Electric cylinders

[EspElement]

Hello guys I have an application where I need to use an electric cylinder to actuate. It goes on a end of arm tool for a robot to adjust arms in and out. My max load dynamic load on the cylinder will be 3000N - i would like for this to be 2-3 times this if i could as a safety factor. The push and pull strengths will not be critical as the arms will move on cams. We extend the cylinder and then actuate it to a certain position thru timing. The speed isn't critical, somewhere between 5-10mm a second is acceptable.

My past boss didn't know what he was doing and picked out some cheapo cylinders that had a max dynamic load of 1000N. Well it didn't take long for us to get calls about them burning up. Obviously the most cost effective solution would be the best but i understand that you get what you pay for and I want something that will do the job right.

Thanks ahead of time!

 

[TheTick]

We use DeWert and Linak.

 

[EspElement]

Thanks for the refrence i searched the Linak site and found a prospect. Im curious to see the costs

 

[DesignerGuy16]

I was looking for a ~1500lbf type electric linear actuator and ended up settling on a parker 8" hydraulic actuator (with pump built in). Was crazy cheap (~$650/ea, vs $3500/ea), and was much faster and reliable than the electric. Also handles much higher force.

Their sizing is limited, but they are tough little beasts if you can use them and don't need servo type location & control.

James Spisich
Design Engineer, CSWP

 

[EspElement]

Thats interesting, thanks for the tip. I will look into that

 

[ScottyUK]

Rexa do a similar product, although it's pricier than the Parker type. It's also haz area qualified. We used them in continuously modulating service on turbine IGVs and they performed reasonably well. I left before they had been in service long enough to comment on long term reliability. I think Moog may have something similar too, and while I'm sure Moog's product will be of their usual first class quality and performance it will also have a first class price tag.


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If we learn from our mistakes I'm getting a great education!

 

[gerhardl]

If you look at:

http://www.auma.com/cms/AUMA/en/products/linearActuators/1,111003,19338.html

You will find a series of multiturn electrical actuators combined with linear units.

Electrical linear units will have limitations and disadvantages against oil hydraulic actuators:

-speed
-operations allowed per time unit
- total length of operation (longer reach than shown available)
-number of mechanical components
-sometimes (depending on size and application) price

If within allowed limitations lifetime cost could in some cases be equal or better than oil hydraulic.

For some applications it would be impractical or unadviceable to use oil hydraulics, but:

If any of the limitations over is critical (including total price!) I agree that oil hydraulics is cheapest and safest alternative, with the additional advantage that 'normally closed (or open) failsafe operation' can easily be obtained by failsafe solenoid valve and main safe position reached by pressurized oil reservoir or in some cases weight loaded cylinder.

If oilhydraulic systems already exists, it would in most cases be far cheaper to use oilhydraulics if extra capacity is presen. Even by high quality longlife oil hydraulic seperate aggregates necessary the cost could be comparable and in many cases far cheaper, as stated by others.

 

[EspElement]

Well as i stated above this is for an end of arm tool on a robot.. so weight is a big factor as well, i want to be as light as possible (within reason) i got some room to spare. the cylinder cant be much wider than 4" from center

I found a cylinder that seems to fit well

http://www.duffnorton.com/products/linear.aspx

It says it has a static load of 8000N but it doesnt seem to be very discriptive, what are your guys thoughts?

 

[sreid]

Take a look at Exlar

http://www.exlar.com

Quality products.

 

[gerhardl]

If this is a robot arm you also need to take into account any dynamic forces if the rod or extended rod also should move an object on a plane or in free air.

Exlar seems more ready to measure and take into account external forces applied in all directions on the rod.

 

[sreid]

Another high quality source is SKF.

http://www.linearmotion.skf.com/en/0/cat-cat122-Actuation_systems.html

 

[ScottyUK]

Today I find Rotork have a range of electro-hydraulic actuators. If they are as good as their electric actuators they should be quite impressive.



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If we learn from our mistakes I'm getting a great education!