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Author Topic: how to make tiny pistons move  (Read 1879 times)

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Offline amrosikTopic starter

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how to make tiny pistons move
« on: October 18, 2014, 12:37:18 PM »

I want to know which of the following methods would be best, to make tiny pistons (8mm diameter of the cylinder, max. 6mm diameter of the piston) move. Of course the piston should have a recoil spring. It is important that the system has a quick response time, about 5 Hz should be no problem.

Indirect methods:

1. Using pneumatics and pushing solenoids.
2. Using a pressure reservoir and magnetic valves.

Direct method:

3. using a self made pushing solenoid in that size, with a neodymium magnetic core.


1. A pushing solenoid is attached to a big cylinder with piston (isolated with a rolling membrane (diaphragm) or a bellow), and that is connected with a thin air hose to the tiny   
piston, again using rolling membranes or a bellow.
As the Solenoid is activated, the volume of the system is decreased, therefore the pressure increased, making the tiny piston push with a certain force. I need a force a 6 N.
I calculated that then the pressure should be about 22 Psi, and , given that the Solenoid has a stroke length of 1 centimeter and that the air hose has a inner diameter of 4mm and a length of 2 meters, we need a force of  about 300 Newton for the Solenoid, to create that pressure.
There is no Solenoid that could do that, in fact the best thing that I know creates 20 Newtons for that stroke length.
Can you do something about it, or is that method already checked off?

2. A pressure reservoir of big volume, holding air at about 22 psi is connected to a 3/2-way valve, which is connected with the tiny piston. Turing of the valve connects the piston with the reservoir, turning it of connects it with atmosphere.

Does that work? How to get those valves, working at these pressure levels? The should not be too expensive, because I need 40 of them.

3. I dont know how to wind the cupper wire with that tiny size restriction, to get 6 N out of it.

I will be grateful for any suggestion. Thank you in advance.

Offline SeekingVision

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Re: how to make tiny pistons move
« Reply #1 on: November 21, 2014, 06:26:02 PM »
The problems associated with solenoids and the windings involve amperage, heat dissipation, and required duty cycles. Those things will give you possibilities such as size needed.
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Offline bdeuell

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Re: how to make tiny pistons move
« Reply #2 on: November 23, 2014, 12:04:41 AM »
method 1

 - I calculated 30.8 psi for a cylinder that can produce 6N from a 6mm piston, air pressure = cylinder force / piston area
 - not sure how you calculated the 300 newton solenoid for the diaphragm as i couldn't find the cylinder stroke requirements or diaphragm/bellow area
 - a 4mm tube seems very big for a 6mm bore cylinder, but it would not affect your pressure/force calculations significantly, it will mainly affect speed.
 - i think the biggest negative of this method is that over time air will leak out of the system and the stroke of your cylinder may decay.

method 2

 - same pressure calculation as method 1, 30.8 psi
 - this would be my recommended method to implement a air cylinder actuator
 - to decrease the reservoir requirements you may be able to use a pump to constantly recharge the reservoir pressure
 - i would try and find off the shelf products but not sure exactly what is yout there for low cost (or what other size/weight restrictions you may have)
 - there are lots of solenoid valves available for industrial automation

Method 3

 - this is probably the simplest system design but the solenoid actuators may or may not be possible/practical
 - all the points made by SeekingVision are valid in solenoid design
 - to assess whether a solenoid will be possible in your space requirements you can look at the specs of commercial solutions and see what the force for a given size is
 - you could also use a magnetic core to increase the force


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