Advantages and Disadvantages of Compression Molding

Molding process of compression moulding is a kind of molding method for thermosetting composite materials. Put a certain amount of material into the compression mould. Under a certain temperature and pressure, the material is heated plasticizing in the mould cavity and pressurized to flow and fill the mold cavity to form. So what are the advantages and disadvantages of the molding process?
Its main advantages are as follows:
1. The product is not easy to deform when it is compressing molding and have good dimensional stability, high precision, good repeatability;
2. High production efficiency, facilitate the realization of specialized and automated production;
3. It can be formed the compression product with complex structure one time and simple operation;
4. High surface brightness, no secondary modification;
5. Low mold cost. It can be mass produced at low cost.
6. No gate, gate or runner, different from injection mold
On the contrary, the main disadvantages are as follow:
1. Compression moulding complex with long cycle.
2. Need person to operate, so that can’t achieve full-automatic.
3. It is difficult to control spillage and waste more. But when you master the molding process, you can continuously reduce the waste of materials
The compression molding process is an ideal choice when used properly. Although the cost of a single part may be higher compared to other technologies, it can help minimize the overall project cost.
Please keep us in touch as below info, if you required.
Taizhou Huangyan MDC Mould&Plastic Co.,ltd
No.35-1 Qingfeng Rd, Huangyan North Industrial estate, Taizhou, Zhejiang, china 318020;
Website: compression mould

Introduce to BMC mold

BMC mold compression molding is to add plastic directly to an open mold cavity with a certain temperature, and then close the mold, the plastic melts into a flowing state under the action of heat and pressure. Due to the physical and chemical effects, the BMC hardens into a plastic part with a certain shape and size that remains unchanged at room temperature. BMC mold compression molding is mainly used to mold thermosetting plastics, such as phenolic molding powder, urea-formaldehyde and melamine formaldehyde molding powder, glass fiber reinforced phenolic plastic, epoxy resin, DAP resin, silicone resin, polyimide, etc. Plastics can also be processed with unsaturated polyester pellets (DMC), sheet molding compound (SMC), prefabricated integral molding compound (BMC), etc.

BMC mold is a thermosetting mold. Compared with thermoplastic mold, bmc mold is irreversible. Products processed by thermoplastic molds can be recycled, reprocessed and reinjected, while products processed by thermoset molds cannot be processed once formed. There is no difference in the structure of the two molds. The difference lies in the processed material: one is a thermosetting material and the other is a thermoplastic material.

BMC is a thermosetting plastic, which is mixed with various inert fillers, fiber reinforcements, catalysts, stabilizers and pigments to form a sticky “putty” composite material for compression molding or injection molding. BMC plastics are highly filled and reinforced with short fibers. Glass fiber reinforced materials account for 10% to 30%, and the length is usually between 1/32 inches and 1/2 inches (12.5 mm).

According to different final application fields, the formulated composite material can accurately control the size, good flame retardancy and tracking resistance, has high dielectric strength, corrosion resistance and stain resistance, excellent mechanical properties, low shrinkage and Stable color. BMC plastic has excellent flow characteristics, insulation and flame retardancy, and is very suitable for various applications requiring precise details and dimensions.

Please keep us in touch as below info, if you required.
Taizhou Huangyan MDC Mould&Plastic Co.,ltd
No.35-1 Qingfeng Rd, Huangyan North Industrial estate, Taizhou, Zhejiang, china 318020;
Website: compression mould

Introduce to SMC molding process

The main raw materials of SMC are composed of SMC special yarn, unsaturated resin, low shrinkage additives, fillers and various additives. SMC has the advantages of superior electrical performance, corrosion resistance, lightweight and easy and flexible engineering design. Its mechanical properties are comparable to some metal materials, so it is widely used in transportation vehicles, construction, electronics/electricity and other industries.

1. Preparation before molding
(1) The quality of SMC sheet has a great influence on the molding process and SMC part quality. Therefore, it is necessary to understand the formulation of resin paste, glass fiber content, etc. before molding.
(2) Determine the shape and size of the sheet material cutting according to the structural shape of the SMC part, the feeding position, and the process. In order to prevent contamination by external impurities, the upper and lower films are only removed before loading.
(3) Familiar with the various operating parameters of the press, especially to adjust the working pressure and the running speed of the press and the parallelism of the table. The mold installation must be level, and ensure that the installation position is in the center of the press table. Before molding, the mold must be thoroughly cleaned and coated with mold release agent. Before feeding, wipe the release agent with clean gauze to avoid affecting the appearance of the SMC part.

2. Feeding
(1) Determine the feeding amount and feeding area. The size of the feeding area directly affects the compactness of the SMC part and the surface quality of the SMC part. It is related to the flow and curing characteristics of SMC, SMC part performance requirements, mold structure, etc.
(2) Feeding position and method. The feeding position and method directly affect the appearance, strength and directionality of the SMC part. Normally, the feeding position of the material should be in the middle of the cavity. For asymmetric and complex SMC parts, the feeding position must ensure that the material flow reaches the ends of the molding cavity at the same time during molding. The feeding method must be conducive to exhaust. When stacking multiple layers of sheets, it is best to stack the materials up and down.

3. After the material enters the mold cavity, the press goes down quickly. When the upper and lower molds coincide, slowly apply the required molding pressure. After a certain amount of curing, the molding of the SMC part ends. During the molding process, various molding process parameters and press operating conditions should be selected reasonably.
(1) The molding temperature depends on the type of resin, SMC part thickness, SMC partion efficiency and SMC part structure. Generally speaking, the forming temperature of thick SMC parts should be lower than that of thin-walled SMC parts. For example, if the thickness of the SMC part is 25-32mm, the forming temperature is 135-145 ℃. And thinner SMC parts can be formed at 171 ℃. It is generally believed that the SMC molding temperature is between 120-155 ° C.
(2) Molding pressure varies with SMC part structure, shape and size. SMC parts with simple shapes only need a forming pressure of 5-7MPa; SMC parts with a complicated shape can have a forming pressure of 7-15MPa. The size of the molding pressure is also related to the mold structure. The molding pressure required by the vertical parting structure mold is lower than that of the horizontal parting structure mold. In short, the determination of molding pressure should consider many factors. Generally speaking, SMC molding pressure is between 3-7MPa.
(3) The curing time is related to factors such as material type, molding temperature, SMC part thickness and color. The curing time is generally calculated at 40s / mm. For thick SMC parts above 3mm, each additional 4mm increases the curing time by 1min.