Plastic injection molding is the process of "pushing" or "injecting" melted plastic (resin) into a mold under extreme pressure. Once the plastic has been injected into the mold, the plastic quickly cools and hardens. Once the plastic has hardened, the mold is opened and the parts are "ejected" out of the mold. The parts are then trimmed and packaged accordingly. This process is accomplished using injection molding machines. Injection molding machines vary in size. The size of a machine is usually indicated by its clamping force which is measured in tons. Techstar Molding has injection molding machines ranging in size from 150 tons to 1000 tons in order to handle both small and large jobs.
Molds (commonly referred to as tooling) are made up of two halves, an "A" half and "B" half. Tooling is usually constructed out of steel, but can also be made out of aluminum for shorter run applications. When each half is clamped together, it forms a cavity making up the form of the part. Each half of the mold is placed inside the injection molding machine. When the machine clamps the two halves together, the plastic is injected into the mold. The mold will generally have "runners" which are little more than "plastic highways" used to move the plastic out to all sections of the mold. Some molds require water passages or "plumbing" which is used to cool the plastic parts more quickly. The more quickly the parts cool, the faster the machine can run. Faster molds equals cheaper parts. Finally, most molds have what are called "knock-out pins" or "ejector pins." As the name implies, these pins kick the part out of the mold to speed up production and assist the operator in removing the parts.
This is one of the most common question of all. The cost of a mold is based on numerous factors. The most prevalent factors are size, complexity, material, and number of cavities. It is impossible to give an accurate price for a mold over the phone without dimensions and certain specifications. Techstar Molding will not quote you a price for a mold without part dimensions and specifications. Please be wary of any company that says they can or will.
The time to construct a mold will vary depending on its size and its complexity. 4 weeks is generally the shortest time necessary to complete a mold.