Pneumatic cylinder stroke length

[loki1976 0]

Hello all, I have changed our machine from mechanical chains, cams and pusher rods because they are always failing. I installed 2 cylinders which are working much better. I need to control 1 of the said cylinders a little better. Currently it has a physical stop from preventing it going all the way down but we are having to move other aspects of the machine for the upper positions all the time. I am trying to understand how I do this with 2 x reed switch's. My idea is once the upper read switch is made apply air to both sides of the cylinder to hold a position. I would also like to do the same on the lower position. I appreciate accuracy is not going to brilliant but that's not a key issue for us. Can anybody please guide me? I 

 

At x counter Ram Up activates. (Y001)

Once upper reed switch is made activate  (Y001 & Y002) to hold upper position.

At x counter Ram Down Activate (Y002)

Once Lower reed switch is made activate  (Y001 & Y002) to hold lower position.

 

I have attached a sample of the toggling of outputs but no idea how to incorporate the switch's.

 

Thanks in advance.

https://discord.gg/ZYjpDza9nu

 

 

Test.gxw

Edited 29 Sep 2023 by loki1976
misc

[Integrator_99 2]

Hello loki1976,
I don't have a lot of experience working with cylinders in the method you describe but I would think a double solenoid with a closed center position is often used for holding positions (maybe something like a 5-way, 3-position, closed center, double solenoid, for example).  What type of solenoid are you controlling the cylinder with?

See Figure 2B here.

Do you need a rod lock to keep the cylinder from dropping if you lose air pressure (E-stop)?

[Nightfly 12]

If this is a normal rodded cylinder then this would not work as the piston inside the cylinder does not have the same surface area on each side (because of the rod).  So given the same pressure is applied to both sides, the side of the piston with the larger surface area (non rodded side) would apply a larger force than the other side making the cylinder extend outwards.

[glavanov 40]

Sounds like a job for proportional valve... : https://www.festo.com/media/pim/682/D15000100122682.PDF

[loki1976 0]

Thanks for the replies all. I understand that this may not be the ideal solution but the budget is low and only have a few months because the company is closing. Can anybody please help me with the logic in the ladder for the description I have given. I just cant figure out how to do the ladder. 

Thank you

[Glenn Covington 3]

How many different stop locations are needed.   In other machines I have seen a small turret block with various lengths of set screws that could be turned manually to the desired stop position.   The cylinder would have a tab attached to the rod end that contacted the various length set screws to position cylinder.

[loki1976 0]

Only 2 positions. It is a odd size stroke required and I have used bumpers but they are not very effective. If i had a sensor for lower pos and then 1 for upper it would enable the operator to move the sensor up for different height products. 

 

Thank you Glenn

[pturmel 160]

If its only going to run a few months more, I'd skip straight to mounting some easily-removable mechanical stops.

(Applying pressure to both sides of a cylinder won't work, as nightfly pointed out, because the pressurized surface areas aren't equal.)

[loki1976 0]

Thank you pturmel, I will probably go ahead and do this method better. I would still like to know how to achieve with a roadless cylinder mind.

 

Thanks 

[IO_Rack 181]

To achieve that, you would need a 3 position valve where the center position is all closed (Pressure and Exhaust), as Integrator_99 has suggested.

[loki1976 0]

Thanks all @IO_Rack could you prehaps so me how a ladder would look for this please?

 

Thank you

[IO_Rack 181]

I don't currently have the Mitsubishi software installed but ladder is ladder. Here is an example in Omron. This is using the solenoid that Integrator_99 has linked to. This is basic sequence programming. There are multiple ways to achieve the same thing.