Precision Injection Molding: Achieving Manufacturing Accuracy

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Accuracy and precision injection molding for plastic parts manufacturing are of utmost importance to manufacturers and plastic product designers. This is why the precision injection molding process has been found to be the most efficient production method in this industry.

Injection molding machine produucing plastic parts

However, to achieve the designed product using precision injection molding, you will require a thorough understanding of its processes, equipment setup, and quality control considerations. These features often help professionals in the industry specify and carry out the needed steps to give end users and investors the satisfaction of the numerous advantages of precision injection molding.

Consequently, we have written this guide to help you fully understand all these processes and the requirements that come with achieving high efficiency in plastic manufacturing using precision injection molding. So, if you are ready, let’s dive in a little deeper. 

1. Understanding Precision Injection Molding

1.1 Overview of Precision Injection Molding Process

The precision injection method’s key factor distinguishing it from the other forms is the attention given to custom-made molds. This has made precision injection mode a game-changer in plastic part manufacturing.

Although it follows the same process as injection molding, the variation in the usual injection molding is the tight tolerance. Under injection molding, the dimensional tolerance difference is +/-0.005. However, with precision injection molding, variation in tolerance is at +/-0.002 or even lesser, which increases the tolerance tightness of the part produced.

Once the mold is customized to suit the desired design, the molten plastic is injected into the mold and allowed to cool and solidify.

1.2 Benefits of Precision Injection Molding

The first and most crucial benefit of precision injection molding is its ability to fashion intricate designs with accurate dimensions. This makes producing any form of a plastic part almost effortless. Furthermore, the tight tolerance of such plastic parts increases the functionality of the part in whatever application it is designed for.

Another significant bonus of precision injection molding is its excellent repeatability. This feature ensures that each part produced is consistent in dimension, creating identical pieces with no flaws. Precision injection molding minimizes the need for further post-processing, enhancing the surface finish and saving production time.

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2. Design Considerations for Precision Injection Molding

2.1 Mold Design for Precision

What makes precision injection molding tick lies in the careful design of the mold. However, there are specific factors you must consider in creating a bespoke mold, including gate placement, cooling channels, and part ejection. How do they affect the mold you may want to know. 

Using a high-quality mold manufacturing concept, designers meticulously place the gate in a way that allows the flow of the molten plastic into the mold without leakages or excess injection of the material. It accepts just the right amount of molten plastic into the mold to avoid any impairment to the final product. The same goes for the cooling channels. 

Proper consideration of how the cooling channel will guarantee optimal cooling and how to save cycle times on each part produced must be well thought out. Additionally, the part ejection must be strategically placed to ensure the part made is ejected without blemish and damage-free.

2.2 Material Selection for Precision Molding

For plastic part manufacturers, choosing the suitable material for the specific design intended is crucial. Materials are given consideration based on past performance, accuracy, and surface finish before carefully selecting them. This standard selection process often aids the goals of the precision injection mold. 

Having fulfilled these requirements, what comes next is the consideration of materials based on their melt flow rate, shrinkage, and thermal stability. 

The way a plastic material melts and flows into the mold determines the pressure requirement. Materials with high flow rates are best suited for thin-walled parts and intricate geometries and dimensions. It ensures the mold is accurately filled, leaving no chance for airflow and sustaining dimensional consistency. 

A part’s preciseness could be impaired by shrinkage as well. A material with minimal shrinkage properties should be employed to lessen malformations in the part produced. Through this selection process, you can maintain the tight tolerance of the piece. 

Thermal stability measures materials’ heat resistance level in forming a plastic component. A low heat-resistant material can result in irregularities. Hence, choosing a material with high heat resistance is often the best. 

2.3 Tooling and Equipment for Precision Molding

The tooling and equipment requirements of precision injection molding are significant contributors to the success of the process. The precision injection molding technique can only be possible with the design and fabrication of custom-made molds. Moreover, these molds are typically crafted using advanced technologies such as high-quality CNC machining to attain meticulously crafted molds and cavities. 

Furthermore, a much more essential tool needed for precision injection molding is the control system. These are sophisticated tools responsible for the speed and pressure the mold is injected with molten plastic. Likewise, they maintain the temperature of the heated and melted plastic.

With these kinds of machines, repeatability is ensured alongside precise molding cycles. And there are even more sophisticated machines in some cases responsible for multi-stage injection machines. They make crafting more difficult intricate geometries and cavities possible.

Consequently, process report systems that are capable of giving complete reports on the appropriate injection speed and temperature must be implemented through all production runs. These are the information operators of the machines monitor for quick readjustments if any misalignment in the machine’s directives. And it also ensures that continuous quality products are manufactured.

3. Process Control and Optimization

3.1 Monitoring and Controlling Key Parameters

Process control and optimization typically begin with monitoring crucial parameters, especially in the high-quality mold manufacturing industry. Parameters such as temperature, pressure applied when injecting molten plastic into the mold, and cooling time. Moreso, the temperature inspections are at two levels, the heating and melting of the granules, then the cooling and solidifying of the molded parts. 

The temperature of the plastic has to be duly regulated to ensure the material is being heated at the stipulated temperature. Temperature control could already determine the outcome of the parts as it provides the flow rate, compactness of the injected material, and mold cooling time. 

After the temperature is sorted, the injection pressure becomes the following parameter to ensure its optimal control. If the pressure in the injection is not controlled, this may lead to partial filling of the mold or short shots. Essentially, injection pressure keeps the flow rate at the appropriate speed and guarantees the precise formation of the part in the mold. Once this is also checked to perform at the right level, operators can move on to check the cooling temperature. 

Cooling is responsible for several factors in precision injection molding. One such is achieving accurate dimension, and another is ensuring all parts are evenly cooled to eliminate internal stresses in the mold and managing the cooling time to save time on production cycles.

3.2 Scientific Molding Techniques

Manufacturers of plastic parts often seek diverse ways of optimizing production runs. They often adopt innovative techniques, including 3D printing technology and precision injection molding. This is to seek possible challenges that manufacturers may encounter in production.

The most prominent way of achieving this feat is via scientific molding techniques. This is a data-focused statistical analysis of the process. It utilizes data gathered to make informed decisions as to how to fully optimize the production of parts using precision injection molding.

The scientific molding technique is data-driven because data is collated from process parameters such as temperature, pressure, cooling, and production runs to check for anomalies or trends. 

Furthermore, the scientific molding technique relies keenly on the design of the experiment (DOE) to gather data and statistical process control (SPC) for the analytical aspect. All of these are put together to find better ways of improving the production process while maintaining quality in service and products.

In fact, sometimes virtual trials are adopted in scientific molding to identify performance parameters that need fine-tuning before commencing the actual production run. This offers time and resource-saving benefits by deploying simulation software to predict potential challenges that are likely to occur or what changes need to be made to adjust the overall process for optimal cycle times.

3.3 Quality Assurance and Inspection

Quality assurance and inspection are irreplaceable and vital standards in any production facility. This is required to ensure every manufacturer and production line continuously adheres to industry standards, ensures product quality, and protects the interest of consumers or users of the manufactured parts, as the case may be.

In precision injection molding, quality assurance is saddled with inspecting dimensional accuracy and visual inspection, and in some cases, proffers non-destructive testing methods to ascertain the quality and certify it for other use. 

Dimensional measurement can be done through coordinate measure machines (CMMs), among other optical measuring tools that help compare and contrast part dimensions with design specifications for corrective actions to be taken where necessary. 

Visual inspection is necessary to ascertain professionalism in surface finish, detect surface flaws, and meet standard industry requirements. 

Non-destructive testing methods such as ultrasound or x-ray tests reveal possible internal stresses or hidden flaws that may render a part produced substandard and unsafe for use. Quality inspectors can implement other quality assurance parameters to track and record quality-impeding measures in the production line to curb errors before it happens. 

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4. Applications and Industries

4.1 Medical and Healthcare

In recent times precision injection molding has increased significantly in market share across several industries. Apart from its early adopters like consumer goods and other industries heavily relying on precision injection molding, other sectors like healthcare and medicine are becoming major players. 

From the production of complex geometrical parts such as prosthetics, surgical instruments, and other healthcare equipment, the medical sector continues to rely significantly on precision injection molding. Again, micro-sized and tight tolerance features of surgical implants, insulin pumps, and fluid connectors also depend on the precision of this innovative production technique. 

Furthermore, the process is well suited to manufacture such instruments with consistency and accuracy and aligns perfectly with the human anatomy. In addition, the medical industry is strict on cleanliness and biocompatibility as it runs the risk of safety in administering these parts for human use. However, precision injection molding has been able to maintain excellence in parts production, majorly due to selecting the appropriate materials coupled with extreme quality control standards. 

Precision injection molding has become indispensable to the medical industry by making available technologically sound and safe equipment that is also easy to administer to save lives.

4.2 Electronics and Technology

In our world today, almost everything we use can be connected to precision injection molding. And as technology advances, most devices are growing smaller and sleeker. Electrical instruments ranging from household connectors to public charging stations for EVs, to mention a few, are all around us. 

In the electrical industry, precision injection molding is responsible for the miniaturization of devices and components. These devices require high precision and concise dimensional accuracy. Our Smartphones, tablets, and gadgets are a typical representation of the benefits contributed by precision molding. 

The production of electrical housings and micro-components, including sensors, switches, and sophisticated devices, is a testament to the fact that precision molding is upholding its quota in electrical and technological components. The functionalities of such manufactured parts are excellent. Not only are they outstanding, but they are also aesthetically a beauty to behold. 

Consequently, precision injection molding has made functional integration possible. This fuses many related parts into one, reducing assembly processes and increasing efficiency while simultaneously ensuring durability and trustworthiness in the electronic device, all in the same vein. Stay tuned as more technologically improved devices and electronic gadgets keep on getting better.

4.3 Automotive and Aerospace

Precision injection molding is extensively utilized in the aviation and automotive industries. This is due to industry standards which are centered on part reliability, durability, accuracy, and fragile yet strong components. The adoption of the precision molding in the aerospace and automotive sectors is to manufacture engine parts, intricate interior parts, and dimensionally precise injection systems. 

In the automotive industry, precision injection molding is deployed for fuel systems, lighting, and interior parts production. These parts are crucial to the overall performance and assurance of the vehicle’s safety.

As it is typically known, the aviation or aerospace industry is a top benefactor of precision injection molding. In the aviation sector, aircraft parts interior and exterior and aircraft engine components are built with precision molding. This is done bearing in mind the importance of strength-to-weight ratios, fuel efficiency, and excellent functionality. 

The ability to create long-lasting parts with intricate geometries and dimensional perfection is to certify the proper fit and performance even in severe environmental conditions. The mechanical strength of these parts affirms the durability and safety of the aircraft. 

The industry requirements for tight tolerance and dimensional precision in the parts used in the automotive and aerospace industry are duly attained by employing the precision injection molding method.


In a nutshell, precision injection molding has transformed plastic parts manufacturing in several ways. Its capacity to achieve precise dimensional feats and outstanding tight tolerances necessary for the overall performance of devices, gadgets, automobiles, and medical instruments is unrivaled. Furthermore, meticulously considering design options, selecting appropriate materials, project requirements, applications, and rigorous quality control measures will assist manufacturers in unleashing the full potential of the precision injection molding technique. And consequently, more technologically advanced, high-performing equipment can be manufactured across various industries. Are you still curious about precision injection molding capacity for manufacturing accuracy?


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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