We often hear that CNC machining centers are divided into hard rails and linear rails, so when purchasing a machining center, we will ask: Is a hard rail better or a linear rail? What is the difference between the two?
What is a hard rail? What is a linear rail
Hard rail refers to a casting in which the guide rail and the bed are integrated, and then the guide rail is processed on the basis of the casting. That is, the shape of the guide rail is cast on the bed, and then the guide rail is processed after quenching and grinding. There are also cases where the bed and the guide rail are not necessarily integrated, such as steel-inlaid guide rails, which are nailed to the bed after processing.
Linear rails usually refer to rolling guides, which are the ones used in linear modules frequently used in the machine tool industry. This type of component is usually called "linear guide". The linear guide itself is divided into two parts: the slide rail and the slider. The slider has internally circulating balls or rollers, and the length of the slide rail can be customized. It is a modular component, a standardized series of separate products produced by a special manufacturer, which can be installed on the machine tool and can be disassembled and replaced after wear. Most of the machine tools in the field of precision machining use high-precision linear rails as machine tool guide rails, which also greatly guarantees the machining accuracy of the machine tools. Imported ones include Germany's Rexroth and Japan's THK. Domestic ones that are relatively good include Nanjing Technology, Hanjiang Linear Rails and Taiwan's Hiwin.
Is the machining center better with hard rails? Or is the linear rail better?
Hard rails refer to castings in which the guide rails and the bed are integrated. Then, based on the castings, there is actually no good or bad saying about hard rails and linear rails. It can only be said that they are suitable or not, because their focus is different. Let's take a look at their respective advantages and disadvantages.
1. Advantages and disadvantages of hard rails and their applications
Hard rails have a large sliding contact surface, good rigidity, strong seismic resistance and strong load-bearing capacity, which are suitable for heavy-load cutting.
Hard rails belong to dry friction. Due to the large contact surface, the friction resistance is also large, and the moving speed cannot be too fast. At the same time, it is easy to produce creeping phenomenon, and the gap between the moving surface will cause processing errors. The maintenance of machine tool rails is of utmost importance. Once the rails are not lubricated sufficiently, they will cause the rails to burn or wear excessively, which are fatal to the precision of the machine tools.
The application of hard rails is suitable for heavy cutting, large molds, high-hardness workpieces and workpieces with general precision requirements.
2. Advantages, disadvantages and applications of linear rails
Nowadays, many machine tools run at extremely high speeds, especially the idle speed, which is largely due to the credit of linear rails. After pre-tightening, the linear rails can achieve zero clearance between the rails and high precision. In terms of service life, the linear rails are much higher than hard rails.
The cutting force that the linear rails bear is smaller than that of the hard rails, but only for the hard rails. In fact, the linear rails of many machine tools have greatly improved their bearing capacity.
The application of linear rails is suitable for high-speed machines, can be cut at high speed, and is suitable for processing products and small precision molds. Nowadays, more precision machining centers use linear rails.
