Simple analysis of high speed cutting technology and its application in automobile engine
Date: 2018/04/18 10:09:43 * : 41
High speed machining is a new and high technology for the 21 world. It has been widely used in the fields of automobile, aeronautics and Astronautics, mold manufacturing and instruments and meters, with high efficiency, high precision and high surface quality. It has achieved great technical and economic benefits. It is a modern advanced manufacturing technology. An important part of it.
Technical features of high speed machining
High speed cutting is the core technology to achieve high efficiency manufacturing. The process intensification and equipment generalization make it highly efficient. It can be said that high speed machining is an essential technology to increase machining efficiency without increasing the number of equipment. Its technical characteristics are mainly manifested in the following aspects:
1) cutting speed is very high. It is generally considered that its speed is 5~10 times higher than that of conventional cutting.
2) the spindle speed of machine tool is very high, generally the spindle speed is above 10000 ~ 20000r/min;
3) the feed rate is very high, usually 15 to 50m/min, up to 90m/min
4) for different cutting materials and tool materials, the meaning of high speed cutting is also different.
5) in the process of cutting, the frequency of the blade's passing (Tooth Passing Freqnency) is close to the dominant natural frequency (Dominant Natural Frequency) of the "machine tool - tool - workpiece" system.
High speed machining
In 1992, Professor H.Schulz of the Darmstadt Industrial University in Germany presented the concept of High Speed Manu facturing (HSM) and the scope of its coverage on CIRP, as shown in Figure 1. It is considered that for different cutting objects, the transition zone (Transition), as shown in the diagram, is the commonly called high speed cutting range, which is also expected or expected by the metal cutting technology related technicians.
Compared with the traditional machining, high speed cutting significantly increases the cutting speed, resulting in the increase of friction between the workpiece and the front tool surface and the increase of the contact surface temperature of the chip and the cutting tool. At the contact point, the high temperature of the friction can reach the melting point of the workpiece material, making the chip softened and even liquefied, thus greatly reducing the resistance to the cutting tool, that is, the cutting force is reduced, the cutting becomes light, and the chip production is more fluent. At the same time, 70% to 80% of the heat produced by processing is concentrated on the chip, and the removal speed of the chip is very fast, so the heat transfer to the workpiece is greatly reduced, and the machining precision is improved. The advantages of high speed cutting technology lie in improving production efficiency, improving machining accuracy and surface quality, and reducing cutting resistance.
Application of high speed machining in automobile engine and its accessories
FTL: using high speed machining center to form an efficient flexible production line (FTL), which is characterized by miniaturization, flexibility and easily changing the processing content. Fig. 2 is an example of an engine company of SAIC which makes use of the production line to process engine block, cylinder head and filter holder.
In order to give full play to the advantages of turning machining center and boring milling center as the representative of high speed machining technology and automatic knife changing function, the machining efficiency should be improved, the principle of concentrating process should be adopted as far as possible for the processing of complex parts, that is, the centralized processing of multi process sequence is required in the one clamping, and the traditional car is desalinated. Milling, boring, thread processing and other different cutting technology boundaries, give full play to the high-speed cutting function of equipment and cutters. At the same time, the new requirements for cutting tools are also proposed, which requires a tool to complete the processing of different parts of the parts, reduce the number of knife change and save the time of changing the knife, so as to reduce the number of tools and the amount of inventory, and to manage and reduce the cost of manufacturing. More commonly used multi-function turning tools, milling cutters, boring and milling cutter, drilling and milling cutter, drilling milling thread chamfering and other cutting tools. Some specific process strategies are used in the mass production line, and special tools, compound tools or intelligent tools are needed to improve the processing efficiency and precision and reduce the investment. Under the condition of high speed cutting, some special tools can reduce the processing time of parts to below 1/10, and the effect is very significant.
Machining of the joint between the top and the main bearing of the automobile engine block
High speed cutting technology for machining the joint between the top and the main bearing of the automobile engine block. The body material is grey cast iron, the tool is CBN, no heavy grinding compound cutting tool, the spindle speed is 12000r/min, and the cutting allowance is 0.02mm. The two key parts of the drawing are milled once, and the important dimension A is guaranteed by the compound milling cutter itself. The process also effectively avoids the flutter caused by the longer spindle bearing joint with a longer blade, which greatly improves the cutting precision, cutting efficiency and surface quality.
FMS: as the product life cycle continues to shorten, the number of varieties will continue to increase. In this case, how to shorten the time of changing the variety has become a key problem. Because of the change in product design, how to adapt its processing equipment flexibly (i.e., flexibility) is a major issue. So FMS emerged from the high flexibility universal machining center. The "high flexible general machining center" described here is different from the general concept of processing centers. They are specially developed for mass production, fully satisfied with the conditions that are included in the FMS for mass production, that is, high productivity, area, easy to discharge, easy installation and displacement, and superior continuous performance, and so on. It is a high speed and compact machining center.
In order to adapt to the urgent need for mass production, MITSUBISHI heavy industry has developed the so-called "shuttle FMS", which is made up of 8 M-H5A three coordinate machining centers and unmanned carrier vehicles (AGV) carrying 2 pallets in front of the machine tool. The carrier is used for the transfer pallets, reciprocating to the plate loading and unloading position and each of the plates. Between machine tools. The operator can only load and unload the workpiece by means of an operation button in one location, and it does not need to travel between the machine tools. The vehicle will wait in front of the machine tool in turn. After the machine is finished, the plate is exchanged between the machine and the carrier, and then the finished product is returned to the loading and unloading station.