A linear actuator is a self-supporting structural system capable of remodeling a circular motion generated by a motor into a linear motion along an axis. Serving to to produce movements such because the pushing, pulling, raising, reducing 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:

industrial automation

servos and pick-and-place systems in production processes

assembly

packaging and palletisation

Indeed, just think of applications reminiscent of 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 the intention to increase its range of action.

All of these applications use one or more linear actuators. According to the type of application and the performance that it should assure by way of precision, load capacity and speed, there are numerous types of actuators to choose from, and it is typically the type of motion transmission that makes the difference.

There are three primary types of motion transmission:

belt

rack and pinion

screw

How can you make sure that you select the appropriate 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 essential thing is to consider the issue from the precise viewpoint – namely the application and, above all, the outcomes and efficiency 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.

High Dynamics

In many areas of industrial design, corresponding to packaging, for example, the demands made of the designer fairly often should do with pace 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 perfect solution when it comes to 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 as long as 10-12m

an X-Y-Z portal with belt-driven axes is typically capable of handling loads starting from extraordinarily small to approximately 200kg

in response to the type of lubrication, these systems can supply particularly 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 a superb solution, as they permit for accelerations of up to 10 m/s2 and speeds of as much as 3.5 m/s on doubtlessly infinite strokes.

The choice of a unique type of actuator would not assure the identical outcomes: a screw system, which is undoubtedly a lot more precise, will surely be too sluggish and would not be able to handle such long strokes.

Long Strokes

Systems created by assembling actuators in the typical X-Y-Z configurations of Cartesian robotics typically, in applications resembling pick-and-place and feeding machining centres alongside production lines, have very lengthy strokes, which can even reach dozens of metres in length.

Plus, in lots of cases, these lengthy strokes – which often involve the Y axis – are tasked with handling considerably heavy loads, usually hundreds of kilos, as well as quite a few 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 rigidity of the rack and pinion system, they are capable of operating along probably unlimited strokes, all whilst sustaining their inflexibleity, precision and efficiency

actuators with induction-hardened steel racks with inclined tooth which slide alongside recirculating ball bearing rails or prismatic rails with bearings are capable of dealing with loads of over one thousandkg

the option of installing a number of carriages, each with its own motor, allows for numerous impartial vertical Z axes.

A belt system is good 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, on the other hand, the designer is seeking most precision – like in applications such as the meeting of microcomponents or certain types of dealing with in the medical field, for instance – then there may be only one clear choice: linear axes with ball screw drives.

Screw-pushed linear actuators offer the very best efficiency from this point of view, with a degree of positioning repeatability as high as ±5 μ. This performance cannot be matched by either belt-pushed or screw-pushed actuators, which each reach a maximum degree of positioning repeatability of ±0.05 mm.