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Rapid injection molding. Image Credit: Shutterstock.com/Moreno Soppelsa

Advantages and Disadvantages of Rapid Injection Molding

Xomety X
By Team Xometry
June 7, 2023
 9 min read
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Rapid injection molding (RIM) has become a preferred technique for producing plastic parts quickly and affordably as a result of the rising demand for product manufacturing. Rapid injection molding does, however, have both benefits and drawbacks, just like any other manufacturing process. Its benefits include: quicker turnaround times, lower costs, and minimal to no waste. RIM is also capable of producing intricate parts with exact tolerances and surface finishes that would be challenging to achieve using other manufacturing techniques.

Companies that provide injection molding solutions can provide this service to customers who need short turnaround times or low-volume production runs. On the other hand, slow initial lead times, higher start-up costs, and expensive design changes are some drawbacks of rapid injection molding. This article examines rapid injection molding's benefits and drawbacks. 

What Are the Advantages of Rapid Injection Molding?

When compared to alternative production techniques, rapid injection molding has many benefits. The following are some of the main benefits of quick injection molding:

1. Mold Can Be Used Repeatedly

Rapid injection molding has the benefit of reusing the mold, which allows for the production of multiple parts without the requirement of a new mold. Rapid injection molding uses high-quality, long-lasting molds, which makes this possible. Since these molds are made to withstand the pressures and temperatures involved in the injection molding process, they will continue to function properly even after numerous uses. For more information, see our guide on 3D Printed Molds for Injection Molding.

2. Universality

In contrast to 3D printing, in which changing the material necessitates significant modifications and perhaps different equipment, injection molding enables the use of a variety of materials without requiring substantial system changes. The creation of a high-grade aluminum mold paves the way for the production of parts from a variety of plastics and other materials, including thermoplastics, elastomers, and composites. Due to its adaptability, rapid injection molding is a desirable choice for a variety of industries, including consumer goods, automotive, and medical.

3. Efficiency

Efficiency is one of the main benefits of RIM, which can be especially helpful when compared to other prototyping methods. Due to the need for extensive programming and setup, producing a single part using traditional prototyping methods like CNC machining can take a long time. However, RIM technologies enable the production of parts with a minimal setup time, significantly cutting down on the total processing time. 

4. No Waste Materials

There is significantly less material waste, as RIM only injects the precise amount of plastic into the mold cavity. This is crucial because excessive waste can quickly add up in cost when making a lot of prototypes for testing. RIM is a cost-effective and environmentally friendly manufacturing solution because it reduces material waste. RIM also permits the use of various materials, including recycled materials, which further reduce waste and encourage sustainability.

5. Strength

The final product is stronger and more durable because RIM uses cutting-edge design for manufacturability techniques to guarantee that it satisfies high-quality standards. High pressure is used to inject the liquefied resin into the cavity, ensuring uniform wall thickness and ideal ejection angles. This produces a part that has no pores, resulting in the highest-quality final product. Contrarily, 3D printing processes may leave unsintered areas or pores in the final material, which may reduce the strength and durability of the part.

6. Surface Finish

Rapid injection molding requires careful attention to surface finish because it affects the appearance and usability of the molded parts. To achieve the desired surface finish, the mold's quality is essential. The mold cavity is frequently created using CNC milling, which is then finished with polishing to remove any flaws. Sharpening the inner corners of the cavity with EDM cutting further improves the surface finish. The resulting surface finish can be as low as Ra 0.8 mcm, giving the molded parts a smooth and consistent finish.

7. Precision

The precision of rapid injection molded parts depends on various factors such as the design of the part, the complexity of the mold, the type of material used, and the manufacturing process. Generally speaking, RIM components are capable of high precision levels that are comparable to other methods. Nevertheless, the tolerances and surface finishes might change based on the particular demands of the application. For the desired precision to be achieved, it's essential to collaborate closely with the manufacturer.

8. Low Cost

In comparison to other manufacturing techniques, rapid injection molding is more affordable. The cost per unit drops as more units are produced, although the initial costs of making the mold can be high. Rapid injection molding provides a higher level of production efficiency and financial viability for higher volume runs than other manufacturing processes like CNC machining or 3D printing. Because of this, rapid injection molding is a great option for companies looking for a low-cost, high-quality solution for mass production.

What Are the Disadvantages of Rapid Injection Molding?

Rapid injection molding has drawbacks despite being an effective and economical manufacturing process. Among these limitations are:

1. High Start-up Expenses

The high start-up costs for RIM are a serious drawback. This is due to the need for specialized tooling, which can be costly for low-volume production runs. Depending on the complexity and size of the mold, the cost of tooling can range from $2,000 to several thousand dollars. When choosing this manufacturing process, it's vital to take the upfront costs into account despite the potential cost savings from reused molds in the future.

2. Initial Lead Times Are Long

Injection molding has a longer lead time than CNC machining and 3D printing. Complex molds must be made, which can take 5–7 weeks to design, plus another 2–4 weeks to manufacture. The molds have cooling and runner systems to help with material flow and cooling speed. Mold production time can be extended by design changes. Having a manufacturing expert can help avoid common mold issues and hasten the design, testing, and production processes.

3. Design Modifications Are Pricey

Injection molding design changes can be costly because they may call for building a new mold from scratch, which takes time and money. In contrast to 3D printing, in which design modifications are simple, injection molding necessitates careful design considerations to prevent undercuts, jagged edges, and uneven wall thicknesses. Decrease the need for pricey design changes and enhance the demolding process by incorporating draft angles and collaborating with an experienced manufacturing partner. 

What Is Rapid Injection Molding?

Rapid injection molding is a manufacturing procedure that uses injection molding technology to produce high-quality plastic components. This process utilizes custom tooling to produce the products of injection molding quickly and cost-effectively. It is an ideal option for prototyping, small-batch production, and on-demand manufacturing. With a shorter production cycle than conventional injection molding techniques, the outcome is high-quality plastic parts that adhere to precise tolerances and design specifications. For more information, see our guide on Rapid Injection Molding.

How Does Rapid Injection Molding Work?

The steps that typically make up the rapid injection molding process are as follows:

  1. Design: Create a design for the plastic part using computer-aided design (CAD) software. This design is then used to create a mold for the injection molding process.
  2. Mold Creation: Create the mold using computer numerical control (CNC) machining or 3D printing technology. The mold is typically made from aluminum or steel and consists of two halves, which can be separated to remove the finished part.
  3. Material Selection: Select the appropriate plastic material for the part. Choose the material based on its properties, such as strength, flexibility, and temperature resistance.
  4. Injection: Heat the plastic material until it melts and then inject it into the mold using an injection molding machine. The machine applies pressure to ensure that the plastic fills the mold.
  5. Cooling: Allow the plastic to cool and solidify. This typically takes a few seconds to a few minutes, depending on the complexity and size of the part.
  6. Part Removal: Once the plastic has cooled and solidified, open the mold and remove the finished part. Trim away any excess material and inspect the part for defects.
  7. Iteration: If any defects are found, modify the design and mold to correct them. Repeat the process until the desired results are achieved.

For more information, see our guide on Types Of Injection Molding Technology.

What Is the Process of Rapid Injection Molding?

Small- to medium-sized plastic parts can be efficiently and quickly produced using the rapid injection molding (RIM) technique. Liquid plastic is injected under high pressure into a mold, which is then cooled and the part is released. RIM offers a quicker turnaround time and lower costs than traditional injection molding, making it a popular choice for low-volume production runs and prototyping.

Is Rapid Injection Molding Production Fast?

Yes, rapid injection molding production is a fast process. To quickly produce injection molded parts of production quality, the rapid injection molding (RIM) process uses a rapid tooling technique. This is made possible by RIM's use of less complex tooling and procedures, which are quicker to set up and adjust and enable quicker turnaround times.

Is the Rapid Injection Molding Product Durable?

It depends. Rapid injection molding (RIM) products' durability will vary depending on the product's design, materials, and intended use. However, in general, RIM products can be very durable. RIM allows for the use of a wide range of materials, including reinforced plastics and composites, that can be chosen based on their specific properties such as strength, flexibility, and resistance to wear and tear.

Summary

This article presented the advantages and disadvantages of rapid injection molding, explained each of them, and discussed overall how rapid injection molding works. To learn more about rapid injection molding, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities, including injection molding and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

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Xomety X
Team Xometry
This article was written by various Xometry contributors. Xometry is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding, urethane casting, and more.