We use hydraulic cylinders in many applications to release brakes and clamp things. The choice of hydraulics is based on them being strong relative to their size. There are a couple of downsides with hydraulics though:
- Expensive cumbersome installation, sealings, long (expensive) holes as channels, hoses.
- Expensive drive unit that requires maintenance
I was inspired by this thread, where a solenoid was suggested. The problem is that my knowledge about electronics is very limited so I thought I should ask for suggestions here first.
Example of hydraulic cylinder
- Ø22 mm (outer), length 38 mm
- Force ~3 kN at 250 bar
- For stroke ~1 mm will often be sufficient
Operation
We have tow scenarios where we use hydraulics:
- For releasing brakes. The breaks are used for security when we have vertical loads. The brake is actuated by spring force but when the drive is powered up the brake is released by applying the force from the hydraulic cylinders.
- For clamping tools. Normally the tools are clamped by spring force and released with force from the hydraulic cylinder when a new tool is mounted.
Both applications are very similar to the clutch in a car.
- Normally there will be only a couple of actuations per hour
- It is a simple motion no need for controlled acceleration/deceleration. Being able to limit the speed would be good for soft operation.
- I'm not even sure there is a need for a sensing feedback mechanism
- Regarding operation lifetime it is similar to the clutch in a car, it would be ideal to get 15 years of maintenance free operation
I struggled with trying to write this in English, please don't hesitate to as for clarification if something is missing or just strange/wrong.
Best Answer
Look at muscle wires / FLEXINOL. Wikipedia article is here. When current is passed through them, they shorten in length thereby generating a pull effect.
Data is available here