) The chips can be quickly removed from the cutting zone.