Injection molding is the most desirable and most commonly used manufacturing process for mid to high-volume plastic part requirements.  Molds are most commonly made from aluminum or steel depending on the number of parts needed.  However, there have been advancements with 3D printed molds typically used for prototype injection molded part quantities.  Upon the creation of mold halves, which are machined to create a geometry-specific cavity, plastic pellets are then melted and pressure injected into the mold, resulting in the desired part.  Excess material and gating is trimmed or removed manually.  Because plastic is the end part material, mold life is normally in the hundreds, thousands and even hundreds of thousands, depending on the part geometry.  Like die casting, a variety of industry-known geometric design features to the end part and / or the mold halves should and often need to be taken into account.  These include draft, fillets, parting lines, bosses, holes, ribs, ejector pin locations and runners.  Over molding produces single parts in two different materials; and insert molding is used when plastic needs to be molded onto another part.