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January 5, 2022

CNC Machining Vs Injection Molding : A Comparative Analysis

CNC vs Injection Molding

CNC machining and injection molding are the most popular manufacturing processes today. Both processes use machinery to produce complex parts, but some differences exist. This post compares CNC machining and injection molding. We look at their pros, cons, and common uses. Let’s take a side-by-side look at how CNC machining compares to injection molding. You’ll know which manufacturing process suits your needs after reading this.

What is CNC Machining

CNC machining is a manufacturing process that uses computer software to control machinery and tools, making it faster, more efficient, and less prone to errors. It involves programming a guide for cutting in 3D, allowing for the creation of intricate parts from various materials such as wood, plastic, glass, or metal. CNC machining offers good job opportunities and requires no college degree, but rather a passion for manufacturing and technology. The job involves skilled operation of advanced machines to create tangible products with precision and accuracy.

a hand about to press the power on button on a CNC machine


  • Consistency: CNC machining provides consistency in the production of parts. Because the machine is controlled by computer software, the process is highly accurate, reducing the likelihood of errors or inconsistencies in parts.
  • Easy to Learn: Operating a CNC machine is relatively easy to learn, thanks largely to the availability of online resources and training programs. With the right training, anyone can operate a CNC machine and produce high-quality parts.
  • Advanced: CNC machines are sophisticated equipment that can handle complex designs and produce intricate parts. The software used to program the machines is constantly evolving, meaning CNC machining is becoming more advanced and efficient.
  • Continuous use: CNC machines can operate around the clock, allowing for continuous parts production without breaks or downtime. This means that large quantities of parts can be produced in less time.
  • Flexibility: CNC machines offer flexibility regarding the types of materials they can work with and the complexity of the designs they can produce. They can work with various materials, including metals, plastics and composites, and produce parts with varying complexity, from simple shapes to intricate designs.


  • Commercial CNC Machines are expensive: One of the main disadvantages of CNC machining is that commercial CNC machines can be expensive to purchase and maintain. CNC machines range from relatively inexpensive hobbyist machines to large industrial ones that cost hundreds of thousands or even millions of dollars. In addition to the initial cost, there are ongoing maintenance and repair costs to consider and the cost of replacing cutting tools and other consumables.
  • Expertise Gap: Another factor to consider is that CNC machining requires skilled operators trained to use the machines properly. This can increase production costs if additional training is required. However, as CNC technology advances, newer machines are becoming easier to operate and the need for highly skilled operators is decreasing.

What is Injection molding?

Injection molding is a manufacturing process where molten materials, usually thermoplastics, are injected into molds to create parts. The plastic is heated, injected into the mold, and then cooled and removed from the mold. This process allows for creating complex parts with small tolerances and multiple features, such as ribs, metal inserts, and holes.

Injection molding is ideal for producing intricate parts that are impractical to make using other techniques, like plastic fabrication or vacuum forming. It offers high repeatability, meaning identical products can be made repeatedly. Although there is an initial high cost for the molding tool, the cost per part is low compared to other plastic processing techniques. Injection molding is a cost-effective solution for large-scale production.

two pieces of injection molds


  • Great precision: Injection molding allows for highly precise parts with tight tolerances and excellent surface finishes. This makes it a popular choice for manufacturing parts for products that require high precision, such as medical devices, electronics, and automotive components.
  • High repeatability: Injection molding offers a high level of repeatability, meaning that identical parts can be produced repeatedly with consistent quality. This is because the process uses a mold to create the parts, ensuring that each part is identical to the previous one.
  • High speed: Injection molding can produce parts at a very high rate of speed, with some machines able to produce thousands of parts per hour. This makes it an ideal choice for large-scale production runs where speed and efficiency are critical.
  • Low cost per part: While the upfront cost of creating a mold for injection molding can be expensive, the cost decreases significantly with larger production runs. This makes injection molding a cost-effective choice for high-volume production.
  • Many choices of available plastics: Injection molding offers many plastic material options, including thermoplastic and thermoset resins. This allows manufacturers to select the best material for the specific application, including durability, strength, and heat resistance. Additionally, many plastics used in injection molding are recyclable, making it a more sustainable choice than other manufacturing processes.


  • Can be more costly than CNC machining: While injection molding can be cost-effective for large production runs, it does require a significant upfront investment. The cost of creating a mold can be high, especially for complex parts with intricate features. Additionally, the cost of the equipment and materials used in injection molding can also be significant.
  • Higher lead time: Another disadvantage of injection molding is the lead time required to create the mold. It can take several weeks to create a mold, slowing the production process. This means injection molding may not be the best choice for small production runs or projects with tight deadlines. In contrast, CNC machining can produce parts much more quickly, making it a better choice for projects with shorter lead times.

Equipment Cost Comparison

When comparing the cost of using CNC machines and injection molding, it’s important to consider what each process requires. To use a CNC machine, you must create a special file CAD and change it to a format the machine can read. Creating a special file and tools for CNC machining can cost a lot, but the machine can produce many precise parts afterwards.

Injection molding requires a mold, which can be costly and require specialized equipment and skills. Once the mold is made, many identical parts can be produced quickly and efficiently. This makes the process a cost-effective choice for large production runs.

The decision between CNC machining and injection molding depends on how many parts are needed. Consider how complex the parts are and what materials will be used. It’s important to consider these factors and weigh each option’s costs and benefits before deciding.


CNC machining is fast for low-volume production, while injection molding is better for high-volume production. CNC machining can produce a few parts quickly, but making a mold for injection molding takes time and money upfront. Once the mold is made, injection molding can produce many parts quickly and efficiently. So, it’s important to consider the volume of parts needed and the time available when deciding between CNC machining and injection molding. Making 10 parts in 2 weeks requires CNC machining as your solution.

If you need 50,000 parts in 4 months, injection molding is the way to go. Injection molding requires time to make the mold and ensure the parts are intolerant. Creating parts using the mold is a fast process, and the upfront time investment of injection molding pays off at high volumes.


When it comes to cost per part, injection molding is usually cheaper. For small production runs of a few to a hundred parts, CNC machining can be cost-effective. However, for larger production runs of hundreds to thousands of parts, injection molding is the more economical choice.


Regarding material options, injection molding is advantageous because it can cover a wide range of plastics, including thermoplastic and thermoset resins. That means it can handle everything from common plastics like ABS to nylon. In contrast, CNC machining offers a wider range of materials for part production. For injection molded parts, however, the material selection is more limited.


CNC machining features more materials. A tighter tolerance can be held, and a better surface finish. The advantage of injection molding is repeatability. Molds can last for millions of parts with minimal wear. The parts from one batch to the next are almost identical. Each part with a CNC machine is put on the machine and more variability.

David D. Hughes

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