This article will take an in-depth look at linear motion products.
The article will bring more detail to topics such as:
This chapter will discuss what linear motion products are and how linear actuators work.
High-precision, linear motion goods are essential components at the core of several items which are generally used in machine tools and equipment for manufacturing semiconductors. These items are utilized to glide an object along a straight path. All manufacturers have created high-performance bearings with diverse methods to stop motion from slowing down as a result of the friction that happens during sliding.
A linear actuator converts a motor's rotating motion into a line of motion. Linear actuators travel forward and backward while conventional electric motors rotate in a circle. The device can slide, tip, and lift objects at the push of a button thanks to the push and pull motion. Operators have precise and accurate control over the production thanks to the design. Because of its fluid motion, the linear actuator has a naturally high-energy efficiency and requires little maintenance over its lifespan. They cost less, take up a lot less space, and are simpler to install than hydraulic or pneumatic alternatives.
While not every linear motion design and sizing project will employ all of these principles, having a solid grasp of them can enable one to make more reliable and cost-efficient design decisions.
Six degrees of freedom and seven (or more) axes of motion are possible in some multi-axis systems. It is critical to understand the distinction between the terms "axes of motion (the system of plotting movement of items within the Cartesian coordinate system)" and "degrees of freedom (as described above/shown in the image below).”
We normally use the Cartesian coordinate system for linear motion, but there are some applications that employ the polar coordinate system, notably those that include articulated robots.
Moments or torques can be produced by a force that is delivered at a distance. It's critical to understand the distinction between moment and torque forces as well as what generates each. Moment forces are static, whereas torque pushes a component to rotate.
Roll, pitch, and yaw are the three terms used to describe rotational forces, depending on the axis on which the component rotates. Roll, pitch, and yaw forces can result in deflection and motion problems in linear guides.
A very narrow contact area is created when two surfaces with different radii come into contact and a load is applied. The surfaces then suffer Hertz contact stresses, which have a substantial impact on a bearing's dynamic load capacity and L10 life.
The degree of conformance between the surfaces determines the position and geometry of the contact area in between ball (or roller) and a raceway. It is crucial to comprehend ball conformance since it is intimately related to the level of Hertz contact stress that a bearing receives.
A load-bearing ball (or roller) experiences slip instead of pure rolling motion because the contact area between the load-bearing ball (or roller) and its raceway is an ellipse and the velocity varies at different locations along the area of contact. Friction, heat, and bearing life all have a direct impact on this differential slip.
The fundamental cause of wear and, frequently, failure in linear bearings is friction, which lubrication helps to decrease. Tribology is the study of wear, lubrication, and friction and explains how these three phenomena interact in intricate ways.
In linear motion systems, tension and compression loads cause stress and strain in the materials. These ideas are particularly crucial for parts like fasteners since they could approach their yield point or tensile strength limit before other system symptoms of deterioration appear.
When needed, linear actuators can move an object or piece of machinery repeatedly and exceptionally precisely along a straight path. The need to move a payload linearly from a rotary-based source of movement is the main justification for designing a linear actuator into a system.
A linear actuator is used to convert rotary motion to linear motion because the majority of typical electric motors are rotary-based. In most cases, a flexible coupling or a belt connects the electric motor to the linear actuator, allowing the motor to be positioned either axially or perpendicularly to the linear actuator. Depending on the needs, a range of motor sizes can be fitted to these actuators.
In addition to rotary bearings that support the lead screw, ball screw, or belt pulleys, linear actuators also feature linear bearings that support the moving payload. They can then function as "stand-alone" devices, which makes it simple to mount them into existing machinery and eliminate the need to develop and build incredibly expensive specialized parts.
A linear actuator system can be linked with a payload carried between points, such as in an X,Y gantry-style stage, to boost its load capacity and stability. The two actuators in this situation are frequently kept in sync with one another using a shaft or belt.
This chapter will discuss the different types of linear motion products based on their categories.
The different types under the linear actuators category include:
A lead screw actuator converts rotary motion from a motor to linear motion using a straightforward screw and nut setup. The most popular ways to generate rotary motion are manually-driven screws or AC-induction motors since they are frequently employed in applications that require only low precision but come with a low cost. Because the screw/nut is less efficient than a ball screw actuator, the actuator's capacity to "back drive" is diminished. This can be advantageous in some situations because it keeps the payload still when not moving. Applications where safety and reliability are more important than precision and performance include agricultural equipment and manual lift systems.
A high-precision nut with revolving ball bearings that rotates around a ground screw thread is used in a ball screw actuator. A typical ball race is quite similar to this in concept because the load is transmitted via the rolling balls. High precision and minimal friction are two key benefits of this technology, providing a very effective way to transform rotary motion to linear motion. The rotating motion is often generated by stepper or servo motors. Ball screw actuators are particularly suited to quick, cyclic applications, as well as repeatable indexing, found in machine tools, scientific equipment, and medical systems.
When using a belt actuator, a moving carriage is coupled to a belt that is carried between two pulleys, and, as the belt rotates, the carriage is moved along the actuator. A motor that is typically located perpendicularly to the actuator and coupled using a flexible connection drives one of the pulleys.
Due to their intrinsic lack of variable movement, they provide a more affordable option in most situations that only require linear movement. Applications requiring long travel and high linear speed, such as packing and automated material handling systems, benefit greatly from the use of belt-driven linear actuators.
Hydraulic actuators are typically employed when a lot of force is needed to activate a valve (like the major steam system valves). The most popular type of hydraulic actuator is the piston type. It is made of a stem, hydraulic supply and return lines, a piston, a spring, and a cylinder. The piston divides the cylinder into two chambers by sliding vertically inside it. The spring is located in the upper chamber, and hydraulic oil is located in the bottom chamber.
The lower chamber of the actuator is connected to the hydraulic supply and return line, which allows hydraulic fluid to flow into, and out of, the lower chamber. The piston's action is transferred to a valve by the stem. The valve is initially held in the closed position by the spring force when there is no hydraulic fluid pressure. Pressure in the lower chamber rises when fluid is introduced.
The force produced by this pressure on the piston's bottom is the opposite of the force produced by the spring. The piston starts to rise, the spring starts to contract, and the valve starts to open when the hydraulic force is greater than the spring force. The valve keeps opening as the hydraulic pressure rises. In contrast, as hydraulic oil is removed from the cylinder, the piston descends and the valve closes because the hydraulic force is now less than the spring force. The actuator's ability to supply or drain oil allows the valve to be set between being fully open and fully closed.
There are two types of pneumatic actuators: piston- and diaphragm-operated. Pneumatic actuators efficiently employ compressed air to provide operational energy. Air from the instrument builds up pressure or force that is applied to the piston or diaphragm. This causes mechanical motion by positioning the valve actuator on the valve stem. There are two main reasons why pneumatic linear actuators are propelled by air- because it is safer than other gasses and because it can be compressed and absorbed with ease.
Pneumatic actuators are very common components in the industrial manufacturing sector because of this and the great degree of control that can be exerted over the conversion of compressed air into kinetic energy while using them.
Position control is provided by servo actuators, which use linear motion to uphold the proper operation of another mechanism or piece of equipment. A servo is a simple device that runs by reacting to feedback that detects errors at its most basic level. A servo motor, a set of gears, and an output bearing make up the three primary parts of a servo actuator. They can be powered electromechanically, pneumatically, or hydraulically. However, electromechanical and pneumatic servo actuators are more prevalent than hydraulic ones. The power, speed, and precision requirements of the application determine the best type of actuation.
Valve actuators are devices that use different screw assemblies to give valves linear movement. Depending on the application, this movement is frequently used to position the valve as well as to open or close it. Metering valves, needle valves, globe valves, diaphragm valves, gate valves, pinch valves, and angle valves are just a few of the many types of valves which utilize valve actuators
The different types of linear guides include:
A guide rail and runner blocks make up a ball rail system (BRS). The BRS comprises four rows of balls arranged in an O shape with a 45° contact angle. One or more runner blocks may move along one of the guide rail's four running tracks. Either from above or below, the guide rail can be bolted into position. V-guide rails are pressed into the mounting base.
Depending on needs, the runner block has either through-bores or threaded holes for direct installation to the neighboring structure. Ball runner blocks are offered in a wide range of sizes, designs, and preload classes, making them suitable for a variety of applications. Of all the profiled rail systems, the ball rail system is the most adaptable.
Although the four raceways of linear roller guides employ rollers rather than balls, they function just like other linear rails. The rail and slider now have a substantially larger contact surface. In order to facilitate the movement of machinery or equipment, roller slides are a viable form of the linear-slide system. They are frequently distinguished by their ability to promote quiet, low-noise motion with little slippage and a long lifespan. Roller slide bearings, also known as roller tables, are used In operations that call for both high precision and repeatable movements like food processing and automotive processes.
The miniature version of the ball rail system has been created for a range of applications that call for ball-bearing longitudinal guides with exceptionally small sizes and high load-bearing capacities. More recently, a new design has been created allowing for a great variety of ball diameters. The guide units have exactly the same load ratings in all four directions. Its high load-bearing capability in all directions then affects the torque around the axes. They have little friction and optimal discharge. The runner block and the guide rail are composed entirely of martensitic steel, which resists corrosion.
Cam roller guides are preloaded by the user before installation, unlike recirculating bearings, which have a fixed preload often achieved through ball selection. To maintain rigidity, speed, and performance as application conditions change or components wear, preload can be further adjusted. Since adjustable preload makes bearing blocks and guide rails interchangeable, this also makes replacement simpler.
The majority of motion components utilized in the automation of transfer, locating, and assembly machinery are linear motion products. As we become proficient with linear bushings, three different types of linear guides—linear bushings, slide guides, and oil-free bushings will be contrasted and described. It's critical to first comprehend how performance varies depending on the component's load capacity. A machine that operates on a shaft with both ends bearing a significant load and uses linear bushings or oil-free bushings has the ability to elastically bend the shaft.
In order to establish a linear guide system to support or direct the movement of equipment in a linear fashion, a linear shaft is a straight, precisely machined bar on which linear bearings operate. These bearings are available in aluminum, 303 stainless steel, 316 stainless steel, hardened steel, and hardened stainless steel.
The different types of screw drives include:
The ball screw assembly is made up of a screw, nut, and balls that roll between the helical grooves of the nut and screw to provide the only point of contact between them. The balls are deflected by the deflector into the ball return system of the nut as the screw or nut rotates, and they move continuously through the return system to the opposite end of the ball nut. The balls then continually escape the ball return system into the raceways for the ball screw and nut, recirculating in a closed circuit.
The Planetary Screw Assembly (PLSA), sometimes known as a roller screw, is a high-performance, low-cost screw drive system that employs precision-ground threaded rollers (planets) that revolve around the screw to transform rotational motion into linear motion. They are simple to integrate into applications that require great load capability, precision, and low environmental impact because of their compact design.
The different types of ball transfer units and tolerance rings include:
Ball transfer units are omnidirectional load-bearing spherical balls positioned inside a restraining device. They operate similarly to a computer trackball in theory (pointing device). A single, giant ball is typically supported by several smaller ball bearings in the design. They are frequently used in an inverted ball-up posture, which is a form of a conveyor system where items are quickly transferred over a number of units. This enables manual transport to and from machines, as well as between other conveyor system parts. They are utilized in business as a component of industrial systems or in airports for the delivery of luggage.
Tolerance rings are a specially-made part with waves or other features that connect cylindrical mating parts. The waves constrict to hold the parts in place as the tolerance ring is put together between them. Each wave functions as a spring, the more force it generates, the more compression it undergoes. In addition to meeting other performance standards, such as the load it must withstand, this force maintains the components together.
The different types of linear axes include:
Due to their small size, compact modules are differentiated by their great power density. The Compact modules are easily identified from the outside by their comparatively flat construction. All varieties have a width to height ratio of about 2:1.
A linear module is a mechanical device that produces linear motion. It can be applied either vertically or horizontally. It can also be coupled to create a particular motion mechanism, such as the multi-axis motion mechanism known in the automation industry as X,Y axis, X,Y,Z axis, etc. A power motor is typically used in conjunction with the linear module. By mounting other necessary workpieces on the slider to create a complete conveying motion device and configuring an appropriate motor's forward and reverse program, it may be utilized to automatically reciprocate the workpiece. Consequently, the goal of equipment mass production and intensive manufacturing is achieved.
These modules serve as high-precision, extra-strong drive units with incredibly tiny dimensions. Integrated ball-rail technology provides optimal travel, large load capacities, high precision, and stiffness. Thanks to the ball screw assembly and backlash-free nut system, there is high positioning precision and repeatability. A double-floating bearing system, big screw diameters and leads, and ball rail systems enable fast movement speed while maintaining high precision.
Ball rail tables are precise, pre-installed guiding systems with top-of-the-line capabilities in small packages. Due to the modular design principle and appealing price/performance ratio, practical combination possibilities, ball rail tables are utilized for a wide range of application areas. For virtually any application, there are ball rail tables with ball screw drives that can be built flexibly as a completel drive system. Ball rail tables with linear motors are available as a fully-integrated, ready-to-install linear motor system for design engineers. Over the course of the service life, movement is precise and dynamic because thrust is produced directly on the load. Because there is no transmission and no mechanism to convert rotary motion to linear motion, there is considerable stiffness.
Omega modules (OBB) may help produce speeds up to 5.0 m/s with ball rail systems featuring tooth-belt drives. Omega modules are freely customizable linear axes in lengths up to 5,500 mm that are ready to be installed in any installation position. Omega modules are especially well-suited for situations where the frame extends into the working area because of the constructive nature.
The accurate, ready-to-install linear motion systems known as "feed modules" offer great performance and compact dimensions. They are particularly well-suited for handling activities that demand high levels of force and torque transmission while also requiring high levels of precision. Feed modules are perfect for vertical motion in z-axes due to their low moving system mass.
Linear slides are another type of bearing that enables frictionless motion along a single axis. They are also known as linear guides or linear-motion bearings. Moving parts in a straight line along any of the three-dimensional axes is frequently necessary for machine tools, robotics, actuators, sensors, and other mechanical equipment. Friction, the force created when two bodies move in opposition to each other when in touch with another object, always opposes unrestricted translational motion. The load operating on the surface in contact and the surface characteristic known as the coefficient of friction determine how much frictional force is applied.
A shaft, a nut with balls, and a bearing make up a ball screw. The screw unit transmits the force between the screw and nut with the help of the balls. A motor's spin is efficiently transformed into linear motion. Therefore, driving components for all types of linear guides frequently use ball screw units. Most of the time, the nut is attached to the moving part when the shaft is being powered. In other situations, the screw really performs the linear movement while the nut is powered.
An extensive range of items are covered by the linear actuator, which is a key component of linear-motion control. A mechanical device known as a linear actuator can apply forces by converting energy from sources like air, electricity, or liquid into motion in a straight line.
Multi-axis systems vary in the kind, size, and arrangement of the combined axes and are composed of combinations of directly-driven linear modules. The utilization of two-axis combinations or three-axis portals depends on the automation task. Systems come in a variety of sizes depending on the needs of the application (load, stroke, dynamics and speed of positioning). For precise placement, axis systems provide at least two linear directions of movement. For various target applications, there are many series. Successful system integration is based on a high degree of positioning, repetition, and movement dynamics accuracy. With incredibly fast control cycles, multi-axis systems enable incredibly precise cutting and positioning operations.
Captive linear actuators that use electric cylinders (also known as electromechanical cylinders) are created as a modular system. Electric cylinders are quickly replacing pneumatic cylinders in a variety of industries due to decreased maintenance costs, improved motion control, and a lengthy list of additional advantages. Internal guiding and anti-rotational capabilities on this incredibly adaptable, linear-motion component are perfect for z-axis and z-theta dual-axis systems. An electric cylinder also has a tubular structure that protects the leadscrew or ball screw from debris and other environmental influences, enabling it to function in challenging circumstances.
This chapter will discuss the different considerations when choosing linear motion products.
In general, these consideration for selecting linear motion products can be categorized into:
In general, a ball screw or linear motor-driven system will be the primary choice if a system needs great precision or repeatability. Additionally, a belt or pneumatic actuator may be thought of as a feasible alternative if the needed accuracy is rather modest. However, these generalizations run the risk of producing a system that is either underwhelming or overly costly.
The inclusion of gearboxes, couplings, connecting shafts, as well as the system's deflection and temperature fluctuations, are only a few of the many elements that impact a system's precision and repeatability. When establishing the needed accuracy and repeatability of a linear system, it's crucial to take into account all of these factors as well as the kind of feedback and control system being employed. A typically "lower accuracy" device, such a belt-driven actuator, may be useful for an application that demands a high level of precision and repeatability by adding external feedback, like a linear scale. Additionally, basic servo controls, like the lead deviation of a ball screw drive, can correct for anticipated errors in travel.
Only the base (usually "X") horizontal axis will be completely supported in gantry and Cartesian applications. The Y axis in gantry arrangements will only be installed at the ends, leaving a significant length between the mounting points unsupported. Similar to this, in Cartesian designs, the secondary horizontal axis (usually "Y") will only have a mount on one end and be supported along just a small portion of the length.
Unsupported actuator deflection may result in binding and early wear. To do beam deflection calculations, however, it is frequently rather straightforward to describe the actuator as a beam and the load as either a point load or a uniform load. The results of the estimated deflection may then be compared to the manufacturer's recommended maximum deflection.
Contaminants such as dirt, dust, chips, and liquids can all have a detrimental impact on how well a linear system performs. A system with strong seals or sealing mechanisms, like a linear actuator with a firmly maintained cover, should be employed to guard against these. To avoid the entry of pollutants, the system can also be put on its side or upside down. However, you should be aware that the actuator's orientation will affect the loads and forces acting on the drive and guiding mechanisms.
The temperature, or more particularly, temperature difference, in the working area, is one environmental aspect that is frequently disregarded. The expansion and contraction of various materials might become troublesome when an actuator is utilized in a location that can experience large temperature variations as a consequence of ambient circumstances or as a result of the process being carried out. For instance, aluminum has about two times the thermal expansion coefficient of steel. Accordingly, binding or unneeded stress may occur when an actuator with an aluminum base and steel guides is utilized in a setting with extreme temperature changes.
Common methods of mounting linear actuators include clamps on the actuator's sides, holes drilled through the housing's base, or mounting slots in the housing. The mounting method may have an impact on deflection in addition to the space required for the actuator. Actuators may be pinned in addition to being clamped in high-accuracy gantry or Cartesian configurations to guarantee parallelism and perpendicularity between axes. The simplicity of servicing a particular system will also depend on the mounting arrangement. A system that is simple to install and remove will be simpler to maintain or replace, which can cut down on unneeded downtime.
The majority of actuators need only simple lubrication, which involves applying grease or oil to parts that come into touch with other metals. The simplest way to lubricate an actuator is through one or more central ports that supply lubricant to all required parts. However, some layouts make central lubrication impractical. It is also possible to lubricate each component individually, although this requires simple access to the various lubrication fittings. Sometimes, there is a chance that the user will decide it's too much bother and forgo using sufficient lubricant, resulting in potentially-expensive issues in the future.
The actuator's location for lubrication access is another thing to think about. A different lubrication technique or mounting arrangement will need to be developed, for instance, if the actuator's side lubrication ports are blocked by other components.
This chapter will discuss the applications and benefits of linear motion products.
Some machines, which are often utilized in machine tools and equipment for producing semiconductors, are built with high-precision linear motion products. The core purpose of linear motion products is, simply, to help move products along a straight line. High-performance bearings have been developed by numerous manufacturers using various techniques to help prevent motion from slowing down as a result of the friction that occurs during sliding.
The rotating motion of a motor is transformed into a line of motion by a linear actuator. While traditional electric motors revolve in a circle, linear actuators move in forward or reverse directions. Their push and pull motions allow these gadgets to slide, tilt, and lift things with the touch of a button. Because of their design, operators have precise and accurate control over the production process.
A linear actuator is a device that transforms rotational motion into push or pull linear motion, which can then be used to lift, lower, slide, or tilt machinery or materials. They offer effective, maintenance-free motion control...
Electric actuators are devices capable of creating motion of a load, or an action that requires a force like clamping, making use of an electric motor to create the force that is necessary...
A linear actuator is a means for converting rotational motion into push or pull linear motion, which can be used for lifting, dropping, sliding, or tilting of machines or materials. They provide safe and clean...
A linear actuator actuates, moves, in a linear, straight, line to complete or start a process. There are a variety of terms used to describe a linear actuator such as ram, piston, or activator. They are very common in...
Ball screws are mechanical linear actuators that consist of a screw shaft and a nut that contain a ball that rolls between their matching helical grooves. The primary function of ball screws is to convert rotational motion to linear motion. Ball nuts are used in...
A lead screw is a kind of mechanical linear actuator that converts rotational motion into linear motion. Its operation relies on the sliding of the screw shaft and the nut threads with no ball bearings between them. The screw shaft and the nut are directly moving against each other on...
Linear bearings are a type of bearing that "bear" or support the load of the carriage during its single-axis linear movement and provide a low friction sliding surface for the guide rails. In a linear guide, the carriage is the component that travels in a straight line, back and forth, along the length of the guide rail...
Linear Rails are ideal for moving items through a production process with great precision and as little friction as possible if creating, packing, and distributing products. Linear Rail is a type of gadget that...
Linear slides, also referred to as linear guides or linear-motion bearings, are types of bearings that allow smooth and near-frictionless motion in a single axis. Machine tools, robots, actuators, sensors, and other...
A roller table is a small, stiff, limited linear guide device with an integrated cross-roller guide. Electrical or mechanical drive systems are frequently used to move a roller table, making it easy to transfer heavy loads...