Compression molding, also known as compression moulding, has become the most commonly used manufacturing process in industries ranging from industrial to maternal and baby. Generally speaking, common materials for compression molding include granular, powdery, fibrous or preformed plastic. In this article, we focus on silicone compression molding. High consistency rubber (HCR silicone), also known as solid silicone rubber or thermoset rubber, is a synthetic elastomer containing the elements silicon, oxygen, carbon, hydrogen, and other elements that add the desired properties, with unique Chemical structure, temperature resistance, and aging resistance. The Compound processing method for this different combination of properties is usually compression molding.

Below we will discuss its definition, how it works, and its applications. In this article, you will learn more useful information about silicone compression molding and what factors you should consider before choosing this process.

What is Silicone Compression Molding?

Silicone compression molding is a conversion process that simultaneously completes shaping and curing in the manufacture of silicone rubber products. The processing method is to punch a certain amount of silicone material into a specified shape and manually place the uncured silicone polymer into the preheated upper and lower flat plates or the mold between multiple plates, then start the hydraulic press to close the mold and follow the process It is stipulated to increase heat and pressure until the macromolecules are fully cross-linked, and finally, a section of vulcanized silicone rubber product is released from the mold.

How does silicone compression molding work?

Silicone compression molding is an orderly manufacturing process. Its process flow generally consists of three important stages, namely pre-molding preparation, molding process, and post-treatment process.

First, heat is usually added to dispersed preforms (mostly strips or discs) to increase fluidity, reduce molding pressure, enhance uniformity of curing, and speed up curing, thereby minimizing molding time. If the preheating temperature is too high or the time is too long, some parts of materials will undergo cross-linking reactions in advance, affecting the fluidity of the polymer.

Second, the thermosetting material molding process generally includes filling, pressing, venting, curing, and removal. If there are inserts that are pressed together, the inserts should be preheated and accurately placed in the required position before adding materials. Materials are generally measured by the gravimetric method. After the material arrangement is completed, the mold can be closed. This process usually takes a few seconds to a dozen seconds. The mold needs to close very quickly to avoid premature solidification or degradation of the material. Immediately after the mold is closed, heat and pressure should be increased simultaneously to transform the polymer into a viscous fluid state and cover the entire cavity. The high-molecular-weight silicone is mixed with the curing agent to initiate a cross-linking reaction and maintain it for a certain period of time, gradually transforming into a product that conforms to the shape of the cavity until it reaches a certain degree of cross-linking and preset mechanical strength. Neutral compounds and other volatiles are generally released during compression molding curing. During this process, technicians need to release the gas and pressure in the mold cavity (usually 1-4 times) to prevent bubbles or delamination and ensure the mechanical properties of the product. Finally, open the mold and take out the silicone products with rough edges.

Third, after de-molding, the mold surface and cavity are usually blown with compressed air. For products that need to be trimmed, manual operation or a frozen trimming machine can be selected for removal based on the number of units produced and the available budget. In order to cure the polymer more completely and reduce the moisture and volatile content, the disassembled products are usually placed in baking equipment for high-temperature treatment to ensure that they achieve the required properties. Depending on the silicone formula, the structure and thickness of the part, and other conditions, the general baking time is set to 1-4 hours.

What critical factors should be considered in silicone compression molding?

Silicone compression molding is one of the most widely used processing technologies for silicone molding. How to evaluate whether this process is suitable for the production of your products in the early stage? The following are factors to consider during the selection phase:

Complexity of component structure

The above are some manufacturability and feasibility assessments that need to be carried out based on different product configurations, production needs, and cost requirements before use. Yuanyi's technical team has rich development expertise and is able to provide you with useful suggestions and professional options during the hesitation period and throughout the development process.

Why Use Silicone Compression Molding?

Compared with the initial investment and maintenance costs of the injection molding process, the press and post-maintenance costs used in silicone molding are low. Due to the simple structure of the mold used in compression molding, it has the advantages of a shorter mold development cycle and lower mold manufacturing and maintenance costs. It has a wide range of adaptability and is suitable for almost all plastics and curing processes, especially plastics that cannot be produced by extrusion technology due to poor flow. Its advantage is that combined with HCR silicone, it can produce larger flat parts, which is a task that cannot be accomplished by extrusion molding.

It also allows for low-cost fillers while maintaining minimal changes in part performance, resulting in lower unit production costs which makes it easy to promote and use in many fields, such as industrial buttons and office automation equipment. It is also used to prototype various parts, which also greatly encourages part manufacturers to launch different test versions in a short period of time.

Silicone Compression Molding Applications

Silicone compression molding is ideal for some common industry applications due to its ability to quickly replicate parts required in a variety of applications. It is used in the manufacture of automotive parts such as sealing gaskets, hoses, joints, and cables, Used to make protective sleeves and seals for electronic products. It can be used to manufacture consumer daily necessities, such as baby care products, tableware, cooking utensils, silicone molds, and home appliances. It can also be used to produce medical machinery with extremely high requirements on grade and elasticity, such as tubes and mechanical parts.

Advantages of our silicone compression molding

As the industry's top manufacturer of silicone products, our engineering team is proficient and masters the molding process and uses this processing method to produce low-to-medium volume series of parts. They are able to provide custom silicone compression molding services from material selection, custom molds, and processing properties (fluidity, curing rate, compression rate, shrinkage rate). Their ability also lies in creating more cavities and ensuring the manufacturability of the product without significantly increasing the cost of the mold, thereby reducing the unit production cost.