Hydraulic, Hybrid, and Electric Injection Molding Machines: Which One is Right for You?

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Hydraulic, hybrid and electric injection molding are examples of the different types of plastic injection molding machinery operating methods and power sources. Each method has its own advantages, limitations, and applicability, so production needs, budget, and accuracy requirements need to be considered when choosing the right plastic injection molding method. In this article, we’ll take a closer look at the pros and cons of hydraulic, hybrid, and electric injection molding so you can better understand their suitability and make the right choice for your project.
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Hydraulic Plastic Injection Molding

Hydraulic plastic injection molding machines (IMMs) utilize hydraulic cylinders to firmly seal two mold halves with significant pressure. The plastic pellets are then melted, transforming into a liquid that is injected into the mold cavity. After the plastic has cooled and solidified, the mold halves are separated, the finished part is removed, and the entire cycle begins anew.

To prevent the mold from opening prematurely due to injection pressure, resulting in excessive material “flash” around the parts, the clamping unit must deliver sufficient locking force to keep the mold closed during injection. Typically, for parts with thin walls and deep draw depths, approximately 3-4 tons of clamp force per square inch of the cavity is required. In contrast, parts with thick walls and shallow draw depths necessitate about 2 tons per square inch.

Modern hydraulic plastic injection molding machines have the capacity to control clamp forces exceeding 8,000 tons and can manufacture parts weighing more than 50 pounds. Hydraulic molding is a favored choice, particularly in the automotive industry, where large and heavy components such as bumpers are frequently produced.

Advantages of Hydraulic Injection Molding

Hydraulic injection molding is the preferred choice when it comes to actuating core pulls, ejectors, valve gates, and producing thick-walled parts with extended hold times. Here are some of its advantages compared to all-electric machines:

    • Increased clamp force for larger parts.
    • Improved injection rates.
    • High resistance to wear and tear.
    • Larger shot size.
    • Enhanced ejection capability.
    • The option to use gas accumulators to compensate for slower clamp movements.
      Lower initial purchase cost.
    • Economical and readily available replacement parts, resulting in reduced maintenance expenses.
    • Simpler control for complex projects.
    • Abundance of units available on the used market due to the method’s popularity.

Disadvantages of Hydraulic Injection Molding

Due to their substantial power, hydraulic machines consume significant amounts of energy even when in a standby state. In contrast to a typical electric machine, which may consume around 2.55 kWh during an injection molding process, hydraulic machines can consume as much as 5.12 kWh. They demand elevated temperatures for the molding process and lengthier cooling times, making them less suitable for clean rooms due to the potential for fluid leakage.

Additionally, hydraulic injection molding machines tend to be noisier and less precise than electric injection molding machines. However, with advancements in control systems and as clamp forces increase, the precision performance of hydraulic machines can also see improvement.

Electric Plastic Injection Molding

Electric injection molding machines represent a significant advancement in the field of plastic manufacturing. Unlike traditional hydraulic counterparts, electric injection molding machines are driven by digitally controlled high-speed servo motors, ushering in a new era of faster, more precise, energy-efficient, and repeatable operations.

The key differentiator lies in the shift from hydraulics to high-tech servos. This transition not only enhances speed but also dramatically improves precision. These electric injection molding machines operate with remarkable predictability, ensuring that once an ideal injection process is achieved, it can be replicated consistently with unprecedented accuracy. The outcome is a noticeable improvement in the quality of manufactured parts, setting a new standard for excellence.

One of the most striking advantages of electric injection molding is its automation capabilities. Once a specific job is programmed into the electric injection molding machine, its digital controls enable it to function virtually unattended. This level of automation significantly reduces labor costs, enhances operational efficiency, and ultimately boosts profitability for manufacturers.

Advantages of Electric Injection Molding Machines

Electric injection molding offers a range of benefits that make it an excellent choice for various applications. Some of these advantages include:

    • Cleanroom Suitability:
      Electric injection molding poses no risk of oil contamination, making it well-suited for cleanroom environments where hygiene and purity are paramount.
    • High Precision:
      This process excels in producing intricate and precise components, making it ideal for small- to medium-sized parts and critical medical products like Petri dishes and syringes.
    • Precision and Repeatability:
      Electric injection molding provides tight precision and exceptional repeatability, leading to reduced scrap rates and higher-quality output.
    • Cleaner Operation:
      Unlike hydraulic systems, electric molding never leaks fluid, ensuring a clean and environmentally friendly manufacturing process.
    • Reduced Downtime:
      Electric injection molding machines experience lower downtime compared to their hydraulic counterparts, contributing to improved operational efficiency.
    • Energy Savings:
      Electric molding can achieve energy savings ranging from 30% to 70%, reducing overall production costs and environmental impact.
    • Quieter Operation:
      Electric injection molding machines operate quietly, with motor noise levels below 70 dB, creating a more comfortable working environment.
    • Rapid Injection Speeds:
      Electric injection molding machines can achieve higher rapid injection speeds, reaching up to 800 mm/sec, enabling faster production cycles.
    • Faster Clamp Motion:
      Electric injection molding machines feature faster clamp motion, further enhancing production efficiency.
    • Shorter Startup Time:
      Electric injection molding machines have shorter startup times and can achieve up to 20% faster cycle times, increasing overall productivity.
    • Lower Unit Cost:
      The reduced material waste associated with electric injection molding translates into lower unit costs, delivering economic advantages.
    • No Consumables:
      Electric molding requires no consumables like oil, which eliminates the need for replacement or cleaning, simplifying maintenance.
    • Lower Power Requirements:
      Electric injection molding machines have lower power requirements, resulting in significantly reduced operating costs and improved sustainability.

Disadvantages of Electric Injection Molding Machines

While electric injection molding machines offer notable advantages in terms of speed, cleanliness, and energy efficiency, they also come with certain limitations:

    • Limited Clamp Forces:
      Electric injection molding machines are unable to achieve the same level of clamp forces as hydraulic machines. This limitation can restrict their suitability for applications that require exceptionally high clamping forces.
    • Higher Initial Cost:
      The initial cost of electric injection molding machines tends to be higher than that of hydraulic counterparts, making them less accessible for some manufacturers.
    • Wear Items:
      Electric injection molding machines are typically toggle-clamp machines driven by ball-screws. Both toggle clamps and ball-screws are wear items that may require replacement over time. The cost of replacing these components can be substantial, and finding replacements on the used market can be challenging.
    • Positioning Accuracy:
      While electric injection molding machines offer high precision, their extremely high positioning accuracy can make them less forgiving in certain applications when compared to hydraulic presses. This means that precise setup and maintenance are crucial to achieving optimal results.

In summary, while electric injection molding machines offer several advantages, such as speed and energy efficiency, they may not be suitable for all applications due to their limitations in clamp forces, higher initial cost, and the potential maintenance challenges associated with wear items.

Hybrid Plastic Injection Molding

Hybrid injection molding machines have been a fixture in the industry for several decades, offering a fusion of hydraulic and electric technologies. By combining the robust clamping force of hydraulic machines with the precision, repeatability, energy efficiency, and reduced noise characteristic of electric machines, hybrids create a dynamic synergy that elevates performance, catering to both thin- and thick-walled parts with finesse. The growing popularity of hybrid machines in recent years attests to their efficiency and user-friendly nature.

One remarkable aspect of hybrid injection molding machines is their ability to optimize energy consumption. In conventional hydraulic presses, a substantial 66% of energy is allocated to screw recovery. In contrast, hybrid machines employ electrified screw rotation, which leads to substantial energy savings. This efficiency not only reduces operational costs but also enables manufacturers to offer competitive pricing to their customers. Essentially, hybrid machines harness the full clamping force of hydraulic counterparts while achieving energy efficiency comparable to all-electric models.

In essence, hybrid plastic injection molding represents a harmonious blend of the best features from both hydraulic and electric technologies. It embodies the industry’s commitment to innovation and efficiency, delivering superior results while maintaining cost-effectiveness.

Advantages of Hybrid Injection Molding

Hybrid plastic injection molding stands out as an energy-efficient and durable process that offers a quicker return on investment. Its distinctive advantages encompass:

    • Servo Pump Flexibility:
      Hybrid systems incorporate servo pumps that allow for continuous adjustments, enhancing precision and adaptability in the manufacturing process.
    • Versatile Product Design:
      Hybrid molding supports a wide range of product designs, accommodating diverse production needs and requirements.
    • Dual Clamp System:
      Many hybrid machines utilize a two-clamp system, offering a robust alternative to the toggle-clamp mechanism, contributing to improved reliability.
    • Cost-Efficiency:
      Hybrid molding presents a median upfront cost when compared to hydraulic and electric options. However, it often delivers substantial long-term savings, making it a financially prudent choice.
    • Closed-Loop Process:
      Hybrid machines operate on a closed-loop process with rapid response times, ensuring consistent and high-quality output.
    • Lower Operating Temperatures:
      The process in hybrid molding operates at lower temperatures, reducing the need for extensive cooling. This not only conserves energy but also prolongs the lifespan of oils and machinery components.
    • Accelerated Return on Investment:
      The efficiencies inherent in hybrid plastic injection molding, such as energy savings and versatility, contribute to a faster return on investment, making it a favorable choice for manufacturers seeking cost-effectiveness.

In summary, hybrid plastic injection molding combines the best attributes of various technologies to offer a balanced and efficient approach to manufacturing. Its ability to adapt, save energy, and provide cost benefits positions it as a compelling solution for businesses aiming to maximize both productivity and profitability.

Disadvantages of Hybrid Injection Molding

Hybrid plastic injection molding, while offering a versatile and efficient solution, presents some challenges, including:

    • Customization Complexity:
      Due to the diversity among hybrid machines, selecting the right press for a specific product can be a complex task. Matching the correct machine to the unique requirements of a production job may require in-depth expertise.
    • Replacement Availability:
      Securing replacement machines for specific applications can be a challenge, as hybrids vary significantly in design and capabilities. Finding suitable replacements may require extensive research and potentially limit production flexibility.
    • Maintenance Expertise:
      Maintenance and troubleshooting for hybrid machines can be intricate, as they combine hydraulic and electric components. Supervisors and technicians must possess knowledge of both hydraulic and electric press systems, which can demand specialized training and skills.

Sungplastic: Helping You Choose the Right Injection Molding Process

Through the above introduction to the three injection molding processes of hydraulic, hybrid, and electric injection molding, we have learned about their respective advantages and limitations as well as applicable scenarios. To choose the processing technology that best suits you, the first priority is to gain a deep understanding of your market requirements and product characteristics. If you need high precision, high speed, and excellent energy efficiency, electric injection molding may be your best choice. If your application requires high pressure and force, then hydraulic injection molding may be more suitable. Hybrid injection molding, on the other hand, offers a balanced solution suitable for many different applications.

Sungplastic is a professional injection molding company, we have advanced production equipment and an experienced team of engineers. No matter what type of product you need to customize, our injection molding machines (hydraulic, hybrid, electric injection molding machines) can provide you with reliable, high-quality plastic parts. Don’t hesitate to contact us today. We will be happy to help you choose the processing technology that best suits your needs and provide excellent injection molding solutions.

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