Hydraulic or Pneumatic cylinder for clamping?

Hi,

I want to make some small spur gears (I know the entire procedure) but at the moment I'm using a simple tailstock to fix a blank into the A-Axis of a mill.
Can anyone recommend a small cylinder and pump(?) which I could use for the tailstock add-on to squeeze the blank against the A-Axis?

Depending on your tailstock you could use a spring loaded center. If that won't work for some reason you could grab yourself a small air compressor, a single acting air cylinder that can apply the amount of force you require (Force=Pressure × Area of piston), and a valve to turn the air on/off.

BugRobotics said:

Depending on your tailstock you could use a spring loaded center. If that won't work for some reason you could grab yourself a small air compressor, a single acting air cylinder that can apply the amount of force you require (Force=Pressure × Area of piston), and a valve to turn the air on/off.

Click to expand...

Thanks for that hint, I think I will get one for safety purpose.
I want to automatise the task of swapping gear blanks in my machine, I want to put the blanks in via a pneumatic system - I'm looking for a solution for the holding part.
I could even imagine installing a second motor on rails on the opposite side of the A-Axis but something needs to push it against it.

At the moment I think a hydraulic system would be better than a pneumatic one for such a purpose (please tell me if I'm wrong).
The spur gears are relatively small.. below 2 inch.

Pneumatic systems are easier and less costly to install.
You will need a pressure reservoir to maintain a force holding the part in place. For a pneumatic system this is the air tank. For a hydraulic system you either need to continuously run the pump or install a very expensive high pressure air over oil tank.
The other consideration is the effective spring constant of the tail stock actuator. A hydraulic system can be much stiffer than a pneumatic system. . This is because hydraulic fluid is incompressible and the higher operating pressures that are possible with hydraulic pumps.

The easiest automated design solution may be to stay with the spring based design and use a pneumatic piston for retracting the spring actuated quill when installing the gear blank. The retaining forces available for a spring design can range from ounces with a light coil spring to thousands of pounds when using Belleville spring washers.

Robert, thank you for your advice!

What would you recommend as switch? just a regular solenoid or is there something better?
I have also ordered a hydraulic system (if I'm not going to use it with my machines I will keep it for playing and testing some control systems with it).

The system components would include a spring loaded pancake pneumatic cylinder and a three way solenoid valve. A four way valve will also work. The valve ports are supply, exhaust, cylinder extend, and cylinder retract. There is also a choice on solenoid port valve size, A larger port will offer a quicker response. If it is too fast the cylinder will slam open. This can be remedied by installing a throttle valve on the cylinder pneumatic line.

The pancake cylinders can be ordered with a internal spring to force a piston extension when air pressure is released. The spring is selected for the holding force required.
Fabco is one source for the cylinders.

You will also need a piston in position interlock signal with a automated system to prevent a collision with the blank loading arm and a quill that failed to retract . The cylinders can be ordered with a adjustable magnetic switch that confirms that the piston is at the end of stroke.

Don't discount pneumatics. We use pneumatic vises to hold stainless parts and do some fairly heavy hogging on automatically tended systems.

If you're really wedded to hydraulics, though, for this I'd suggest an air over oil intensifier rather than a whole pump and control circuit. That way, the controls are pneumatic, the valves are pneumatic and the hydraulic circuit is super simple.. That'll get you high clamping force with a very small cylinder, which is the only reason I can see to want hydraulic here, without the complexity.