CNC Knowledge: Line rail or hard rail, which is better?

We often hear about linear rail and hard rail machining centers. What are the differences between them? I think many people in the industry don’t know what a hard rail machining center is. , what is a linear rail machining center, what is the difference between the two and which one is better to use.

Linear machining center

The full name is linear guide machining center machine, which generally refers to rolling guide rails. There are two common structures: ball guide rails and roller guide rails. The difference is that ball guide rails are point contact type and roller guide rails are linear contact type. The principles are also the same. drive the slide.

advantage:

1. The linear guide rail is supported by rolling parts, and its rolling sliding performance is stronger than the friction sliding performance of the hard rail, and there is no creeping phenomenon;

2. Due to its low coefficient of friction, it moves quickly;

3. In addition, because the friction coefficient is low, the wear is low;

4. Generally, linear guide rails are made of better materials and more precise equipment, so their precision is also higher;

5. It is easy to maintain later. After the guide rail is worn, the linear rail is easy to replace, but the hard rail is more troublesome because the gap needs to be adjusted.

Disadvantages: Due to their smaller contact surface, they are less rigid than hard rails.

Hard rail machining center

Typically, the guide rail and bed are molded as one piece. The material number is generally not lower than HT250, and the Brinell hardness of the machine body is between HB180 and HB240. After the guide rail part is quenched by high frequency or ultrasonic frequency, the hardness is generally above HRC50°, which makes it have excellent wear resistance (steel inlaid guide rails are also a type of hard rail). Rigid rails used in CNC machining centers are generally rectangular structures, commonly known as rectangular guide rails.

Advantages: The sliding contact surface of the hard rail is large, which makes the machine tool rigid and stable.

Disadvantages: Due to the large contact area, the friction resistance is also large, wear is rapid, the moving speed is limited, and defects such as crawling phenomenon are likely to occur. Therefore, most machining center manufacturers use the plastic process of guide rails to reduce the wear and crawling defects of hard rails.

Which is the best machining center for linear rails or hard rails?

The linear rail has fast speed and high precision. It is suitable for high-speed machines, can cut at high speed, and is suitable for processing small precision molds. Linear rails are pre-tensioned to achieve zero gap between rails. The hard rail has dry friction, large load and high strength, which is suitable for heavy cutting. The movement of hard rails requires space on the moving surface to move, and the friction coefficient is large, which is prone to adhesion and leads to machining errors. It is mainly used under heavy loads. Suitable for processing parts with high hardness and low precision requirements.

Actually, there is no right or wrong difference between hard rail and linear rail, I can only say if they are suitable. Because their processing purposes are different, linear rail machining centers tend to process parts with low hardness and high precision, while hard rail machining centers focus on processing parts with high hardness and low precision requirements.