Injection Molding: A subtractive manufacturing process. It involves first creating a high-precision metal mold (typically steel or aluminum), then injecting molten plastic (or other materials) under high pressure into the mold cavity. The material cools and solidifies, and the final product is ejected. It is suitable for mass production.
3D Printing (Additive Manufacturing): An additive manufacturing process. It constructs a three-dimensional object directly from a digital model by building it up layer by layer using materials (such as resin, plastic filament, metal powder, etc.). It is suitable for prototyping, small-batch production, and parts with complex or customized structures.
Detailed Comparison Chart
| Characteristic | Injection Molding | 3D Printing |
|---|---|---|
| Production Volume | Ideal for mass production. Once the mold is created, the per-part production speed is extremely fast and cost very low. | Ideal for small batches and single pieces. No mold is needed, so the cost and time for one part versus one hundred are similar. |
| Unit Cost | High upfront cost (mold fabrication), but very low per-part cost thereafter. | Low upfront cost (no mold), but relatively high per-part cost, which does not decrease significantly with quantity. |
| Production Speed | Very short cycle time (seconds to tens of seconds per part), but requires weeks to manufacture the mold. | Slow printing time per part (hours to days), but printing can start immediately without waiting for a mold. |
| Material Selection | Very extensive. Thousands of engineering plastics and elastomers are available, with predictable and stable performance. | Limited but rapidly growing. Primarily photosensitive resins, PLA, ABS, nylon, metal powders, etc. Material performance is generally inferior to injection molded parts. |
| Design Complexity | Limited. Must account for draft angles, parting lines, and undercuts; geometry cannot be overly complex. | Almost unlimited. Can create hollow, nested, and highly complex geometries (e.g., topology-optimized structures), which is its greatest advantage. |
| Part Quality | High surface finish, excellent consistency, and isotropic mechanical properties. | Visible layer lines on the surface, often requiring post-processing. Mechanical properties can be anisotropic (weaker bonding between layers). |
| Design Iteration | Difficult and expensive. Design changes require modifying or remaking the mold at high cost. | Extremely easy. Simply modify the 3D model file to print a new version, making it ideal for prototype testing and iteration. |
Pursuing low-cost, high-efficiency mass production with traditional geometric designs? Injection molding is the undisputed king.
Need rapid prototyping, small batches, or highly complex/customized parts? 3D printing offers unparalleled flexibility and speed.