It’s widely known that plastic injection molding can consistently produce thousands or even millions of plastic components or products for OEMs, aftermarket suppliers, packaging companies, and consumer goods manufacturers.
Plastic injection molding has the ability to produce a wide variety of products varying in size, complexity, and composition.
Applications for this highly repeatable and reliable process reach from automotive, HVAC, and commercial filtration to markets such as appliance, lawn garden, and medical, etc.
Once a part has been designed by an engineer, a toolmaker will craft a metal mold, usually out of steel or aluminum.
The mold can have a single cavity or multiple cavities, precision-machined to form the desired part.
Part and mold design can be very precise, even achieving (or exceeding) a very tight tolerance of +/- 0.02mm.
A variety of polymers, including thermoplastics, thermosets, and elastomers, can be used for plastic injection molding.
Pellets or granules of the selected material are heated in the barrel of an injection molding machine until the mixture is pliant enough to be injected into the mold.
A ram- or screw-type plunger forces the correct volume or “shot” of material to fill the cavities under pressure while the two halves of the mold are clamped tightly together.
The material cools and hardens into the shape of the part and is then removed from the opened mold so the process can begin again.
There are 8 benefits of plastic injection molding
Plastic injection molding reliably creates a high volume of consistent, high-quality units, and there are several other compelling reasons to consider the process:
- It enables the complex metal to plastic conversions, lowering overall part costs by reducing several machining operations into a single molding process.
- Plastic components are lower in weight than machined or cast metal parts.
- When plastic can be used instead of metal, corrosion is no longer an issue.
- Plastic injection molds allow greater design freedom for parts because they allow the addition of radii or soft edge areas that would require extra machining (at an additional cost) in metal parts.
- Another element of design freedom is the ability to create highly detailed parts with complex geometry. Because the plastic material is pushed into the mold under high pressure, it fills the cavity completely and is pressed against the mold harder than in other molding processes. The plastic will thereby conform to even tiny, intricate shapes and details within the mold.
- It is also possible to combine different materials into the same part for greater utility with fewer assembly processes. With 2 shot molding, you can use a hard and soft plastic to create a sealing edge or soft-touch edge or use two different colors. Insert molding allows a non-plastic component to be incorporated, such as a metal screw built into a plastic cabinet knob.
- The plastic injection molding process involves a high degree of automation, which can provide significant savings in production costs. Many of the steps can be completed by machines or robotics controlled by a single operator, reducing labor costs and overhead. The process can also be performed more quickly and efficiently, increasing production output.
- There is little to no material waste generated by this process, as leftover scrap plastic can be re-ground and reused.
Plastic injection molding reliably produces parts and components economically and efficiently.
It also gives you a range of material and design options that can reduce the overall cost by decreasing the weight of equipment or a vehicle, reduce costs associated with its use.
It’s time to reevaluate your processes and see how plastic injection molding can benefit your company.
TDL has more than 20 years of experience with plastic injection molding, and our team of experts offers knowledge from a variety of molding and manufacturing backgrounds.
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Some Basic knowledge of injection molding
What is injection molding?
To put is basically, injection molding is the process of forcing melted plastic into a mold cavity.
Once the plastic has cooled, the part can be ejected. It is useful when the parts are too complex or cost-prohibitive to machines.
With this process,
Injection molding is a plastic-forming process used in the production of most (about 70%) of plastic parts.
Other plastic-forming processes include blow molding, pressure-forming, and thermo-forming.
Injection molding is generally used in the high-speed manufacture of low-cost, high-volume parts, like video cassette cases, plastic cups, printer parts, refrigerator parts, automotive parts, and electronic parts, etc.
The process of injection molding begins with a barrel full of hot, liquid plastic.
The plastic is rammed at high pressure into a mold.
Once the plastic fills the mold, it is allowed to cool and solidify.
The finished part is then extracted (usually automatically) from the mold.
The mold defines the shape of the part, as well as the path by which the molten plastic flows from the barrel.
A simple mold has several features:
- Fixed and Moving Platens – These are rectangular blocks of aluminum or steel into which the shape of the part is cut.
- Cavity – When the fixed and moving platens are touching, the space formed by the cut-out portions, called the cavity, defines the shape of the part.
- Sprue – The sprue is a hole cut into the center of the fixed platen. The molten plastic flows from the sprue to fill the cavity.
- Runners – Runners are channels cut into the platens that direct molten plastic from the sprue to the gates.
- Gates – Gates are small openings between runners and cavities. These are the points at which plastic enters the cavity. They are generally small so that the finished part may be easily broken away from the useless sprue and runner material.
There are six major steps in the injection molding process
An injection molding machine consists of three basic parts; the mold plus the clamping and injection units.
The clamping unit is what holds the mold under pressure during the injection and cooling.
Basically, it holds the two halves of the injection mold together.
During the injection phase, plastic material, usually in the form of pellets, are loaded into a hopper on top of the injection unit.
The pellets feed into the cylinder where they are heated until they reach molten form (think of how a hot glue gun works here).
Within the heating cylinder, there is a motorized screw that mixes the molten pellets and forces them to the end of the cylinder.
Once enough material has accumulated in front of the screw, the injection process begins.
The molten plastic is inserted into the mold through a sprue, while the pressure and speed are controlled by the screw.
The dwelling phase consists of a pause in the injection process.
The molten plastic has been injected into the mold and pressure is applied to make sure all of the mold cavities are filled.
The plastic is allowed to cool to its solid form within the mold.
It usually uses a cooling process in mold base, the cooling process was made compact with an injection machine so it can do automatically by setting in the injection machine.
5. Mold Opening
The clamping unit is opened, which separates the two halves of the mold in two plates model, if, in three plate models, the mold will separate in three halves, include the cutting runner process.
An ejecting rod and plate eject the finished piece from the mold.
The un-used sprues and runners can be recycled for use again in future molds.
The ejection of parts usually doing by an ejector system which consists of an ejector rod, spring, ejector plate, and ejector backing plates.
Generally, step process in the injection molding process are clamping – Injection – Dwelling -Cooling – MoldOpening- Ejection
Kemalhas more than 20 years of experience with plastic injection molding, and our team of experts offers knowledge from a variety of molding and manufacturing backgrounds.
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