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Injection Molding 101

What Is Injection Molding?

Injection molding is a form of mass production typically used when there is a need for many identical parts. Injection molding involves the injection of heated materials into a mold, which then cool and solidify into the desired shape. Once the mold has been designed and created, it can be used to manufacture thousands or even millions of identical parts, making it suitable for mass production of parts used in many industries. These industries include aerospace, medicine, automotive, and more. 

Injection-molded products can be made using metal, glass, rubber, elastomers, confections, and plastic. This versatility makes it an excellent option for those needing mass-produced parts. 

Why Utilize Injection Molding?

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One of the most attractive injection molding features is that you can scale up production to almost any level. Initial costs for the design and mold can be prohibitive for small production runs, but once these initial costs are paid, the price per unit for injection molded parts is meager. Additionally, as production scales up, the cost per unit tends to drop remarkably. 

The turnaround time for parts manufactured using injection molding is rapid. The ability to produce hundreds of parts per minute with a single injection molding machine makes the process ideal for mass production.

Additional materials can be mixed in with plastic, allowing for a final product with greater strength.

Injection-molded parts have a very high level of consistency. As a result, the variation between different pieces is negligible, and this consistency improves the reliability of the parts. 

Injection molding is considered to be very environmentally friendly when compared to other manufacturing methods. Many different forms of manufacturing have high scrap rates and wasted material. Injection molding, however, has a relatively minimal amount of waste involved. In addition, much of the plastic that is leftover from the process can be recycled, further minimizing waste.

Much of the injection molding process is automated, which reduces cost, and produces a reliable and consistent product with low error rates.

Injection molding can be used to make parts with a highly detailed design due to the molding process. Many other manufacturing methods are unable to produce items with a high level of detail. This issue helps make injection molding an attractive option to those looking to produce more complex parts with little tolerance for error.

What Industries Use Injection Molding?

Due to the variety of materials supported and the high level of consistency provided by injection molding, the process is suitable for producing parts needed by a wide variety of industries, including:

CONSTRUCTION 

Home and building construction both utilize many parts that are manufactured using injection molding. In addition, many applications in the construction industry have high requirements for part quality, consistency, and durability, making injection molding a popular choice for many parts used in the industry.

AUTOMOTIVE

Consistency and safety are essential factors for parts used in the automotive industry, and injection molding is commonly used to meet these requirements. Additionally, the ability to customize the color and finish of injection-molded parts allows the level of versatility that automakers require. As a result, many interiors, exterior, and under-the-hood auto components are all manufactured using injection molding. 

FOOD & BEVERAGE

Food containers, beverage caps, filtering components, conveyor systems, straws, and other food and beverage items are all commonly produced through injection molding. Because of food safety requirements, you can use only certain materials for the manufacturing of these items. With injection molding, manufacturers can use BPA-free and other non-toxic plastics to produce items that you can safely use to hold food and withstand temperature changes.

MEDICINE

Many types of medical equipment utilize injection molded parts, including heart pumps, monitors, laboratory equipment, and many more. Injection-molded parts can meet any special requirements for the medical industry, including resisting breakage, contamination, and temperature changes.

TELECOMMUNICATIONS

Much of the information in the world transmits through the use of fiber-optic cables, which require special adapters and parts to function correctly. Many of these parts are made using injection molding, making the process critical to this crucial industry.

HOUSEHOLD GOODS

Many everyday household items are made using injection molding. For example, toys, plastic bottles, plastic food containers, and many other common household goods are manufactured with this process.

ELECTRONICS

Computer monitors, keyboards, laser printers, cell phone components, and many other electronic items all contain parts manufactured with injection molding.

How Does Injection Molding Work?

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Before the actual injection molding process begins, you must create a 3D design of the product itself. A STEP file is one of the common file types used for this. You must also consider the design, desired material, shape, and any additional features. Then, upon manufacturer approval of the design, the mold itself is created. 

The mold is a precision-machined metal piece that consists of the core and the cavity and is used to form the materials into the desired shape. 

The mold is usually made from aluminum, steel, pre-hardened steel, or beryllium-copper allow. The type of material used for the mold can have an impact on the entire process. For example, a steel mold can be more expensive but more durable and can construct more parts before needing replacement.

Aluminum molds are less costly but do not last as long as steel molds. One advantage of an aluminum mold is that it can dissipate heat, allowing for a reduction in the time required to mold each part better. This increase in speed can help manufacture more parts in a shorter amount of time.

The molding process consists of five key steps:

1. Clamping

Since the mold itself comprises two pieces (the core and the cavity), these pieces must be held together by a clamping unit. As the material is injected, the clamping unit pushes the two halves of the mold together and holds them tightly in place.

2. Injection

A hopper feeds the materials into a barrel. This barrel contains an auger, which is essentially a screw-shaped device that rotates to feed the material into the injection machine. Heat and pressure are applied to the barrel and auger to melt the pellets into liquid form, and this liquid is then injected into the mold cavity through a sprue and runners. 

As the liquid enters the mold, the displaced air exits the mold through vents. High pressure ensures the mold fills as completely as possible. A mold may also have multiple cavities, allowing many products to be made with each injection.

3. Cooling

After the material injects into the mold, it will begin to cool and harden. This cooling is facilitated by coolant flowing through channels around the mold. The mold remains closed until the material hardens into its final shape. Once the cooling period has ended, the mold can be opened again. The cooling time can be affected by both the thickness of the part and the type of material used. The time it takes to make each part is called a cycle, and a longer cooling time impacts the duration of each cycle.

4. Ejection

The part may stick to the mold, so an ejector rod or ejector pins are used to eject the molded part. 

The part is caught by a bin placed under the mold. Once the part is ejected, the process begins again to create the next part.

5. Finishing

The sprue and runners are trimmed from the part, leaving only the final product. Some injection molding machines utilize a hot runner system, which eliminates both runner and sprue. This utilization minimizes the amount of waste but can increase the cost of the injection molding machine. 

The Injection Molding Cycle

The amount of time to complete a single cycle depends on a few factors, including:

MOLD CAVITIES

You can use a mold with multiple cavities when making a smaller part. With multiple cavities, each time liquid is injected into the mold; multiple parts are created. Therefore, the amount of time per cycle will be increased, but more parts are produced with each cycle.

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MOLD CYCLE 

The mold cycle can be defined as the amount of time it takes to complete a single injection molding process. However, the calculation of this time does not have a well-defined formula and depends on several factors like: 

  • Type of Material

The density of the material used can increase the amount of time required for cooling, influencing the length of each molding cycle.

  • Part Thickness

A thicker part will require more time to cool, increasing the length of each cycle. Check out our article on minimum wall thickness in plastic injection molding to learn more.

  • Type of Molding Machine

Electric molding machines are typically faster than machines using hydraulic motors, reducing the length of each cycle.

  • Runner and Sprue Trimming

The time necessary to trim the runner and sprue after cooling can affect the length of each cycle. Hot runners can eliminate the need for trimming, or robots can automatically perform the trimming, increasing speed.

Anatomy of an Injection Mold Machine

There are different types of injection molding machines. Some are motorized, while others are driven by hydraulic motors. There are also hybrid units that utilize both servo and hydraulic motors. 

An injection mold consists of four main parts, each of which contains secondary parts.

BASE

The base, also called the machine bed, works as a frame to mount the clamping unit and injection unit. Due to the heavy stress load on the machine, the strength and durability of the base are essential, making heavyweight steel beams the material of choice for most injection mold machines.

CLAMPING UNIT

The clamping unit holds the two halves of the mold together to prevent leakage and is responsible for opening and closing the mold halves, as well as ejection of the part.

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Mold

  1. Cavity: The cavity is the shape of the part that is being manufactured.
  2. Runners: The runners are channels that enable the plastic to flow into the cavity.
  3. Sprue: The sprue is the primary channel that the liquid flows through.
  4. Parting Line: This is the break between the two halves of the mold. When separated, it allows the parts to be ejected from the mold.

Barrel

  1. Hopper: The hopper is used to store the pellets before they are heated and fed into the barrel.
  2. Heater Bands: The heater bands wrap around the barrel and apply heat to help melt the pellets into liquid form.
  3. Auger: The auger, or reciprocating screw, turns to propel the pellets forward. The friction from the turning of the screw also creates heat to assist in melting the pellets.
  4. Nozzle: The nozzle is located on the tip of the barrel and directs the melted liquid into the actual mold.

Our Jaycon team has created a short animated video to detail the basics of the injection molding process. (See below).

More Than Just Injection Molding

Jaycon Systems is a product design, prototyping, and manufacturing company that specializes in injection molding. We can provide mold tooling, plastic injection molding, post-processing, and product packaging. Whether you need a prototype unit or mass production of millions of parts, our solutions can scale to meet the needs of any size application.

We have facilities in both Florida and Shenzhen, China, that utilize high-end injection molding equipment. We have the capacity for up to 50 injection mold tooling sets per month and can meet production needs of up to 800,000 pieces per month.

We can provide injection molded parts using a variety of materials, including:

  • All thermoplastics and elastomers
  • Acrylonitrile butadiene styrene (ABS)
  • Polyethylene
  • Polycarbonate
  • Polyamide (nylon)
  • High impact polystyrene
  • Polypropylene
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We are also able to support requirements for many popular add-ons, including:

  • Anti-UV
  • Fire retardants
  • Talc
  • Antibacterial agents
  • Plasticizers
  • Other additives
  • Chrome finish

In addition to the initial plastic injection molding, we are also able to provide many post-processing services such as:

  • Box-build assembly
  • Electroplating
  • Hydro-dipping (water transfer)
  • Pad printing
  • Screen printing
  • Laser etching
  • Overmolding
  • Insert molding
  • Ultrasonic Welding
  • Molded-in color
  • Molded-in symbols
  • Hot stamping
  • Internal and external Threads
  • Metal stamping

From Concept to Production with Jaycon’s Injection Molding Services

Successful projects start with a good plan. We work with you every step of the way to ensure the optimal design, manufacturing, and quality control of your parts. Our engineers can help you choose your material and surface finish, and our injection molding process minimizes the appearance of markings typical to injection molding.

The first step is to submit your STEP files through our contact form. A Jaycon engineer will respond with a custom injection molding quote within 24 hours. This secure contact form ensures the safety of your files, as well as a mutual NDA you can sign before the submission of your STEP files. Then, Jaycon will show you how we can help turn your design into reality.