Pneumatics shematics

[Abacus]

Anyone a pneumatics expert?

I have a Cassese CS199MXL which is tempermental , but the main problem I have is that I just don't understand how a certain part can operate from the schematic.

heres the schematic (page 13)

http://www.cassese.com/manuels/199%2...%20299MXL2.pdf

Here's what happens/supposed to happen

The "pre-clamping" knob is set to let air to the footpedal, so the pre-clamping piston is not being used here
1) You push the foot pedal
2) Air goes to the "or" shuttle valve (top right of diagram) and then on to the clamping piston which extends
3) The piston makes contact with the "security clamping" plunger (bottom middle of diagram) which sends air to the other "or" shuttle valve and then onto the 5/2 pilot/pilot valve, activating the valve
4) The air also goes to the "stapling button" when this is pressed air is sent through a pilot/spring valve activating it, removing air from the indicator "lamp", and allowing the valve from 3 above to activate, and also putting air to the bottom of the 5/2 pilot/pilot valve which because it is now active sends the "stapling" piston up
5) At the top of the piston stroke, the "end of travel" sensor is activated which should send the piston back down.
6) You release the stapling button and the process can be started again by releasing the foot pedal, or the button can be re-pressed and another staple is fired on top of the first one.

Now what I don't understand is how (5) actually happens? From the schematic, when the "end of travel sensor" is activated, air is sent to the "or" valve (which is already activated by the "security clamping" plunger in (3) above) and then on to the 5/2 pilot valve which is already in the activated position, i.e. it shouldn't have any effect, but I know it does!

Sorry for the long ramble, but I'm confused.

[Not your average framer]

Clicking on your link does not enable me to see the schematic. Perhaps you could check if the link is faulty.

I used to be a design engineer and know how this sort of stuff works. If I could see the schematic, I would expect that I would have a good chance of explaining things for you.

In the meantime, check out "DeMorgan's theorum" as this may help to clarify the use of the "or" valves.

http://hyperphysics.phy-astr.gsu.edu/hb ... organ.html

Although the normal expectation is that any active state input applied to any of the device inputs will generate an active state output, if the design engineer understood De Morgan's theorum then he could be defining the normally inactive state as the state required to produce function activation, in which case the "or" valve is being used as a reverse logic "and" valve.

If you really want to understand how engineers like myself design and understand stuff like this, the check out "Boolean Algebra", "Venn Diagrams", "Veitch diagrams", "Karnaugh maps" and "Truth Tables". It's a lot to get you head around at first, but it's quite straight forward once you have got the hang of it.

Do a web search on the terms I have highlighted in red for more info.

[Abacus]

Sorry for the duff link, this one should work

http://www.cassese.com/manuels/199%20&% ... 99MXL2.pdf

[Not your average framer]

O.K., I've printed out the schematic and now understand why you find this confusing. Part of the difficulty is that Cassesse have not included any part numbers on the schematic for these pneumatic components, so we cannot relate the schematic directly to any other information about how the individual components are configured to work.

Also, even if they had, I doubt if the numbers would correspond to the actual manufacturer's numbers, so it's unlikely that we would be able to download the corresponding product data sheet and therefore be able to fully examine how each component is configure to operate in every possible mode of operation. So, we have to make full use of any clues given by the schematic and make some reasonable deductions, in order to arrive at a sensible explaination.

O.K., so here's what I think is happening:

If you compare the symbols used for the valves which directly control the "Wedge position locking", "Stapling" and "Clamping" cylinders, you will be able to two of these device symbols show the inclusion of a return, or release spring. Since these particular devices show only one control input, then it must be assumed that both valves in the same device are controlled by the same control input.

So now, if we return to the valve used to control the "Stapling" cylinder you will see that there is no symbol for a spring associated with this valve, but in it's place is an extra control input and this is where we are forced to make a reasoned assumption.

My assumption is that this valve uses this extra control input to carry out the missing function which would have been provided by the spring and that in the event of both inputs being applied at the same time that one input has been configured to automatically overide the other.

This in turn would lead to the air pressure in the "Stapling" cylinder exhausting through the exhaust port on the valve and as a result the return spring associated with the "Stapling" cylinder, this would return the cylinder to it's non-activated position.

Now we've solved that one, what is the tempermental problem you are encountering? If the problem is related to the pneumatic control devices, maybe we can work out a possible cause and how to diagnose the problem.

[Abacus]

Thanks mark, both for your time and end explanation.

The "temperamental" bit is indeed related to what you have explained above. I.e. the stapling piston does not return on its own when the end of travel is triggered. You have to release the stapling button. Other owners tell me the piston should return on its own.

The pilot/pilot valve (the one without a spring return) is a v5212-06a as below

http://www.emc-machinery.com/V_series_P ... Valves.htm

Which makes it a 5 port 2 direction twin coil air operated pilot/pilot valve

Phew!

I might just buy a new valve and try it, but they are around £65 so I was looking for confirmation of the fault first.

[Abacus]

The "or" valves are these es-06

http://www.emc-machinery.com/V_series_P ... Valves.htm

[Not your average framer]

I'm not convinced that changing this valve will solve the problem, as it could also be a problem with the "end of travel sensor".

Would I be correct in thinking that the "Security clamping" control valve is provided as a manual overide provision in the event of the "end of travel" sensor failing to operate? If this is so, does the "Stapling cylinder" return to it's normal position when this valve is operated? If yes, then the problem will be the "end of travel" sensor. If no, then it's the valve without the return spring.

These sort of components should have a very long operating life and it may be worth trying to clean, or lubricate the faulty valve, before finally resorting to replacing it with a new valve.

Another thought, does the valve without the spring have an exhaust port silencer, if so has it become blocked? If so removing the silencer should restore correct operation. Replacement silencers are usually obtainable, but some manuacturers may only be willing to sell you the valve and silencer as a complete assembly. If so you may need to shop around.

[Abacus]

No mark, the security clamping device is activated when the work is clamped, I.e. it stops you pinning if the clamp is not activated. This valve actually activates the pilot/piot valve when the other side is deactivated when the stapling button is pressed.

The end of travel valve is working as far as I can tell (when I detach the output pipe and press the plunger the valve lets air out).

There is nothing on the exhaust ports of the pilot/pilot valve, and it doesn't seem to be a part which can be taken apart.

[Not your average framer]

In that case, I think you have already diagnosed the faulty component.