Plastic is one of the most-used materials for creating large numbers of consumer products. In addition, many industries use plastic components as substitutes for their metallic counterparts. As a result, numerous techniques for producing plastic materials are also emerging, though the most popular methods remain creating compression molds and injection molds.
Plastic is one of the most-used materials for creating large numbers of consumer products. In addition, many industries use plastic components as substitutes for their metallic counterparts. As a result, numerous techniques for producing plastic materials are also emerging, though the most popular methods remain compression molding and injection molding.
Molding is a unique manufacturing process involving rubber, plastic, and similar polymers. It generally involves adding these raw materials – heated to liquid form – to a mold cavity in order to create a specific component or product. As the raw material cools, it hardens and takes up the shape of the mold cavity.
However, molding processes or techniques are not the same. For example, compression molding and injection molding techniques are different. This begs the question: which of these should you choose for your specific needs?
To make the right choice, it makes sense to highlight the differences between compression molding and injection molding.
Compression Molds
Compression molding is a molding technique involving the use of heat and pressure. In compression molding, the raw material – rubber, plastic, or other polymers – is placed in a mold cavity and then heated.
After a while, the operator inserts plugs into the top of the mold cavity. These plugs have a 2-pronged function: they seal the mold cavity effectively and pressurize it.
Since the raw material is exposed to pressure and extreme heat, it starts curing within the mold cavity. This activity’s outcome is forming a new component or product.
Benefits of the Compression Mold
Compression molding has several benefits that appear much better compared to injection molding. Some of these benefits include:
- Low initial investment and tooling costs, making it perfect for large-volume manufacturing applications
- Ease of maintaining mold tooling
- Preservation of chemical and mechanical properties of raw materials
- Enables more efficient or effective color changeovers
- Ensures superior visual appearance since gate vestige is avoided
- Capable of using Bulk Molding Compound (BMC) and Sheet Molding Compound (SMC) to create composite panels with chopped fiber strands – rather than continuous fiber-impregnated sheets – distributed throughout the entire bulk material.
- It supports a wide range of sizes and shapes, making it possible to create components or items with thick or thin walls in a wide variety of shapes.
- Compression molds are not required to withstand the extremely high internal pressures experienced with injection molds. Instead, they only experience compression forces from above, making compression molds less expensive.
Downsides of the Compression Mold
- Minimized molding depth
- Products or components may show a few odd parting lines
- It is unsuitable for a large production or complex parts runs because it is mostly a slow and manual process. The cycle time between components or products is much slower than injection molding. This is because the components need to be set before removal.
- It is fractionally less consistent than injection molding
- Secondary machining may – and is usually – required after compression molding.
- Components with high levels of complexity cannot be created using this molding technique. Materials used in compression molding are generally viscous and do not flow too well into small and complicated features.
The compression mold technique gives durable and strong components or products. For this reason, many industries employ this molding process for their unique applications. Some of the applications of compression molding include:
- Electronic and electrical components
- Circuit breakers
- Reciprocating compressor components
- Plastic dinnerware, etc.
Injection Molds
On the other hand, injection molding involves a molding technique defined by injection technology. It generally involves the injection of the raw material into the mold cavity. But before then, the plastic resin pellets – which are the raw materials – are melted by applying extreme heat.
The operator uses a screw to pull the material into a hopper during injection molding. As this material gets heated, it is injected into the mold cavity. As you can see, the injection molding process also utilizes heat and pressure.
Molds are usually composed of a minimum of 2 parts held together with hydraulic rams. This ensures that the high-pressure molten plastic injected into the mold does not escape the parting line.
These molds have cooling channels that help cool the plastic components long enough to be ejected from the molds without damaging them.
Benefits of Injection Molding
Injection molding has several benefits over compression molding. These benefits include:
- Fast and efficient production of uniform plastic components or products, making it possible to produce hundreds of millions of components or products per machine annually
- Low production costs due to rapid manufacturing speed and high levels of automation
- Heat and pressure can be precisely controlled
- Capacity to mold in tamper unique evidence features
- Tolerates an incredibly wide range of materials
- Durable and solid final components or products
- Supports complex mold designs
- Minimal labor is usually required
- Boosts customization and versatility
But despite these benefits, injection molding is not without a few downsides, as highlighted below:
- Small numbers of production can be very costly
- High tooling cost
- Requires extremely high plastic injection pressures during production. This makes constructing a mold capable of withstanding these high pressures is necessary. This adds to the tooling costs highlighted in the previous point.
The injection mold technique is highly suitable for a wide variety of applications thanks to its versatility. It can be used for creating nearly everything, ranging from intricate to complex appliances and components.
Compression Mold vs. Injection Mold: Which Should You Choose?
Compression molding and injection molding techniques have been highlighted in this article, including their respective advantages and disadvantages. The time has come for you to make your choice. Which mold technique should you choose: compression molding or injection molding?
Your choice of molding technique depends primarily on your unique needs. For instance, if you intend to create large volumes of complex components or products so that you can test them out within a short period, injection molding should be your #1 choice. In addition, due to its incredible precision, you don’t need post-processing with this technique.
However, if you desire a process that supports a wide range of sizes and shapes, making it possible to create components or items with thick or thin walls in a wide variety of shapes, then compression molding is the best for you.
Conclusion
Compression mold and injection mold techniques are unique processes for creating plastic components or products. As a result, several industries use them to create a wide range of plastic-based products and components for machines and other equipment.
The molding technique you choose should be based on your specific needs or what you plan to do. Therefore, look into your research and use the information this article shares to make an informed decision.
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