Demystifying Injection Molders: Types and Role for Plastic Parts

Table of Contents

Injection molding machine facility
Injection molders or molding facility

1. Introduction

If you are familiar with the world of injection molding then you probably have an idea of an injection molder’s impact on the success of the whole process. However, what you and most newbies to this injection mold landscape might be unaware of is the extent to which this component determines the achievement of quality for each project.

Consequently, this article seeks to address this point. We delve into the little details that most people looking from the outside are not able to decipher including the types of injection molders, their various applications, and the advantage of specific types over other forms.

Ultimately, you should be well-versed in the art of specifying a suitable injection molder by the time we reach the conclusion of this guide. So, without wasting time, let’s dive in.

2. What is an Injection Molder?

The natural place to start is usually to have a clear understanding of the subject matter which will require an answer to the question “What is an injection molder?” in this case.

Injection molding is a manufacturing process that requires the melting of raw materials, often plastic pellets using a molder from where the melted plastic is transferred into the molds. These molds help to shape the molten plastic to the expected product envisaged at the design and high-quality mold manufacturing stage.

At its core, an injection molder is a specialized machine designed to take raw plastic material and transform it into specific shapes and forms needed for various products in an injection molding process.

Furthermore, the injection molder is equipped with a reciprocating screw or plunger that forces the molten plastic into the mold cavity, which is shaped to match the final product. Again, the molds are primarily two-part elements with exactly identical features which when coupled form a cavity into which the molten plastic material is poured.

However, due to the peculiarities of each project, different molders are considered suitable for different projects. Designers never fail to consider several factors including materials, production volume, and the required finish of the product when specifying an appropriate molder for a particular project.

Essentially, injection molders serve as the architects of accuracy. Thus, it’s important to grasp the different models and technical details of these machines in order to maximize their potential for a range of production applications. 

Servo hydraulic injection molder 1
Servo-hydraulic injection molder

3. Types of Injection Molders

Now we come to the meat of the matter which is identification of the different types of molders available for the injection molding process. The impact of this in specifying a befitting molder for a specific project cannot be overemphasized considering that the quality and precision of the project significantly depends on the molder used.  

However, two primary categories dominate the landscape despite the numerous versions of molders available today. The servo-hydraulic and hydraulic machines are quite dominant with each offering distinct advantages and considerations.

Servo-Hydraulic Injection Molders: Over the years, this version of molders has gained prominence in the injection molding landscape as they’ve shown to be efficient and accurate. Additionally, their combination of both hydraulic and electrical systems in their operation has further boosted their precision resulting in more acceptance across the industry. For the hydraulic system, a servo motor strictly controls the speed powers as well as the pump further increasing the efficiency of this machine.

Again, the speed of flow and the injection pressure of the molten plastic are handled by the combination of this hydraulic and electrical system resulting in quality and consistent product.

However, the servo-hydraulic injection molder is mostly employed in injection molding projects where the precision of intricate parts is of critical concern to replace methods like high-quality CNC Machining. The offering of superior repeatability and energy efficiency reduces both material waste and operational costs. Also, medical, aerospace, and electronics industries are some popular sectors where this type of molders find extensive use cases as they require a high degree of precision.

Hydraulic Machines: This molder is more traditional than the servo-hydraulic versions considering that they have a longer history in manufacturing though they still maintain their reliability for various use scenarios. In their case, hydraulic machines are more robust than their servo-hydraulic counterparts and this is a result of their use of entirely hydraulic systems to power the clamping forces required for the project. Though their precision might relatively be less than their servo-hydraulic counterparts, they are still very much applicable in a lot of the injection molding projects carried out in several industries.

Hydraulic injection molders are well-suited for applications where high-pressure molding is essential, such as automotive and packaging industries. Their durability and ability to work with a wide range of materials make them versatile workhorses in manufacturing.

Material pouring into the hopper of the injection molding machine
Material poured into the hopper of the injection molding machine

4. The Injection Molding Process

While we may have briefly touched on the process of turning raw plastic pellets into finished plastic products, going into the little details of the process is essential to give you wholesome knowledge.

For starters, the process of combining heat and pressure to transform solid plastic pellets into fluid form requires an Injection molder to preheat the plastic pellets to melt them.

The molten plastic is then skillfully injected into the mold cavity by a trained craftsman. As clay would solidify in a sculptor’s fingers, the tight and unyielding mold itself cools and solidifies the plastic into the required shape.

Ultimately, a crisp, precise plastic product gracefully emerges from the mold like a ballerina in the limelight. Moreover, each component of the injection molding machine—the injection unit, the clamping unit, and the mold itself—is a critical part of its performance.

More importantly, the accuracy and effectiveness of the injection molding technique is a pillar of contemporary manufacturing. This is because it allows for the production of complex and reliable plastic components that serve as the foundation of many sectors, including the electronics and automotive industries. 

Intricate details for injection molded parts
Intricate details for injection molded parts

5. Applications of Injection Molders

While the injection molder is at the heart of injection molding processes the essential application of their different types is often based on their versatility. This is the reason for their extensive use cases across several industries including the high-quality mold manufacturing industry.  

Let’s take the automotive industry where the creation of auto parts is considered a highly detailed process requiring one of the highest levels of precision.

The scene is set by injection molders, creating complex components with the dexterity of a master craftsperson. These machines play a crucial role in producing the cars that fill our roads, from dashboard components to bumpers and grilles to interior and exterior parts.

Also, for the electronic industry where quality and accuracy of parts are of great concern, especially with miniature parts, injection molders ensure the achievement of high quality without neglecting aesthetics.

They manufacture the cases for cell phones, the connectors for circuit boards, and even the keys on your keyboard, ensuring that the gadgets we use every day are both practical and aesthetically beautiful.

Additionally, injection molders play the function of protectors in the medical industry, where cleanliness and safety are of utmost concern, by creating parts for medical equipment and devices. They produce everything from syringe barrels to complex components for diagnostic equipment and their accuracy and reliability benefit patients.

Nevertheless, injection molders are present in several other industries, including consumer goods, packaging, and toys putting their versatility on display for the world to glean. The artistry of injection molders and their vital role in shaping the products that define our daily experiences have come a long way.

6. Choosing the Right Injection Molding Machine

While understanding the process of injection molding and the impact of molders in the whole process can be beneficial, knowing the steps to choose the right injection molding machine is invaluable. When navigating this choice, one must consider a multitude of factors that, when harmonized, result in the creation of precise and efficient plastic parts. Just imagine it as a puzzle where each piece must fit perfectly.

Firstly, the kind of injection molding machine is one important factor you must never lose sight of. The machine type establishes the tone for the entire production process, similar to selecting the right brushstroke for a painting.

The accuracy of a servo-hydraulic machine is comparable to using a fine-tipped brush for detailed art for difficult and delicate work. On the other hand, a hydraulic machine is like a broad brush for large-scale tasks where robustness is essential, painting a larger canvas with power and longevity.

Next, material compatibility is another puzzle piece considering that plastic materials respond differently to the capabilities of injection molders.

Similar to harmonizing colors on a palette to obtain the ideal color, the temperature and pressure profiles must match flawlessly.

Additional aspects of this complex decision-making process include production volume, design complexity, and energy efficiency.

In the end, selecting the ideal injection molding machine necessitates a thorough comprehension of the project’s requirements, much like an artist needs to have a thorough understanding of their materials (canvas, paints, and tools). Precision-crafted plastic parts are produced as a consequence of the seamless marriage of innovation and workmanship when this process is carried out with care.

Injection unit for molders
Injection unit for servo-hydraulic molders

7. The Advantages of Servo-Hydraulic Injection Molding

While the benefits of injection molders are numerous, especially their versatility that allows them to serve several industries, there are still some of these benefits that are unique to servo-hydraulic molders.

In the world of injection molding, servo-hydraulic machines are frequently regarded as accuracy specialists similar to additive manufacturing methods like 3D printing technology. However, almost endless benefits that echo throughout the manufacturing landscape are provided by these machines, which are distinguished by their mix of electronic accuracy and hydraulic power.

The precise movements of an experienced painter creating a work of art are comparable to how a servo-hydraulic injection molder coordinates the injection’s speed, pressure, and position. Each of these parameters is attended to with steady accuracy, creating a masterpiece.

One of the most prominent characteristics of servo-hydraulic devices is their energy efficiency, which is comparable to the start-up of a high-efficiency engine. Because they only use the energy required for the task at hand, these devices significantly reduce waste and operational costs. Also, modern sustainability ideals are in accordance with this green strategy, making them not only effective but also efficient.

Ultimately, it becomes evident that precision is a strength for servo-hydraulic injection molders.

Manufacturers use servo-hydraulic machines for tasks requiring precise repeatability, sophisticated designs, and tight tolerances. Additionally, these machines are excellent at producing components for sectors like electronics and medical equipment, where accuracy is crucial.

8. Hydraulic Machines in Injection Molding

While the servo-hydraulic injection molder is unique and has specific uses, the hydraulic machine is also not left out in its unique uses. Similar to the durable engines powering heavy-duty automobiles on the road, hydraulic injection molding machines are the dependable workhorses of the injection molding industry. Especially for particular applications where endurance and clamping power are crucial, these machines are the go-to option because of their strength and unmatched power.

Imagine them as a steady, unyielding anchor in a storm. As a result of their hydraulic systems, hydraulic injection molders are able to provide the required force for plastic injection, using their sheer strength. Consequently, this force allows them to withstand difficult materials or high-pressure demands.

Again, these machines are well-suited for large-scale projects where high clamping pressures are required. For instance, in sectors like the automotive industry where toughness and stability are essential, hydraulic machines are the workhorses that define the production environment. They produce reliable, high-quality outcomes and flourish in conditions where high-pressure molding is necessary.

Hydraulic injection molding machines are crucial in production, especially in applications that require the ultimate durability and robustness, even though they may lack the finesse of servo-hydraulic machines. 

Hydraulic machines, like the dependable engines that drive industrial giants, are the trusted partners for projects where durability is essential in a world where each machine type has its special characteristics.


In a nutshell, injection molders have a constant multifaceted role in the injection molding landscape especially in shaping the quality and precision of plastic products. However, understanding the different characteristics of the two main types of molders, the servo-hydraulic and hydraulic molders is one recipe for injection molding success. 

Precision, durability, material compatibility, and energy efficiency are all of these factors that help in the selection of the right injection molding machine to compose their manufacturing masterpiece.

In the realm of manufacturing, injection molders are incredibly adaptable instruments, creating complex components for sectors like electronics and medical devices as well as driving massive car operations. Their accuracy, effectiveness, and strength guarantee that the plastic components they produce continue to reliably shape our modern world.


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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