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What is 2-Shot Overmolding?

2-Shot Overmolding is any process where one material is injection molded over a previously injection molded substrate. In our case, we are premolding the electronics with LPM, and overmolding with a more durable engineering thermoplastic. This approach yields molded electronics with superior abrasion and chemical resistance, biocompatibility, and more.

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[ Unmolded ] :  Premold  : Overmold  :  Cutaway 1 : Cutaway 2 

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    Unmolded : [ Premold ] : Overmold : Cutaway 1 : Cutaway 2 
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    Unmolded : Premold : [ Overmold ] : Cutaway 1 : Cutaway 2
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    Unmolded : Premold : Overmold : [ Cutaway 1 ] : Cutaway 2

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    Unmolded : Premold : Overmold : Cutaway 1 : [ Cutaway 2 ]

The 2-Shot Overmolding Process

[ Premolded ] :  Moldset  :  Overmolding :  Overmolded  :  Test

Premolded :  [ Moldset ]  :  Overmolding :  Overmolded  :  Test

Premolded :  Moldset  :  [ Overmolding ] :  Overmolded  :  Test

Premolded :  Moldset  :  Overmolding :  [ Overmolded ]  :  Test

Premolded :  Moldset  :  Overmolding :  Overmolded  :  [ Test ]

Cavist’s 2-Shot Overmolding approach combines the benefits of low pressure molding and conventional injection molding. The process begins with a low pressure, premolded device. Now that the electronics are safely encapsulated, we can use a high pressure injection molding process to completely seal and protect with a rugged thermoplastic outer layer.

Why 2-Shot Overmolding?

Many medical or consumer electronics applications require things like solvent resistance or biocompatible overmolding materials with an FDA rating. For projects like this, Cavist will employ a 2-Shot approach. First, overmolding the electronics to protect them, and then finishing the overmold with a material that meets the needs of the customer.

Cavist 2-Shot Overmolding Video

Cavist 2-Shot overmolding
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Moldflow Analysis : Your First Shot

Simulating the first low pressure molding shot allows us to confirm our gating location and avoid things like trapped air and unsightly flow fronts. It also allows us to get a look at things like heat and pressure distribution, which can be extremely important when overmolding delicate components like batteries.

2-Shot Overmolding : Shot 1

Cavist 2-Shot Moldflow Shot 1
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Moldflow Analysis : Your Second Shot

When the second step is done with high pressure (conventional) injection molding, it is important to have a solid understanding of how the material will flow, and how the electronics can be supported in the mold. By conducting a thorough simulation, we can understand how the material flow will interact with the fragile items within the tool cavity.

2-Shot Overmolding : Shot 2

Cavist 2-Shot Moldflow Shot 2
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The Right Materials

Overmolding electronics with conventional thermoplastic molding materials is a serious challenge. The pressures and temperatures of most thermoplastics will destroy a PCB during the fill stage. The electronics must be properly supported and buffered with an initial premold step. Cafeful selection of the right overmold materials will ensure good adhesion between the two layers and minimal heat/pressure load on the electronics.

Value in Innovation

Cavist has been pioneering in the protection of electronics for over 20 years. Beginning with the patented design of the most advanced low pressure molding equipment to solve a common problem in the electronics industry, sealing and protecting electronics, cable assemblies and PCBs. Cavist 2-Shot Overmolding is simply the next step in innovation. When we see a need for a new way to help customers solve a problem, we do what we do best, we innovate.

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