Strength of suction cup with G1/4 Male connection threaded in aluminum plate.

[PatCouture]

Hi!

Before I go into calculating the thread strength itself. I would like to know what do you think of this assembly: I have a robot tool to design that will use 42 suction cups. I'm planning to hold the suction cup with a welded structure made of aluminum (6061-T6). I would like to make threaded holes (G1/4) for every suction cup in the aluminum plate of 5/8" thick.

Do you think the threads will hold considering:

- Suction cup thread material is steel
- Suction cup is rated at 660N hold capacity.
- The male thread is 10mm long.
- I would like to have a safety factor of at least 4

I know it's best to have 1.5 to 2.5 times thread diameter for length of engagement in aluminum and I'm far from that. Other options are to use bulkhead connector to pass through the plate and have a nut. Or instead of aluminum I use a steel plate (Much heavier though). Or maybe insert HeliCoils in the holes?

Thanks in advance for your time.

Patrick

 

[BUGGAR]

A deciding issue may be how often do you have to replace the suction cups. Short threads in aluminum (even 6061 T6) loose their tolerance through re-use, although the rods can still be tightened.

 

[tbuelna]

A 10mm long thread engagement of the suction cup fittings in 6061-T6 alum will likely provide far more load margin than the factor of 4 you require. 660N is not much load for the G 1/4 x 10mm long thread connection you describe.

 

[PatCouture]

Thanks for your help.

Buggar: I hope we don't have to replace the suction cup too often but even if it's once or twice a year it's still worth considering.

tbuelna: One factor that convince me to keep the thread in aluminum is if the robot happen to collide the part he is holding with a structure then the suction cups will lose their grip before stripping the threads. Also the pitch of G1/4 is 1.33mm so I will have more than 6 threads engaged in the aluminum so I should be ok

Thanks again

Patrick