Have you ever opened a drawer in your desk? Or moved a sliding door? What about operating a conveyor belt in an automation line? With any of these activities, chances are you have used a linear guide rail.
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A linear guide is a block-and-rail system that helps support motion. The linear block moves forward and backward along the plane on which the rail is positioned. The motion is created along the rail via recirculating bearings that are inside the block and making contact with the rail. Linear guides are used in a variety of industries. For example, machine tables use linear guides to move in the X, Y, or Z direction. Due to their ease of movement, linear guides are used to transport objects with a large mass.
There are different types of contact guides used in today’s industry. Rolling contact guides use a ball, roller, or cam roller to move the linear block. Stainless steel ball bearings are used in the ball guide, rotating between the moving and fixed machine parts. The roller guide uses metal rollers to achieve the same motion. For cam rollers, they are supported by ball bearings moving between the parts.
Rolling guides also are classified according to whether or not they have recirculation rolling elements. Rolling elements recirculate within the linear block and move with the block instead of separately, almost like the tracks of a tank. In these cases the stroke is only limited by rail length. In guides that do not contain recirculation, the rolling elements (bearings) move at half the speed of the block. Therefore, they only cover half the distance.
For hydrodynamic sliding guides, both the linear block and the rail are in contact. When the linear block starts to move, a lubrication file starts to gradually form. The film only separates the block and rail completely at high sliding speeds. The machine parts in contact can be metal/metal or metal/plastic. The metal/plastic combination helps reduce friction until the lubrication film is formed.
MINI-X is a line of miniature guide rails for high-tech fields produced by Schneeberger. The line consists of MINIRAIL, MINISCALE PLUS, and MINISLIDE MS/MSQ. The rails are used in applications that require high precision and tight space requirements. Some of the common areas of use are biotechnology, medical technology, robotics, and nanotechnology.
MINIRAIL is a linear guide that offers long-term lubrication, LUBE-S, for maintenance-free operation up to 20,000 km and is available in unlimited rail length. The linear guide has a maximum speed of 5 m/s and an acceleration of 300 m/s2. The tight clearance assembly of the rail and block protects the guide, offering low risk contamination. It is compatible for vacuum operations to 10-7 mbar. The operating temperature range is -40°C to 80°C.
The MINIRAIL comes in both standard and wide sizes. The standard sizes are 7-, 9-, 12-, and 15-mm wide. Each standard size has four different block sizes. The dynamic load capacity range is 645 to 6,200 N. The wide sizes are 14-, 18-, 24-, and 42-mm wide and have two different block sizes available per rail. The dynamic load range capacity is 1,230 to 6,200 N.
MINISCALE PLUS is offers the same design features as the MINIRAIL, but includes an optical incremental measuring unit. The dimensional scale is part of the guideway’s surface with a scale increment of 100 µm. The sensor is built into the carriage and illuminates the dimensional scale, recording the optical signals. Measurements are made as part of the normal operation, reducing errors. The MINISCALE PLUS has the same speed, acceleration, and temperature characteristics as the MINIRAIL. The sizing options are the same as the MINIRAIL.
The MINISLIDE MS uses the Gothic arc profile. The profile offers better contact surfaces with the bearings which provide 15 times higher load capacities when compared to a 90 degree V-profile. The MS guides have a maximum speed of 1 m/s and acceleration of 50 m/s2. Their temperature range is -40°C to 80°C and can operate in a vacuum of 10-7 mbar. The MINISLIDE MS range includes sizes 4- and 5-mm wide with travel distances from 6 to 42 mm. The dynamic load capacity of the MS guide rails is 207 to 1109 N.
The MINISLIDE MSQ offers integrated cage control and a two-row profile guideways, which allow high load capacities. MINISLIDE MSQ guides have a robust cage control system to eliminate cage creep, which is when the cage moves out of the center position due to uneven weight, high acceleration, vertical installation, or temperature differences. The gear rack pinion is integrated directly into the carriages and guideways to help eliminate any creeping.
The MSQ guides have four tracks and are arranged in a circular “O” profile shape, ensuring large inner spacing. The tracks offset by 90 deg. offer even force distribution for high loads. The MSQ line has a maximum acceleration of 300 m/s2 with a maximum speed of 3 m/s. The guides operate at higher temperatures than the MS line with a range of -40°C to 150°C. Their vacuum capabilities are the same as the MS guides. The MINISLIDE MSQ offers sizes of 7, 9, 12, and 15 mm wide with travel distances of 20 to 102 mm. They have a dynamic load capacity of 609 to 4820 N.
Nippon Bearing has added new rails to its slide way product line, featuring the studroller system. The studroller is a new anti-creep concept which adds studs to their current crossed-roller slideways or bearings. Crossed roller bearings work the same as ball-bearing slides, except that their shape is cylindrical. The rollers crisscross each other at 90-deg. angles, moving between two parallel guides. The rollers rest between V-grooved bearing raceways. The crossed roller bearings offer a line of contact versus a point contact found in ball bearings.
The line of contact provides more rigidity and less deformation. Erosion is slower due to consistent contact between the carriage and base. Since the bearings do not recirculate, they do not create a source of vibration. The studroller mechanism is created by adding studs to the center of the cylinder bearings. The studs are retained in place by depressions machined along the path of the rail, ensuring they will not slip. This makes them well suited for vertical- and high-speed applications and helps prevent creeping. The rails are stainless steel and use resin retainers. They are suitable for high-precision applications, including clean-room and medical applications.
Nippon Bearing’s NVS slides consist of a set of four rails, two R-retainers, and eight end pieces. The NVS rails are stainless steel and use resin retainers. The NVS rail contacts are centered. NVS guides can handle dynamic loads of 1,360 to 391,000 N. The guides should be used in temperatures no greater than 80°C.
The Gonio Way RVF rails, also designed by Nippon Bearing, have linear installation faces or blocks that travel on a curved track. They are useful when there is a need to change the gradient or obtain an accurate gradient angle without having to change the center of rotation. The RVF is made of a curved tracking base with ground V-grooves, flat installation surfaces, and curved roller cages. It also uses the crossed roller slideways. The RVF dynamic load capacity ranges from 1,180 to 2,860 N and its operating temperature range is -20 to 110°C.
Curviline is a linear guide rail that offers constant or variable track radii. It uses radial ball-bearing rollers and is ideal for curved machine housings, door systems, or customized packaging applications. The rail can have both straight and curved paths in one rail.
The rails come in two widths: 16 mm or 23 mm. The block was sliders with four rollers arranged in pairs and maintains the preload over the length of the rail. The max operating speed is 1.5 m/s with a max acceleration of 2 m/s2. Zinc plated rail and block can withstand temperatures of -30°C to 80°C. The max load is 1130 N.
An example of hydrodynamic sliding guides is NSK’s SPACEA series, designed for vacuum lubrication, materials, and thin-film technology for space exploration. For vacuum environments, NSK developed E-DFO, a clean lubricant that forms a hydrocarbon oil film on the raceway surfaces of the linear guides and balls. This results in lower particle emissions and outgassing (low mass number versus a low ion current), and has a longer life when compared to existing fluororesin coating or solid lubrication in vacuum environments. The E-DFO coating is clear, colorless, and has a low vapor pressure.
NSK has recently replaced its LH-LS series rails with the new NH-NS series. The NH-NS series has a load rating 1.3 times greater than its predecessor. It also has two times the lifespan. For the NH-NS series, the firm offers the NSK K1 lubrication unit. The NSK K1 combines oil and resin in single unit by impregnating the resin. It is installed at the front of the linear block.
The unit provides maintenance-free operation, adding to the lifespan of the unit. The NH-NS series has smoother ball circulation and a reduced noise level. For example, at a feed speed of 180 m/min, there was a 3 dB noise decrease from 69 dB to 66 dB when comparing LH to NH series. The maximum temperature should not exceed 50°C when using the NSK K1 unit.
The NH series offers a large load rating and comes in six different configurations. The NH-AN and –BN guide lines are square type linear block and have a dynamic load capacity of 11,300 to 246,000 N. The NH-AL and NH-BL have a square low-profile block with a dynamic capacity of 26,800 to 153,000 N. The final NH types are the NH-EM and -GM that have a dynamic load range 11,300 to 246,000 N and are a flange type linear block. The NS series provides a compact low-profile shape. The NS-CL and -AL offer a square low-profile and the NS-JM and -EM offer a low-profile flange block. Both have a dynamic load capacity of 5,750 to 42,000 N.