Basics Injection Molding

Injection Molding Basics

Most solid plastic materials are produced by a process called injection molding. During the process of plastic injection molding, plastic resin pellets are heated until they melt. The melted liquid plastic is introduced, under pressure (injected), into a mold. The mold may be made up of any metal such as steel or aluminum. The molten form is then allowed to cool down and set into a solid form. The plastic material thus formed is then retrieved out of the mold.

The injection-molding process has been around for nearly 150 years. Reciprocating screw injection molding machines were introduced in the 1960s and are still used today. The injection molding machine comprises an injection unit, where material is prepared for injection into the mold, and a clamping unit, where the injected plastic is captured in the mold under conditions of temperature and pressure to form the finished product.

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:

injection mold

  • 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 plastic 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.

Advantages of Injection Molding

Basics of Injection MoldingThe major advantage of plastic injection molding is that it is very cost effective and fast. Unlike a “cutting” manufacturing process, injection molding reduces the possibility of undesired sharp edges. This process produces smooth and finished products that require no further finishing. Not only is the injection molding process simpler and more reliable than others methods, but it is also extremely efficient. Here are some of the top advantages of the injection molding process:

Fast and efficient: The plastic injection molding process is extremely fast compared to other methods and the high production output rate makes this process even more efficient and cost-effective. Once the injection molds have been designed to specifications the actual molding process is very fast compared with other methods of molding, allowing for more parts to be manufactured from a single mold. Manufacturing speed is dependent on the complexity of a mold design, but on average only about 15 to 30 seconds pass between cycle times.

Complexity of part design: Injection molding can handle extremely complex parts, and uniformity, as well as the ability to make millions of virtually identical parts. Since the plastic injection molds are subjected to extremely high pressure it is possible to add a large amount of detail to the part’s design.

Waste reduction: A high-volume injection molding company shares a commitment to quality, sustainability, and optimal safety. The benefit to the environment is by only using required amount of plastic to build parts. Recycling excess plastic benefits environment and minimizes waste.

Lower labor costs: Much of the injection molding process is automated and controlled by a single operator or mold technician. This keeps labor costs at a minimum. The molding equipment typically runs with a self-gating, automatic tool to keep operations streamlined and production ongoing, requiring minimal supervision.

Strength: While it is possible to use fillers in the injection molds, these fillers reduce the density of the plastic while being molded and help add to its finished strength after the molding process. Finding the proper balance of design considerations determine the part’s need for strength and stability. The strength and durability of plastics has increased over the years. Modern lightweight thermoplastics can withstand even the most rugged environments.

Versatility in materials and color: Choosing the right material and color for a project are two of the essential factors in creating plastic parts. One mold can produce may variations of your product. Color and material type are relatively easy to change in injection molding machines.

Injection Molding Production Highlights

>  Instant mold and part quote
>  Low cost, quick build and quality production
>  ICOMold’s Lifetime Warranty on Production Molds
>  Online project management
>  Trouble-free part modifications

>  No size limitations
>  Any commercially available material and surface finish

What is the process for injection molding production?

ICOMold’s instant online plastic injection molding quote and mold frame sharing technology enables us to simplify and shorten both the quoting and tooling manufacturing process for custom plastic injection molding.

  1. Load your 3D CAD file to get an instant mold and part quote
  2. Upon order confirmation, ICOMold starts the mold and part order process
  3. Tooling design review by ICOMold engineers
  4. Upon design approval, ICOMold begins building your injection mold
  5. Customer examines samples for approval
  6. Part production begins

Family Injection Molding Case Study
Go to our plastic injection molding and CNC machining case studies page to see how we helped customers on their projects.