Extrusion Molding vs. Injection Molding | AIC & Plasti-Co®

April 29, | aic

When it comes to the design of custom plastic parts, you need to know the options available to your business. Many ways of producing plastic parts exist. If it is your job to manufacture those parts for your own products or your clients’ products, you need to know the method best suits your needs.

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This brings you to injection molding vs. extrusion molding. Both methods are common for the production of plastic parts, but each has its own pros and cons. Each process is better for certain tasks compared to the other. Discover the difference between injection molding and extrusion molding so you can make the right choice for your business’s needs.

What Is Extrusion Molding?

The extrusion molding process involves forcing heated material through a shaped, cut piece of metal, or die. The continuous nature of extrusion molding results in a continuous form of chosen length. After the heated material is pushed through the die, it cools and sets, reaching its final state. This is a popular form of materials molding for items like plastic drinking straws, hoses, industrial piping, plastic rails and other long, cylindrical parts and products.

In other words, extrusion molding extrudes material through a die, often via forced pressure before the die. This act of forced compacting reshapes the initial material into the desired resulting shape and size. Here are the advantages and disadvantages of this molding process.

Extrusion Molding Advantages

The process and results of extrusion molding give it the following advantages:

• Low costs: Thanks to the high efficiency of the extrusion molding process, costs can be much lower than other molding methods. Extrusion molding often uses thermoplastics, which you can reheat several times while maintaining its quality. This means you can reuse leftover materials, saving you money on material and disposal fees.
• Consistent operation: Extrusion molding machines can operate 24 hours per day, barring any machine failures. This means you can produce your product continuously, reducing your chances of experiencing an inventory shortage.
• Flexibility: You have great flexibility in the types of products you can make via the extrusion molding process. As long as the material can maintain its continuous nature, you can create products of various shapes and sizes, including plastic sheets. You can also adjust the softness or hardness of the resulting material, leading to complex products with changes in how the surface feels depending on your needs.
• Post-extrusion alterations: Another benefit of plastic extrusion is how you can alter the final product. For instance, you can make 100 feet of hose at once, then cut it per order for the customer’s needs. And since the material stays hot after extrusion, you can also manipulate the material to customize its shape. It’s easy to alter what you make via the extrusion process, so you can have confidence in producing in bulk.

Extrusion Molding Disadvantages

Although extrusion molding has many advantages, you should also consider the two main disadvantages of this process:

• Variances in size: The hot material can expand after extrusion, which is a process known as die swell. Die swell occurs due to a combination of many variables, so it can be impossible to predict with 100% certainty how the final product will come out. Manufacturers must accept the fact that the extruded material may be imperfect.
• Product limitations: You can only make materials of specific, consistent shapes and sizes with extrusion molding. For instance, plastic soda bottles start wide and narrow toward the end to accommodate a cap. Standard extrusion molding cannot accomplish this type of product variation.

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What Is Injection Molding?

Injection molding is similar to the production method of molten die casting. First, a heated liquid, like plastic, fills a mold. After a cooling process, the solid plastic leaves the mold in its finished shape.

Manufacturers use injection molding to create products of diverse shapes and sizes, including chess pieces, cups, plates, combs and other three-dimensional products with complex size and shape variances.

Injection Molding Advantages

The injection molding process has several advantages, including the following:

• Numerous design possibilities: Injection molding uses pressure to push the injected liquid into the mold. This allows the final product to take on many unique shapes and sizes. If your business needs to make complex plastic parts or products, then injection molding is the best method.
• Low scrap rates: Since injection molds can be so precise, the injection molding process yields little scrap. This means you can enjoy more accuracy in the amount of material you need and save money on material and disposal costs.
• Product consistency: When consistency in your final product is essential, injection molding is the way to go. You can know that the second part you produce will be the same as the first, and so on. There will be very little — if any — variation among the produced plastic parts.
• High product strength: Since injection molding is similar to a die-cast method, the final products are one piece of plastic, even when taking on complex shapes. This means you can avoid breaking points or having to attach pieces together. The mold yields one complete product with the potential for high strength and durability.

Injection Molding Disadvantages

It’s important to consider the pros and cons of every option you’re considering. Here are some disadvantages of injection molding you should be aware of:

• Expensive upfront costs: The design, testing and tooling requirements at the front end of the injection molding process give it a high upfront cost. Going through stages of designing and testing the prototype mold is essential to a successful finished product, but it takes more time and money than extrusion molding.
• Small runs of parts are uneconomical: The above disadvantage extends into the fact that small runs of parts will be extremely uneconomical to produce. Injection molding is an excellent option when there is a need for plastic parts in bulk. Because of the expense and time of the initial phases, it’s simply uneconomical to choose injection molding for small orders of plastic parts.

When you need plastic molding machines or components for your existing machine, AIC Plasti-Co® is the one to call. We know how important the right plastic molding machine is for your business. So whether your company specializes in injection molding, extrusion molding or both, we’re ready to help you in the way you need.

Contact us online for more information. Our professionals would love to answer your questions and help you take the next step.

Molding is one of the most common manufacturing processes involving materials such as plastics, rubber, and similar polymers. However, it is essential to note that molding processes vary from each other. For example, custom compression and injection molding, the two most popular molding processes, remain mysterious to some people. And the following guide offers a basic overview of both methods.

What Is Custom Injection Molding?

We’ll start with a consideration of how injection molding works. Custom injection molding is the most utilized manufacturing process for fabricating plastic parts. It is a plastics manufacturing technology capable of very high production volumes.

Injection molding is a process that applies the “injection” technique.

The process is carried out by injecting liquid plastic into a stainless-steel mold, where the product is gradually formed under high pressure. The mold is outfitted with various customized cavities to form the product. When the melted plastic has been injected, the material begins filling out the cavities and the rest of the mold. The products are left to cool and are later ejected by pins.

Because of its versatility, injection molding is regularly used for various applications. Everything from automotive parts to small, intricate pieces of surgical equipment can benefit from the process. Its other applications involve medical devices and dental parts, food & beverage packaging, engineering prototypes, cable assemblies, and window and door components.

What Is Compression Molding?

Compression molding is more suitable for medium-sized production, usually rubber and silicone. The compression molding tool makes even stiff, high-durometer rubber materials perfectly vulcanized and dimensionally stable.

In general, compression molding is defined by applying heat and pressure. Although this is similar to injection molding, the procedure is completely different. The compression molding process involves heating a mold and placing preheated material inside. After that, the mold is closed to heat and compress the contents into the desired shape. The heating process—also known as curing—ensures the final product maintains integrity and shape. Once cooled, products are removed from their molds.

Compression molding gives strong and durable products. Thus, many industries tend to employ this technique for their applications. For example, some typical compression molding applications include body armor, circuit breakers, plastic dinnerware, and electrical and electronic components.

Custom Injection Molding vs. Compression Molding

Injection Molding: Pros & Cons

(1) Advantages:

• Efficient and Fast Production of Uniform Components

Injection molding is a high-volume production method that can produce millions of parts per machine annually.

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Injection molds have shorter cycle times and fewer secondary operations. Additionally, multi-cavity tooling injection molding allows multiple parts to be produced every cycle, which benefits high-volume part production.

• Enhances Versatility and Customization

Equipped with various customized cavities, this molding type is highly versatile. Besides, consumer products can be easily updated.

• Low Production Costs

With shorter cycle times and repeatable manufacturing, injection molding lends itself to lower scrap and piece prices due to tooling efficiency.

• Supports Complex Mold Designs

The desired shape can be simple to complex with the help of computer-aided design for specialized items.

(2) Disadvantages:

Custom injection molding requires a large investment cost. Foremost, the price of the machine itself can be high. Secondly, as it requires very high plastic injection pressures, the mold must be built to withstand these pressures. This adds cost to the tooling. Also, it’s costly for a small number of products. But you can always find a reliable supplier instead of investing in the production lines alone.

Custom injection mold design costs may be high, but keep in mind that these costs are easy to recoup over long and large production runs.

Compression Molding: Pros & Cons

(1) Advantages:

• Ease of Maintaining Mold Tooling

Since the process often employs high-strength materials, many products created via compression molding are sturdier and more resilient than those manufactured using other molding processes.

• Low Initial Tooling Costs and Investment

The cost of molding equipment is low, so the initial investment in compression mold is less expensive.

• Enable More Efficient Color Changeovers

Like injection molding, compression molding is considered to be cost-effective and highly efficient. What’s more, it provides more color changeovers to satisfy unique requirements.

• Preserve The Mechanical and Chemical Properties of Materials

Compression molding can make composite panels using sheet and bulk molding composites. These panels do not have continuous fiber-impregnated sheets, but rather chopped fiber strands distributed throughout the bulk material.

(2) Disadvantages:

The disadvantage of molding is that mold manufacturing requires secondary machining. And the molding cycle of the whole production process is long and inefficient, and it has a large physical consumption for the staff. Limited by the press, it is most suitable for mass production of small and medium-sized composite products.

Summary

This article presented the topic of custom injection molding vs. compression molding, explained what they are, and discussed the different attributes of each.

The type of molding best suited for your project will depend on many factors. When those factors point to injection molding as the most effective option, partnering with an experienced service provider makes a significant difference in the outcome that you experience, influencing factors from quality to speed. Find expert help with custom injection mold solutions on your project today from Keymould and explore the advanced options available to you now.

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