What Xiao Gong has always understood is this: If a general machining center is used to make products, it buys linear rails, and if it is processing molds, then buy hard rails. The accuracy of linear rails is higher than that of hard rails, but the hard rails are more durable.
Today this article finally made it clear, dedicated to friends of dry machining, collection!
Hard track characteristics
1. The advantages of hard rail:
1. It can withstand larger loads and is suitable for roughing machine tools with large tool volume and large feed.
2. Because of the large contact area of the guide rail, the machine tool runs more smoothly, which is suitable for machine tools with high requirements for machine vibration, such as grinders.
2. Disadvantages of hard rail:
1. The material is not uniform. Because it is generally cast, it is easy to produce casting defects such as sand inclusion, porosity, and looseness in the material. If these defects exist on the guide rail surface, it will have a negative impact on the service life of the guide rail and the accuracy of the machine tool.
2. Processing is more difficult, because this type of guide rail is generally connected to the main parts of the machine tool such as the base, column, workbench, and saddle. Therefore, in the process of processing, its shape and position tolerances, roughness requirements, and timeliness Processing, quenching and other processes are difficult to control, resulting in the processing quality of parts that cannot meet the requirements of assembly.
3. Assembling is difficult. The word "assembly" means to assemble as well as to assemble. The matching process is a process of combining technology and physical strength. It cannot be done by ordinary workers. It requires a relative quantity of skills. The overall accuracy of the machine tool can be completed by an assembly worker who is quite sure of it. At the same time, it needs to be equipped with a blade, flat ruler, square ruler, square ruler, dial indicator, dial indicator and other corresponding tools to complete it.
4. The service life is not long. This can only be done in relative terms. Under the same maintenance and use conditions, the service life of common hard rails is less than the service life of linear rails, which is very much related to their movement methods. In terms of friction, the hard rail runs under sliding friction, while the linear rail runs under rolling friction. In terms of friction, the friction on the hard rail is much greater than the friction on the linear rail, especially in lubrication. In the case of insufficient, the friction of the hard rail is even worse.
5. The maintenance cost is too high. The maintenance of the hard rail is far greater than the maintenance of the linear rail in terms of difficulty and maintenance cost. If the scraping margin is insufficient, it may involve the dismantling of all the large parts of the machine tool. Re-hardening and machining, or even re-casting the large part, and the wire gauge only needs to be replaced with the corresponding wire rail, which will not greatly affect the use of related large parts.
6. The running speed of the machine tool is low. Because of the way of movement and the friction that the hard rail bears is too large, it usually cannot bear the running speed too fast. This is contrary to the current processing concept. In particular, many factory workers do not have the corresponding maintenance knowledge of machine tools. Many times they only know the use of machine tools, but to a large extent ignore the maintenance of machine tools. The maintenance of machine tool tracks is the most important thing. Once the track is not sufficiently lubricated, It will cause the track to burn or wear out, which is fatal to the accuracy of the machine tool.
Line rail characteristics
1. The advantages of linear rail
1. The assembly is convenient and simple, and high-quality assembly can be completed with a little training. Because the precision of the machine tool is very large, the degree of accuracy determines the accuracy of the transmission mechanism. The transmission mechanism is generally composed of a wire rail and a screw rod, that is to say, the accuracy of the wire rail and the screw rod itself determines the accuracy of the machine tool, while the linear rail and the screw rod are generally They all exist in the form of standard parts. As long as you choose the corresponding accuracy provided by the manufacturer, there will generally be no big problems.
2. There is a large choice, whether it is from the structure of the linear rail or the precision level, the lubrication method or the load-bearing capacity, the processing method to the operating speed and other parameters, you can choose any configuration according to the specific conditions of the machine tool you design. The type of linear rail you need.
3. The running speed is fast. Now many machine tools are running very fast, especially the idle speed. This is largely due to the credit of the linear rail, because the running mode of rolling friction and the high-precision processing ensure the machine tool. The accuracy and stability of high-speed operation greatly improves the processing efficiency and processing accuracy.
4. The machining accuracy is high. Because the linear rail is a standard commodity, its material and processing methods have entered a benign controllable range. Therefore, most of the machine tools in many finishing fields use high-precision linear rails. As a machine tool guide rail, this also greatly guarantees the machining accuracy of the machine tool. Domestically, there are Nanjing craftsmanship, Hanjiang line rail, Taiwan has silver line rail, Germany has Rexroth company, Japan has THK line rail and so on. These brands are greatly enriched and meet the market's demand for various requirements of line rails. I personally like to choose Japanese THK, which has stable performance and fine workmanship, but the price is high.
5. Long service life, because the running mode of the linear rail is rolling friction, the steel ball in the slider drives the movement of the feeding part by rolling on the rail, and the friction that this rolling friction bears is smaller than that of the hard rail. There are many, so both the transmission efficiency and the service life, the linear rail is much more ideal than the hard rail.
6. Low maintenance cost. In terms of maintenance cost and convenience, the linear rail has its natural advantages and convenience, because as a standard part, the replacement form of the linear rail is the same as the replacement of a screw. , Of course there are some precision adjustments, but compared to the hard track, it is really convenient.
7. The delivery cycle is short. The general delivery cycle of the line rail can be completed within half a month, unless you choose foreign brands, such as Rexroth and THK. In fact, these two brands also have corresponding processing plants in China. , As long as the line rail model you choose is not very biased, basically the delivery time of about half a month can still be guaranteed, and the line rail of Taiwan Bank can even achieve a one-week delivery cycle, but the same The hard track does not have such a good time control ability. If the movement is relatively large, such as re-casting, the cycle may be more than a few months.
2. Disadvantages of linear rail
1. The carrying capacity is relatively small. This kind of relatively small is only for hard rails. In fact, the line rails of many large factories have greatly improved their carrying capacity through some structural designs. Of course, they are relatively hard rails. In terms of carrying capacity, it is still relatively small.
2. The stability is somewhat weaker than that of the hard rail, such as the ability to resist vibration, but I still want to emphasize that this kind of weakness is relative to the hard rail. In fact, the stability of many linear rails is also done now. It is very good, as long as the equipment you design is not too special, it is generally able to meet the needs.
3. Special attention should be paid to the protection of the linear rail during transportation and assembly, because as a standard part, its unique structural characteristics put it in an embarrassing situation that is more susceptible to damage, such as a slender shape which leads to the linear rail. Insufficient rigidity, it is easy to bend and deform under squeezing, which leads to loss of precision; another example is that because steel parts are not treated with rust prevention, they will easily come into contact with water or other solvents during transportation and assembly. Phenomena such as rust and corrosion occur, which leads to loss of accuracy.
