Frequently Asked Questions About Injection Molding

Learn the Answers to Injection Molding FAQs

If you work in manufacturing, you understand the importance of choosing the best materials, equipment, and processes to build parts that will eventually be made into products. In the plastic industry, there are several ways to manufacture plastic components– from plastic extrusion, compression molding, vacuum casting, thermoforming, and more, the options for how to create the components that will be made into objects are vast.

Injection molding remains one of the most cost-efficient, reliable, and fast ways to produce high-quality, durable plastic parts. Our injection molding company has answers to the most frequently asked questions about the process of injection molding, its many benefits, and what it offers to professionals manufacturing plastic parts across multiple industries.

Injection Molding FAQs

What is injection molding?

Answer: Injection molding is a manufacturing process used for the large-scale production of plastic parts and components that make up objects. Injection molding is used in many industries, including consumer products, automotive parts, medical tools and equipment, telecommunication materials, and more.

During the plastic injection molding process, plastic polymer materials are fed into an injection barrel, heated to a liquid state, and injected into a molding tool that is shaped like the component being produced. Once the materials are cooled, they are extracted from the mold. You are left with a completely finished, usable product or a product ready for further customization like paint and other aesthetic and functional design details.

What's the difference between injection molding and thermoforming?

Answer: While both injection molding and thermoforming are popular manufacturing processes to create parts for products out of plastic materials, they have some key differences that set them apart.

The main differentiators between injection molding and thermoforming are:

  • Tooling: Thermoforming tooling uses a single-sided mold, whereas a double-sided 3D mold is used for injection molding.
  • Materials: Thermoforming can use a variety of thermoplastic materials such as polystyrene or polycarbonate in the form of plastic sheets, but with injection molding, tiny, plastic pellets are used. Both plastic sheets and plastic pellets are available in a variety of colors, but thermoforming sheets come in different varieties of thicknesses and finishes, whereas the plastic pellets used for injection molding do not have those additional options in materials.
  • Production: During the production process for injection molding, tiny plastic pellets are heated into a liquid form and then injected into a mold to create the part or product. With thermoforming, flat plastic sheets are heated until the sheets become pliable, and are then molded and suctioned to the molded shape using either a vacuuming or pressure technique.

What are the 4 basic steps to injection molding?

Answer: The 4 injection molding stages are:

  1. Clamping: Both sides of the mold are clamped together tightly and attached to the injection molding machine.
  2. Injection: The plastic pellets are fed into the molding machine, heat applied to the surrounding barrel serves to melt the plastic into a liquid form, and the melted plastic then injects into the clamped mold.
  3. Cooling: After the liquid is inside the mold, it is allowed to sit and cool, hardening and taking the shape of the mold.
  4. Ejection: When the cooling process ends, the mold opens and releases the newly formed part, ejecting it from the injection molding machine, then continuing the process again to create a new part within the mold.

How many times can an injection mold be used?

Answer: An injection mold can be used anywhere from hundreds, thousands, or even millions of times. The longevity of a mold and the injection mold machine is based on the environment in which it is kept, how regular maintenance is performed, the frequency in which the machine is cleaned, and other extenuating factors that have to do with the proper use and care for the equipment.

What are the main parameters for injection molding?

Answer: There are 5 main parameters for the process of injection molding to form plastic parts and components. Each parameter is considered a Critical Process Parameter (CPP). This means that in order to have the output of a quality product, all of the parameters must be maintained throughout production.

These injection molding parameters are:

  1. Temperature
  2. Pressure
  3. Speed
  4. Time
  5. Measurement

What is injection mold temperature?

Answer: Processing temperatures during injection molding is essential to obtaining the desired result for the final product output. The temperature of the mold is essential to maintaining the timing for which the plastic polymers melt into a liquid, the rate at which it flows into the mold, the solidification process, and the overall quality of the final product.

The two types of temperatures that are crucial to production are:

  • Melt temperature: The temperature of the polymer materials as they pass through the nozzle and hot runner to enter the mold. This temp affects resin viscosity, resin molecular weight, and shrinkage of parts. Melt temps for the use of polypropylene should be between 400 to 480 degrees Fahrenheit.
  • Mold temperature: The temperature of the surface of the mold itself, plays an important role when the liquid enters the mold as well as during the cooling and solidifying process. This affects the creep and fatigue resistance, molecular weight, wear resistance, and durability of the parts being formed. When mold temps are inconsistent, it can lead to cracks or other imperfections in the product. Mold temps should be between 176 to 194 degrees Fahrenheit.

What pressure is used in injection molding?

Answer: When making a part with injection molding, several types of pressure are important. The amount of pressure depends on calculations for each specific part being created and is based on the size, shape, and overall needs of the item being produced.

The various types of pressure used in the injection molding process are:

  • Injection pressure: The force applied to fill the mold with the liquid to form the mold. The amount of pressure needed is calculated based on the size and shape of the mold and parts.
  • Holding pressure: The pressure is contained and held on the melted resin after the mold is filled. The pressure is maintained for a particular amount of time depending on the needs of the product.
  • Clamping pressure: the amount of force used to hold the 2-sides of the mold together.
  • Back pressure: The pressure used to affect the uniformity in pigmentation and melting of the plastic.
  • Nozzle pressure: The pressure within the nozzle where the liquid resin flows to the mold.

What is the cycle time in injection molding?

Answer: There are 4 steps to the injection molding process– from start to finish, the process to complete production of a part can take anywhere from 2 seconds to 2 minutes to complete all 4 steps explained above.

What type of plastic should be used for injection molding?

Answer: When choosing the best plastic for injection molding, the most commonly used materials are:

Q: How thick can an injection mold be?

Answer: Wall thickness for injection molding can be anywhere from 1mm to 4mm.

Q: Which side should plastic inject from?

Answer: The two sides of the injection mold are called the A-side called the cavity and the B-side called the core. The A-side is affixed to the side of the injection machine, whereas the B-side is attached to the moving clamp. Plastic resin is injected into the cavity or A-side during the injection molding process.

Contact Advanced Plastiform for Your Injection Molding Project

If you are considering using injection molding to form a product prototype or to create a high-volume output of manufactured parts, Advanced Plastiform, Inc.’s plastic engineering team of professionals is here to help.

Producing high-volume injection molding parts and products for over 30 years, we serve communities in North Carolina, South Carolina, Maryland, Pennsylvania, Georgia, Tennessee, and Virginia.

Contact us to request a free quote or fill out the form below to get started on your injection molding project.

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