Electric Linear Actuators.

I like what I've found at the link that you posted. Thank you.

GA from me

Nice link,

GA

thanks,

phoenix911

It is true that the advance of electric cylinders -made possible by the evolution of PM (rare earth PM) and electronic controls (microprocessors) - is impressive. Never the less the diversity of the applications puts some limits to the full replacement at least for the technology level of to day.

One of the limitations is the power density to which the miniaturisation is connected, the other is the need of the conversion electric power to mechanical power on the spot which increases also dimensions and cost per unit. A 3rd aspect is the power/unit which is in some applications not possible to obtain with electric cylinders. Especially when high force and high speed are requested the electric cylinder is not everywhere competitve with pneumatic or hydraulic units. Maintenance cost is an other aspect since a pneumatic ram well designed will need only a seals replacement, an electric cylinder requires the replacement of the spindel and the nut (most loaded components) and this costs much more.

I think that all technologies as electric, pneumatic or hydraulic have their reasons to exist and their niches where they could not be avoided. I am well placed to say this since I worked and stll work in the servohydraulic/ servopneumatic and servoelectric field with all connections to measurements (force, pressure), controls (proportionnal valves of both kinds single or more stages) and last but not least controls, I am involved in what is today called mechatronics.

In fact the choice of a drive should be made without any a priori with the only goal to have the optimal solution. Unfortunately it is not the case due to either too narrow specialisation or tradition of the company, the choice is biased and not all solutions are optimal by far. The optimal solution in fact depends on the application.

I may give you an example if you have to lift a mass of 1kg (I am from Europe so that for me metric units are more familiar) one has a choice for the actuator between the 3 technologies depending on the rest of the system the choice can either be monotechnology or not. If you have to move a mas of 10kg and the cost is a problem then the choice stays between electric and pneumatic solutions again depending on several criteria as number of units per system, aso. But if you have to lift 600 T the choice is limited to hydraulics and even more limited to high pressure hydraulics (600 to 1000 bar). I practiced all technologies and again it is an error to focus on only one.

Bud went more into circuits I was less in circuits involved and much more in the concept of the components.

I've worked with hydraulics, pneumatics and electrics, and would suggest becoming familiar with all three. Linear actuators are replacing pneumatics in many applications, but for simply slamming a cylinder from one end to the other (with positioning handled by mechanical stops) pneumatics is hard to beat, form a (short term) cost perspective. Efficiency of electrics is much better, but on an actuator-by-actuator basis, it is hard to come up with a cost justification, given that pneumatics are typically available all around the plant. If one were starting from scratch, it might be possible to make a case for very limited use of air, but often pneumatic functions are essentially irreplaceable -- an obvious case being various "blow off" functions used to separate a piece of material from a roller, etc.

So, I don't think pneumatics will be replaced completely by linear actuators, (and certainly, the change will not be as dramatic as some vendors of linear actuators would like you to believe -- effective linear actuators have been around for decades already, after all) but we will increasingly see linear actuators in use.

I think it is important to be conversant in all three technologies, both from a design and maintenance standpoint.