A life of a modern inhabitant of the Earth is surrounded by versatile electronic devices and mechanisms to facilitate daily routines. As a rule, we do not pay much attention to such trifles like sliding doors, lift tables or chairs, and other solutions of motion control. Yet, they are knit together by a common element known as an actuator.
A driver is another name for that element. In other words, the tool induces a straight movement. In that context, movement can denote ejecting or retracting, elevating or lowering, pulling or pushing etc. If you look around, you will see a variety of solutions when actuators are deployed in both household use and commercial application.
How linear actuators work
Unfortunately, the said technology enjoys no popularity among regular people. Besides, the name “actuator” is often unknown to the public. Such variations as “activators”, “movers”, “pistons” and others are usually used instead. However, how you feel comfortable to name linear actuators does not matter. The most important thing is a proper operation. And it is a very interesting issue.
Hand mechanisms relied upon the conversion of manual operation into a motion namely pulling the rod in or out. The twenty-first century tends to replace manual power with electricity. On that account, meet an electric actuator’s heart namely the motor. However, the energy processing results in a rotary movement but a linear one. So, there is why another essential element is required.
Lead screw rotates either clockwise or counterclockwise, which makes the shaft to either extend or retract. In other words, the shaft acts as a nut on the screw. Indeed, if you rotate a nut to the right, it gets deeper and vice versa if you need to unscrew it.
So, pieces of the puzzle begin to come together. We have a DC motor (or other option like a stepper one) that rotates a lead screw, which, in turn, moves a rod in or out. Such simple structure can be improved by adding other elements to increase either the force or the velocity. For example, gearbox between the motor and screw is used to make your linear movement faster or slower according to your demands.
Main linear actuator parts
We have already reviewed the working concept of the said technology and mentioned all the constituent elements. Still, it is essential to have a detailed focus on each part to know all possible flaws and benefits. So, let’s start with the heart of an electric actuator.
The acronym is referred to direct current rather than District Columbia or Depth Control. I’m sure you know that. That component is where all the magic begins. Electric power comes from a source of energy (battery) with a subsequent conversion into the shaft revolution. DC motors differ by type and capacity.
Besides, each unit is composed of a rotor (1), fixed coil (2), commutator (3), and the mentioned motor shaft (4).
- is the rotating inner part of the actuator’s heart.
- is a unit to generate a stationary magnetic field.
- is the connection of electric magnet to the coil. There are two connections to change the electric polarity.
- interconnects the rotor and gear.
That is how the process looks like. Electricity comes to the fixed coil and induces the current flow directed to the rotor. The magnetic field produced by the interaction of these parts derives revolutions.
You may encounter that element under the name of a spindle as well. It extends or retracts the inner rod creating a linear motion. Thread of the lead screw can differ in accordance with load and speed requirements. V-shaped and square-shaped solutions are the most performant for that element. These are characterized by a high lift effectiveness and low level of friction. Trapezoidal shape, which you might encounter under the name of ACME is less effective but has a larger bearing capacity.
Rod That Extends and Retracts
A tube usually represents the extending/retracting rod. It is made of a robust material (aluminum or steel). That part is the external point of contact. It is run into the threaded drive nut. Extension and retraction are performed when the nut gets to the left or to the right of the screw.
A limit switch is an element to stop the shaft in extreme positions. In other words, it controls the rod in a fully pulled in or out position. It is important to understand that it is done not physically but electrically by cutting power supply to the DC motor. Its function is to prevent the rod from over retracting or overextending.
Manufacturing Process of Actuators
If you want to learn the manufacturing process of Lamborghini or Cadillac, you go to YouTube and enjoy a profound content with a detailed description of principle stages. Unfortunately, such opportunity is not available for the said useful tools. However, technological operations of most electronic devices have much in common. Thus, a typical linear actuator manufacturer has to come through the following stages.
Almost any manufacturing process begins with the drafting or designing of a certain product. During this stage, all necessary calculations on elevating capacity, velocity, extension/retraction, duty cycle and other specifications are performed.
This stage includes the elaboration of test samples and their exploitation in conditions that correspond to the intended purpose. During tests, versatile potential defects are detected and fixed in the following samples. The testing procedure is deemed successfully accomplished when no defects were detected in the test sample. The product is approved for production.
We have described all major parts of the said mechanism. At the same time, production of linear actuators denotes an assembly of all constituent parts. Today, it is a common practice that versatile elements are procured from other manufacturers. However, certain producers may diversify their operating process and concentrate the building of all parts by using own resources and at one place.
Yet, a detailed assembly procedure is introduced below:
- DC motor is fastened within a casing. The shaft is attached to the screw by means of the gearbox;
- The screw enters the rod, which retracts to the full extent;
- Lubrication of all moving parts is performed. On certain facilities, lubrication may be accomplished before the connection of moving elements;
- Connected elements are placed in the casing. The lack of looseness and extraneous material is verified;
- Internal space of the casing is filled with lubricating and electrically insulating liquid;
- Movable supporting portion and motor are submerged in the liquid;
- The procedure of preventing the formation of bubbles between the movable supporting portion and the liquid is performed. The procedure foresees decelerating the liquid before the completion of the step of filling;
- Solder joint of the casing is the final assembly stage;
- After the assembly, a product-proof test should be performed.
Here is a rough description of how the described devices are being built. Certainly, the more complex structures are characterized by a larger set of constituent parts and specific operations.
Linear actuator supplier and manufacturer are two different notions that should not be confused. However, certain companies like Progressive Automations produce and sell own motion control devices. Such approach to run the business wins consumer confidence and raises the company’s reputation. We hope that regardless of the brand you choose, your actuators will work reliably and for a long time.