Overmold Possibility

[iautry1973]

Unless you did it as a two shot process or secondary process to cover it you will have to have some metal showing. Something needs to hold the metal plate in place in the mold if not it would float in the mold and give you odd parts. So you would have some small areas of uncovered metal.

[nemanja]

Hi,

Is surface important? We do some sort of "holders" that we put on metal plates. They put metal plates in wanted position, but on other hand they are visible on surface. Holders are molded from same plastic as final overmold.

[rickbatey]

First thing make sure you have enough part thickness to allow the inserts to become totally encapsulated within the part. You will need to support the inserts in a way that holds them in place as the polymer fills the cavity to keep from getting pushed around. That would require a core function and the means to start the retraction in the sequencer so you can find the perfect timing. The strips may require Pre-heating due to different cooling rates between polymer and metal strips or to keep the melt front from freezing prematurely.
Lastly since we don’t know what you’re trying to mold; I’d offer that this could possibly be achieved using metal fibers added the polymer; possibly a wire screen inserts, or carbon fiber filled resin. If you want some sort of shielding for a computer, you could have the parts plated in say copper.
BR,
Rick

[JayDub]

I like the idea of using plastic blocks to locate the part, but here are a couple of other issues to consider:

The overmolded plastic shrinks, but the metal doesn't. You have thicker sections of plastic between metal strips and thinner sections over the strips. The metal constrains how the plastic can shrink, so you may end up with more warpage than you would with the plain plastic panel. Also the plastic over the strips is severely constrained in how it can shrink, so depending on the plastic and the size of the metal strips it could crack or split.

[Jendalf]

Hello,

interesting topic.
I would go the way of holding or fixing the strips into the cavity too.
Inserts like Nemanja has, can be one way. The other is tool design with core positioning like Rick introduce. Or You can also combinate this two things together.

You can use spring/preassure loaded core unless you know (or can predict) the cavity preassure vs preassure needed for core pushing (it can be changed as You need by spring change).
Or You can time the core into pull position dependig on the time or cyclus state (core pull - starting holding preassure etc.) and than fill the gap by holding preassure.

In the overmolding its critical the gate position.
What is bad news - the simulation of this is not well evolved. Only Autodesk moldflow has some function for overmolding.

Also very important is to choose right grade of polymer for Your appliaciton.

J