Plastic injection molding is a popular process that produces identical plastic parts and goods. A mold is created and then filled with a molten plastic material to take on the design of the product once it hardens. This process is fast, precise, and cost-effective, especially for high-volume orders. D&M Plastics has nearly 50 years of experience in the production of high-precision injection-molded parts with the durability, design flexibility, and reduced assembly costs that our customers have come to expect.
The Plastic Injection Process
Plastic injection molding follows a precise set of steps to ensure every workpiece is created with consistent quality and structural integrity. Once the mold is created and manufacturing is about to begin, the process goes through the following:
1. The Material Enters the Barrel
Granular or powderized plastic material is poured into the barrel of an injection molding machine down a hopper. Because the material is granular, it can be premixed with other plastics and additives to create a custom substrate for the products. Granular plastics also have a high degree of surface area for easy heating and control.
2. The Material Melts and Mixes
Injection molding machines use two different mechanisms (sometimes in combination) to melt the granular plastics into a molten fluid. The first is the direct application of heat. The second is heat through friction. To melt plastic through the second mechanism, a corkscrew twists through the filled barrel, raising the temperature and pressure as it drives the melting material toward the mold. This ensures the material is well-mixed and evenly heated.
3. The Shot Sizes Are Measured
Each mold needs a precise amount of molten plastic to fill the mold completely without running the risk of errors, air bubbles, or excess material going to waste. This precise amount is called the shot. Factors such as the shot size and injection pressure impact the speed of injection, which ultimately determines the consistency of the material quality throughout the workpiece.
4. The Mold Closes
Molds are made of two pieces that sandwich together, with the internal cavities making up the dimensions of product the mold will produce. The mold must close with enough pressure and strength to resist movement once the pressurized plastic is injected into the mold. Manufacturers must also keep the mold closed for long enough to allow for thorough cooling and hardening but not so long it holds up the production process.
5. The Plastic Is Injected Into the Mold Cavity
The injection machine pushes the molten plastic fluid into the mold’s cavity. The material is injected with enough pressure to ensure it reaches all of the pathways and edges of the mold cavity and the mold is filled before the material can cool and harden. Both the speed and pressure of the injection determine the quality of the finished part.
6. The Molten Material Cools
Once the molten material leaves the heat nozzle barrel of the injection machine or the hot runner system, it immediately starts to cool and solidify. It will take on the shape of the mold cavity and start to gain its permanent characteristics of hardness, bendability, and color.
7. The Mold Opens
Professional manufacturers will ensure the mold is closed for enough time to set the plastic and no longer. Once the determined time has elapsed, the mold will automatically open.
8. The Part Is Ejected
Mechanisms within the mold or injection machine will push the newly created workpiece out of the mold and onto an assembly line below. From there, the piece can be taken for any smoothing, finishing, and packaging steps that are part of its total production process.
The Cycle Begins Again at Step #4
Now that the mold is empty, the injection process can begin again. Professional systems move from step to step quickly for a seamless cycle of production.
Choose D&M for High-Quality Plastic Injection Molding
At D&M Plastics, we specialize in high-quality molding services from start to finish. We maintain over 30 presses and a cleanroom to produce an extensive array of standard and custom plastic parts. We’ve been an industry leader in reliable production and excellent customer service for almost five decades. Contact us today to learn more about our capabilities or request a quote to start your order.