A rail system helps a CNC machine move in different axes and keeps its movement in the right position. A CNC machine needs to move without losing its precision. Otherwise, the desired cutting operation cannot be achieved. Therefore, a rail system is an essential component of a CNC machine. There are two different types of rail systems: hard rails and linear rails. There are several differences between these systems. We will focus on 12 essential differences in this article.
Generally speaking, while hard rails are associated with old-fashioned CNC machines, linear rails are accepted as a modern rail system for modern CNC machines. We observe that many advanced CNC machines use linear rails in different forms. Nevertheless, hard rails are still used in some machines. Using these rails may be advantageous for some cutting works. This article will elaborately inform you about these two rail systems and list 12 essential differences between them. We hope we can help you understand the basic differences and choose the right system for your machines.
What is a Rail System?
In CNC machines, the precise movement of cutting tools is crucial for the success of cutting operations. Rail systems are designed to facilitate the movement of cutting tools. They guide the movement along different axes, allowing cutting tools to move in the right position. They ensure accuracy and precision in the CNC machining process. A rail system consists of two parts: a guide and a carriage. The carriage smoothly moves along the guide, thereby providing the movement of the cutting tool. Hard rails and linear rails have different systems to provide movement.
Functions of Rail Systems in CNC Machines?
Guiding the movement of the CNC machine
The CNC machine moves along the X, Y or Z axes through the smooth motion along the path provided by the rail system.
Ensuring the precise movement of cutting tools
The smooth surface of the rails enables the cutting tools to perform the exact motions necessary for the cutting operation.
Enhancing the stability of the CNC machine
Rails facilitate the movement of the CNC machine and make it more stable.
Reducing vibrations
When vibrations are not prevented, the CNC machine cannot perform the precise movement. Rails help the CNC machine to move smoothly, thereby preventing vibrations.
Increasing the speed of the CNC machine
Without a rail system, it would be overly hard to perform movements along axes in CNC machines. Thanks to the smooth motion provided by rails, CNC machines operate much faster.
Hard Rails
Hard rails are integrated with the bed and rails have to move on the casting. They can only create motion through sliding surfaces, and for this, lubrication is needed. This creates much friction and, as a result, slows down the CNC machine. On the other hand, the bulky structure of hard rails makes the CNC more stable and rigid. Thanks to this feature, hard rails can support heavy loads.
Advantages
They increase the stability and rigidity of the CNC machine.
They are especially good for heavy-load cutting jobs.
They have a simple structure
Thanks to their robust structure, they produce few vibrations.
Their hardened structure makes them stronger. They are not as vulnerable as linear rails to damage.
Disadvantages
Because of the large contact surface, the friction coefficient is high.
And, as a result of the high friction coefficient, they wear and tear easily.
It is hard to operate and assemble them.
They are slower compared to linear rails.
The motion provided by them is not as accurate and precise as the motion created by linear rails.
Linear Rails
Linear rails use rolling elements like rollers or balls. These elements decrease the friction caused by sliding and help the CNC machine to move more smoothly in different axes. As a result, the machine needs less cutting power and can make the linear motion more precise. This is directly reflected in the success of cutting operations. The CNC machine is capable of making the exact linear movement as programmed and can flawlessly perform cutting operations that require tight tolerances, even in microns. Eventually, the cutting operation becomes more speedy, accurate, and precise.
At this point, we must note that linear rails are commonly preferred in modern CNC machines. They have advantages over hard rails in terms of speed, the quality of the cutting job, longevity, and maintenance. We will further discuss its advantages and disadvantages over hard rails in upcoming sections. Here, we just want to emphasize that linear rails are the current trend in the modern CNC machining industry.
Types of Linear Rails
Round Shaft Rails
These linear rails stand out for their simplicity. Along with their simple design, they are easy to install, use and maintain. They allow for flexible movements, so the CNC machine can perform the most complex cutting jobs. Yet, its sliding mechanism is simple, which allows for the easy operation of the CNC machine.
Profile Rail Guides
These linear rails stand out for their stiffness and strength. Their carriage system is based on steel balls. As a result, they have a high load-bearing capacity and therefore are appropriate for heavy loads. They are commonly used in large CNC machines, especially for drilling and milling operations. They are also versatile, allowing for flexible movements for a specific cutting operation. Despite their stiffness and firmness, profile rail guides move smoothly and, in this way, help the CNC machine make the exact movement. Finally, they have a long service life and, if you properly maintain it , you can extend their service life.
Advantages
The sliding movement of linear rails produces small friction due to the smooth movement of rails that use balls or rollers. Therefore, the cutting process is executed quite fast, and cutting problems like crawling are prevented. This is why linear rails are preferred in CNC machines used in industries that require high-speed machining.
Thanks to the small friction, linear rails do not wear and tear quickly. Apart from this, these rails are made from high-quality materials. Both of these factors extend their service life, and you can make their service life even longer by properly maintaining them.
Along with their high speed and longevity, they greatly help the CNC machine execute the cutting job accurately and precisely. This is possible because the cutting tool can make the exact movement in any axis through the smooth and precise movement of rails. In brief, they can meet tight tolerance, even in microns, demanded by the modern industry.
In addition, they are easy to maintain. You can easily assemble and disassemble them. Replacing the rails is also easy.
Disadvantages
They may underperform for large loads. Exposing too much load may also damage them. If you use the rail in that way for a long time, their accuracy and precision may be reduced. Although you can partially solve this problem by employing lubrication, we do not advise using linear rails for heavy loads.
They are not as stiff and strong as hard rails because of their small contact surface. This shortcoming may cause stability problems and vibrations and make liner rails vulnerable to damage.
Finally, they are more costly than hard rails. This cost may prevent small businesses from investing in linear rails.
12 Essential Differences between Hard Rails and Linear Rails
In this section, we will focus on 12 essential differences between hard rails and linear rails by making a comparison based on different criteria:
Structure
While hard rails are cast on the bed and integrated with it, the contact surface of linear rails is limited because they use rolling elements for the movement.
Speed and Performance
As underlined above, the big friction created by a large contact surface slows down hard rails. This ultimately affects their overall performance. Consequently, linear rails outperform hard rails in terms of speed and performance.
Precision and Accuracy
Rollers and balls enable linear rails to move smoothly in any axis. Therefore, they are more able to execute the exact movement programmed and commanded by the CNC machine. The hardened structure of hard rails hinders their movement capability. In conclusion, linear rails can perform more accurate and precise operations than hard rails.
Heavy Loads
The robust structure of linear rails allows them to have a higher load-bearing capacity. Conversely, linear rails underperform for heavy loads. Moreover, you can damage them if you insist on using them for such work.
Longevity
Thanks to the small contact surface and small friction created by it, the service life of linear rails is longer. In contrast, because hard rails are integrated with the bed and have to move on the casting, they produce large friction. Ultimately, it makes their service life shorter.
Maintenance
You have to constantly lubricate hard rails to ensure a smoother motion. They also wear and tear easily. Furthermore, because of the robust structure, it is hard to maintain them. On the other hand, you can lubricate and maintain linear rails less frequently and it is not so hard to maintain them.
Assembly and Processing
In general, it is more difficult to assemble and process hard rails.
Price
Linear rails are more expensive than hard rails. For this reason, small manufacturers may not afford to invest in these machines. Shortly, we can say hard rails are more affordable and accessible.
Resistance against Damage
The robust structure of hard rails makes them stronger against damage. Conversely, linear rails are more vulnerable to damage.
Rigidity and Stability
Hard rails are more rigid and stable. Hence, they produce few vibrations. Although linear rails are not as rigid and stable as hard rails, their smooth motion produces few vibrations, too.
Repair Costs
Because of their simple structure, the repair costs of hard rails are likely to be low. When it comes to linear rails, although their breakdowns are rare, if it happens, repairing may be costly
Manufacturers
While hard rails are generally preferred by small and medium-sized manufacturers, linear rails are generally preferred by large manufacturers that prioritize high-speed manufacturing.
12 Essential Differences between Hard Rails and Linear Rails (Summary)
| Hard Rails | Linear Rails | |
| Structure | Cast on and integrated with the bed | Use rollers or balls |
| Speed and Performance | Low speed and performance because of large friction | High speed and performance thanks to rolling elements |
| Accuracy and Precision | Hardened structure hinders accuracy and precision | Smooth movement increases accuracy and precision |
| Heavy Loads | High-loading capacity | Not appropriate for heavy loads |
| Longevity | Wear and tear easily | Long service life |
| Maintenance | Hard | Easy |
| Assembly and Processing | Hard | Easy |
| Price | Affordable | Costly |
| Resistance against Damage | Strong against damage | Vulnerable to damage |
| Rigidity and Stability | Few vibrations due to rigidity and stability | Not very rigid and stable but produces few vibrations due to the smooth movement of rails. |
| Repair Costs | Low | High |
| Manufacturers | Preferred by small and medium-sized manufacturers | Preferred by large manufacturers |
Hard Rails or Linear Rails: Which One is for You?
So far, we have mentioned hard rails and linear rails in detail and explained 12 essential differences between them. It is now time to discuss what to consider to choose the correct rails for you.
Hard rails are old-fashioned rails and fall behind liner rails in terms of speed, performance, accuracy, precision, and longevity. However, they are especially good for heavy loads. They are more affordable and accessible and provide a simple design. It may be a good choice for small and medium-sized manufacturers that cannot afford linear rails.
The major setback of linear rails is their price. They are also not good for heavy loads. If your manufacturing requires high speed and performance and ultimate accuracy and precision, you should opt for linear rails.
These are our conclusions and recommendations and it is up to you to choose one.
Which Rail System Do We Use and Why?
We follow the current trend and use linear rails in our CNC machines. The linear rails we use are designed to eliminate the basic setbacks of linear rails. In other words, these rails have a high load-bearing capacity and are therefore appropriate for heavy loads, and ensure ultimate accuracy and precision, If your concern is price, you do not have to worry.
Final Words
This article summarized the essential differences between hard rails and linear rails. Considering these differences, choose the right rail system for you.