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Linear Actuators: what they are and how to choose them
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. Helping to produce movements such because the pushing, pulling, elevating, reducing or inclination of a load.
The most typical use of actuators includes combining them with multi-axis Cartesian robot systems or utilizing them as integral parts of machines.
The main sectors:
industrial automation
servos and pick-and-place systems in production processes
meeting
packaging and palletisation
Indeed, just think of applications such as plane, laser or plasma chopping machines, the loading and unloading of machined pieces, feeding machining centres in a production line, or moving an industrial anthropomorphic robot along an additional external axis in an effort to broaden 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 assure when it comes to precision, load capacity and pace, there are various types of actuators to select from, and it is typically the type of motion transmission that makes the difference.
There are three most important types of motion transmission:
belt
rack and pinion
screw
How can you make sure that you select the suitable 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 necessary thing is to consider the issue from the fitting viewpoint – namely the application and, above all, the results and efficiency you're expecting. As such, it is worth starting by considering the dynamics, stroke size and precision required.
Let’s look at these in detail.
High Dynamics
In lots of areas of industrial design, resembling packaging, for instance, the demands made of the designer fairly often should do with pace and reducing cycle times.
It is no shock, then, that high dynamics are commonly the starting point when defining a solution.
Belt drives are sometimes the best solution when it involves high dynamics, considering that:
they permit for accelerations of up to 50 m/s2 and speeds of up to 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 line with the type of lubrication, these systems can provide particularly long 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 are usually a wonderful solution, as they allow for accelerations of as much as 10 m/s2 and speeds of as much as 3.5 m/s on potentially infinite strokes.
The selection of a different type of actuator would not guarantee the same outcomes: a screw system, which is undoubtedly a lot more precise, will surely be too gradual and would not be able to deal with such lengthy strokes.
Lengthy Strokes
Systems created by assembling actuators within the typical X-Y-Z configurations of Cartesian robotics usually, in applications such as pick-and-place and feeding machining centres along production lines, have very long strokes, which may even attain dozens of metres in length.
Plus, in lots of cases, these lengthy strokes – which often contain the Y axis – are tasked with dealing with considerably heavy loads, often 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 definitely an actuator with a rack and pinion drive, considering that:
thanks to the rigidity of the rack and pinion system, they're capable of operating along doubtlessly unlimited strokes, all whilst sustaining their inflexibleity, precision and efficiency
actuators with induction-hardened metal racks with inclined teeth 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 a number of carriages, each with its own motor, permits for numerous unbiased vertical Z axes.
A belt system is right for strokes of as much as 10-12m, whilst ball screw actuators are limited – within the case of lengthy strokes – by their critical speed.
Positioning Repeatability
If, alternatively, the designer is seeking maximum precision – like in applications such as the meeting of microcomponents or certain types of dealing with in the medical area, for example – then there's only one clear selection: linear axes with ball screw drives.
Screw-driven linear actuators provide the very best efficiency 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-driven actuators, which both reach a maximum degree of positioning repeatability of ±0.05 mm.
Website: https://www.firgelliauto.com/collections/linear-actuators
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