A linear actuator is a self-supporting structural system capable of transforming a circular motion generated by a motor right into a linear motion along an axis. Serving to to produce movements such because the pushing, pulling, raising, lowering or inclination of a load.
The commonest use of actuators entails combining them with multi-axis Cartesian robot systems or utilizing them as integral parts of machines.
The primary sectors:
servos and pick-and-place systems in production processes
packaging and palletisation
Certainly, just think of applications resembling aircraft, laser or plasma cutting machines, the loading and unloading of machined items, feeding machining centres in a production line, or moving an industrial anthropomorphic robot along an additional external axis in an effort to increase its range of action.
All of these applications use one or more linear actuators. Based on the type of application and the performance that it must guarantee when it comes to precision, load capacity and velocity, there are various types of actuators to choose from, and it is typically the type of motion transmission that makes the difference.
There are three most important types of motion transmission:
rack and pinion
How can you ensure that you select the fitting actuator? What variables does an industrial designer tackling a new application must take into consideration?
As is usually the case when talking about linear motion solutions, the important thing is to consider the problem from the fitting viewpoint – namely the application and, above all, the outcomes and performance you’re expecting. As such, it is price starting by considering the dynamics, stroke size and precision required.
Let’s look at these in detail.
In many areas of business design, such as packaging, for example, the demands made of the designer very often need to do with speed and reducing cycle times.
It’s no surprise, then, that high dynamics are commonly the starting level when defining a solution.
Belt drives are sometimes the ideal solution when it comes to high dynamics, considering that:
they permit for accelerations of as much as 50 m/s2 and speeds of up to 5 m/s on strokes of as long as 10-12m
an X-Y-Z portal with belt-pushed axes is typically capable of handling loads ranging from extremely small to approximately 200kg
in line with the type of lubrication, these systems can provide notably lengthy maintenance intervals, thus making certain continuity of production.
Wherever high dynamics are required on strokes longer than 10-12m, actuators with rack and pinion drives tend to be an excellent solution, as they allow for accelerations of up to 10 m/s2 and speeds of up to 3.5 m/s on doubtlessly infinite strokes.
The choice of a different type of actuator wouldn’t assure the identical outcomes: a screw system, which is undoubtedly much more exact, would definitely be too slow and wouldn’t be able to deal with such lengthy strokes.
Systems created by assembling actuators in the typical X-Y-Z configurations of Cartesian robotics typically, in applications corresponding to pick-and-place and feeding machining centres alongside production lines, have very lengthy strokes, which may even reach dozens of metres in length.
Plus, in lots of cases, these lengthy strokes – which usually involve the Y axis – are tasked with dealing with considerably heavy loads, usually hundreds of kilos, as well as numerous vertical Z axes which operate independently.
In these types of applications, the best choice for the Y axis is certainly an actuator with a rack and pinion drive, considering that:
thanks to the inflexibleity of the rack and pinion system, they’re capable of operating alongside potentially unlimited strokes, all whilst maintaining their inflexibleity, precision and efficiency
actuators with induction-hardened steel racks with inclined enamel which slide along recirculating ball bearing rails or prismatic rails with bearings are capable of handling loads of over a thousandkg
the option of installing multiple carriages, every with its own motor, permits for numerous impartial vertical Z axes.
A belt system is ideal for strokes of up to 10-12m, whilst ball screw actuators are limited – in the case of lengthy strokes – by their critical speed.
If, on the other hand, the designer is seeking most precision – like in applications such as the assembly of microcomponents or certain types of handling in the medical discipline, for example – then there may be only one clear selection: linear axes with ball screw drives.
Screw-pushed linear actuators supply the best performance from this point of view, with a degree of positioning repeatability as high as ±5 μ. This efficiency cannot be matched by either belt-driven or screw-pushed actuators, which each attain a most degree of positioning repeatability of ±0.05 mm.