What is Injection Molding?
Injection molding is a popular manufacturing process that facilitates producing a large volume of high-quality, uniform and cost-effective plastic parts. During the injection molding process, a plastic or resin material is heated to its melting point and then injected into a custom mold. The part forms inside the mold and is released once it has properly cooled. Injection molding is automated and can be repeated thousands and sometimes millions of times, creating exact copies of a custom part.
The first step of getting a plastic part injection molded is to have a computer-aided design (CAD) model of the part produced by a design engineer. The 3D CAD model then goes to an injection molding company where a plastic mold maker (or toolmaker) will make the mold (tool) that will be fitted into an injection molding machine to make the parts.
Molds are precision-machined usually from steel or aluminum and can become quite complex depending on the design of the part. Plastic materials shrink at different rates when they cool, so the mold has to be constructed with consideration for the shrinkage rate of the material being used for the parts. In other words, a formula is applied in the construction of the mold to slightly increase the size so that when the plastic shrinkage occurs, the part will be to the dimensional specifications of the CAD model.
Dorchase has been working with customers all over the world and in many different industries. We are a low-cost leader producing high-quality injection-molded plastics with a quick turnaround. We are an ISO 9001:2008 certified injection molding company.
Injection Molding Basics
The actual process of plastic molding is just an expansion of this basic process. The plastic goes into a barrel or chamber by gravity or is force-fed. As it moves down, the increasing temperature melts the plastic. Then, the molten plastic is forcibly injected into the mold under the barrel with an appropriate shape. As the plastic cools, it solidifies. The plastic molded like this has a reverse shape of that of the mold. A variety of shapes can be produced by the process. The process of plastic molding is cheap due to the simplicity involved and the quality of the plastic material is modifiable by changing the factors involved in the custom injection molding basics process:
- The pressure of injection can be varied to change the hardness of the final product. Injection pressure causes the material to flow. Pressure increases as mold filling becomes more complex. There is a direct relationship between injection pressure and injection line pressure.
- The thickness of the mold affects the quality of the part produced. On average, the minimum wall thickness of an injection molded part ranges from 2mm to 4mm (.080 inch to .160 inch). Parts with uniform walls thickness allow the mold cavity to fill more precisely since the molten plastic does not have to be forced through varying restrictions as it fills.
- The temperature for melting and cooling determine the quality of the plastic formed. In injection molding, the temperature of the melt in the cavity is generally between 200 and 300 degrees, the melt is formed in the cavity, cooled and solidified into a product profile.
Insert Injection Molding
Insert molding is a process that starts with placing metal, ceramic, or other plastic parts into the plastic injection mold. After those parts have been properly placed, the mold is filled with molten plastic in the regular injection molding process.
Gas Assist Injection Molding
Gast assist injection is a process that utilizes an inert gas to create one or more hollow channels within the injection-molded plastic parts. At the end of the filling stage, the gas is injected into the still liquid core of the molding. From there, the gas follows the path of least resistance and replaces the thick molten ejections with gas-filled channels.