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, raising, reducing or inclination of a load.

The most typical use of actuators involves combining them with multi-axis Cartesian robot systems or using them as integral components of machines.

The principle sectors:

industrial automation

servos and pick-and-place systems in production processes

assembly

packaging and palletisation

Indeed, just think of applications equivalent to plane, 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 order to expand 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 velocity, 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 important types of motion transmission:

belt

rack and pinion

screw

How can you make sure that you select the precise actuator? What variables does an industrial designer tackling a new application need to take into consideration?

As is usually the case when talking about linear motion solutions, the essential thing is to consider the problem from the right 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.

High Dynamics

In lots of areas of commercial design, equivalent to packaging, for example, the calls for made of the designer fairly often must do with speed and reducing cycle times.

It is no shock, then, that high dynamics are commonly the starting point when defining a solution.

Belt drives are often the best solution when it comes to high dynamics, considering that:

they allow for accelerations of up to 50 m/s2 and speeds of as much as 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 ranging from extraordinarily small to approximately 200kg

according to the type of lubrication, these systems can offer notably lengthy maintenance 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 an excellent solution, as they permit for accelerations of as much as 10 m/s2 and speeds of up to 3.5 m/s on probably infinite strokes.

The selection of a unique type of actuator would not guarantee the identical outcomes: a screw system, which is undoubtedly much more precise, would certainly be too gradual and wouldn’t be able to handle such long strokes.

Lengthy Strokes

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

Plus, in many cases, these lengthy strokes – which often involve the Y axis – are tasked with handling considerably heavy loads, often hundreds of kilos, as well as quite a few vertical Z axes which operate independently.

In these types of applications, your best option 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 working alongside doubtlessly unlimited strokes, all whilst maintaining their inflexibleity, precision and efficiency

actuators with induction-hardened steel racks with inclined teeth 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, every with its own motor, allows for numerous unbiased vertical Z axes.

A belt system is ideal for strokes of as much as 10-12m, whilst ball screw actuators are limited – in the case of long 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 handling in the medical subject, for instance – then there may be only one clear choice: linear axes with ball screw drives.

Screw-pushed linear actuators supply the best efficiency 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 maximum degree of positioning repeatability of ±0.05 mm.