Things You Should Know About Plastic Injection Molding

Plastic injection molding is one of the most common manufacturing processes for creating parts. This is due to the many advantages that this method of production provides, including its ability to produce very complex shapes with high precision and at very low costs. However, there are some things you should keep in mind before you begin your next project using this process.

Injection molding uses enormous amounts of pressure during the injection process to create a solid, high quality part. The mold needs to be able to withstand these tremendous forces or else the molded part will have poor surface finish and may not be dimensionally correct. The plastic used in this process must also be able to withstand the temperatures and pressures that will be applied during the injection process.

During the injection process, raw pellets of the chosen thermoplastic are fed through a screw that is turned gradually by the machine. This causes the temperature to gradually rise until it reaches the melting point of the material. As the screw turns and the barrel melts the pellets, they are injected into the mold through a gate that is placed at the end of the barrel. Once the right amount of material has been injected into the mold, the screw stops and the two halves of the mold close. This creates a force known as clamp pressure that holds the two sides of the mold together tightly so that no plastic escapes during injection. The runner system then spreads the molten plastic across the face where the two halves meet, connecting the spurs to the gates. The runner system is cut off from the part after ejection and is the only waste that is generated by this process.

The design of your injection molded part is critical to the success of your project. A well-designed part will be free of defects that can impact quality and increase production costs. These include undercuts, warping, and drag marks. Undercuts occur when certain areas of the part cool and shrink more quickly than other sections. This can cause the interior of the part to bend, forming a small hole in the surface. Parts with non-constant wall thickness are most prone to this defect. To avoid undercuts, it is possible to redesign the part with shut-offs or sliding side-action cores that will move in as the mold closes and slide out before the mould opens.

Another issue that can impact the quality of injection molded parts is warping. When some sections of the part solidify and shrink at different rates, it can cause uneven stresses that result in warping. The best way to prevent this is to use a draft angle on the walls of your part. Lastly, parts with vertical walls without a draft angle are very prone to drag marks. These marks can be caused by the plastic scraping against the walls of the mold during ejection.

Injection molded parts are often used in the agricultural industry because of their durability. These parts can withstand harsh weather conditions and are resistant to corrosion. They are also lightweight, allowing agricultural machinery to work more efficiently.

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