A linear actuator is a self-supporting structural system capable of reworking a circular motion generated by a motor into a linear motion alongside an axis. Serving to to produce movements such as the pushing, pulling, raising, lowering or inclination of a load.
The most common use of actuators involves combining them with multi-axis Cartesian robot systems or utilizing them as integral elements of machines.
The primary sectors:
servos and pick-and-place systems in production processes
packaging and palletisation
Indeed, just think of applications resembling plane, laser or plasma reducing machines, the loading and unloading of machined pieces, feeding machining centres in a production line, or moving an industrial anthropomorphic robot alongside an additional exterior axis with a view to develop its range of action.
All of those applications use one or more linear actuators. In keeping with the type of application and the performance that it must assure in terms of precision, load capacity and pace, 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 predominant types of motion transmission:
rack and pinion
How can you make sure that you choose the appropriate actuator? What variables does an industrial designer tackling a new application have to take into consideration?
As is often the case when talking about linear motion solutions, the important thing is to consider the difficulty from the appropriate viewpoint – namely the application and, above all, the outcomes and efficiency you are expecting. As such, it is price starting by considering the dynamics, stroke length and precision required.
Let’s look at these in detail.
In many areas of business design, resembling packaging, for instance, the calls for made of the designer fairly often need to do with velocity and reducing cycle times.
It is no shock, then, that high dynamics are commonly the starting level when defining a solution.
Belt drives are often the best solution when it involves high dynamics, considering that:
they allow for accelerations of as much as 50 m/s2 and speeds of as much as 5 m/s on strokes of so long as 10-12m
an X-Y-Z portal with belt-pushed axes is typically capable of handling loads starting from extremely small to approximately 200kg
in response to the type of lubrication, these systems can offer significantly lengthy upkeep intervals, thus guaranteeing continuity of production.
Wherever high dynamics are required on strokes longer than 10-12m, actuators with rack and pinion drives are typically a wonderful solution, as they allow for accelerations of up to 10 m/s2 and speeds of as much as 3.5 m/s on potentially infinite strokes.
The selection of a special type of actuator would not guarantee the identical results: a screw system, which is undoubtedly a lot more exact, will surely be too slow and would not be able to handle such lengthy strokes.
Systems created by assembling actuators within the typical X-Y-Z configurations of Cartesian robotics typically, in applications akin to pick-and-place and feeding machining centres along production lines, have very long strokes, which can even reach dozens of metres in length.
Plus, in many cases, these long strokes – which often involve the Y axis – are tasked with dealing with considerably heavy loads, typically 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 unquestionably an actuator with a rack and pinion drive, considering that:
thanks to the inflexibleity of the rack and pinion system, they are capable of operating alongside potentially unlimited strokes, all whilst maintaining their inflexibleity, precision and efficiency
actuators with induction-hardened steel racks with inclined tooth which slide along recirculating ball bearing rails or prismatic rails with bearings are capable of dealing with loads of over a thousandkg
the option of putting in a number of carriages, every with its own motor, permits for quite a few unbiased vertical Z axes.
A belt system is good for strokes of up to 10-12m, whilst ball screw actuators are limited – in the case of long strokes – by their critical speed.
If, however, the designer is seeking maximum precision – like in applications such because the meeting of microcomponents or certain types of dealing with within the medical area, for example – then there’s only one clear choice: linear axes with ball screw drives.
Screw-driven linear actuators provide the very best performance from this perspective, with a degree of positioning repeatability as high as ±5 μ. This efficiency can’t be matched by either belt-pushed or screw-driven actuators, which both attain a most degree of positioning repeatability of ±0.05 mm.