When it comes to plastic part production, injection molding is among the least expensive processes available. Due to the initial investment of the mold, return on investment should be an important consideration when making the decision on what type of part manufacturing process to use.
Part Manufacturing Considerations:
Part manufacturing volume is a major consideration. If you anticipate needing lower volumes in the tens or perhaps even hundreds of parts per year, plastic injection molding may not be for you. You should also consider other part manufacturing processes such as fabrication, polymer casting, 3D printing, or vacuum/thermo-forming, depending on the geometry of the part.
However, if you do anticipate larger part manufacturing quantities that would justify the initial investment of an injection mold, you must also consider the shape of the part when determining what process to use. Below is a rundown of various plastic part manufacturing processes and the geometry that best suits them
Part Manufacturing Processes:
Injection Molding: A part with relatively consistent wall thickness, and no internal voids.
Blow Molding: Think of a balloon being dangled inside of a cavity, injected with air, and formed in the shape of the cavity. Bottles, Jugs, Balls. Anything small with an internal void.
Vacuum (Thermo) Forming: Somewhat interchangeable with injection molding, this process starts with a sheet of heated plastic, and is vacuumed onto a form and cooled to create the desired shape. Packaging clamshells, lids, trays, blisters, as well as vehicle door and dash panels, refrigerator liners, utility vehicle beds, and plastic pallets.
Rotational Molding: Larger parts with internal voids. A slow but relatively efficient way to manufacture smaller quantities of large parts such as gas cans, oil tanks, bins and refuse containers, boat hulls.
Fabrication: Used for smaller quantities of parts due to high labor costs, this process usually involves cutting and gluing sheet stock to match your specifications.