These different types of molding processes involve different techniques. Two of the more commonly used techniques are compression molding and injection molding.
But which one of these manufacturing processes is better suited for your needs? Read our detailed comparison of compression molding vs. Injection molding to find out the best technique for your needs.
As the name indicates, in compression molding the materials are compressed to attain the desired shape. During this process, the raw materials placed in the mold cavity are heated. Specially designed plugs are then inserted into the melted plastic from the top.
The plugs seal the cavity and apply high pressure to the material. Under high temperatures and high pressure, the raw material starts to cure in the mold cavity and a new product or component is created.
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Injection molding manufacturing technique can be used for the mass production of products from a variety of different materials having different mechanical properties such as glass, metal, polymers and elastomers. In contrast to compression molding, the materials in injection molding are injected into a closed mold cavity which results in the production of identical items every time.
With injection molding large volumes of products can be manufactured that are consistent in their final shape. First, a mold is created with steel or aluminum. The mold is made up of two parts, the cavity and the core. These two parts are brought together by high pressure from the machines.
Silicone or plastic is then melted and injected into the mold. The mold can then be tempered or cooled to the desired temperature.
The initial cost is very high in the case of stainless steel mold for the production of large volumes of parts. The design and manufacturing of injection mold can also take a long time. If the production volume is low the cost per part would increase. In this case, it would be better to consider aluminum molds.
To produce stainless steel mold the initial lead time is long. It can take up to 12 weeks to manufacture the steel mold cavities.
There are also some design constraints that must be considered while designing the molds. Such as the placement of ejectors, gates and cooling lines, avoiding defects like sharp edges and controlling the thickness of the walls to make the production process smooth.
Injection molding has a number of applications ranging from consumer toys to components of airplanes.
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Plastic and other related raw materials can be molded through many different processes. While comparing compression molding vs. injection molding you should understand which method is suitable to your particular needs. Which method is more efficient and which one can be used for a wide range of designs and prototypes?
Both injection molding and compression molding make use of heat and pressure to attain the desired shape of the plastic raw materials. However, there are some key differences that can help you choose the best option. Read further to find out.
Compression molding is a relatively simple process that requires few components such as the raw polymer, heated mold and the plug. The process proceeds as follows.
Injection molding on the other hand requires a larger number of components including injection units, feed hoppers, heaters, hydraulic cylinders, clamping units and others. Here is how it is done:
In injection molding, rigid thermoplastics can be used along with thermoplastic elastomers and urethanes. Compression molding often makes use of flexible materials such as silicone and rubber. Compression can also be applied to BMC (Bulk moulding compound) and SMC (Sheet moulding compound) to produce rigid components.
The injection molding process does not result in any flash and thus no wastage of the material takes place. If there is some leftover material it can be melted and used again. Compression molding does have flash around the products which cannot be used again. Thus, some of the material gets wasted in each cycle. Injection molding is, therefore, more efficient in terms of material utilization.
In terms of processing speed, the injection molding process is significantly faster than the compression molding. The injection molding cycle time is only a few seconds as compared to a few minutes cycle time of the compression molding. This is mainly due to the curing time required for the compression molded components before their removal from the molds.
If you are interested in more complicated designs with high precision then injection molding is your best option. Injection molding provides the ease of experimenting with different design ideas more conveniently. Moreover, injection molding also allows you to test a product in the actual setting before the manufacturing actually starts.
This is why injection molding is used to make intricate designs and is used in the manufacturing of headphones, plastic containers, protective gear and other plastic and silicone products.
Compression molding mainly focuses on simpler parts because of less sophisticated procedures and components of the technique. Parts such as electrical housing, bottle caps and round inserts are formed through compression mold which explains their simpler designs.
The cost for both injection and compression molding varies with the type of material used, the product requirements, and other factors. In general compression molding costs less as compared to injection molding but the per-part prices are higher due to longer cycle time and post-production processing. Thus, compression molding is better for less complex parts and low production volumes.
The initial cost of injection molding is high due to the larger investments required for tool designing and building. But once the molds have been formed they can be maintained easily and help in the production of large volumes of products. The post-production processing is also reduced which cuts the labor cost. Thus for the production of complex parts in higher volumes, the injection molding procedure is the path to choose.
It is a long-standing debate as to which type of molding process must be used. Each molding process has its own pros and cons. If you are interested in making large volumes of complex products with low cost and better visual appearance then injection molding is the best option.
Injection molded products are also durable and it is easier to change their sizes. Many different varieties of materials can be used in injection molding technique, multiple layers can be created and mass production is also possible with high consistency. All these benefits make injection molding an amazing manufacturing solution.
On the other hand compression molding must be opted in case the parts being formed are bigger in size, simpler in shape and need to be produced in smaller volumes because the process is time-consuming.
At Hongju Silicone, we specialize in both compression and injection molding and offer a variety of products. Our step-by-step design guide can help you get the best tips on product design and molding techniques that can be used.
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As said before there cannot be a definite answer to which molding process is the most efficient. It all depends on the type of outcome you want, the production requirement and the complexity of the design.
Choosing the right methods depends on your understanding of the process and the ability to assess which process meets your needs best.
Still confused about the best option for your needs? Visit our webpage to find more information on molding and our products. Or want to solve a specific molding problem? Contact our team of experts now and we will be happy to assist you with the best solutions.
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