Injection Molded Plastics
Injection molding of thermoplastics is a process that melts the plastic material and then injects it into the mold where it cools. All details of the mold are reproduced in the finished part. Those details can be as fine as ribs or screws.
The molding machine has an injection unit to melt and transfer the plastic into the mold. A second component is the clamping unit that secures the mold against injection pressure. The clamping unit also allows part removal. Currently there are two injection machine designs: a two-stage version and a reciprocating screw type. Injection molding presses can be rated up to 450 tons with shot capacities up through 60 ounces. They can accommodate a variety of resins.
Peripheral equipment in molding operations should include granulators, chillers, conveyors, water tower, temperature controllers, resin dryers and vacuum system. Mold making requires EDM, CNC and conventional milling and grinding machinery.
To provide a complete service, the supplier should also have a full line of inspection equipment such as coordinate measuring machines, gages, moisture meters, calipers, micrometers and testers. This equipment should also be backed up by an engineering staff capable of product design and review.
The products derived from injection molding are used in electronics, crafts, pumps, meters, vending machines, automobiles, computers and office machines.
There are a number of advantages to consider when evaluating injection-molded plastics versus metal products. Most important is that it is more economical than metal. Plus, molded plastic processing is faster than metal-forming parts and injection molded pieces are complete, requiring no secondary operations or painting.
Most of the initial cost of a plastic part is the cost of injection tooling. Efficient molders use aluminum tooling out of either 6000 or 7000 series aluminum billet. Aluminum cuts over 50% faster than mild steel, and this means half the machining time costs as compared to steel molds. The molds can be designed to be used with no automatic draws or push offs as well. This means tools faster and at a lower cost than conventional tooling.
Does this sound like you: "We might need a hundred parts for now and a thousand a month starting next year."
You don't want to buy tooling twice, once for the prototypes, and another time for moderate production or a bridge to high production needs. You would also like to avoid paying for more tooling than you really need right now, especially if the product might change significantly. Look for a molder who will design the tooling up-front to allow for the expansion of capacity of parts later on. This means making the tool in such a way that the addition of cooling lines, automatic injection and use in a high production injection machine is possible when it is needed. You have the best of all worlds, low initial tooling costs for the initial prototypes, and the ability to use the same tool and produce cost effective production parts with a minimal cost of upgrading the tool at the time it is needed.
Think modular, pay for what you want only when you need it.
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