Sensing Cylinder Position without Magnetic Piston

Archie · Nov 10, 2016

Does anyone know of a switch that can be mounted to a round body cylinder that is able to sense a piston without a magnet? I am working on a machine with a stainless steel round body cylinder in which I would like to know when it reaches a certain point. I'm hoping to do this without changing the cylinder to one with a magnetic piston.

mendonsy · Nov 10, 2016

BEI Sensors has some stuff that might work, but I suspect it would be a lot less expensive to just replace the cylinder.

Archie · Nov 10, 2016

It is a 36" stroke cylinder with a 1 1/2" bore that sells for about $300USD. The bigger problem is that it has about a 2 week lead time.

gas · Nov 10, 2016

Most of those cylinders use an aluminum piston. Likely a long stroke cylinder will use a chrome plated steel rod.
Maybe you can find a prox that will "see" the absence of the rod.
Long shot good luck

James Mcquade · Nov 10, 2016

Archie,

what is the brand of the cylinder and the part number?
I have access to several guys and they might be able to help.

james

Archie · Nov 10, 2016

James Mcquade said:
what is the brand of the cylinder and the part number?
I have access to several guys and they might be able to help.

Bimba SR-1736-DXPY-00MC

Gil47 · Nov 10, 2016

If it is end of stroke.
Then I have seen a case where pressure switches on the air lines
were used to indicate the end of stroke
either full pressure or no pressure.

Aabeck · Nov 10, 2016

If sensing the rod-in-far-enough then how about clamping something on the shaft itself and using an external proxy near the cylinder entrance?

Archie · Nov 10, 2016

Gil47 said:
If it is end of stroke.
Then I have seen a case where pressure switches on the air lines
were used to indicate the end of stroke
either full pressure or no pressure.

It actually doesn't have pressure on the blind end of the cylinder because it is used as a counter balance to a hanging load. There is only a constant pressure on the rod end with a pressure relief valve. It's purpose is to prevent it from drifting down and also equalize the torque required for the motor to raise and lower the load.

If sensing the rod-in-far-enough then how about clamping something on the shaft itself and using an external proxy near the cylinder entrance?

I need to sense a distance of about halfway extended

skeet · Nov 10, 2016

Archie said:
It actually doesn't have pressure on the blind end of the cylinder because it is used as a counter balance to a hanging load. There is only a constant pressure on the rod end with a pressure relief valve. It's purpose is to prevent it from drifting down and also equalize the torque required for the motor to raise and lower the load.

I need to sense a distance of about halfway extended

Maybe one of the external track mounted Tempos?
http://www.mtssensors.com/products/industrial-sensors/r-series-sensors/index.html

PapaSmiff · Nov 10, 2016

Can you use an external photoeye looking at the load? When it's unblocked, it's OK.

I would guess you might need another photoeye or some other sensor to let you know if the cylinder has failed and the piston is fully extended ...

Mill_Control · Nov 10, 2016

Might be better to sense the position of the load. Either too low or high enough. Trying to control with a mid stroke sensor could get really squirrely because you won't know which side of mid stroke you are.

Archie · Nov 10, 2016

As a temporary solution, I used a photoeye to sense the load. It's not a good long term solution because it is just outside of a grit blaster. Over time it's about the equivalent of putting a photoeye in the line of fire of a sand blaster. I was hoping to sense the cylinder position where the sensor would be out of the grit blast "over-spray" and as an added benefit have something easy to adjust. This sensor tells the grippers when to release the load onto a belt and the only way to tweak that height with the current photo eye is to adjust a timer.

Racer5039 · Nov 10, 2016

Archie, Take a look at String pots, would give you a 0-10V out. I have used these and had great luck. http://www.stringpots.ca/

bkottaras · Nov 10, 2016

Aabeck said:
If sensing the rod-in-far-enough then how about clamping something on the shaft itself and using an external proxy near the cylinder entrance?

Archie, if you have the clearance, install a split colar on the rod/shaft as Aabeck suggested and use a prox.
Much cheaper than anything else and much better control than your photo eye.

Sensing Cylinder Position without Magnetic Piston

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