January 29, 2023
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Linear rails and linear rods perform the same role: they are both parts of a CNC machine responsible for moving loads on a straight line from one part to another using an actuator.

Both offer exceptional performance in their own domain, but the decision to use either can be confusing if you don’t know exactly what you’re looking for or if you don’t have experience in CNC. In this article, we’ll help you understand the difference between linear rails and linear rods and why a CNC linear rail kit is suitable for your project. 

Table of contents 

What do they both have in common?

Differences between linear rails and rods

When should you choose rails over rods?

Fatigue and lifespan of linear rails and rods

Comparing the cost of linear rails and rods

CNC linear rails are better than rods

What do they both have in common?

CNC linear rails and linear rods are both used for smooth and precise motion in industrial and DIY applications. Both are made from high-quality hardened and galvanized carbon steel through a cold drawing process which allows them to withstand heavy use.

But in most cases, a CNC linear rail system is easier to use than a linear rod system because rails can be screwed or bolted in place before being fitted with runners.

Both systems are self-lubricating. However, rods operate in a sealed system to prevent grease from leaking out, which is good for the food and pharmaceutical industries.

Differences between linear rails and rods

Linear rails are more rigid and longer lasting compared to linear rods because they are made from solid steel with no weak joints or connectors.

In addition, the T, U, and V-like design of rods, which was borrowed from structural steel bars, allows the rail to bear more weight. It can carry up to 750 lbs.

Linear rails are more precise compared to rods meaning you can easily get accurate cuts. This is because the rail’s profile prevents the system from flexing even under vibration. 

Lastly, rails are compact, which is beneficial when working in tight spaces.

When should you choose rails over rods?

There are many factors to consider when choosing whether to use CNC linear rails or linear rods for your project. Here are some things to keep in mind:

Rails are more expensive than rods, but they offer a smoother motion and greater precision.

Rails are also easier to install and require less maintenance than rods.

Rails can handle heavier loads than rods, making them ideal for commercial projects.

Rods are more versatile than rails and can be used in a wider variety of applications.

When should you choose rods over linear rails?

Despite rails having the upper hand, there are some situations when you will have to go for CNC rods.

Hygiene

Linear rods work in a sealed system which contains grease and prevents leakages. This makes them suitable for producing sensitive products such as tooth crowns and useful in the food industry and health sector.

Flexibility

Most linear rods are designed to extend further than their cylindrical length, and they can also integrate with other movable parts of the machine.

In some industries other than CNC, linear rods’ ability to rotate the head provides a greater reach into inaccessible parts. This is useful in curving out angled spaces.

Linear rods are cost-effective.

Linear rods are an ideal choice for hobbyists or small businesses that don’t need as much precision in their work as required in aircraft manufacturing and robotics or don’t want to invest in expensive machinery and manpower.

Fatigue and lifespan of linear rails and rods

How long do linear rails and rods last is a frequently asked question by CNC design engineers? It is a good question when weighing how much to invest in rails or rods.

Physically, it is impossible to determine how long a rail will last, but theoretically, we can use Lundberg and Palmgren’s theory to calculate nominal life expectancy as a function of load size on a rail’s bearing. Using the theory, you will find out that a CNC linear rail has a lifespan of 100 Km.

In real life, however, factors such as friction, the weight impacted on the rail, and the type of material a CNC is working on determines the rail’s lifespan. According to preliminary calculations from the theory, it may be 90 to 95% of 100Km.

Comparing the cost of linear rails and rods

In terms of cost, CNC linear rails are pricier. A quick search online shows that a set of four CNC linear rails can cost anywhere from $100 to $300, while a set of four linear rods can cost as little as $75. However, there are a few things to keep in mind when considering the cost.

First, CNC linear rails will last much longer than linear rods – so over time, they may actually end up being the cheaper option.

Second, CNC linear rails offer higher precision than linear rods – so if your project requires extreme accuracy, they may be worth the extra investment.

Third, it’s important to keep in mind that CNC linear rails are easier to use than linear rods because they can be mounted directly onto a CNC machine without having to create any attachment brackets or purchase additional parts. This may not seem like a big deal, but if you’re working on multiple projects and have an assembly line setup, every little bit of time counts – so using linear rails can save you both time and money in the long-run.

Finally, rails simplify cutting software by only requiring one type of motion (linear) rather than two (linear and rotary for rods). This allows you to simplify your workflow significantly and can even enable you to cut faster, which is time-saving and cheap.

CNC linear rails are better than rods

In general, CNC linear rails are more precise, durable, and easier-to-install compared to linear rods. However, linear rods may be a better choice for lighter-duty applications or projects on a tight budget. Ultimately, the best option for your project will depend on your specific needs and requirements.

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