Help with studio 5000

[Eddy D]

@drbitboy:

I think if an e-stop is reset Press 2 will still retract immediately if it was between limit switches. Unless the stop button was pressed...I think it could be easily remedied with an e-stop condition dropping out the Auto Run. That was probably implied?

I do agree with the anti-pattern statement. An e-stop reset probably should not be moving parts/machinery...?

In my head thinking about this exercise I was thinking it was a vertical application. So that is why I wanted to hold both presses retracted when stopped...

In this new scenario if we are extending Press 2 and then press the stop button, with neither limit switches active, it will not finish the extend stroke which was my initial intention. Which way is better? Hard to say since its not a real word application.

I do say that this looks nicer.

 

[parky]

Just one word of wrning:
On the one with a double acting solenoid a small pulse on either solenoid will trigger the cylinder to go either way, it will depend on the type of solenoid but in general unless it is a centre off a small pulse will send the shuttle for main air via the pilot so an e-stop or removal of the power will not stop it until it reaches its position there are block & bleed type to hold it's position but without knowing the actual type of solenoid valve it is impossible to know.

 

[Eddy D]

An e-stop usually turns the main air off too? That would stop the cylinder from moving.

Or are we talking about vertical application?

 

[drbitboy]

In my head thinking about this exercise I was thinking it was a vertical application. So that is why I wanted to hold both presses retracted when stopped...

Oh yeah, that makes sense. Wrong "analogy" on my part (to borrow from another thread).
_

 

[parky]

It depends on the operation, air takes time to dump, often the air dump is on a delay from the e-stop (air safety dump), some cylinders have block/bleed valves so it stays in position or locking bolts, it really depends on the type of machine, I have come across many where the air dump is off a safety delay to allow position to be obtained with lock bolts, some where the guards not the e-stop dump the air. all I am saying that removing the solenoid power depending on the type of solenoid will depend on it's type of operation, all things are designed for safety in mind. As for vertical, again lock bolts are preferable to air lock bolts, i.e. air removed from air lock bolts but main air is delayed to allow cylinder to retract before, lock bolts released befor main air is removed

 

[I_Automation]

An e-stop usually turns the main air off too? That would stop the cylinder from moving.

E-stops on stamping presses only turn off the ability to move the ram or feeder. If there is a conveyor, vibrating chute, or other item in the bed that would be shut off too.


A stamping press E-stop DOES NOT shut off:
The drive motor driving the clutch
The air to counterbalances or parts blow-offs
A hydraulic pump if the clutch is hydraulic, not pneumatic
Another hydraulic pump if the die is in place by hydraulic clamping

The servo drive to the feeder that is holding the steel in place
The servo drive to a motorized straightener that is holding the steel there in place
The air to the pneumatic brake on a coil reel holding the reel in place.


Also, the E-stop on a robot does not drop air, or vacuum, to the end effector or relieve tension on a motorized grip that would cause the robot to drop whatever it is holding when the E-stop is pressed.


The safety audit for designing a machine has to take into account what can't happen at an E-stop along with what must happen.

 

[parky]

I Auto has it, I deliberately missed out the fact that on some presses (in the above case, the E-stop does not release the air) not directly but after a timed safety interlock, because I left out the fact that on one particular type of press if the head dropped if air was dumped the sealing head would make contact with the parts & possibly catch fire, this is something I worked closely with the Health & Safety inspectorate, Although they agreed that "air lock" could stay on we decided to implement auto lock bolts, this way, we could release the air & the bolts would retain the head in position.
In actual fact, the residule air in the cylinder & providing a good seal even if the lock bolts failed (not likely) the head would fall at a very slow rate.
Anyway, getting back to the original regarding assignments, many seem to be poorly thought out, not only should the students learn how to code a system but look at the whole picture, as we have seen, little information, the tpye of solenoid valves, certainly if I was doing a project I would like a drawing of the mechanical, an explanation & the types of solenoids & a functional operation.