CNC machining or Injection molding?How should we choose the proper manufacuring process for plastic parts?


For plastic parts, the most common manufacuring processes are CNC machining and injection molding. When designing parts, the engineers sometimes have already considered which process to use to make the product, and made corresponding optimizations for the production process, so how should we choose between these two processes?

Let`s see the concepts and advantages and disadvantages of these two manufacturing processes first:

1. CNC machining process

CNC machining usually starts with a piece of material and after multiple removals of material, a set shape is obtained.

CNC plastic processing is one of the main ways of making prototype models at present, mainly processing ABS, PC, PA, PMMA, POM and other materials into the physical samples we need.

The prototypes processed by CNC have the advantages of large molding size, high strength, good toughness, and low cost, and have become the main ways of prototype production.

However, for some plastic parts with complex structures, there may be production restrictions or high production costs.

2. Injection molding

Injection molding is to dissolve the granular plastic, then press the liquid plastic into the mold through high pressure, and obtain the corresponding parts after cooling.

A. Advantages of injection molding

a. Suitable for mass production

b. Soft materials such as TPE and rubber can be used in injetion molding.

B. Disadvantages of injection molding

a. The mold cost is relatively high, resulting in high start-up cost. When the production volume reaches a certain amount, the unit cost of injection molding is low. If the quantity is not enough, the unit cost is high.

b. The update cost of parts is high, which is also limited by the mold cost.

c. If the mold is composed of multiple parts, air bubbles may be generated during injection, resulting in defects. 

So which manufacturing process should we choose? In general, depends on speed, quantity, price, material and other factors 

CNC machining is faster if the number of parts is small. Choose CNC machining if you need 10 parts within 2 weeks. Injection molding is the best choice if you need 50000 parts within 4 months.

Injection molding takes time to build the mold and make sure the part is within tolerance. This may take weeks or months. Once this is done, using the mold to make the part is a very quick process.

About the prices, which is cheaper depends on the quantity. CNC is cheaper if producing a few or hundreds of parts. Injection molding is cheaper when production quantities reach a certain level. It should be noted that injection molding processing needs to share the cost of the mold.

In other hand, CNC machining supports more materials, especially some high-performance plastics or specific plastics, but it is not good at processing soft materials. Injection molding has relatively few materials, but injection molding can process soft materials.

It can be decided from the above that the advantages and disadvantages of CNC or injection molding are obvious. Which manufcturing process to be used is mainly based on speed/quantity, price and material. 

Star Machining company will suggest suitable manufacturing process for our customer according to your requirements and product characteristics. Whether it is CNC processing or injection molding, we will use our professional team to provide you with perfect products and best services.

Post time: Apr-15-2023