Custom Silicone Compression Molding for Small Rubber Plugs

A silicone plug measuring only about 20 mm may look like an easy part to manufacture. At a production quantity of 20,000 pieces, however, the real question is not whether the first part can be molded—it is whether the insertion profile, flange and overall fit remain consistent throughout the batch.

For this U.S. electronics project, we manufactured 20,000 custom black silicone rubber plugs using silicone compression molding. Each component measures approximately 20 × 20 × 25 mm, with a hardness of around 50 Shore A.

The design is compact, with a smaller push-in section and a wider circular flange. These two areas determine how the plug enters the mating opening and how it seats against the surrounding product surface, making them more important than the small overall size might suggest.

Project Overview

A Small Molded Part Where Fit Comes First

The plug consists of two main functional areas.

The smaller projecting section enters the corresponding opening in the electronic product. The larger flange remains outside and determines where the component stops and how it sits against the surrounding surface.

For a part like this, controlling the mating geometry matters more than applying unnecessarily tight tolerances to every surface.

If the insertion section is too large, assembly may require excessive force. If it is too small, the plug may fit more loosely than intended. Variation in the flange can also affect the final seating position.

This is why our custom silicone compression molding projects are reviewed around the actual functional features of the part, not simply its overall dimensions.

When mating-part information is available, it can also help identify which dimensions deserve particular attention during tooling, sample verification and production.

50 Shore A Is More Than a Material Specification

The silicone hardness for this project was approximately 50 Shore A.

For a push-in rubber component, hardness and geometry work together. The material needs to deform during installation and recover afterward, while the molded profile determines how the plug engages with the mating feature.

Changing one without considering the other can change the way the part fits or feels during assembly.

We therefore treat Shore hardness as part of the functional requirement. Customers can specify the required silicone material, hardness, color and dimensional requirements according to their application.

For electronic products, this is particularly useful when a small silicone component needs to combine flexibility with a defined installation fit.

What Changes When the Order Reaches 20,000 Pieces?

A few approved samples establish that the design and mold can produce the intended part.

Volume production introduces a different challenge: repeatability.

For this 20,000-piece order, production control focuses on the characteristics that can influence downstream assembly, including:

• insertion profile and diameter;
• flange dimensions and seating area;
• overall height;
• molded edge condition;
• excessive flash;
• visible deformation;
• surface consistency;
• specified material and Shore hardness.

The exact inspection requirements follow the customer's drawings and identified critical features.

The objective is not to make every dimension tighter than necessary. It is to keep the dimensions that matter to fit and assembly stable throughout the production run.

Flash Control on Small Silicone Plugs

Flash deserves particular attention when a silicone component is this small.

During compression molding, silicone is formed in the mold under pressure. Tooling condition and process parameters can influence the amount and location of material around the parting line.

On a component measuring approximately 20 × 20 × 25 mm, a small amount of excess material can become significant if it appears around the push-in section or seating surface.

Location therefore matters.

A normal molding line in a non-critical area is different from flash that changes how the plug enters an opening or sits against the product.

For these small compression molded silicone parts, inspection is focused on functional edges and interfaces rather than applying the same cosmetic standard to every hidden surface.

Why Compression Molding Makes Sense for This Project

The customer required 20,000 identical parts rather than a handful of development samples.

At this quantity, dedicated tooling and silicone compression molding provide a practical route to repeat production. Once the mold and process conditions are established, the same custom geometry can be reproduced efficiently across the batch.

There is another advantage: the customer does not need to redesign the electronic product around a standard rubber stopper.

The insertion profile, flange, height and other local features can instead be manufactured according to the customer's own product design.

This makes custom silicone rubber molding particularly useful for non-standard plugs, stoppers, buttons, seals and other small flexible components used in electronic and industrial assemblies.

From Customer Drawing to Volume Production

Our silicone projects begin with customer-specific product requirements rather than standard catalog dimensions.

For a new custom silicone rubber part, useful information typically includes:

2D Drawing → 3D CAD Data → Silicone Specification → Shore Hardness → Color → Critical Dimensions → Quantity → Mating Requirements

After the design is reviewed, tooling can be manufactured and samples produced for verification.

Where fit is important, the customer can check the molded samples with the actual mating component before the full production quantity is released. Any necessary adjustment can then be addressed before moving into volume manufacturing.

For this U.S. project, the approved design moved into production of 20,000 black silicone plugs for use in an electronic product.

Custom Silicone Compression Molding Services

YS Precision provides custom silicone compression molding services for electronic and industrial applications, from initial sample verification through volume production.

We manufacture customer-specific silicone plugs, stoppers, buttons and other small molded components according to supplied drawings and technical requirements. Material, Shore hardness, color, geometry and critical fit features can be defined according to the application.

This project is a good example of why a small rubber component should not be judged only by its size. The plug is approximately 20 mm, but producing 20,000 pieces with a consistent insertion profile, flange and molded condition is what makes the manufacturing process matter.

If you are sourcing custom silicone rubber plugs or compression molded silicone parts, send us your 2D/3D drawings together with the material, Shore hardness, color, quantity and mating requirements. We can review the part before tooling and volume production.