Linear Actuators are a class of mechatronic systems with some unique design constraints. As a result there are dozens of approaches, dozens of vendors, the option of designing the actuator from scratch, and, frankly, a lot of confusion. The problem lies in the fact that the actuator as a subassembly is the combination of a number of separate technologies. This means there are a number of design tradeoffs incorporated into the resulting actuator that must be acceptable in order to use that actuator.
Categorizing linear actuators is not entirely straightforward because many categories overlap. The “motive power” category can be any type of power source, rotary motor or linear motor powered. Linear motor solutions are much more commonplace in linear actuators today due to declining costs for this technology choice. But in a linear motor based actuator, the linear motor is both the motive power and the mechanical transmission at the same time.
Categorizing linear actuators by their mechanical transmission style is another approach. The most common categories are screw type, belt and linear motor. But the motive power for a screw based actuator could be a stepping motor or a servo motor. The stepping motor is predominant because of it’s suitability for positioning, but it may be underpowered for some applications where a servo is needed. So the linear actuator transmission category can have overlaps because of the different motor types that are used in conjuncion with it.
Price seems to be one means of eliminating the ambiguity. Stepping motor and lead screw combinations are popular because they are economical and maintaining 0.001″ accuracy is very easy. Linear motor systems are capable of .5 micron accuracy with little or no friction, acceleration and speed that is incredible, but generally the higher performance comes at a higher price.
But in the end, the selection process is best guided by the criteria of the application. The list is, thankfully, short. Load weight or force that must be generated, speed, accuracy and life expectancy or number of cycles of operation. This last is probably the key determinant in system selection. Long life or high cycling goals lead to linear motors actuators with little or no friction. You have to familiarize yourself with the overall field because the tendency of confusing the technology and the application needs.
At the recent Semicon gathering of manufacturers involved in semiconductor manufacturing, a lot of attention is given to the mechatronic content of machinery. And as far as I have been able to determine from many different market research projects, semiconductor manufacturing is one of, if not, the largest market for mechatronics every. So it’s also not a surprise that a lot of vendors come to the Semicon show with their latest and greatest product offerings.
Among the most interesting, Nanomotion continues to extend the reach of piezoelectric linear motors, yet another technology choice within the linear actuator sphere. Piezo motors have only one moving part, and meet the high precision, high reliability criteria. With increasing usage, there has been decreasing cost for this unique solution, along with superior position feedback technology and excellent packaging for space constrained applications.
In addition, IKO has released a number of new linear actuator assemblies, both screw driven and linear motor driven. They are also showing a number of unique 2-axis configurations one of which is the thickness of a tape reel and is targeted to unloading parts for electronic pick and place machinery.
Brilliant examples of manufacturers continuing to integrate mechatronic technology to make it more convenient for the customer.