What is Compression Molding in Carbon Fiber Manufacturing?

 In carbon fiber product manufacturing, compression molding is a versatile technology. The innovative process involves placing a pre-heated composite material into a mold cavity and applying pressure to compress and shape the material into the desired form, creating a wide range of carbon fiber products. This method is commonly used for the manufacturing of high-quality carbon fiber sheets, rods, tubes and parts. The carbon fiber parts are used in industries such as automotive, aerospace, and sporting goods for creating lightweight and strong carbon fiber components. The carbon fiber industry relies on the molding process for parts of accurate dimension, superior mechanical properties of carbon fiber and excellent surface finish. The labor-intensive technology takes pride in versatility and accuracy. To explore the prospects of the technology it is essential understand the compression molding process and its applications in the composite industry.

What is Compression Molding?

The details of the carbon fiber manufacturing process are in its name. A mold cavity is heated, raw carbon fiber materials are placed and then subjected to heat and pressure to create the desired shape. This process allows for the production of complex shapes with high strength-to-weight ratios.

Divided into four basic steps-

1. Prepare a heated mold. Then a precisely measured amount of raw carbon fiber material (sheet or prepeg) called the charge, often preheated is placed into the open cavity of the mold.

2. This step involves closing the mold. The raw material is forced to spread and fill the mold cavity. A hydraulic press ensure that the carbon fiber (prepreg, sheet or other form) reaches all corners and crevices of the mold.

3. The mold with the compressed material is maintained under heat and pressure. The process of thermosetting makes the material undergo a chemical reaction, permanently hardening it into the desired shape. The curing process is based on the carbon fiber produced. A carbon fiber sheet will have a differing curing time than a rod or any other shape.

4.  The product has cured. After the pressure and heat has been released, the mold opens. Now, the finished part is ejected from the mold cavity. In many cases, excess material (flash) will be needed to be trimmed for a clean finish. 

Now, most compression molding methods follow the four steps. The manufacturing method can be further classified into other specialized methods.

1. Cast Molding

In this process, the composite material is placed into a mold and then compressed using a hydraulic press. The method is cost-effective and efficient, specially for large scale production. Cast molding for carbon fiber products is commonly used in the automotive and sports industries. The method is used for lightweight and high strength car body panels, sports helmets and tennis rackets.

2. Bladder Molding

The technique uses an inflatable bladder of silicon or rubber placed into the mold before the carbon fiber composite material. The mold is then heated and the bladder is inflated pressing the composite material against the heated mold giving it the desired shape.

Bladder molding is commonly used in the aerospace industry to produce parts such as wings and fuselage panels. It is also used in the manufacturing of medical equipment and orthopedic parts such as prosthetics and braces.

3. Transfer Molding

The technique uses a plunger to transfer the composite material into a heated mold. The composite material is forced it into the mold cavity. The mold is then heated to cure the composite material and give it its final shape.

Transfer molding is commonly used in the electrical and electronic industries for producing parts such as circuit boards and electrical connectors.

Besides the three common methods, there are specialized techniques such as injection molding. With the advancement in the carbon fiber industry, new technologies and methods are being explored to expand the potential of the composite material to create incredible high strength and low weight products.

Now, looking at the advantages and disadvantages of compression molding a manufacturer can decide whether to use the technology for their carbon fiber production.

Advantages of Compression Molding (H3)

1.    A relatively simple and straightforward compared to other molding and manufacturing processes. For some part designs this makes it easier for operators to perform, which translates to lower overall production costs.

2.    Lower tooling costs is an added bonus, as it does not require special equipment and expensive complex tooling. It typically means less capital investment. Although it is a labor-intensive process it can still be cost-effective.

3.      Great for producing large items and thicker parts.

Disadvantages of Compression Molding (H3)

1.      A higher chance of post molding costs.

2.      Slower processing times.

3.      Not suitable for all complex designs.

Applications of Compression Molding Process (H3)

The compression molding process finds numerous applications in the carbon fiber composite industry. Some of them include:

Aerospace Industry: The process is used to produce a wide range of aircraft components, including structural parts, landing gear, and engine components.

Automotive Industry: Car body panels and even engine parts for lightweight, high-performance parts results in fuel efficiency, improved performance, and reduced emissions.

Sports Equipment, including bicycle frames, golf club shafts, and tennis rackets.