Cylinder's surface condition of gas springs (gas struts)

[Amir Sedieqy]

I've discussed part of these question somewhere else, and Edstainless kindly gave me helpful instructions, but I realized I have to be more specific about it. I'm new to this forum and hope I'm doing the right thing.
I'm planning to manufacture gas struts used in kitchen cabinets; therefore, firstly, some guide books or standards about the needed cylinder surface (surface finishing and tolerance) and compatible o'ring and rod seal of this cylinder-piston mechanism would be very helpful.
The gas strut is filled with 6-7 bars Nitrogen and the cylinder have 14mm ID and 12cm length. The piston consists of a steel rod and a plastic piston head. Obviously, there is a rod seal between the rod and cylinder, and an o'ring around the plastic piston head. I cannot use seamless tubes since the end price would not be able to compete with current gas struts. I've been suggested by Edstainless plug draw welded pipes(tubes) in order to eliminate the weld seam inside the tube. How close would the inside surface after drawing be to the desired surface? Is this the most efficient way?

 

[EdStainless]

Testing, testing, and testing.
The seal material, the working pressure range, and the amount of force involved all fit in.
In struts these are normally lip seals and the ID of the tubes are very smooth. There is a lot of 'sticktion' but in a strut this isn't as much of an issue as with pneumatic cylinders. Leakage in more important here.
I hope that others will add their information to assist you.

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P.E. Metallurgy, consulting work welcomed

 

[BrianE22]

Usually the manufacturer of the seal will state the need tolerance, roundness and surface finish of the cylinder. For o'rings, Parker provides that info in their o'ring handbook.

 

[3DDave]

Never mind - they need a seal to operate the metering port on the piston. Polishing of the rod and honing of the cylinder bore is typical. I expect the rod to be electropolished.

 

[moon161]

Parker o-Ring handbook

 

[hydtools]

See also Omniseal

https://www.seals.saint-gobain.com/products

Ted