RTV Molding: The Overview of Silicone Molding

While 3D printing has recently emerged as the favored approach for developing early prototypes, injection molding has long been the go-to technique for mass manufacturing. Determining when and how to switch from low-volume production utilizing 3D printing to high-volume manufacturing, however, is the difficult part. It might be difficult to strike the ideal balance between up-front costs, production costs, and product quality. Silicone mold (RTV mold) can be used as a viable alternative for low-volume production demands in this situation.
Next, more information of RTV mold and RTV molding process as below.

What is RTV Molding

Silicone molding, often referred to as room temperature vulcanizing (RTV) molding, offers an excellent solution for small batch manufacturing. RTV mold material excels at preserving intricate and minute details, with tolerances akin to those found in 3D printed components (minimum features of 0.025 inches or 0.6mm).

RTV Molding Process

To begin, a pattern of the intended item must be created. In some cases, you may already possess an existing item that you wish to replicate, in which case the silicone can be directly applied, provided the material is suitable. Alternatively, patterns can be crafted from wood, metal, or through 3D printing. Utilizing 3D printing for the mold pattern has shown the potential to significantly reduce lead times (by up to 90%) and lower costs (by up to 70%), contingent upon the original part’s geometry.

Once the pattern is prepared, the silicone is blended with a curing agent and poured over the pattern. The curing process may extend for up to 24 hours, resulting in a robust and flexible mold that becomes ready for use almost immediately.

Urethanes, a category of thermoset plastics, represent the most frequently employed casting material. They offer a diverse range of mechanical, visual, and electrical properties, reducing the need for extensive post-production work.

The molds can be effectively employed for producing batches of up to 100 parts, though their typical usage range falls between 15 to 30 units per mold, contingent on the casting material.

Costs

The cost breakdown for room temperature vulcanizing (RTV) units comprises three distinct line items, each contributing to the overall expense:

Pattern Cost
The pricing of the pattern is contingent on how you generate the geometry. For replicating models, using an off-the-shelf unit may suffice. Otherwise, the primary methods for producing patterns are 3D printing, followed by subtractive CNC machining.
After creating a model, a mold maker typically applies a primer and texture to achieve the desired surface finish for the final product.

Mold Cost
The primary consideration for mold cost revolves around the volume of silicone required. Silicone, priced at approximately $11 per cubic inch, is not an inexpensive material.
Other crucial factors to consider include determining the necessity of slides, the quantity of pieces the mold will yield, and the desired lifespan of the mold.

Unit Cost
The cost of individual units depends on the geometric volume of the part and the extent of post-processing required. Simple parts with minimal material requirements tend to have a low unit cost.

Once you have calculated the expenses associated with the three aforementioned line items (pattern, mold, and unit cost), it is prudent to divide the total by the number of units the mold can produce. This provides a more accurate understanding of the per-unit cost.

Here’s an illustrative example of a cost breakdown:
Pattern: $320
Mold: $900
Unit: $70 per unit
Mold Life: 30 sets
Per Unit Cost: Approximately $110

While $110 per unit may initially appear costly, it represents a substantial savings compared to the cost of producing each part individually. Moreover, the lead time for this method is typically significantly faster than that of crafting an injection-molded tool.

Assessing and Comparing RTV Molding

Let’s take a concise look at the key advantages and disadvantages of RTV molding (Room Temperature Vulcanizing molding):

Pros

Reduced Lead Time and Upfront Costs: RTV molding offers significantly shorter lead times and lower initial expenses compared to injection molding.
Lower Production Costs: The production costs associated with RTV molding are notably more economical than 3D printing.
Minimal Post-Production: RTV molding requires minimal post-production processes, streamlining the manufacturing workflow.
Diverse Material Properties: RTV mold provides access to a wider range of casting material properties compared to 3D printed materials. Mechanical properties can be tailored by selecting the appropriate material, allowing for close simulation of production parts.

Cons

Limited Mold Lifespan: RTV mold typically needs to be reproduced after producing around 20 to 100 units.
Potential for Surface Contaminants: The presence of surface contaminants can hinder the curing process during RTV molding.

Comparison with 3D Printing

3D printing excels at swiftly transforming concepts into tangible prototypes with minimal lead time. However, as production volume increases, costs escalate, even when using in-house equipment.
Larger part sizes approach the printer’s capacity, resulting in exponential cost increases. Printing individual parts significantly prolongs the manufacturing process.

Comparison with Injection Molding

While injection molding remains the preferred choice for large-scale production, silicone RTV molding offers distinct advantages.
RTV mold is versatile and stress-resistant, enabling the incorporation of intricate design features, draft angles, and undercuts that may not be feasible with traditional injection molds.
It’s important to note that RTV mold is best suited for low-volume production, typically involving runs of fewer than 500 units. Careful analysis is necessary to determine when to transition to injection molding for higher production volumes.

When to Opt for RTV Mold

For small-volume production, below 10 or above 50 units, the choice between 3D printing and RTV molding is relatively straightforward.
The decision becomes more complex for production volumes of 20 to 30 units. Small 3D printed parts can be produced efficiently in parallel, making them cost-effective even at higher volumes.
Large and intricate parts, particularly those approaching the printer’s bed limit, significantly extend production times. In such cases, even lower production volumes, around 10 units, may warrant the use of molds.
The selection of the most suitable production method depends on various factors, including product size, part geometry, and production volume. It is essential to carefully evaluate these unique product features to determine the optimal solution.

RTV Molding at Sungplastic

RTV molding involves the use of a two-part silicone rubber compound that cures at room temperature to create a flexible and durable RTV mold.

Our services include：
RTV mold or silicone part manufacturing
Small to large custom quality silicone RTV moulds
Support unique design, surface finishing and post-processing
RTV silicone rapid prototyping
RTV silicone injection molding
Mass production
Small batch manufacturing

Welcomed the consultation about RTV mold or RTV molding!

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