Overmolding

[MiKelPD]

Hi All,

I have had some success in overmolding TPE's to a rigid Thermoplastic material, but am wondering if anyone has any experiences in overmolding or two shot molding a rigid thermoplastic to a rigid thermoplastic.

More specifically I'm looking for data in regards to bond strengths of different materials that have been made with this process.

I am also wondering if I can obtain a water tight seal (6 ft of water) using the above mentioned method.

Also, looking for information and people knowledgeable on the tooling end for this process.

If anyone could point me in the right direction it would be greatly appreciated.

Thanks
Mike

 

[Like2Strike]

The success of the two materials bonding with each other depends on which materials you select. The most efficient way to to calculate the bonding is to look at the melt temperature of the primary part in relation to the over-molded part. Then the component should be prototyped to verify the bond. This is the best way to validate your component.

I have over-molded (mostly prototype) many materials and have some predictable results to offer. Although I can not give any recommendation without knowing what materials are being considered, in your application.

Live Aloha

Frank M.
Tradewind Resources

http://www.tr-usa.com

 

[MiKelPD]

Frank,

Your initial comments are encouraging on the bonding of two materials. Do you have experience in the components obtaining a water tight bond between the two substrates. And if so, have you seen problems in specific areas, ie bosses, sharp corners, etc.

As far as materials we commonly use ABS, PC/ABS, PC, and Acrylic.

Thanks for the input.

Mike

 

[Like2Strike]

Mike,

Your reference to water-tite leads me to ask how you would define water-tite and in what parameters?

The best thing to do is design well, prototype and then validate your process.

A rule of thumb in plastic is "Plastic does not like sharp corners". This is due to stresses being put on the material as it passes over the sharp areas within the tooling. This condition causes shearing and generates heat which can affect the performance of the polymer.

Although, if you have sharp corners on your primary component. A stronger bond will be created within that area, since more heat is created within this section. You should also note that in the gate area the best bond will be created. The hot flow of the polymer at the gate area is at prime and due to the flow passing by the exit of the gate the greatest friction is created.

Generally the problem I have seen and have had to correct is the placement of gating, so that the gate area does not pierce a hole through the primary part from the hot flow.

Live Aloha

Frank M.
Tradewind Resources

http://www.tr-usa.com

 

[patprimmer]

Automotive tail light assemblies are often made on multi barrel machines with each colour being ingected into a multi stage mould.
They are often the same material, but different colours and are mostly Acrylic, but sometimes PC.
Acrylic or PC suppliers should be able to help, as should machinery suppliers. Engle used to do multicolour machines, and I think Battenfield and Arburg also do them