Trying to use vibration to insert tubing- need guidance

[swelter]

I am sliding a small metal cylinder into plastic tubing (nylon) and keep getting high frictional forces (ie it jams or damages the plastic)- I can't use lubrication - so I thought about vibration to keep it dynamic- any thoughts or guidance?

 

[mechengdude]

Thoughts -

Do you have a length to diamter issue?
Do you have the ability to use either of the following to aid in assembly - heat to expand the nylon or expand the nylon with air pressure during assembly.

good luck

 

[Strong]

The tubing has considerable damping for vibration energy. If I were to try vibration, I would probably excite the tube at its ring frequency. This would be the first vibration mode where the diameter expands and contracts. There are formulas available to calculate this frequency. A small diameter thin wall tube will have a very high frequency and the actual displacement will be low. I doubt that bending vibration modes would help, but that is another possiblility.

For temperature method try cooling metal tube and warming plactic tubing and then work very fast before temperatures equalize.

Walt

 

[TPL]

Try cooling the cylinder using the spray that plumbers use to freeze central heating pipes (Arctic spray? - from a Hardware store)

 

[swelter]

Thanks for the vibration insight. Is there an on-line reference for the ring frequency calculation?
To answer the length:diameter ratio question, it's 60:1, so there is a lot of friction condition and potential for damage / failure to complete the insertion.
I do have a cooling option available (I use electronics cleaner duster spray from a can), it's just not a long term, operator friendly option. I also have compressed air-vortex chillers available, but they get noisy.

 

[Tmoose]

It works if you keep it "dynamic" ?
Spin the cylinder during insertion?

I can expand and pop the handgrips right off my motorcycles with compressed air. How much would the nylon have to expand to make clearance?

 

[PulseMaster]

Not gonna work. Too much damping in the plastic, and you'll kill the vibration in the section of interest as you slide the cylinder in. Think pressure and temperature like these guys are saying