Silicone Molding Process Guide

Complete Guide to the Silicone Molding Process

In automotive, medical, food-grade, wearable, and industrial products, silicone molding processes are all very flexible, durable, and heat-resistant in nature. Knowledge of the molding techniques and design considerations becomes essential when custom soft seals, hard industrial parts, or precision medical components are the goal.

This silicone molding process guide reviews the main types of silicone molding, design tips for molds, the choice of silicone grade, and matters concerning post-curing; thus, it is a great overview for anyone interested in silicone manufacturing with RUBBER SILICONE MOLDS.

What are the different types of silicone molding processes?

The silicone molding processes encompass many methods to suit different shapes and sizes of products or different production volumes. Compression molding constitutes pre-measured silicone being pressed into a heated mold. This is suitable for simple, medium to large parts. LSR injection molding technique involves mixing liquid silicone and injecting it into a mold. It is ideal for medical parts, thin-wall components, and high-volume productions.

Transfer molding pushes silicone into the cavities through small channels, offering better control for parts with inserts or fine details. Extrusion and drip molding are for continuous profiles or very tiny precision parts. The best method will depend on the design of the part, material selection, and speed of manufacture.

How to design a mold for silicone molding?

Good mold design will affect quality and consistency significantly. An accurate mold design should be arrived at after taking the following points into consideration:

Gate placement: This regulates the flow of silicone into the mold. A properly positioned gate ensures smooth flow and helps reduce leakage or defects.
Venting: Since silicone can trap air, vents let the air escape, preventing bubbles and voids in the final product.
Parting line: Place the parting line where it’s least visible or where it supports an easy flow of material.
Wall thickness: Do your best to keep the walls evenly thick so that you will not have bending, shrinking, or uneven curing problems.
Shrinkage: Silicone shrinks slightly during curing; hence, the mold must be sized to the final part.
Inserts and undercuts: These require strong, well-designed molds and, in some cases, automated ejection for easy demolding.

Well-designed molds will enable fast production and keep parts consistent and genuine.

Common defects in silicone molded parts, and how to prevent them?

Prevent air bubbles when air becomes trapped; carry out degassing of the silicone and slow pouring.
Increase viscosity and ensure good mold venting before pouring silicone; if not, the silicone will become too thick to fill properly.
Tearing occurs with the part with thin sections; provide smooth transitions in design and use a good quality release agent.
Compression Set Determination: Measures how well seals maintain their shape under compression
Surface defects show up from the dirt of molds; always clean and maintain the mold.
Warping is due to inconsistent curing; keep a steady curing temperature.

How to choose the right grade of silicone for molding?

Choosing the grade of silicone always depends on usage. Although the right choice depends on performance needs, safety requirements, and cost, here are a few important considerations:

Flow properties- Liquid Silicone Rubber (LSR) is ideal for injection molding because it flows easily, while thicker HCR (High Consistency Rubber) is better for compression or transfer molding.
Shore hardness: Starts from very soft (Shore A 10) to very firm (Shore A 80). Softer grades are preferred for seals or baby products; harder grades are more suitable for industrial parts.
Cure system: Platinum-cured silicone has low shrinkage. This is most suitable for either medical or food-grade applications. Peroxide-cured silicone is more cost-effective for general industrial applications.
Temperature resistance: silicones that can resist high temperatures are needed for parts used in automotive or electronic applications.

Post-curing: Does it really matter for silicone molded parts?

Post-curing is a heating operation of silicone parts to allow complete curing to take place and to volatilize unwanted residues. It’s not always required, but in some situations, it becomes the most important option.

When it is necessary: Post-curing is needed for applications like healthcare, food-contact products, high-tolerance components, and materials that must retain strength or resist low compression set.
Benefits: Post-curing improves heat resistance, compressive strength, odor removal, and the ability to meet stringent requirements.
When it may be unnecessary: For general industrial parts, low-price items, or certain LSR grades that are supposedly cured through ambient conditions.