A project ahead is to move a lever between 0 degrees and ca 90 degrees. At the ca 90 degree position the movement will tighten a locking device on a numerically controlled rotating table. Wear will be and therefore one end of the move is ca 90 degrees. The first pic, at 0 degrees, is the force free end. The second pic is where some torque is needed. Between thumb and finger, 1 Nm ought to be enough and need not to be really precise.
The lever is fitted into a screw (6 mm) and the screw pulls a block to lock the table. Pic below.
When the table is moving, from one angle to another, the locks ( 2 of the same kind) must be released. When the rotation is done, the locks should be applied in order for the mill to engage and do its job, cutting. The duration of "locked" can be considerable, 10 seconds up to minutes. Ah, the block is turned up side down in the pic.
Because of the environment, I suggest a double acting air cylinder and make a new handle to match the air cylinder piston rod. The air direction can be controlled by two solenoid valves and them controlled by ?, Arduino, CNC machine?
Is 1/4 turn going to be enough to lock/unlock the table?
Yes, the environment will be metall chips "flying around" at some extent. As cleaning, brushing, is frequently used in milling, turning, it's not really a problem. The mill is manually operated and the CNC table is used for precision moves, angle accuracy etc.
Air pressure has the advantage of making mechanical pressure without being overloaded. I have no education, nor experience of "Pressure and pys" but I do have a little 120 PSI compressor that could be used.
Yes, 90 degrees is more than enough. The locking takes place during some 10, 20 ... degrees and most of the stroke is considered "free".
Answering too quickly. Yes, an Arduino (UNO) will be used to control the 2.2 Nm, 3 Amp, stepper motor. (A 3 Nm is available if needed.) The mechanical interface is ready and some code as well. Using buttons commanding and/or serial monitor communication, or both, is still to be decided.
Only manual operation of the mill.
A 24 volt power supply will be used. A heatsinked 3.5 Amp driver as well. All laying and waiting.
I was thinking of something like that but to be sure of releasing the lock a light push away is wanted. If the locking mechanism is not well released the rotating table might get hooked up on the locking block. 2 motors.. possible but not really wanted... There are 2 locks making it 4 motors. It's not realistic to let 2 motors handle both the locks. They sit 180 degrees apart on the 5" table and the table is intended to be used in 2 orientations, both standing and laying.
I once worked on a product (automatic cat flap) that use a "lock" held closed by a "knee" with a light spring, with a small solenoid to knock at the back of the "joint" to open it whilst under axial pressure.
I guess your issue is to do with preventing an RT from moving under cutting forces. It may be possible to avoid the need to lock it by careful planning of the machining so the force is always against the worm?
Working against the worm gear is not good enough. Vibrations are varying, being unfortunate to cause chatter affects the RT positioning. You don't see machinists practicing it, they lock the mechanism.
The RT has a diameter of 5 inches and it will sit on a mini mill table. Pneumatic use quite some space.....
I can't quite see the difference between working against a worm and working against a leadscrew, a wormwheel is like a nut bent into a circle and a worm like a leadscrew. Anyway when the RT is locked you can only do radial milling, for circumferential milling you have to rotate the table so you can't lock it! Yes machinists (like me) lock the axes they aren't using but if you don't have at least one unlocked there's no point in milling.
My rotary axis I use on the CNC mill is based on a standard dividing head which does have a small amount of backlash. I have done spiral milling of an experimental gear and knurling, both times using g-code that only turns one way, without issues.
Watching the experienced guys they usually lock the table, the dividing head, etc. when they do the cut. Yes, backlash, play is one reason. Increased rigidity is another word I can think of. As the mini mill isn't very rigid I want to use all means to create the best stability.
Yes, turning only one way is the number one rule.
I base my point of view on guys like Joe Pie, Abom79, Tubalcain, Keith Rucker...
I intend to use manual milling only.
One possible approach is using proximity switches indicating unlocked position/status and only allow turning when the RT is unlocked. Of course, letting the controller release the lock, make the move and lock upon a command would be nice.
