Small actuator/piston Design

[deesnyas]

Hey peoples Im having issues with a design regarding a small actuator. I looked to buy one but all to expensive and too big. I only need a 1 to 2 inch stroke and I know firgelli automation offers one but starts at about 6 inches way too big. It'd be best to fit in a 5 inch cube enclosure.
Here are the specs
-Fit in 5 inch cube box (small-total height with stroke less than 5 inches)
-1 to 2 inch stroke
-about 15 lbs lifting force
-relatively fast

Any help would be appreciated even if just a forward to another thread

 

[Boncuk]

You can go either way:

pneumatic or electric.

Festo pneumatics has a widespread offer of miniature cylinders, single pressure or dual pressure (double piston for push/pull)

The electric way would be a solenoid, also available as single action or push/pull devices.

If power is an issue I suggest to use pneumatic cylinders. They can be operated at pressures up to 7bar (112PSI).

Boncuk

 

[deesnyas]

Thanks much for your reply. I have looked quite a bit at pneumatics but they require air pressure of which could come from a small compressor but my project is to be a compact design and the noise of the compressor might also be an issue.

Solenoids get very large and expensive when looking at more than 1 inch and over 10 lbs.

Electric seems nicest but there are no strong short-small actuators i have found...

More suggestions my friends

 

[superfrog]

the largest size model servo should just about fit the bill I believe, but you would be at the limit of the reasonable working envelope, plus it would not be very good at holding.

You probably would be better off with some kind of threaded rod/motor system. Maybe some kind of machining leadscrew with end travel switches?

 

[deesnyas]

Yeah that is good only i have been staying away from making my own because I need it to be as low maintenance as possible and it would eventually require oil, unless it is some type of self sustaining system. I would rather buy one instead of design one, or design one that isn't requiring maintenance. Not being lazy just practical.

 

[Mr RB]

I would use a windcreen wiper motor, with a short lever on its output shaft. Low cost, very rugged with plenty of power and speed available.

You could even attach a pot on its shaft too since you only need about 45' or 60' total rotation.

 

[Boncuk]

Yet another idea:

Using a threaded iron rod (M8 to M12) and connecting geared motor to it you can drive the nut at high speed and have a lot of power.

I built such a device for a model sailboat winch to avoid entangled cables when passing through the wind. (Don't know the English term. The maneouver is turning the boat through tailwind - Halse)

The sail has be pulled almost alongside the boat to be released quickly when turning through the wind.

The higher the M-value of the rod the steeper the thread. M12 makes about 2mm per revolution.

To avoid jamming of the nut when the maximum length is reached remove the thread at both ends of the rod and use push springs to press the nut onto the thread again when reversing rpm, about like this (attachment).

Boncuk

 

[superfrog]

You certainly do not want a triangular thread, you want a square thread for this application. That saida triangular one might just work fine.

 

[stevez]

I'd agree that an Acme or square thread might be preferred and also agree that a common thread might be sufficient. Worth noting is that McMaster-Carr, MSC and other suppliers (who sell small quantities) have Acme rods and nuts at low cost (low in my opinion). Small Parts Inc might be another source.

 

[Boncuk]

Hi superfrog and stevez,

the drawing was made using the Eagle schematic editor.

Although the thread might look triangular it should represent a normal DIN-thread like used for screws.

I also guess that even using a triangular shaped thread the accuracy is of less importance if limit switches or Hall-sensors are used.

If you take a close look at any thread of a screw you'll find it triangular.

The threaded rods I mentioned are used in building constructions to support loads (e.g. cable bridges) mounted to the ceiling and height adjustments are easy with them. They are sold in Germany in home markets by the meter.

Boncuk

 

[shortbus=]

Hi, have a look at this; https://www.surpluscenter.com/item.asp?UID=2009111809535723&item=5-1554&catname=

If that doesn't work, here are a few more options; https://www.surpluscenter.com/sort.asp?UID=2009111809535723&catname=&byKeyword=yes&search=actuator


These guys have been in business a long time. I go to them first when I need something like this. Hydraulics , air cylinders any type of power transmission, gas and electric motors or bearings. etc.

Cary

 

[superfrog]

boncuk

Leadscrew - Wikipedia, the free encyclopedia

Square thread form - Wikipedia, the free encyclopedia
Acme thread form - Wikipedia, the free encyclopedia

It is a matter of torque under load rather than of precision. The precision they give to machining equipement is because of the decreased sticking torque.

 

[deesnyas]

Shortbus=

Thanks much for the link. I actuatorlly like that actuator and the price is great. Its still a compromise so Imma hold off a little longer.

superfrog; boncuk; and steve
Screws are nice I'll follow up on the research.

Mr. RB
I have definately been interested in the windshield wiper motors they are strong and fast, but also take up a bit of space. AME makes a bunch and their prices especially in quantity are great! I was thinking one of these motors and a cam shaft with a transfer arm to lift the load. I'm sure I can get one of these professors to machine the little parts :O

Still open for suggestions

 

[Externet]

Try a 12V solenoid canibalized from an automobile boneyard, to open trunk/door locks. Do not know about the 15 lbs ! , but may be small, fast and about 1" action ...
There are other 'pintle' servos in cars that may be applicable, power antenna mechanisms, headlight cover shutters...

 

[Mr RB]

You can get smaller version of the wiper motors, they are used as electric window motors. They are usually not rated for continuous use though, they get a bit hot.

As for square vs normal thread, at such a tiny figure of 15 pounds force you could use any thread, even something wimpy like a 1/4" threaded rod would do that.

 

[shortbus=]

The wiper(or any)motor or a solenoid by it's self will not work. Not if the load is to be held in one position. The solenoid would but it would need to be powered at all times.

The actuator i showed is a motor powered screw. Shut the power off and it stays at that point by the mechanical advantage of the screw.

I know it doesn't give the length of travel , 1.0" that you need, but by machining a 1/16" off of the "boss" where the screw goes in you could get the travel you need.

The actuator says it's from a power seat in a car. If this is just a one-off project a trip to the junk yard could possibly get you one with a longer travel.

Cary

 

[Boncuk]

boncuk

Leadscrew - Wikipedia, the free encyclopedia

Square thread form - Wikipedia, the free encyclopedia
Acme thread form - Wikipedia, the free encyclopedia

It is a matter of torque under load rather than of precision. The precision they give to machining equipement is because of the decreased sticking torque.

15 lbs of load is a laugh, isn't it?

 

[superfrog]

depends on the size of the screw. It can be a laugh or a lot

 

[deesnyas]

Okay Im pretty confident in the lead screw

Any idea of the type of motor/lead screw set I might use? Or at least some information on the strength of the motor I should be looking for to move the load.

Thanks Shortbus For the forward, Im thinking that this motor isnt going to work even thought the price and load capacity are super AWESOME. It is going to be an OEM part and Imma need ALOT of em. like 2...jk.

In my own exploring I found Welcome | garageFab.cc. Its just a cartesian robot set pretty much but they have a stepper motor and lead screws and all that good stuff.

Responses will be appreciated!

 

[shortbus=]

Hi, not knowing what your end product is I can't really help much farther. But if you are going to be using a lot of them/manufacturing a product, you know that the price goes down with volume. Here's a place to start; Electric Actuators | Electrical Actuators | Electric Valve Actuators

It will link you to a bunch of web sites of actuator manufactures. You probably know if you can adapt an existing actuator to your needs you won't have to pay for tooling and R&D saving more costs.

Hope this helps you, Cary