What Are the Major Components of Plastic Injection Molding Machines?

Regardless of the type of injection molding machine, they all contain some basic components that are used to produce high volumes of plastic parts. The diagram below illustrates the primary components of Injection Molding Machines.

Below is a brief list of the different parts found in the typical injection molding machine. Note that model-specific parts will not be highlighted to provide the most inclusive summary for injection molding machines.

• Hopper: The hopper is essentially s large funnel that accepts stock material and feeds it into the machine.
• Barrel: The barrel contains the reciprocating screw and is the outer housing of the machine. The barrel is wrapped in heater bands and is tasked with both containing the material and the heating portion of the cycle.
• Reciprocating screw: This is the corkscrew component that moves back and forth with every cycle (powered by either an electrical or hydraulic drive system), conveying material through the heating sections, through the nozzle, and ultimately into the injection mold.
• Heaters: The heaters supply thermal energy through the barrel, converting solid plastic pellets into molten plastic as they are pushed by the reciprocating screw. Heaters allow for precise temperature control and are usually staggered in temperature for gradual heating.
• Nozzle: The nozzle dispenses molten plastic from the barrel and into the mold cavity. The nozzle usually sits within a depression in the mold known as the injection mold bushing and is heated to ensure that the plastic does not lose temperature before entering the mold.
• Mold: The mold contains the mold cavity and additional supporting features like ejector pins, runner channels, cooling channels, vents, etc. Molds are commonly separated into two halves: the stationary side (closer to the barrel) and the mold core (on the moving platen), but can also come in more sections depending on the specific machine being considered.
• Mold Cavity: The mold cavity is a negative of the desired part shape plus supports, gates, runners, sprues, etc., and it will be the location where molten plastic fills, cools, and is ejected from.
• Movable Platen: The platen is part of the clamping unit and clamps the mold together and releases the mold core when revealing the finished part. This component is either hydraulically or electrically driven and ensures that no material escapes the mold when injection occurs.

What Is the Most Common Use of Plastic Injection Molding Machines?

Plastic injection molding machines allow for the mass production of plastic parts. They can produce over 10,000 parts in a workday (depending upon machine and part design) with virtually no defects or variance between each part. Their use is only limited by the size of the machine and the imagination of the designers. Injection molding has so many uses that nearly every household in the US has had contact with dozens of injection molded items, if not more.

Where Can I Buy a Plastic Injection Molding Machine?

If interested in desktop injection molding machines, common suppliers like Alibaba, Amazon, and other retailers can provide good options. However, it will be necessary to connect with direct manufacturers if looking for a high-volume, large-scale injection molding machine. There are also extensive aftermarket sources for used injection molding machines, however, these involve the risks associated with any aftermarket purchase and may require maintenance/repair.

Are Plastic Injection Molding Machines Expensive?

Yes, plastic injection molding machines are the most expensive part of the injection molding process, second only to the molds themselves.

Injection molding machines vary in price depending upon type, where worktop/desktop machines cost anywhere from $2,000-$20,000, and large industrial models range from $50,000 to over $200,000. Also, these prices do not include the facility upgrades, skilled worker costs, maintenance fees, and monitoring equipment needed for such a system. This massive overhead incentivizes companies to outsource their injection molding to dedicated companies with existing infrastructure. Only those companies with a core need for injection molding and a developed, high-volume product would consider purchasing an injection molding machine-otherwise, the investment is not recommended.

Are Plastic Injection Molding Machines Easy To Maintain?

It depends on the specific injection molding machine, but generally no, there are considerable maintenance demands from injection molding machines. It is recommended to perform daily visual checks to catch early problems, and at least 4-5 hours per quarter for a general maintenance checkup. A dedicated full maintenance day is required annually to identify issues, perform adjustments, and replace aging parts.

Parts that need an especially keen eye are oil filters (regardless of indicator status), valves, safeties, hoses, machine cylinders, power lines, lubrication points, nozzle alignment, and control modules. Finally, injection molding machines can be temperamental with seasonal changes, so be extra vigilant during transitional months and during extreme temperature days. A lack of preventative maintenance will not only stall the machine, but any profits made from it, so performing regular checks will decrease headaches over the long run (and extend the lifespan of the machine, allowing you to extract more value from the investment in this technology).