I designing a part to be manufactur

[Baraa Karam]

I designing a part to be manufactured, the part is like a cap (red part) for an enclosure. it has an internal thread of M54x1. the cap has to be sealed to prevent any liquid to enter the the enclosure. the cap is will be opened regularly to access the internal components. so I have designed the cap as shown. the "blue" boss will press the O-ring to provide the required sealing.
My question is: is it possible to manufacture the cap like that?

 

[hydtools]

It's possible. But why not a simple flat gasket?

Ted

 

[Baraa Karam]

so there will be no problem in manufacturing the internal thread of the cap?
because I thought that the blue boss will block the threading tool to reach the full length of the thread.

for the gasket how do you think it is possible to place it and make sure that it won't fall when opening and closing the cap?

 

[IRstuff]

Don't understand your image; when the parts unscrew, the red goes right and green goes left? If so, how does the gasket not get cut in half? In such cases, shouldn't the gasket be on a vertical face?

Also, your "boss" is what, 2-mm thick? That seem a bit thin to handle the compression force on the gasket.

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[hydtools]

Put in a thread relief at the blind end of the thread. It will serve as a gasket retaining feature. Add an adhesive, if necessary. Get rid of the boss.

Ted

 

[Baraa Karam]

yes the red parts goes right, green goes left. I used an o-ring (black part) it should be squeezed in its groove when the cap screw.
the parts will be made from Al 6061, I guess it would stand for the compression force.

I would try the gasket idea, and I think that if I used a PTFE material for the gasket and fit it partially inside the thread relief it would stay in place, rather than using an adhesive.
What do you think?

 

[btrueblood]

I'd dispute the idea of a flat gasket. Gaskets are more prone to damage and debris than an o-ring, and an o-ring of common size is more easily available for replacement. Also, the o-ring configuration chosen will be wiped of debris on every make-up of the joint, and has a controlled amount of compression for sealing regardless of how tightly the threaded joint is made up (as long as the oring is fully engaged, which is a big range). The flat gasket requires the user to tighten the joint every time to effect a seal, and as the gasket deforms over time/usage, it becomes more difficult to make a reliable seal (because the cap is bottoming on the housing before the gasket gets fully compressed).

 

[Baraa Karam]

The problem with the o-ring (regardless of where it is being placed between the cap and the housing), (as far as I know) is that it needs to be lubricated to avoid damaging it during the screw of the cap. while it may stay lubricated for few times of opening and closing after the first installation, it will eventually dry and get damage.
How can that be solved?
knowing that the enclosure has to be moved back to maintenance department to replace the damaged o-ring.

 

[hydtools]

Use a PTFE oring. Make sure the lead-in angle on the boss is 15 to 20 degrees to not damage the oring.

Ted

 

[Baraa Karam]

can you draw a sketch of your idea?

 

[hydtools]

Ted

 

[btrueblood]

Use silicone grease to lube the o-ring, it doesn't dry within ordinary usage lifetimes. Or put a small vial of whatever lubricant under the cap to relube the seal every so often.

"knowing that the enclosure has to be moved back to maintenance department to replace the damaged o-ring" - that's a crappy design then, if users can't replace the oring in the field. Not sure what is so super difficult about swapping an oring...

 

[IRstuff]

"knowing that the enclosure has to be moved back to maintenance department to replace the damaged o-ring"

Sounds like something a car company would do ;-) Wasn't there some cars that required lifting or dropping the engine to change oil or spark plugs? Certainly, car companies have been notorious for using non-standard tools for assembly, so as to prevent the buyer from properly maintaining their own cars.

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[desertfox]

Hi Baraa Karam

I cannot see how you can assemble the joint in your first post without damaging the o’ring.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[CWB1]

Assuming you clean up the first image to account for tolerances, radii, etc yes it is manufacturable but likely pricy and prone to user errors. If possible, I would prefer use an O-ring face seal on the end of the threaded stub.