Many modern linear actuators don't look substantially different in form or function from their earliest antecedents, though the precision with which they're produced and the power sources generating the motion have changed significantly over the centuries since the production of the first linear actuator.
It's difficult to pin down an exact date for the creation of the earliest linear actuators, but tools resembling those used in modern machine shops probably arose at some point in the years of the Industrial Revolution, alongside the many other machine tools invented and refined during the period. By the 1800s, English and American machinists, manufacturers, and industrialists were working with a number of tools reliant upon linear actuators.
Several basic types of linear actuator and their close antecedents were invented or standardized through the 1800s with the further evolution of machining, hydraulics, and pneumatics.
If we jump forward to late later half of the 20th century, we see Bent Johnson's invention of the first electric linear actuator in order to improve a friend's wheelchair in 1979. Within a few years, the electric actuator had spread to agriculture and other industries, where it served to revolutionize automation in an assortment of fields.
Today, leaps forward in engineering, materials, and physics have allowed the invention of myriad forms of linear actuator, and the further refinement of various technologies used in the production of actuators. Even the simplest micro linear actuator in 2017 carries centuries of advancements in machining, standards, and materials manufacturing in its design.
Designing and Engineering Linear Actuators
When determining a design for your linear actuator or actuators, there are countless factors to take into consideration. One of the first things you'll need to determine is the viability of standard linear actuator designs for your project. If standard can't be made to work efficiently, it's time to start looking at custom options.
- Input voltage
- Load speed
- Load capacity in lbs
- IP rate
Notable Types of Linear Actuator
Simple linear actuator models, which typically convert rotary motion to linear motion. Normal ball screw actuators, leadscrews, rack and pinion, belt drive, and cam actuators all fall into this category.
Also called hydraulic cylinders, these linear actuators involve a hollow cylinder with a piston inserted into it. The incompressible nature of liquids allows unbalanced pressure on the piston to create linear displacement. This category of actuator includes hydraulic car jacks and similar devices, but more commonly refers to devices leveraging a hydraulic pump for force.
Linear actuators which leverage the property of certain materials to expand with the application of voltage, the piezoelectric effect. You'll see these discussed as ultrasonic actuators and used in the manipulation of fluid films. The relative weakness of the effect make piezoelectric linear actuators a choice for applications requiring highly precise positioning involving short ranges of motion. Repeatability with piezoelectric actuators can also be a concern.
The same basic mechanism seen in various mechanical actuators drives the linear motion of an electro-mechanical actuator, but with the significant difference of using an electric servo motor to generate rotary motion rather than a knob or handle. There are a huge number of variants on the basic electro-mechanical linear actuator, including but not limited to:
- Simplified design
- Standard design
- Compact designs
A type of motor similar to a rotary electric motor, but which utilizes repeated magnetic field structures across the length of the actuator to produce motion. Doesn't require a lead screw for conversion due to the motion of the motor, but offers a fairly low load capacity due to the limitations of the materials used. Viable in many environments which would be otherwise hostile to motors and linear actuators, and significantly long-lasting by nature.
Telescoping Linear Actuator
Various types of specialized actuator used where space is limited. These include, but are not limited to:
- Telescopic cylinder actuator
- Rigid belt actuator
- Segmented spindle
- Rigid chain actuator
- Helical band actuator
The specific application and type of linear actuator you're using may require or suggest the use of various additional components, tools, and accessories.
With electro-mechanical linear actuators, for example, you may need to use speed controllers, digital timers, fuses, monitoring tools, and various other electrical accessories to optimize your use and management of your actuator.
Some makers may also offer customized accessories for adjusting standardized actuators to specific tasks, or for simple convenience and ease-of-use. Make sure to ask your manufacturer about any recommended or available accessories for use with your actuators.
Using Linear Actuators
Because of the wide variety of applications and the myriad fine details of using linear actuators, it's difficult to offer universal instructions for their implementation and use. Follow manufacturer instructions and the advice of your mechanics and engineers for optimal efficiency, efficacy, and safety.
While all linear actuator installations will be different, there are a few key concepts you'll want to keep in mind regardless of any specifics.
- Know all of your goals and and what to expect in advance.
- Familiarize yourself with instructions before putting anything together.
- Follow all manufacturer instructions for all involved parts and systems.
- Check components individually where possible before starting the system.
- If something looks, feels, or sounds wrong, stop and confirm with the manufacturer.
Caring for Linear Actuators
A linear actuator, like any mechanical component, will last far longer and operate far more efficiently if properly cared for.
A linear actuator should be attended to frequently by someone familiar with the component and its function. As a general rule, if something looks wrong, sounds wrong, or feels wrong in operation, it deserves attention--even if it hasn't become a problem yet.
When a linear actuator goes bad, it can go very bad, with implications for the rest of your system. Take the time to identify and resolve problems with your actuators early and they'll cost you far less time and money in the future.
Different linear actuators in different applications and environments have different requirements for lubrication--so make sure you check with your manufacturer and engineers to figure out the best lubrication type and schedule to keep your actuators operating at peak efficiency. This becomes increasingly important the more precise and finely tuned your system is--and the more critical efficiency may be.
If you're using ball screws, for example, you've invested quite a bit to be able to achieve efficiency of 90% or higher; poor lubrication practices will drop that by as much as 85%, leaving you worse off than you'd have been with a naturally less efficient linear actuator.
Linear actuators should be stored in their factory packaging until you're ready to use or install them, to prevent to buildup of dust and other debris on the surface of the unit. How long it's safe to store your linear actuator, and what adjustments or shifting you should do to keep it in functional condition, will depend on the type of linear actuator you're using. Adjustments every few months to keep oil evenly distributed are recommended in most cases, however.
Check in with Manufacturer
If something strikes you as wrong with your linear actuator, your best bet for identifying the problem and resolving it will be to check back with the manufacturer. The detailed specifications of linear actuators lead to quite a few niche problems that a typical mechanic or engineer may not be able to spot and resolve.
Compliance concerns for linear actuators will be on a case by case basis, with the specific requirements and expectations varying between industries, applications, environments, labor laws, and various other federal, local, and industrial regulations. That said, there will always be 'common sense' considerations you'll want to keep in mind to minimize risk and liability.
Because so many linear actuators end up requiring a fair degree of customization to their role, there are few hard standards to go on in the industry.
Outside of the topics we've already discussed, there are a few specifics to keep in mind when shopping for linear actuators—especially if you're going to need to make additional purchases in the future for maintenance, expansion, or ongoing manufacture.
Choosing a Manufacturer
There are two ways to measure the quality of a linear actuator manufacturer: by their quality as a manufacturer in general, and their quality as a manufacturer for your specific needs. Combining the two will get you the best possible outcome for the foreseeable future.
Versatile. A good manufacturer works to make the product you need, not shoehorn your requirements into one of their standard offerings regardless of how well it fits. While you can certainly save time and money by working with standardized equipment, it's not always efficient or effective to do so. Make sure you're working with a manufacturer that understands that and knows how to adjust to its customers.
Reliable. Judging reliability may seem like a difficult thing without committing to a manufacturer, but you can tell quite a bit before you even request an estimate. First, pay close attention to the way support staff communicates with you; do you have to leave a message and wait for someone to get back to you on their own schedule, or do you receive prompt and immediate responses to your inquiries? You should also look at references and look for any complaints against the manufacturer with appropriate groups.
Experienced. Experience counts for a lot in manufacturing linear actuators and related equipment. Because of the wide variety of applications and order types coming through an actuator manufacturer's hands, you want them to be able to quickly and effectively adjust to make your project as perfectly as possible. It's best to avoid being a learning experience for a manufacturer when possible.
Transparency. You should always know what you're getting and what you're paying for when working with a manufacturer. This includes a thorough understanding of what you're paying for shipping, a lack of tacked-on costs after your initial estimate, and clear and concise terms on warranties, guarantees, and support agreements. If there's a delay or a problem, you should hear about it as soon as someone has time to call you--not days or weeks later when they realize they can't cover it up.
Support. A good linear actuator manufacturer should be your first and final stop for information on maintaining and repairing your linear actuator. In a broader sense, you can judge quite a bit about the overall quality of a manufacturer by observing the quality of the support staff managing customers, service requests, and other secondary and tertiary responsibilities. If the customer support isn't adequate, the manufacturing probably lags as well.
Specific application. A suitable manufacturer for your needs will have familiarity with your specific application, or something similar. At absolute worst, they should have more than passing familiarity with the particular type of linear actuator you need for your project. A manufacturer that understands your needs can help you avoid missteps, waste, and errors in production, installation, and operation of your linear actuator. When looking at references, it's best to look closest at those most closely resembling your own needs and expectations.
Logistics. Logistical considerations play a major role in procuring components such as actuators. Make sure your expectations for shipping, handling, procurement, and other factors align well with a potential manufacturer.
Scheduling. Manufacturers don't often have infinite flexibility in their schedules. Make sure their availability generally matches your needs now and in the future, lest you end up put on a backburner while higher priority customers and clients receive their orders.
Volume. If a manufacturer can't keep up with your volume requirements, they're obviously not going to be a good fit. ON the other hand, some manufacturers may require commitments to higher volumes than you're interested in. While there's some leeway here as you could conceivably buy in bulk just to have replacements handy down the line, it's usually best to work with a manufacturer that operates at the same scale you need.