Creating the Lightest Pneumatic System

[ebarker]

This is slightly off topic from the OP but I have some questions;

1) in the past there was a max CV rating on pneumatic solenoids. The only limitation is 1/8 NPT.

2) in the past there was a max volume of stored air.

I see no limitations on those items this year. Is that everyone's interpretation ?

Many years ago the KOP had a simple Festo pneumatic valve that you connected to each end of the cylinder, and to the supply. There was ONE electric solenoid that operated the valve. We prefer to use that type of valve.

I'm interested in these valves from Automation Direct.

There are the double and single solenoid types, very economical. Can someone explain the advantage of double versus single solenoid.

Thanks, Ed

[jijiglobe]

To shave pounds off of a pneumatic system you can use an offboard compressor and plastic air tanks. Then the only noticable weight comes from your pistons which is not something you can work around. Keep in mind that an offboard compressor needs to be controlled by the robot because of some odd rules.

[Al Skierkiewicz]

Ed,
The volume limitation was by number of storage devices and that limitation was removed long ago. The Cv specification was removed as redundant this year since the 0.160 id tubing and associated fittings limit the volume and some manufacturers are no longer printing Cv specifications.

[FrankJ]

Hi Ed:
Aside from being a supporter of First AutomationDirect is a next day delivery for you & they have good stock.
The AutomationDirect valves are legal this year (Cv.78) The nominal pressure rating is 20-115 PSI. The way I read the rules means a separate relief valve unless you have something that says otherwise.

R77-D. Solenoid valves that are rated for a maximum working pressure that is less than 125 psi rating mandated above are permitted, however if employed, an additional pressure relief valve must be added to the low pressure side of the main regulator. The additional relief valve must be set to a lower pressure than the maximum pressure rating for the solenoid valve,

One reason to use a double solenoid valve is for spring center. The center position can either block or connect the A & B ports. So the cylinder will stop or flop when the solenoids are not powered. Another reason would if you want the valve to stay in the position last set rather than a spring return to the "off" position.

[Mike Schreiber]

Originally Posted by FrankJ

Hi Ed:
Aside from being a supporter of First AutomationDirect is a next day delivery for you & they have good stock.
The AutomationDirect valves are legal this year (Cv.78) The nominal pressure rating is 20-115 PSI. The way I read the rules means a separate relief valve unless you have something that says otherwise.

Al,

My question isn't whether these valves are legal, it is whether I need to add the extra relief valve because the maximum working pressure is below 125 psi (R77D). The same question goes to these AutomationDirect valves. It doesn't make sense to me to add it because they will never operate above 60psi, but according to my interpretation of the rules I need it. I understand the difference between failure pressure and operating pressure, but which does "working" refer to? Are the SMC valves only okay because IFI has said they'll operate up to that pressure, and what about the varieties of SMC valves VexPro doesn't sell?

[nuttle]

Norgren 16-004-003 is a little lighter than the usual 16-004-011, but also allows you to omit a brass fitting (if you're using the new compressor). Likely not worth worrying over though. You can also get smaller pressure gauges that should be a little lighter, if you're really trying to save a little weight/space. I also like Clippard TV-2SP for the dump valve but I'm not sure if it saves any weight as I don't have one handy...

[Al Skierkiewicz]

Mike,
The specs are a little confusing. The way I read the sheet you linked, the pressure rating is recommended operating pressure. The sheet gives a range of 0.15 to 0.7 MPa but it does not specify a max operating pressure.

[Mark McLeod]

Originally Posted by ebarker

There are the double and single solenoid types, very economical. Can someone explain the advantage of double versus single solenoid.

They both perform the same actions as far as extending/retracting a cylinder.
The difference is that a single solenoid has a home position that it always returns to when the robot is Disabled, while the double solenoid always remains in the last position it was set to.

A single solenoid is preferred when you have a mechanism that must always be stowed in a home position, or a mechanism that you want to activate at the very end of a match no matter what. It can be a little less safe, because the mechanism will activate whenever the robot is Disabled.
An example from last season might be a low bar hanger that would retract automatically when the match ended giving you 10 pts as long as the robot was in position.

A double solenoid is a good choice when you want a mechanism to remain in the last position you chose. Especially when there is no particular home position, like a gripper. It's a little safer because the mechanism doesn't suddenly move whenever the robot is disabled.