permanent fixings in a moulded plastic component

[opticsman]

Hi All. I want to fix thinnish, flat moulded plastic components together without screws if possible. Something like a bayonet into a female latching/mating hole . Ideally once clicked together it would be a permanent fixing. For example I have a rectangular strip ( say 25 X 150 X 2 mm thick ) that I want to bend into a cylinder and somehow fix the ends togther to form a permanent cylinder. Similarly i'd like to fix the end of ( another ) plate at right angles to a 2mm thick plate. I have seen some neat fixing arrangement in consumer products in the past but didnt look into how they worked at the time. These will all be moulded items so I can have features in the moulding as long as they can be moulded ( eg no re-entrant profiles). If anyone has any suggestions I'd appreciate it.Many thanks in advance . Opticsman.

 

[Pud]

If you do a search for "Snap fits plastics" there's plenty of data.

The problem you will have is if you mould a flat plate and rely on snap features to keep the end product truly circular you will be disappointed. It is likely to end up as a "tear drop" profile as the joint will never be as stiff as the homogeneous material. You might mould a near shape component but I still feel (from experience) that the same problem will be there - although to a much lesser degree. Same applies for 90 degree plates. Rigidity will be a problem unless ultrasound welding or (possibly) adhesives are used which will be very material dependent.

Cheers

Harry

http://www.tynevalleyplastics.co.uk

 

[MikeHalloran]

If you need a cylinder, mold a cylinder.

You can get away with topological transformations in rubber, and to a degree in aluminum, but not so much in plastic.



Mike Halloran
Pembroke Pines, FL, USA

 

[opticsman]

Thanks. I can support cylindrical shape with circular cross member (that itself would need to snap fit to vertical wall of cylinder ) it mainly the snap fit features I want to find out more about ( wrt joining thin plastic components) . This item is intended as an idiot proof self-assembly item so i want it to be easy to fix and be permanent once fixed. What about crushable pins in this context? Would it be easist for layman to do? I suppose i could go for screws as last resort but wanted to keep the number of components to a minimum. Thanks again. Opticsman.

 

[cloa]

Try joinlox
Australian new invention of the year.

http://www.joinlox.com