If the general machining center is used to make products, linear rails are purchased. If it is used to process molds, hard rails are purchased. Linear rails have higher precision than hard rails, but hard rails are stronger and more durable.
1. Advantages of hard rails
● It can withstand greater loads and is suitable for rough machining machines with large tool volume and large feed.
● Because the contact area of the guide rail is large, the machine tool runs more smoothly, which is suitable for machine tools with high requirements for machine tool vibration, such as grinders.
2. Disadvantages of hard rails
● The material is uneven. Because it is generally cast, it is easy to produce casting defects such as sand inclusion, pores, and looseness in the material. If these defects exist on the guide rail surface, it will have a very adverse effect on the service life of the guide rail and the accuracy of the machine tool.
● The processing is difficult, because this type of guide rail is generally connected to the main parts of the machine tool such as the base, column, workbench, saddle, etc., so during the processing, its shape and position tolerance, roughness and over-limit requirements, aging treatment, quenching treatment and other processes are difficult to control, resulting in the processing quality of the parts not meeting the assembly requirements.
● The assembly is difficult. The word "assembly" means both assembly and matching, and this matching process is a process that combines technology and physical strength. It is not something that ordinary workers can complete. It requires a relatively large number of skills and assembly workers who have a good grasp of the overall accuracy of the machine tool. At the same time, it is also necessary to equip it with scrapers, flat rulers, angle rulers, square rulers, dial indicators, micrometers and other corresponding tools to complete it.
● The service life is not long. This is only relative. Under the same maintenance and use conditions, the service life of the general hard rail is shorter than that of the linear rail. This has a lot to do with their movement mode. The hard rail runs by sliding friction, while the linear rail runs by rolling friction. In terms of the friction force, the friction force of the hard rail is much greater than that of the linear rail, especially in the case of insufficient lubrication. The friction of the hard rail is even worse.
● The maintenance cost is too high. The maintenance of the hard rail is much greater than that of the linear rail in terms of difficulty and maintenance cost. If the scraping allowance is insufficient, it may involve dismantling all the large parts of the machine tool, re-quenching and machining, and even more so, recasting the large part. The wire gauge only needs to replace the corresponding linear rail, which basically will not greatly affect the use of the relevant large parts.
● The running speed of the machine tool is low. Because of its movement mode and the excessive friction, the hard rail usually cannot withstand too fast running speed, which is somewhat contrary to the current processing concept. In particular, many factory workers do not have the corresponding maintenance knowledge of machine tools. In many cases, they only know how to use machine tools, but largely ignore the maintenance of machine tools. The maintenance of machine tool tracks is of utmost importance. Once the tracks are not sufficiently lubricated, they will cause the tracks to burn or wear excessively, which are fatal damage to the accuracy of machine tools.
