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Precision Injection Molding

Precision Injection Molding

Plastic components are an essential part of various products across all industries. Precision injection molding makes creating plastic parts for vehicles, tools or instruments for medicine, aviation, defense, agriculture and many other industries possible. Even the plastic kitchen appliances you use every day, like whisks or spatulas, were likely created using precision injection molding. This process creates high-quality components quickly and accurately.

Cutting-edge technology makes precision injection molding possible, and the manufacturing process continues to evolve to be more data-driven, precise and accessible for more sectors. This brief guide explores precision molding and injection techniques as well as the benefits and challenges of precision molding.

What Is Precision Injection Molding?

Precision injection molding is a manufacturing process for producing plastic parts of all sizes. The method melts polymer granules and injects the molten plastic into a mold using high-pressure techniques. The plastic then cools and solidifies into its final shape. This process is excellent for creating high volumes of identical parts at a lower price per part. It is also faster and more efficient than alternatives like 3D printing.

Manufacturing Process in Precision Molding

Procession molding starts with the need for a specific part, moves on to designing molds for those parts and concludes with producing the part using a specialized machine.

Injection Molding Machines

Precision injection molding machines are large, long machines with three primary parts — an injection unit, a clamping unit and the mold. Each primary part has its own function and secondary parts:

  • The injection unit’s secondary components include a feed hopper, barrel, reciprocating screw, heaters and a nozzle. This unit’s primary function is to melt polymer granules and inject the liquid plastic into the mold.
  • The clamping unit consists of a fixed and movable platen, a runner system, a water cooling system, tie rods, an ejector plate and the mold itself. The clamping unit helps secure the mold and ensures it opens at the correct time.

The Precision Molding Process

Here is a brief look at how the various elements of procession molding all come together to complete the process:

  • Design engineers create custom molds for each new component and create a highly accurate mold in the shape of the product part. The mold is divided into two halves.
  • When the injection molding machines operate, the solid plastic is put into the hopper and mixed with reinforcing additives.
  • The granules move to the barrel to be mixed and heated.
  • The reciprocating screw moves the heated plastic to the mold. Both the barrel and reciprocating screw perform by building up pressure.
  • The molten plastic is injected into the mold through the runner system.
  • The cooling system helps the plastic solidify.
  • Once fully cooled, the mold opens and the ejector plate pushes out the completed part. The mold closes, and the process starts again.
  • The whole process can take less than a minute to complete before it is repeated.
  • The parts are typically ready to use and require little post-processing.

Understanding Tolerances in Precision Injection Molding

Understanding Tolerances in Precision Injection Molding

Creating accurate molds is vital as it directly affects how the component fits with other parts or how well it functions. That is where the concept of tolerances comes in — it refers to how much a part can deviate from the prescribed measurements of the mold, which is critical for ensuring product quality. If you deviate too much or too little, the part can end up too big or too small and be unusable. This affects lead times and budget if many parts are rejected.

Tolerances are also what sets precision injection molding parts apart from conventional injection molding. The tolerance for conventional injection molded parts is about 0.005 inch, whereas the tolerance for precision molded parts is much less — about 0.002 inch and even 0.001 inch for some applications.

One of the greatest considerations for tolerances is the type of material used for the molds. Different materials have unique properties and shrink at varying rates. If a material shrinks significantly, it will lead to greater deviations from the desired dimensions. Another consideration is maintaining and monitoring injection molding equipment, as wear and tear over long periods can cause less accurate molds. Injection molding machines need to operate at precise and consistent parameters regarding temperature, pressure and even the speed at which the liquid plastic is injected into the mold. These parameters are crucial for producing consistent quality parts.

Other factors that affect tolerances include:

  • Component geometry: The more intricate the design, the more challenging it becomes to produce an accurate mold.
  • Mold design and quality: Poor quality molds will not cool evenly, leading to parts warping or other defects.
  • Ejector pin placement: Incorrect injector pin placement can lead to marks on the components or other small distortions.

You can reduce the impact tolerances have on product quality in several ways:

  • Choose quality materials with low shrinkage rates and constant cooling rates.
  • Work with engineers to optimize mold designs.
  • Monitor parameters closely to ensure strict process control measurements.

Applications of Precision Injection Molding

Various industries rely on precision injection molding to mass produce vital plastic parts, including:

  • Toys
  • Bottle caps
  • Phone cases
  • Furniture parts
  • Dashboards and bumpers for cars
  • Syringes and parts for medical devices
  • Electrical connectors and protective sleeving for electronic components

Benefits of Precision Injection Molding

There are many advantages of precision injection molding:

  • The process is faster and more efficient than other molding methods, especially when producing high volumes of parts.
  • It produces strong, durable parts with quality finishes.
  • The process is easily repeatable, which allows for higher quality and consistency.
  • Manufacturers can use multiple types of materials in different colors simultaneously.
  • Unlike alternatives, precision injection molding allows for producing complex geometrical shapes.
  • Precision injection molding can be more sustainable than other manufacturing processes because there is little waste. Manufacturers can generally collect scrap plastics and reuse them. Continued innovations will also see injection molding becoming more sustainable.
  • There are generally lower labor costs during manufacturing, as a large part of the process is automated.
  • There is little to no post-processing required as parts are ejected with a finished appearance.

Challenges in Precision Injection Molding

The advantages of precision injection molding make the process a worthy investment, but there are some challenges and considerations to be aware of:

  • Financial considerations: Setting up and operating precision injection molding machines is initially costly. It’s often more cost-effective to work with an injection molding partner than to invest in machinery yourself.
  • Design considerations: Molds need precise engineering to produce quality parts, which requires the expertise of skilled workers.
  • Production considerations: Precision injection molding is a highly efficient process, but the entire supply chain needs to be cohesive for the process to make sense logistically.

You can alleviate some of these challenges by working with an experienced precision injection molding partner, especially if you produce a large volume of parts or parts with intricate designs.

Choose K S Tooling as Your Precision Injection Molding Partner

Precision injection molding plays a vital role in moving the manufacturing industry forward, and choosing the right precision injection molding company for your business is key. Since 1989, K S Tooling, Inc. has been providing OEMs of all scales with innovative production solutions. We are one of the best toolmaking companies in the industry, and you can rely on us for actionable services and products that upgrade your business with high-accuracy injection molding. We provide premium parts for various markets, including aerospace and defense, medical, consumer products, automotive and datacom.

Contact us today to learn how you can streamline production and consolidate costs with our expertise in precision injection molding and product development.

Choose K S Tooling as Your Precision Injection Molding Partner