Compression molding process


Compression molding is a universal manufacturing proces […]

Compression molding is a universal manufacturing process, and large and small manufacturing companies use this process to manufacture various parts, from large aircraft parts to small baby bottle nozzles.
1. What is compression molding?
Compression molding is a manufacturing process in which two heated molds are used to compress and compress a certain amount of molding material (commonly called a charge) into a desired form.
2. How does compression molding work?
The working principle of the compression molding process is as follows:
(1) Create molds-molds can be produced in a variety of ways, including machining, die-casting, and 3D printing.
(2) Setting up the machine-depending on the specific machine or equipment you are using, this may include cleaning the mold, turning on the heating, and other setting processes.
(3) Prepare materials-select the type of material to be used and determine the appropriate amount of material. If the loading amount is too large, the excess material will ooze out of the mold and produce flash, and you need to cut it off manually.
(4) Loading-Place the loading in the center of the bottom mold.
(5) Molded parts-close the mold, apply pressure, and then wait for molding. Many manufacturers also use heat during the compression process, which softens the raw materials and helps speed up production.
(6) Release parts-take out the finished product.
(7) Clean parts-resin burrs on the edges must be manually cut or removed, and parts may need to be cleaned before final assembly.
3. Compression molding and injection molding
Compression molding and injection molding are very similar, but there is one major difference between them. In compression molding, the mold is filled with materials and closed, while in injection molding, the material is injected into a closed mold cavity. Today's manufacturers often use compression molding and injection molding for different types of parts at the same time. For more complex parts, injection molding is usually a better choice, while for relatively simple designs (including super-large flat products that cannot be produced), molding is a good choice. Compression molding is a low-pressure production method, so mold costs are usually lower. It also wastes very little material and has advantages when using expensive materials. Generally speaking, mass production is more suitable for injection molding, while compression molding is used for small and medium batch parts production.
4. Advantages and disadvantages of compression molding
Now that we have discussed the difference between compression molding and injection molding, let us have a deeper understanding of the unique advantages and limitations of this manufacturing process.
(1) Cost-effective. If you need to produce simple, mostly flat large parts, compression molding is usually the most cost-effective manufacturing method. Due to the low pressure, the mold cost is affordable, and the mold can usually be used for a long time without warping or needing to be replaced. To offset the costs associated with the long cycle time of compression molding, manufacturers can use molds with multiple cavities to produce multiple parts in the same cycle.
(2) Produce solid parts. The structural stability of molded parts is very high. Compression molding is also used to make parts using composite materials, which means that durable, corrosion-resistant parts and products can be easily manufactured by this method.
(3) Design flexibility. For engineers and product developers, compression molding is also an excellent manufacturing tool. For example, low-cost compression molding can be used to complete prototyping. You can use computer-aided design (CAD) software to design a simple stamper, perform 3D printing, and then use a simple bench vise to form various types of materials.

Although the use of compression molding has many benefits, it does have its limitations. Compression molding is not suitable for manufacturing complex parts, such as those with severely inclined angles or small parts. Compared with a large number of molding methods, the cycle time can be as long as several minutes and is therefore slow. For example, the cycle time of injection molding is usually only a few seconds. Therefore, the labor costs associated with compression molding may also be relatively high. It is necessary to manually remove burrs and burrs from the molded parts, which will take up more time and labor costs. In addition to all these limitations, compression molding is still an important manufacturing method that can be used to produce the various products we use every day.

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