We often hear that CNC machining centers are divided into hard and linear rails. When customers choose a machining center, they ask: Which is better? What is the difference between them?

What is a hard rail? What is a linear rail?

Hard rails refer to a cast part where the guide rail and machine body are integrated, and the guide rail is machined based on the casting. The shape of the guide rail is cast on the machine body and processed into a guide rail through quenching and grinding. There are also cases where the body and guide rail are not integrated, such as the embedded steel guide rail, which is nailed to the body after processing.

Linear rails usually refer to rolling guides, commonly used in linear modules in the machine tool industry today. We often refer to this type of component as "linear guides".

The linear guide rail is divided into two parts: the slide rail and the slide blocks. The slide blocks have internally circulating balls or rollers, and the length of the slide rail can be customized. It is a modular component that is a standardized and serialized individual product produced by specialized manufacturers. It can be installed on machine tools and disassembled and replaced when worn out.

Many machine tools in the precision machining field use high-precision line rails as machine tool guides, greatly ensuring the machining accuracy of the machine tools.

Is it good to use hard rails for machining centers? Are linear rails better?

Actually there is no such thing as good or bad between hard and linear rails, only whether they are suitable or not because their emphasis is different. Let's take a look at their respective advantages and disadvantages.

1. Advantages, disadvantages, and applications of hard rails

The hard rail has a large sliding contact surface, good rigidity, strong seismic resistance, and strong load-bearing capacity, making it suitable for heavy load cutting.

Hard rails belong to dry friction. Due to the large contact surface, the frictional resistance is also high, and the moving speed cannot be too fast. At the same time, the crawling phenomenon is prone to occur, and gaps on the moving surface can lead to machining errors. The maintenance of machine tool rails is of utmost importance. Once the rail lubrication is insufficient, it can cause the linear to burn or wear out, which can be fatal to the accuracy of the machine tool.

Hard rails are 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 operate at fast speeds, especially in terms of idle speed, largely due to the contribution of the linear rails. The pre-tensioning treatment of the linear rails can achieve zero gaps between linear rails with high accuracy; In terms of service life, linear rails are significantly longer than hard rails.

Compared to hard rails, linear rails bear less cutting force, but in fact, many machine tool linear rails have greatly improved their load-bearing capacity.

Linear rails are suitable for high-speed machine tools and for high-speed cutting, processing products, and machining small precision molds.

There is also a special type of machining center that has two axes as linear rails and one axis as hard rails.

3. Two-linear one-hard machining center

A two-linear one-hard machining center is a relatively special machining center. The so-called "two-linear one-hard" usually refers to linear rails for the X and Y axes and hard rails for the Z axis. This type of machining center has some characteristics of both linear rail and hard rail machining - fast speed and good rigidity. However, these characteristics are still slightly weaker compared to pure linear rails type and pure hard rails type.

The two-linear one-hard machining center can not only process molds but also process products. However, its production efficiency is slower than that of a pure linear rail machining center, and the quality of the processed products will not be significantly different. Its applications are also quite extensive.