When designing a part, it is best to consider in advance which process will be used to manufacture the model and optimize it accordingly.
Among plastic parts, the most common processing methods are CNC machining and injection molding . So how do we choose between these two processes?
1.CNC machining
CNC machining usually starts with a block of material and after multiple passes of material removal, a set shape is achieved.
CNC plastic processing is one of the main methods of making prototypes at present. It mainly processes ABS, PC, PA, PMMA, POM and other materials into the physical samples we need.
The samples processed by CNC have the advantages of large forming size, high strength, good toughness and low cost, and have become the mainstream method of prototype production.
2.Injection Molding
Injection molding is a process in which granular plastic is dissolved and then the liquid plastic is pressed into a mold under high pressure. The corresponding parts are obtained after cooling.
Advantages of injection molding
- Suitable for mass production
- Can process soft materials such as TPE and rubber.
Disadvantages of injection molding
- The mold cost is relatively high, resulting in high startup costs. When the production volume reaches a certain amount, the unit cost of injection molding is low. If the volume is insufficient, the unit cost is high.
- The cost of updating parts is high , which is also limited by the cost of molds .
- If the mold consists of multiple parts, bubbles may be generated during injection, resulting in defects.
Which process to choose
Generally speaking, this can be seen as a trade-off between a few different characteristics: speed/volume, price, materials .
Speed/Quantity
If the number of parts is small, CNC machining is faster. If you need 10 parts within 2 weeks, choose CNC machining. If you need 50,000 parts within 4 months, injection molding is the best choice.
Injection molding requires time to build the mold and ensure the part is within tolerance. This can take weeks or months. Once this is completed, using the mold to make the part is a very quick process.
Price
Which is cheaper depends on the quantity . If you are producing a few or hundreds of parts, CNC will be cheaper. When the production quantity reaches a certain level, injection molding will be cheaper. It is important to note that the cost of the mold must be shared with the injection molding process.
Materials
CNC machining supports more materials, especially some high-performance plastics or specific plastics, but it is not good at processing soft materials.
The materials that can be molded are relatively few, but injection molding can process soft materials.
As can be seen from the above, the advantages and disadvantages of CNC or injection molding are obvious. The choice of processing method is mainly based on the trade-offs of speed/quantity, price and material.
