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Silicone Part Production With 3D Printed Tools

This report provides a step by step guide on 3D printed tooling for silicone part production, with best practices and customer case studies.

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Contents

  • Introduction
  • Five Things You Will Learn
  • About Silicones
  • Forming Silicone With 3D Printed Tooling 
  • 3D Printing Resins and Silicones Compatibility 
  • Additional Best Practices 
  • Selecting a Mold Type 
  • Customer Case Studies
  • Step-by-Step Guide
  • Moving From Prototyping to Manufacturing
  • Conclusion 

Introduction

Soft rubbery parts have applications across many industries, from custom hearing aids, to entertainment props and prosthetics, to handles and grips on consumer goods. Designers can incorporate robust, bendable and stretchable true silicone parts into their portfolios using SLA 3D printed tooling and silicone rubbers readily accessible from hardware stores, art and jewelry supply resellers, and other common suppliers.

Silicone is a popular material to fabricate soft end-use parts as well as produce soft molds for casting rigid materials. In fact, silicone “molding and casting” terminology is broadly used to reference any multi-step method that employs silicone rubbers. Here we differentiate between two processes: “silicone mold making” and “silicone part production.”

In silicone mold making, sometimes also called silicone molding, castable silicone is used as a mold material for replicating a rigid master model. Silicone rubber is poured around a 3D printed master, and then the cavity in the silicone mold is filled with another castable material. This is often a rigid material that begins as a liquid and then cures upon cooling or a chemical reaction, such as thermoplastics, resins, cement, wax, or plaster, and in some cases expanding materials such as polymer foams.

This guide covers silicone part production, which employs a 3D printed mold to contain castable silicone for the production of soft, rubbery end products.

This report includes examples of silicone part production from consumer brands OXO and Dame Products, limb prosthetic innovator PSYONIC, product design firm Glassboard, entertainment effects company Dreamsmith, and medical device company Cosm. Each brand employs a different variation of silicone part production to achieve different results. These include:
  • Compression molding of silicone putty: A fast-curing silicone putty is packed into two sides of a 3D printed mold, which is clamped together with a benchtop vise. This method is often used for gasket prototypes and closely mimics tooling used in mass production.
  • Injection filled mold for liquid silicone: This is the most common method used to form a single continuous silicone prototype using a two-part or multi-part mold. In many cases the mold is configured such that gravity aids the silicone filling process. Silicone is injected into a channel at the top of the mold, and the mold cavity gradually fills from the bottom. Liquid silicone is finally released through outlets and air channels at the top of the mold.
  • Overmolding for complete or partial silicone encapsulation of hardware: Hardware is suspended in a two-part or multi-part mold. Liquid silicone is then injected into the mold cavity, either completely or partially conforming around the hardware.
  • Eggshell mold for custom silicone goods: The mold is a thin (<1 mm) shell that conformally envelopes the target silicone injection cavity. After the silicone is cured, the 3D printed shell- like mold is cracked away to reveal a silicone part. Since this is a sacrificial mold that cannot be reused, this technique is used to create one single custom part.
  • Design, printing, and casting methods share fundamental steps even across different industries and applications. We will walk you through a detailed design example for an injection filled overmold, taking into account advice and best practices provided by our featured customers.

Five Things You Will Learn:

  1. Selecting a silicone for your application
  2. How to encapsulate hardware using overmolding
  3. Best practices for designing critical features of 3D printed molds
  4. Tips for silicone-resin compatibility
  5. Key differences between prototype and production tooling

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