How to choose mold when producing rubber O-rings using a rubber injection machine or a vacuum compression molding press ?

Is it better to use a double-layer mold or a three-layer mold?

Our answer is: Common O-ring double-layer molds are more widely used, but the specific selection of the number of layers of molds should be adjusted appropriately according to the customer's production capacity and product requirements.

Large O-rings are more suitable for three-layer molds, which can form two products at a time and improve production efficiency.

If it is small, you can make a two-layer mold, which has the advantages of reducing production costs and reducing scrap rates etc. 

The specific advantages of double-layer molds are as follows:

 1. Lower scrap rate

The two-layer mold has a shorter runner and direct rubber material feeding, and the material utilization rate is high; the three-layer mold needs to design a long runner and a multi-layer diversion system, which prolongs the production time and increases the scrap (about 5%-15% additional loss) 

2. Shortened vulcanization cycle ‌

The two-layer mold has higher heat conduction efficiency: fewer components, compact structure, easier to control mold temperature evenly, and the vulcanization time is 10%-20% shorter than the three-layer mold, and the production capacity is significantly improved. ‌

 3‌. Low defect risk ‌

The two-layer mold has a short rubber filling path, which reduces the risk of bubbles and under-vulcanization; the three-layer mold is prone to uneven heat transfer due to long runners and multiple layers, resulting in local over-vulcanization or under-vulcanization ‌.

 4. Structural and cost advantages

The two-layer mold has a simpler structure, consisting only of a fixed mold and a movable mold, so that it has a low manufacturing cost and high efficiency. In contrast, the three-layer mold has a more complex structure and is higher cost due to the addition of a runner plate.

 5. Low maintenance cost.

The simple structure of two-layer molds means fewer wear parts, and it is easier to clean and maintain. The stripper plate guide column, runner nozzle and other parts of three-layer molds need frequent maintenance, and the downtime is longer.  

Three-layer molds are suitable for large-scale, high-precision demand scenarios, and their advantages are as follows:

1. High-precision sealing surface control.

The three-layer structure forms a double parting surface, which can accurately control the flow direction of the rubber material and meet the high-precision sealing requirements.

 Application areas: aerospace hydraulic seals (such as perfluoroether rubber rings for rocket thrusters), ultra-clean seals for semiconductor equipment.

 2. Complex cross-section one-time molding.

The middle mold can integrate multi-stage retaining ring grooves or special-shaped runners, and directly mold a combined sealing structure to avoid secondary assembly. At the same time, it supports segmented vulcanization processes (such as seamless docking technology for large-size O-rings) to solve the joint strength defects of products with a diameter of >500mm in traditional processes.

 Application areas: seamless molding of super-large O-rings for nuclear magnetic resonance equipment.

3. Improved production efficiency

Three-layer molds have more cavities which can realize multi-cavity synchronous production to improve production efficiency.

In summary, three-layer molds are the core equipment for mass production of high-end O-rings, especially for super-large size, composite structure, high pressure/extreme working condition seals. The two-layer mold is an economical solution for small and medium-sized, medium and high hardness, large cross-section and low-cost standardized O-ring products. The core advantages are low cost, high reliability and hard rubber adaptability. It is more widely used in common products such as rubber O-rings.

 As an expert in rubber machinery and mold solutions for the rubber molding industry with 25 years of experience, we have provided professional turnkey project services in more than 100 countries. We can provide you with rich experience in rubber product molding technology services, whether it is equipment or molds, we can provide a complete set of solutions. For more information, please feel free to contact us , and our team will provide you with one-on-one consultation.

Posted by Alice Xiao

Email: Alice@hwayimachine.com 

Wechat/whatsapp: 0086 15073426303