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PCM Mould

The use of prepregs has gained popularity over the last few years and has become an effective alternative for the high-volume production of structural parts. With this technology, it is possible to produce high-performance structural parts (up to 70% FVF) with cycle times as low as 2 minutes.

PCM (Prepreg Compression Molding) is a process for manufacturing resin-impregnated fiber-reinforced parts based on the production of complex geometries with high strength-to-weight ratios in a compression process with lower processing pressures compared to the injection process.

The technology involves placing the prepreg on a PCM mold and then further molding it in a press (at low or medium pressure) in a heated mold. PCM technology can be applied to SMC molding or carbon fiber molding to produce automotive parts or aircraft components.

What is prepreg?

Prepreg is a pre-molded glass fiber imitation into a blank that matches the product's structure, shape, and size. This blank is then hot pressed into the product by adding a resin mixture during the molding process. It is compared with the mass molding plastic, using longer fibers (25mm, 38mm, and 50mm three lengths) and higher fiber content (20% a 40%), the mechanical properties of the product are better. Since the prepreg material basically does not flow during the PCM molding process, the prepreg material can only be pressed for products with greater depth and shape dimensions and less complex shapes. Prepregs are very strong, extremely light, and unstoppable in a growing number of industries. These composites of two or more materials develop new properties that the starting materials alone do not possess. Fiber-reinforced plastics, in particular, possess maximum strength and stiffness as well as exceptionally lightweight. In addition, there are other benefits, such as corrosion resistance and long service life. With the help of modern production processes, these high-quality materials can be optimized for various applications and tasks. The required PCM molds have been designed and manufactured by MDC for more than 20 years.

carbon fiber prepreg

What are the methods of preparation of prepregs?

The methods of prepreg preparation can be divided according to the glass fiber delivery medium and the mode of operation. The preparation of prepregs is an important part of the PCM process, which is carried out with the help of performers. There are many performers, and there are two types of performers: air type and water type, depending on the carrier medium (or carrier) of the glass fiber. The air type is divided into closed type (pressure ventilation chamber type) and open type (open jet injection or fiber direct injection type).

Typical formulations used for prepregs are shown in the table

Component Dosage / portion Ratio within the press Final composition within the molded product
Polyester resin (viscosity 3.5 Pa •s) 68. 0 65% 48.7%
Styrene monomer (to bring resin viscosity down to 0. 8 Pa •s) 7
Tert-butyl hydroperoxide initiator 0.6
Muches or calcium carbonate filler 25. 0 16.3%
Internal release agent 0.1
Colorant 0.5~5.0
Glass Fiber Reinforced Material - 35% 35%

Prepreg compression molding process

  1. 1. Check the prepreg quality. Mainly check the looseness of the prepreg, the pilling of the blanks, and the amount and uniformity of the binder. If the blank is too loose, it will be easily "scoured" during molding; too dense will prevent the penetration of the resin mixture. Excessive hairiness of the blank and too much adhesive will produce wrinkles when molding. All of the above problems will affect the uniformity of the product quality.
  2. 2. Preparation of the PCM molds. Before pressing, purify the PCM mold, especially the shear edge part.
  3. 3. Prepare for adding material. Weighing the prepreg, adjusting the quality of the blank block by increasing or decreasing the thin layer of glass fiber, and also adding reinforcing materials locally as needed.
  4. 4. Resin mixture infusion. The resin mixture is weighed (or measured by metering) according to the amount and infused onto the preformed blanks in a certain way. The filling of the resin mixture can be done before or after the preform is placed in the mold. The most basic filling method is the "X" shape, from one corner to the other, which avoids bubbles or bulges. The efficiency can be improved by filling outside the press. If the face of the resin infusion is the face of the part being finished, then the face felt can be placed on top of it before closing the press.
  5. 5. Closing the mold. The press closure speed is a two-speed system, with a fast closure speed of 125 mm/s and a slow closure speed of 1.25 mm/s. The slow closure speed is to prevent the liquid resin mixture from spilling and the fibers from being squeezed out of the overflow gap.
  6. 6. Molding pressure. Generally 1.72~2.75MPa.
  7. 7. Curing time. The circumference time of small parts is 1~3min, while the curing time of large parts can be up to 20min.
  8. 8. molding temperature. Generally 105 ~ 150 °
  9. 9. parts out. When the curing reaction is completed, the press is opened and the parts are removed with the help of compressed air, copper chisel, and vacuum unloader.
  10. 10. Cooling and shaping. After demolding, the parts are sometimes cooled in a fixture to prevent warping and deformation. After cooling, trimming, debossing and drilling can be carried out.

Prepreg compression molding process

Advantages of Prepreg Compression Molding

  • Precise control of part geometry. This allows you to create parts with more detailed internal features, such as holes and ribs. Parts with very high mechanical properties and a high quality surface finish that MDC can customize to meet customer requirements.
  • Cost-effective manufacturing process. Prepreg compression molding is relatively inexpensive compared to resin transfer molding (RTM), which requires an additional step to apply the resin to the fiber preforms. RTM also has higher tooling costs than prepreg compression molding.
  • Wide range of applications. Prepregs can be used for applications requiring high strength and stiffness as well as low density. The process is suitable for manufacturing complex parts with varying thicknesses, as it allows local reinforcement by using different types and thicknesses of fibers in different areas throughout the part structure. Used to manufacture a wide range of products, including ship, aircraft and automotive parts, sporting goods and recreational equipment, furniture, life-saving equipment and medical devices.
  • Low capital investment required. Prepreg molding is a highly automated production process with very short cycle times (5-30 minutes). In addition, it allows for better control of wall thickness and eliminates the need for manual trimming after fabrication because there is not a lot of scraps left at the end of production. MDC's high-quality PCM molds have a long life span and greatly reduce your investment in tooling.

Disadvantages of prepreg compression molding

  • High cost: Prepreg materials are expensive, so the final cost of your part will be high.
  • Weight Reduction: Since prepreg materials tend to be heavier than other types of composites, your parts will not lose much weight compared to other manufacturing methods.
  • Storage: The resin in prepregs is in a semi-cured state, so they must be shipped and stored in a cool place.

PCM mould

MDC Mould manufacture and develop custom PCM mold and prepreg compression molding systems in a variety of sizes and configuration levels. All molding solutions are tailored to the customers needs. When we receive your order, professional sales staff will understand your project needs in detail. Based on part requirements, we will help you design and manufacture PCM molds.

In addition, our services include product design, custom prepreg customization, part post-processing steps, and more. And we will provide videos and images throughout the project cycle to report the progress of the project in time to reduce your worries. Remember, MDC is one of the professional PCM mold manufacturers in China. Get your own molds now at the cheapest price!

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