CNC Machining vs. Injection Molding

CNC machining is a type of manufacturing process that obtains the intended product by shaving off layers from a block of material. Another producing process, injection molding, is a kind of process that acquires the desired parts by injecting materials into the mold that is made ahead of time and ejecting the product after it is cooled off.

Before choosing between CNC Machining and Injection Molding, one needs to consider different characteristics of their products.

Volume and Speed

The products’ volume is essential when it comes to the speed of producing the intended products. When the desired parts’ volume is low, CNC machining would be faster. The time it takes to make a mold before injection molding begins is extremely time-consuming as it can take weeks or even months. Consequently, if only a small amount of products are in need to be made within a short period of time, it would be wise to go for CNC machining.

However, for injection molding, once the mold is made, it takes no time to finish the following process of injection and ejection. Therefore, if someone wants to make a large batch of products with ample time, injection molding can be a good option.


Other than speed and efficiency, the costs are also tightly related to the volume of products. While the unit cost of making each product through CNC machining does not change much as the quantity goes up, that of injection molding drops significantly once the mold is made. In other words, it may be a good choice to choose injection molding over CNC machining at a high volume.


While CNC machining is compatible with a wide range of materials from plastics to woods, injection molding clearly has more limited material options since it involves melting the original materials into the liquid form first.

However, since CNC machining shaves the shape out of the material, it can be hard to be put into practice on soft materials. Therefore, when the original material is soft, injection molding would be more practical than CNC machining. Furthermore, injection molding is capable of using multiple kinds of plastics at the same time, which cannot be achieved through CNC machining.


The design of the final products also plays a big role in the selection between CNC machining and injection molding. If the final products are designed differently, it is not cost-effective to opt for injection molding, since the expensive mold is only used for a few times.

However, if the design of the intended parts is consistent, injection molding is not only cost-effective but also able to finish the task consummately due to its nature of making exactly identical products.


In a word, it is best to consider several aspects such as volume of product, speed, cost, original materials, and the design of the desired products before choosing between CNC machining and injection molding since different traits of the two processes regarding to their distinctive manufacturing ways as well as the short term and long-term costs.

For people who need a medium or high production volume of CNC or Injection Molding parts, tasks can be well finished with the help of a professional manufacturing company. RapidDirect is an industry-leading designer and manufacturer of rapid prototyping services, whose CNC machining and 3D printing service features streamlining the manufacturing process with automation, wide range of compatible materials, a high degree of accuracy and precision and rapid manufacturing for medium to high production volumes.

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