Linear Rails

Are linear rails better?

Linear rails produce a high degree of accuracy and stability compared to round rods with linear bearings. They have better mounting, and smoother motion which improves print quality and machine reliability. 

What are linear rails used for?

Linear rails are used in different applications in industrial machine and motion system design. Linear Rails are designed to support the movement and load of a mechanical motion system.

Linear rails are used in different applications. Different levels of stiffness in different directions can have stresses on a given plane, or in some cases you may want the rail to slightly flex in one plane opposed to the other.

• Placing the surfaces for the rollers strategically, for example in a location that is unlikely to get contaminated, or where the maximum force will be applied.
• Curved paths, so that the carriage can move along a line that is not straight.

Accuracy of Linear Rails

Linear rails provide a high level of accuracy and stability compared to round rods with linear bearings or other methods.

Linear Rail Applications

Linear rails are used in different applications.

Different levels of stiffness in different directions can have stresses on a given plane, or in some cases you may want the rail to slightly flex in one plane opposed to the other.

Curved paths, so that the carriage can move along a line that is not straight.

Linear Rail Alignment

• Make sure the linear rails are parallel to each other to prevent binding. 
• Check for flatness and alignment of the paired sets of rails.
• Check the perpendicularity to the mid-plane between the two rails.

1. Make sure the linear rails are parallel to each other to prevent binding. Check for flatness and alignment of the paired sets of rails.
2. Check that the gantry is perpendicular to the mid-plane between the two rails. If the gantry becomes over constrained it will cause the stepper motor to skip steps.
3. Check the Z-axis lead screws aligned and concentric to the stepper motor shafts. If not, mechanical binding may occur. The gantry can’t really tilt, so the linear rails could be damaged over time. It’s important to not over constrain the z-axis, because it can cause z banding. 

Mounting Linear Rails

Linear rails can be mounted along the full length of the rail, rather than the specific area of motion, thus increasing the accuracy of their positioning and rigidity. The contact surface between the rollers and the bearings is flat, cylinders can be used instead of spheres. This minimizes mechanical stresses, and the amount of play within the system. This increases mechanical longevity and allows for increased bearing load. The bearings only allow for one degree of movement.

Linear Rail Mounting

The contact surface between the rollers and the bearings is flat, cylinders can be used instead of spheres. This in turns diminishes the mechanical stresses, and the amount of play, increases longevity and allows for more bearing capacity, among others. Linear rails can be anchored along their full length to aluminum extrusion profiles, thus increasing the accuracy of their positioning, stiffness and their bearing capacity.

Rail Parallelism

The parallelism of the linear rails or linear guide system is key for proper movement of a motion system. As the number of rails and carriage blocks used within a system increases the more important it is to ensure the rails used are parallel. Unnecessary load can result if the the linear rails or linear guide are not parallel within a manufacturer’s specified parallelism tolerance.

Linear Rails Bearings

The bearings on a linear rail provide proper constraint of movement. There must be two rods with linear bearings to provide the same results of linear rails.

Light Weight Linear Rails

Linear Rails Bearings

When it comes to applications of consumer-grade FDM 3D printers the advantage of 3d printers with linear rails is print quality and reliability.

• The mechanical stresses involved in 3D printing are reduced.
• The movement is constrained along a straight path.

While 3d printer designs with rods + linear bearings are cheap, effective, simpler and lightweight, all characteristics that are highly desirable in a 3D printer. In general, linear rails are preferred over rods because they offer greater precision and smoother motion which can  improve print quality and reliability. Specific machine designs benefit from use of linear rails.Depending on the mechanical arrangement of the linear guide system, movement will require rigidity and support from load or gravity.

Linear Rails vs Rods

In most applications, linear rails are prefered over rods. Although, there are specific designs that may benefit from rods. For example, a cantilever arrangement may be better due to linear rails constrain movement in all but one direction, and the orientation offers maximum rigidity against gravity.

While 3d printer designs use rods with linear bearings are cheap, effective, simpler and lightweight, all characteristics that are highly desirable in a 3D printer.

Many of the earlier 3d printers were designed around cheaper mechanical parts such as carbon rods or stainless steel smooth rods which were once commonly used and recommended. As the cost of linear rails become cheaper and cheaper due to the economy of scale and increasing number of buyers and large volume production of manufactures and suppliers. 8mm steel rods and linear bearings are slowly being somewhat phased out but still used on cheap kits found on Aliexpress. 

What are linear rails made of?

Most linear rails are manufactured from hardened steel and are corrosion-resistant. Hard strength steel or stainless steel is a cold-drawn and ground down to the profile shape and assembled to a linear rail carriage block.

How do you use a linear guide rail?

Align and ensure parallelism of the linear guide for proper accuracy. 

Are linear rails worth it?

Upgrading your 3d printer to linear rails will increase the smoothness of the motion and movements along the axis mounted. Linear rails can improve print quality through smoothness and precision which will decrease artifacts found on 3d pints.

How do you repair linear rails?

Here’s the methods to repair linear rails.

1. Clean remove the dirt and grease from the rail and carriage block.
2. Lubricating light machine oil.
3. Run in the carriage along the rail.
4. Replace the stainless steel bearing balls if needed.
5. Clean and polish the rail channels.

What is a linear rail carriage block?

The linear rail carriage block moves along the rail track groove and constrains the components of the linear slide and provides motion with the direction of a specific axis.

3D Printers With Linear Rails

• Workhorse 3D Printer

• Solidcore CoreXY

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