Custom Injection Molding
With the ability to injection mold shot sizes up to 580 lb. and wall thicknesses in excess of 5 inches, EnviroTech Custom Injection Molders is anything but typical. With more than 50 years of experience we have become the world leader in large, thick wall plastic parts. Time and time again our customers have turned to us for their Custom Injection Molding needs because other suppliers claimed their products were impossible to manufacture. From polycarbonate fighter jet canopies with perfect optics to void-free 200 lb. pipe fittings, the possibilities are almost endless.
THE PLASTIC INJECTION MOLDING PROCESS
Injection molding is a common way to manufacture plastic parts. Parts manufactured using injection molding vary in size, shape and complexity. Injection molded plastic parts are used in a variety of situations from engine parts to medical equipment. The functionality and use of an injection molded part determines the type of raw plastic material or resin that should be used in the injection process. Plastic is melted in the injection molding machine and then injected into the mold, where it cools and solidifies into the final part. The steps in the molding process can be complex based on the plastic resin used and part complexity.The process cycle for injection molding varies based on the part size and thickness, times may vary from a few seconds to 30 minutes. Since EnviroTech’s proprietary bulk injection molding processes allows us to mold larger parts, the cycle-time tends to be longer. The main injection molding process steps include clamping the mold shut, injecting the resin into the mold, cooling the molten resin, and ejecting the part.
PLASTIC MOLDING STEPS
The two halves of the mold are securely clamped by means of a hydraulic press or motor. Both halves of the mold must be carefully designed so that the part will be able to leave the mold without being damaged or getting stuck.
Resin material, generally in the form of plastic pellets, is fed into the machine. The resin is then heated and melted as it travels down the barrel of the machine. When fully molten, the plastic is injected quickly into the mold, typically by a reciprocating screw or plunger.
After filling the mold, the plastic is allowed to cool fully. The time required to cool may vary depending on the part size and wall thickness.
The mold is opened and air quickly fills the vacuum of the cavity half of the mold, sometimes causing part shrinkage. Ejector pins are then used to remove the part from the core half of the mold. Molds must be designed carefully, incorporating a proper draft angle and making sure all part surfaces are reachable in a straight line perpendicular to the parting line. This will allow parts to be removed from the mold without any damage.
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- Shot size from 2 oz. to 580 lb.
- Void free wall sections in excess of 5 inches
- Economical production runs – 50 to 50,000 pieces per year
- Complex configurations
- Lightweight parts – 80% lighter than most metals
- Corrosion resistance – Plastics can operate in severe chemical environments
- Abrasion resistance – Plastics offer superior abrasion resistance