Linear Slides

About Linear Slides and Linear Slide Manufacturers Including: Ball Bearing Slides, Dovetail Slides, Linear Stages, Machine Slides, Roller Slides, Roller Tables & XY Tables.

Linear slides are devices which travel along linear bearings to provide precision linear motion for many different types of automated machinery. Motorized linear slides, such as machine slides, XY tables, roller tables and some dovetail slides are bearings which are moved by a drive mechanism; not all linear slides are motorized, and non-motorized dovetail slides, ball bearing slides and roller slides provide low-friction linear movement for equipment powered by inertia or by hand. All linear slide movement provides linear motion based on bearings, whether they be ball bearings, dovetail bearings or linear roller bearings. Advanced linear slides, such as XY tables, linear stages and machine slides, may be built and configured to provide movement along multiple axis.

The precisely controlled automated movement required by robotic assembly machinery, automatic packaging equipment, CNC machining equipment and CAM automated machines is provided by linear slides. Precision eyeglass assembly, testing, gauging, robotic welding, instrumentation and many other precision processes use either rotary tables (which are restricted to circumferential movement around a rotary wheel), roller tables, machine slides or multi-axis X-Y sliding tables for movement. The linear motion provided by linear slides allows equipment to move precision distances along x, y and sometimes z axis, giving automated equipment an extensive range of movement. Controllers and engineers calculate and program specific coordinates for automated equipment movement based on the linear slides' number of axis.

Dovetail slides, ball bearing slides and roller slides are different bearing configurations. Like all bearings, dovetail slides are comprised of a stationary linear base and a moving carriage. Dovetail carriages have a v-shaped, or dovetail-shaped protruding channel which locks into the linear base's correspondingly shaped groove. Once the dovetail carriage is fitted into its base's channel, the carriage is locked into the channel's linear axis and has free, low-friction linear movement. Ball bearing slides' single axis linear movement is aided by ball bearings housed within the linear base. The carriage slides along the ball bearings with very little friction. Roller slides work similarly to ball bearings, except that the bearings housed within the carriage are cylinder-shaped instead of ball shaped, and roller bearings (or "linear bearings") are often criss-crossed to provide heavier load capabilities and better movement control. Ball bearing slides and crossed roller slides are both capable of handling heavy loads with minimal friction and repair.

Multi-axis linear slides are configured from combinations of dovetail, ball bearing, roller and crossed roller slides. XY tables are flat surfaces mounted on ball bearing slides or roller slides with multiple linear bases. To create multiple axis, linear bases are often stacked on top of one another, with the top "Y" axis acting both as a carriage to the bottom base and as the base which holds the table. These types of XY tables, used frequently for the movement of robotic, are often called "positioning tables". Machine slides and roller tables may have one or multiple axis with shafts or tables which push, pull or position CNC machining equipment or automated assembly machinery. Dovetail slides, ball bearing slides and roller slides move along one axis and may be activated by a drive mechanism, inertia or by hand.

Linear slides cannot provide the power in thrust or torque that linear actuators, pneumatic or hydraulic cylinders can. While linear actuators are built for thrust power, linear slides are designed for precision movement control. Although linear slides must often bear thousands of pounds of equipment weight, horizontal movement along the bearing slides is very low friction, and not much torque is required as opposed to the more forceful physical work done by linear actuators.

Plant conditions are important to consider when choosing a linear slide; most ball bearing and roller slide types require bearing housings to be sealed away from contaminating dirt. Dovetail slides require regular lubrication, as do ball bearing slides and roller slides, although dovetail slides are more resistant to corrosion and contamination. Depending on the weight of the load, ball bearings within XY ball bearing tables and slides can acquire a significant amount of wear, and may need to be replaced regularly.

Linear Slides Images Provided by Velmex, Inc.

Linear Slide Image Provided by Del-Tron Precision, Inc.

Linear Slide Types

• Ball bearing slides, also referred to as "ball slides," are the most common type of linear slide because of their self-lubricating qualities, which increase their reliability. Ball bearing slides, which perform with a smooth linear motion, typically use four hardened and ground shafts that surround the balls at four different points.
  
• Crossed roller slides utilize rollers that crisscross each other and usually move between a group of four semi-flat and parallel rods, which surround them. The design of crossed roller slides allows them to carry up to twice the load of ball bearing slides and to absorb larger impacts.
  
• Dovetail slides are used in high load applications that require long travel distances and/or damping. Dovetail slides consist of a saddle or flaring tenon and a fixed base.
  
• Linear positioners consist of a drive that is attached to a fixed slide base and two extended springs that pull the slide top toward the screw end, against which it is firmly held. As the screw is turned clockwise, it moves the slide top forward along the linear axis, and because of the spring pressure, the screw retracts when turned counter-clockwise, resulting in a smooth linear rotation.
  
• Linear stages are reliable single- or multi-axis mechanical systems that position a payload and consist of few components, including a linear motor, bearings, encoder, limit switches, cable carrier and bellows. Linear motor positioning stages move payloads vertically or horizontally without mechanical transmission devices and at varying rates of acceleration and speed.
  
• Machine slides are precision products used in CNC machining.
• Precision slides consist of a carrier, a base and ways fitted together with a gib and gib screws, which allow for adjustment to ensure accurate movement. Precision slides are basically motion guides that are used to feed and retract parts, tools or fixtures on all kinds of equipment.
  
• Roller slides use perpendicular rollers and have a higher load capacity than ball bearings.
• Roller tables are the quietest type of bearing table.
• Rotary stages rotate on an axis, typically positioned in the center, and provide rotary motion used in positioning and moving objects. Rotary stages are utilized to adjust the roll, pitch and yaw of objects, as opposed to linear stages, which position objects in space.
  
• Standard slides integrate roller or ball guides to permit the engineering of complete systems easily and with a minimum of assembly time.
• XY tables are motorized linear slides, with linear motion based in bearings and driven by a drive mechanism, typically a linear motor.

Linear Slides Terms

Actuator - A mechanism used for controlling or moving an object indirectly, as opposed to manually.
 
Auxiliary Carrier - An optional carrier for linear slides that increases the load capacity.
 
Axial Loading - A load with a force moving along a shaft or another type of axis.
 
Base Mount - To attach linear slides by either fastening directly to "T" slot nuts located in the slide base or by using the base mounting.
 
Bearing - A device whose support allows smooth, low friction motion between two loaded surfaces moving against each other.
 
Breakaway - The minimum amount of force or pressure needed to actuate movement of a device, such as a cable, cylinder or rotary actuator, through a complete stroke.
 
Carrier - A device attached to the linear slide, commonly with a bearing system, and responsible for supporting and moving the load.
 
Center of Gravity (COG) - A single point at which the weight of an object is most concentrated. The object would remain in equilibrium if supported at the COG.
 
Coefficient of Friction - A measurement of resistance of a single object sliding across another.
 
Dead Length - The part of a linear slide or band cylinder that is necessary for mechanisms and mounting. Dead length plus stroke length equals the total length of the linear slide or band cylinder.
 
Deflection - The amount of bend under a specific weight load.

Gib - A wedge-shaped piece of metal or wood designed to hold structural parts in place and/or provide a bearing surface.  

Inertia - The amount of resistance of an object to change velocity. If a linear slide has a large inertia, more torque will be required to move it.
 
Leadscrew - A device that changes rotary motion into linear motion.
 
Proximity Sensor - A device that senses the end of a stroke on a linear slide. Proximity sensors supply signal to any of various controllers.
 
Rotary Actuator - An actuator that provides rotational movement.
 
Rotor - The shaft on a rotary actuator that rotates on its own axis.
 
Shock Absorber - A device implemented with linear slides to decelerate heavy loads at high speeds.
 
Stroke Length - The distance the carrier and its load move on the linear slide.
 
Tenon - A finger-shaped projection that fits into a corresponding hole.
 
Torque - The twisting or turning force that produces rotation.