When designing a part, it is best to consider in advance which process to use to manufacture the model, and optimize accordingly for the production process.

Among them, the most common processing methods for plastic parts are CNC processing and injection molding. So how do we choose between these two processes?

CNC machining

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. It mainly processes 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 mainstream method of prototype production.
However, for some plastic parts with complex structures, there may be production restrictions or high production costs.

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.

Advantages of Injection Molding

1. Suitable for mass production
2. It can process soft materials such as TPE and rubber.

Disadvantages of Injection Molding

1. 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.
2. The update cost of parts is high, which is also limited by the mold cost.
3. If the mold is composed of multiple parts, air bubbles may be generated during injection, resulting in defects.

Which process to choose?

In general, this can be seen as a trade-off between several different characteristics, namely: speed/quantity, price, material.

Speed/quantity

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.

Price

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.

Material

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 seen from the above that the advantages and disadvantages of CNC or injection molding are obvious. Which processing method to choose is mainly based on speed/quantity, price and material. Hope the above content can help you!