When designing a part, it's a good idea to consider which process to use to make the model and to optimize that production process accordingly.
The most common processing methods for plastic parts are CNC machining and injection molding. So how do we choose between these two processes?
1. CNC machining
CNC machining usually starts with a single piece of material removed several times to obtain the set shape.
At present, CNC plastic processing is one of the main ways to make hand board models, mainly processing ABS, PC, PA, PMMA, POM, and other materials into the physical sample parts we need.
The sample parts processed by CNC have the advantages of large molding size, high strength, good toughness, low cost, etc., and have become the mainstream way of hand-board production.
However, some plastic parts with complex structures may have production restrictions or higher production costs.
2, injection molding.
Injection molding dissolves the granular plastic, then press the liquid plastic into the mold through high pressure and gets the corresponding parts after cooling.
Advantages of injection molding
1、Suitable for mass production
2. Can process soft materials such as TPE and rubber.
Disadvantages of injection molding
1. The mold cost is relatively high, leading to high start-up costs. When the production volume reaches a certain quantity, the cost per piece of injection molding is low. If the quantity is not enough, the cost per piece is high.
2、The renewal cost of parts is high, also limited by the cost of molds.
3、If the mold consists of more than one part, the injection may produce bubbles and defects.
which process to choose
Generally, this can be seen as a trade-off between several characteristics: speed/quantity, price, and material.
01. Speed/Quantity
CNC machining is faster if the number of parts is negligible. If you need 10 parts in 2 weeks, choose CNC machining. If you need 50,000 parts in 4 months, injection molding is the way to go.
Injection molding takes time to build and ensures the part is within tolerance. This can take weeks or months. Once this is done, building the part using a mold is a rapid process.
02. Price
Which is cheaper depends on the quantity. CNC will be cheaper if a few or hundreds of parts are produced. When producing a certain quantity, injection molding will be cheaper. It is important to note that the injection molding process must share the mold cost.
03. Materials
CNC machining supports more materials, especially some high-performance plastics or specific plastics, but is not good at processing soft materials.
Injection molding has relatively fewer materials, but injection molding can process soft materials.
As you can see from the above, the advantages and disadvantages of CNC or injection molding are apparent. The choice of which processing method is mainly made by weighing speed/quantity, price, and material.