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Electric Vs Hydraulic Injection Molding Machine: What's the Difference?
Created on 11.18
Picking the right injection molding machine is key when you're working with plastics. Whether you go with an electric or hydraulic machine can really change how your final product turns out, what it costs you to produce, and how much energy you use in the process.
This guide will walk you through how these machines work, what's good and bad about them, and help you figure out which one fits best with what you're trying to do.
What Is an Injection Molding Machine?
Injection molding machines are key for making plastic parts. They melt plastic and shoot it into a mold that forms the plastic into the shape you want. You've got three main kinds: hydraulic, electric, and hybrid, and each one works best for different jobs.
Hydraulic machines are great for heavy-duty work because they deliver a lot of force, which is needed for jobs like high-pressure molding. Electric machines are becoming a go-to option for small to medium-sized tasks since they use less energy, offer more control, and are easy to keep in good shape. (Latin America Injection Molding Machine Market Analysis)
How Do Electric and Hydraulic Injection Molding Machines Work?
Both electric and hydraulic machines do the same thing—melt, inject, and mold plastic—but how they do it is pretty different because of what powers them and how they're controlled.
Electric machines use servo motors and parts like ball screws or timing belts to move. Hydraulic machines use pumps, valves, and cylinders to make and control movement.
Let's check out how each one works.
The Working Principle of an Electric Injection Molding Machine
Electric injection molding machines use servo motors to turn the motor's spin into straight-line motion. This controls how the machine injects, clamps molds, and takes out the finished product.
Here’s how the process works, step by step:
- Melting the Plastic: Plastic pellets are fed into the machine. A screw, driven by a motor, spins and melts the plastic. Barrel heaters add extra heat to turn it into liquid.
- Closing the Mold: A motor moves a toggle with a ball screw, which closes the mold tightly. At the same time, the injection part moves up to meet the mold opening.
- Injecting the Plastic: The motor changes the screw rotation to forward motion, pushing the melted plastic into the mold at a controlled rate and force.
- Holding Pressure and Cooling: After the plastic is injected, the motor continues to apply pressure. This stops plastic from flowing backward and compensates for any shrinkage as the plastic cools and hardens.
- Opening the Mold and Removing the Part: The motor then opens the mold. Another motor pushes rods to eject the finished part.
This servo control system repeats tasks very well and reacts quickly, which gives good control over each step. Electric injection molding machines work for very exact, clean, and energy-saving jobs.
The Working Principle of a Hydraulic Injection Molding Machine
Hydraulic injection molding machines use oil pressure to move. Things like clamping, injecting plastic, holding pressure, and ejecting parts all run with hydraulic cylinders, valves, and a hydraulic circuit.
Here’s how it works:
- Melting the Plastic: Like electric machines, raw plastic melts from a spinning screw and heat.
- Clamping: The hydraulic system employs a cylinder to lock the mold tight using a lot of pressure. Then, the part that injects the plastic moves up so the nozzle touches the mold.
- Injecting: Oil goes into the injection cylinder, moving a piston that pushes the screw ahead. This makes the melted plastic fill the mold fast and with a lot of pressure.
- Holding Pressure and Cooling: The oil pressure stays even to prevent plastic from flowing backward and to adjust for the plastic shrinking as it cools and gets hard.
- Opening the Mold and Ejecting: Once it’s cool, the machine lowers the pressure, opens the mold, and uses a hydraulic ejector to push the finished part out.
Because they inject with a ton of force and react fast, hydraulic injection molding machines are usually used for large, thick, or very high-pressure plastic part making.
Comparing Features: Electric vs. Hydraulic Injection Molding Machines
Electric Injection Molding Machines
Advantages:
- Energy Efficiency: Servo motors only use power when moving, cutting energy use by up to 70% compared to hydraulics.
- Environmentally Friendly & Low Maintenance: Since there's no hydraulic oil, you don't have to worry about leaks or messes, making for a greener and easier-to-maintain setup.
- Quiet: Without noisy pumps and valves, servo motors keep noise and vibration down, which is better for workers.
- Precision & Control: Servo motors offer great control over position, speed, and pressure. This makes them perfect for precise molding needed in medical, optical, and electronics work.
Disadvantages:
- Load Limitations: Servo motors might get overloaded and stop working if you're pushing them to maximum injection pressure.
- Power Constraints: Right now, electric systems can struggle when it comes to really big, heavy-duty jobs.
Hydraulic Injection Molding Machines
Advantages:
- High Power Capability: deal for big molds and thick parts that need a lot of pressure.
- Mature Technology: Hydraulic systems are reliable, simple, and easy to fix because they have been around for many years.
- Cost-Effective: Usually, they cost less at first than the all-electric options.
Disadvantages:
- Higher Energy Consumption: Hydraulic pressure runs all the time, so it uses more energy and makes more heat.
- Environmental Concerns: Oil leaks and water use for cooling can cause pollution and higher repair costs.
- Noise and Vibration: Hydraulic systems can be loud and shaky, which isn't great for the people using them.
- Lower Precision: Not as accurate as servo-driven systems when it comes to controlling speed and pressure.
How to Choose the Right Machine?
- Choose electric machines if your priority is precision, energy efficiency, and clean production.
- Choose hydraulic machines if you need raw power, large mold capacity, and lower upfront cost.
The difference between electric and hydraulic injection molding machines ultimately lies in their power systems and performance priorities. Understanding how each technology functions will help you make an informed investment for your production line.
Frequently Asked Questions (FAQ)
1. Which type of injection molding machine is better for saving energy?
Generally, electric injection molding machines are better at saving energy since they only draw power when the motors are running. With hydraulic systems, the oil pump is always on.
2. Can both electric and hydraulic machines make parts that are equal in quality?
Yes, they both can. Electric machines are often better for making very precise parts consistently. Hydraulic machines are known for their toughness and strength, so they are good for more demanding jobs.
3. How long do hydraulic injection molding machines typically last?
If you maintain it well, a hydraulic injection molding machine can last for 10–20 years or even longer. It depends on how often you use it and your maintenance practices.
4. Does the machine type affect how fast the process runs?
Electric machines usually operate more quickly and steadily because their motors respond rapidly. Hydraulic machines might be a little slower, but they provide more power.
Want to know more about better molding tech and ways to save energy? Check out Sountec Plast—we're a reliable company that can provide high-performing injection molding systems.
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