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RTV Molding

3D Printing for Silicone Molds

3D printing makes it possible to produce a prototype pattern in less than 24 hours. Plus, without the traditional constraints of machining, your designs can be more complex without driving up cost.

Overview of the application

Silicone molding — also known as room temperature vulcanizing (RTV) molding — creates finished products for prototyping, functional testing and short-run production. Considering tool life and cycle times, it is ideal for small quantities (25 – 100 castings) because it offers lead times and costs that are well below that of machining or injection molding.

Silicone molds are made by pouring silicone rubber over a pattern. After curing, the resulting firm but flexible mold can produce parts with extremely complex geometry, intricate detail and tight tolerances. The parts are cast from a silicone mold made with thermoset materials (commonly urethanes) that are available with a vast array of mechanical, thermal and electrical properties.

Value of using FDM or PolyJet

Traditionally, patterns are fabricated from wood, plastic or metal, which can be expensive, have long lead times and require skilled labor to oversee the pattern-making process. As a result, designers may have to limit or simplify the geometry of the pattern to accommodate these factors.

Benefits & Best Fit for PolyJet

PolyJet 3D printing technology is an innovative alternative to machining patterns for silicone mold making. It builds patterns layer by layer, using data from computer-aided design (CAD) files. With its inkjet-like process, PolyJet delivers extremely high-resolution patterns with smooth surface

As a result, PolyJet patterns are typically mold-ready and have subtle details that can be transferred to the urethane castings. For high-gloss or clear finishes, a little polishing is all that is needed. Additionally, complex and intricate patterns can be made without adding time, cost or challenges to the design process. With PolyJet, silicone molds can be ready to make parts in as little as 24 hours.

For larger quantities of castings or multi-part assemblies, family molds are ideal. These multi-cavity tools can produce several pieces with each casting cycle, but each cavity needs its own pattern. Since machined patterns are made in a series, the mold is delayed. Numerous PolyJet patterns — as long as they don’t exceed the capacity of the 3D printer — may be produced in one build, and at a fraction of the time required to make them individually.

Benefits of PolyJet

Average lead time savings:70% – 90%
Average cost savings:30% – 85%
Quality: Smooth, nearly mold-ready surfaces
Fine textures and details
Complex, intricate designs
Efficiency gains:Automated pattern-making
Little or no pattern preparation

*Typical time and cost savings derived from numerous end-user analysis, testimonials and feedback. Actual savings may vary based upon numerous factors, including traditional time/cost, part geometry and utilized technology.

PolyJet is a Best Fit

Quantity:Small volume (5 – 250 castings)
Size:6 mm – 300 mm (0.25 in – 12 in)
Design:Complex, intricate and highly detailed
Revisions:Design modifications are likely.
Multiples:Family or duplicate molds for multi-piece casting
Benefits & Best Fit for FDM

Silicone molding with FDM patterns is a three-step process:

  1. Make the FDM pattern (also known as a master pattern or mold master).
  2. Make the mold by covering the FDM pattern with silicone and allow it to cure.
  3. Cast the urethane in the mold.

FDM technology provides an alternative method for producing patterns for silicone molds. FDM is an additive manufacturing (3D printing) process that builds plastic parts layer by layer using data from computer-aided design (CAD) files. With fast FDM pattern creation, mold making can start shortly after pattern design, even when the pattern is complex. Low cost FDM materials also have greater longevity, strength, and heat resistance than those used with other additive manufacturing technologies. These characteristics allow manufacturers to create silicone molded products faster and less expensively than ever before.

The weight of silicone rubber and heat from an accelerated curing process can cause patterns to bow, buckle or break. However, FDM thermoplastics are inert, so the finished patterns do not inhibit the curing reaction, nor are they affected by the heat and weight. The result is accurate molds.

Additionally, FDM materials are strong and durable. This makes it easy to extract the pattern from the mold without damage so the pattern can be reused to make future molds. Being dimensionally and physically stable, a single pattern can make molds for months or even years to come. And if a prototype or a cast urethane part reveals the need for design changes, a new pattern can be designed and ready for use within hours.

Benefits of FDM

Average lead time savings:Up to 90%
Average cost savings:Up to 70%
Greater performance: Inert: Will not inhibit curing
Strong: No pattern distortion
Stable: Store indefinitely
Durable: Extractable without breakage
Lightweight: Sparse fill interior option

*Typical time and cost savings derived from numerous end-user analysis, testimonials and feedback. Actual savings may vary based upon numerous factors, including traditional time/cost, part geometry and utilized technology.

FDM is a best fit

Design:Complex, intricate
Large parts
Internal cavities
Thin walls
Revisions likely
Molds:Duplicate molds required
Heat accelerated cure silicones
Dual-purpose patterns: prototyping and mold making
Size: (XYZ)25 mm (1 in) to 915 mm (36 in)
Quantity:5 to 100 castings
Life expectancy:Reuse pattern to create multiple molds
Pattern stored for re-use
Our Technologies

With three complementary 3D printing technologies designed for a range of applications, Stratasys is a powerful partner in the product development department, in classrooms and labs, and on the production floor.

FDM Technology. 3D print durable parts with real thermoplastic. FDM Technology is a powerful Stratasys-patented additive manufacturing method.

  • Real thermoplastics
  • Advanced functional performance
  • Strong, durable and stable over time
  • Economical

FPolyJet Technology. 3D print precision prototypes in a wide range of materials. PolyJet 3D printing technology is a powerful additive manufacturing method patented by Stratasys.

  • Simulated plastics and elastomers
  • Multi-material 3D printing
  • High precision and fine detail
  • Smooth surfaces

Compatibility

SeriesIdeaDesignProduction
FDM233
PolyJet055

Application compatibility: (0 – N/A, 1 – Low, 5 – High)