Rubber Pad EPDM/NBR/SILICONE/FKM Silicone Ring Seal Plug Gasket Washer Molded Rubber Grommets Bushings

Hangzhou Bright Rubber Plastic Product Co., Ltd. is one of the leading manufacturers and suppliers of rubber pad epdm/nbr/silicone/fkm silicone ring seal plug gasket washer molded rubber grommets bushings in China. If you're going to buy rubber pad epdm/nbr/silicone/fkm silicone ring seal plug gasket washer molded rubber grommets bushings made in China, welcome to get more information from our factory. We also accept customized orders.

Product Description

Production Methods of Rubber O-Rings

The production of rubber O-rings is a transformation process from "raw rubber" to "elastic sealing parts," centered around three core stages: compound preparation, molding & vulcanization, and post-processing. Depending on product specifications, precision requirements, and batch sizes, several mainstream production methods have been derived:

1. Core Molding Processes (Three Mainstream Paths)

This is the critical step that determines the dimensional accuracy and production efficiency of O-rings:

Compression Molding – The Most Common

Process: Weighed rubber preforms (blanks) are manually or automatically placed into preheated metal mold cavities. A hydraulic press closes the mold under pressure, allowing the rubber to flow, fill the cavity, and cure.

Characteristics: Low tooling cost; suitable for multi-variety, small-batch, and large-batch standard parts. However, it involves relatively high labor intensity, and the parting line flash is thicker, requiring subsequent deflashing.

Injection Molding – High Efficiency & Precision

Process: Rubber compound is plasticized in the injection barrel and injected into a closed, heated mold under high pressure for rapid curing.

Characteristics: Highly automated, short cycle times, minimal flash (sometimes flashless), high dimensional accuracy, and excellent consistency. However, it requires significant investment in equipment and molds, making it suitable for high-volume, high-precision orders (e.g., automotive, electronics).

Transfer Molding – The Middle Ground

Process: The rubber compound is first placed in a transfer pot above the mold. A plunger forces the material through sprues and runners into the closed mold cavity.

Characteristics: A compromise between compression and injection. It produces less flash than compression molding and offers better dimensional accuracy, suitable for medium-volume orders with specific precision requirements.

2. Special Method for Large/Non-Standard O-Rings: Extrusion & Splicing

Process: Rubber is extruded into a continuous cord (rubber rope) via an extruder. The cord is cut to the required circumference and joined end-to-end using vulcanized splicing​ (butt, miter, or lap joints).

Application: Ideal for oversized diameters (e.g., several meters) or custom one-off O-rings without the need for expensive large molds. However, the sealing performance at the splice joint is typically slightly lower than that of a one-piece molded ring.

3. General Manufacturing Workflow (Using Compression/Injection as Examples)

Regardless of the molding method, the upstream and downstream processes are generally consistent:

Material Preparation & Mixing: Select the base polymer (e.g., NBR, FKM, VMQ) and mix it with curatives, carbon black, and oils in an internal mixer or on a two-roll mill to create a homogeneous "compound."

Preforming (for Compression): The compound is pre-processed into rubber strips or pellets matching the weight and shape of the final O-ring to ensure accurate shot size.

Curing/Vulcanization: Inside the mold, under specific temperatures (typically 150°C–180°C+), pressure, and time, the rubber cross-links, transforming from a plastic state to an elastic state while forming the O-ring shape.

Deflashing: Removal of excess flash from the parting line. High-volume production typically uses cryogenic deflashing​ (freezing the flash with liquid nitrogen and blasting it off with media). High-precision parts may use water jet cutting, while small batches rely on manual trimming.

Post-Curing: For materials like FKM or VMQ, parts are baked in an oven for several hours to remove volatile byproducts and stabilize physical properties and dimensions.

Inspection & Packaging: Parts are inspected for dimensions (ID, CS), hardness, appearance, and compression set. Qualified products are cleaned and packaged.

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