Linear Motion - Linear Bearings & Guides
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Linear Bearings & Guides
Developing thrust is only one part of linear motion. The load needs to be supported while it moves. The ideal bearing enables that to happen while simultaneously preventing non-axial motion and minimizing friction and vibration that might degrade performance. As a result, the choice of bearing can make or break system performance.
Linear bearings and guides should be limited to around 20 feet or less. The components do not lend themselves to butt coupling, which makes exceeding 20 feet quite difficult. A wide range of linear bearings and guides exist. Some are stable in all directions while others can only handle moments around certain axes, e.g. yaw but not pitch. Specifying a bearing that addresses only the forces involved can save money. This is where Motion Solutions engineers can help.
Motion Solutions began as a bearing consultancy. The founders chose a lineup of suppliers who produced components capable of delivering the performance they needed. They developed sophisticated equipment and processes to fine tune performance. This has become a part of the core expertise of our organization, and our engineers and technicians still apply these methods today.
We are experts in refitting linear guides for different preloads, and do so in house at our facilities in Southern California. We offer linear guides with in both steel, stainless steel, as well as aluminum. We can also provide customization. Let us know your application and we will be more than happy to help you select the correct linear guide.
Linear bearings leverage rolling elements to deliver smooth motion with good planar running accuracy. Guides can range in size from centimeters to meters. Our skilled staff can fine tune devices for specific characteristics including low friction, no stick/slip, and smooth linear motion even under high-load conditions. Because they can maintain their high-efficiency and high-functionality characteristics for an extended period of time, they meet a wide range of needs, from general industrial to precision machinery.
Caged ball guides provide high-speed operation in all mounting orientations. The use of a ball cage eliminates friction between ball elements. This reduces noise and maintenance while increasing responsiveness. Caged ball guides have a high vibration resistance due to improved damping characteristics and ultra-high load capacities.
Caged roller guides are suited for high-speed applications demanding rigidity, ultra-heavy load capacities, and stable, smooth motion. The use of roller cages eliminates friction between rollers and increases grease retention, leading to long-term, maintenance-free operation.
The more complex the demands of the application, the more refined the solution. Crossed-roller bearings leverage cylindrical rollers instead of balls to increase the surface area supporting the load. Within the bearing, the rollers are positioned orthogonal to one another; hence, the name. This enables the bearings to easily support loads from multiple directions.
Crossed-roller bearings are good for high-precision applications. Unlike the balls in ballscrews, crossed rollers do not recirculate. This property reduces fluctuations in frictional resistance. Static and dynamic frictional resistance are nearly the same. The drawback is that crossed roller bearings are limited in travel to the region with the rollers. Practically speaking, this restricts travel to 300 mm or less.
Tables & Slides
Tables are high-precision, manually operated mechanical positioning components. They encompass a guide or bearing mounted to a base and fitted with a mount for the load; they may also include micrometers.
They provide travel on the order of 25 mm or so with micrometer scale resolutions. Tables typically incorporate crossed-roller bearings making them highly rigid and able to handle thousands of pounds.
Slides are similar to tables, but are built around ball bearings. As a result, they are not as robust as tables. They can carry loads of a few pounds but will deflect if excess load is applied to an edge or a corner. The chief characteristic of a slide is its ability to deliver very smooth motion. Applications include medical devices and laboratory instrumentation.
Round shafting systems act as key structural elements in automation. They consist of one or more round rails fitted with bushings that enable the load to move along the shaft. Bushings typically move axially as well as rotationally. They are not intended to transfer torque.
Bushings are available with a variety of characteristics, including sliding contacts and ball-based contacts. Although they are commonly cylindrical, they can also be arc shaped to enable the bushing to pass over areas of intersection with other shafts. Preload can be adjusted to tune sliding or rolling friction.
Round shafting systems perform many of the same functions as linear guides but in less-demanding systems. They are designed to handle lighter loads, but can provide a cost-effective solution for the right applications. They are very popular in industrial automation, for example.
Ball Spline Systems
Ball splines are specialty linear bearings that combine nearly frictionless axial motion with highly constrained rotational positioning. They consist of a grooved nut that moves up and down a central shaft with matching grooves. Balls run in these splines to enable nearly frictionless axial motion. At the same time, the shape of the grooves and the shaft are such that the nut is rotationally fixed so that it can stabilize the load and/or transmit torque. Ball splines are particularly well-suited to applications with overhung or moment loads.
Caged ball splines benefit from the motion of evenly spaced ball elements to produce high-speed responsiveness. In addition, ball cage technology eliminates the collision and mutual friction of ball elements, reduces operating noise, and decreases production of particulates.
Medium-torque models have large load capacities in the radial and torque directions as each spline on the shaft is held by dual rows of ball elements in order to provide a preload.
High-torque models have an even larger load capacity and negligible angular backlash. These designs increase overall rigidity by providing a preload via dual rows of ball elements that hold each spline in place.
Rotary models are available with gear teeth on the flange circumference for torque transmission, or without teeth to enable unrestricted rotation on support bearings integrated with the outer surface of the spline nut.
Hybrid ball screw/splines have both helical threads and straight splines for rotational and linear motion on the same shaft. The ball screw and spline nuts have dedicated support bearings directly embedded on their circumferences.