In the modern plastic processing industry, injection molding presses are core production equipment, and their technology is developing rapidly. Servo injection molding machines and hydraulic injection molding machines are the two mainstream models on the current market. They have significant differences in energy consumption, precision, speed, maintenance costs, etc. This article will compare the technical characteristics, performance and applicable scenarios of the two plastic injection machines in detail to provide a reference for equipment selection.
Differences in working principles
1. Working principle of hydraulic injection molding machine
Traditional hydraulic injection molding machines use three-phase asynchronous motors to drive hydraulic pumps and transmit power through hydraulic systems. The continuous operation of the motor drives the oil pump to generate hydraulic energy, which is controlled by the proportional valve or servo valve to control the flow direction and flow of the oil circuit, and finally drives injection, mold closing and other actions. This system has “overflow loss”, that is, when the maximum power is not required, the excess hydraulic energy returns to the oil tank through the overflow valve, causing energy waste.
2. Working principle of servo injection molding machine
Servo small injection molding presses use servo motors to directly drive pumps or hydraulic systems integrated with motors. The servo controller accurately controls the motor speed and torque according to actual needs to achieve “oil supply on demand”, which almost eliminates overflow losses. Advanced servo systems can also achieve full electric control, completely abandoning hydraulic circuits, and directly driving each actuator through servo motors and ball screws.
Performance comparison
1. Energy efficiency performance
Servo small plastic molding machines have obvious advantages in energy saving:
Typical power saving rate is 30-70%, and can reach 80% under some working conditions
Energy consumption in standby state is only 5-10% of that of hydraulic presses
Fully electric servo models save more than 50% energy than hydraulic models
Due to overflow loss and friction loss, the energy utilization rate of hydraulic automatic injection molding presses is usually only 30-50%, while the servo system can reach more than 85%. Taking a 200-ton model as an example, the annual electricity bill of a hydraulic press is about 100,000 yuan, and the servo machine can save 30,000-60,000 yuan.
2. Precision control
The servo system provides more precise motion control:
Injection speed control accuracy: servo ±0.1%, hydraulic press ±0.5%
Position repeatability: servo ±0.01mm, hydraulic press ±0.03mm
Pressure fluctuation: servo <±0.5%, hydraulic press ±1-2%
This high precision is particularly suitable for precision injection molding applications such as optical components and medical products. The servo can compensate for process parameter fluctuations in real time through closed-loop control, while the hydraulic system is greatly affected by factors such as oil temperature changes and leakage.
3. Production efficiency
Servo technology has advantages in speed:
Injection acceleration can reach 3-5m/s², which is 30-50% faster than hydraulic presses
Cycle time is shortened by an average of 10-20%
Response time <20ms, 2-3 times faster than hydraulic valves
However, in large-tonnage models (>2000 tons), hydraulic systems still maintain advantages in low-speed and high-thrust conditions. Servo machines are more suitable for high-speed production of multi-cavity precision molds.
4. Noise level
The working noise of servo automatic injection molding presses is usually 65-75dB, which is 10-15dB lower than that of hydraulic press. The all-electric model can be reduced to below 60dB, which greatly improves the working environment. The noise of hydraulic press mainly comes from oil pump and pressure valve, especially in the pressure holding stage.
Cost analysis
The price of servo pvc injection molding machine is 20-40% higher than that of hydraulic press of the same level, and the price difference of all-electric model can reach 50%. However, with the popularization of technology and the increase of output, the price difference is gradually narrowing. For enterprises with long-term continuous production, the higher initial investment can be quickly recovered through energy-saving benefits.
About Maintenance
| Aspect | Hydraulic Systems | Servo Systems |
|---|---|---|
| Oil Change Interval | Every 2000–5000 hours | Extended 2–3× longer for hydraulic servo; none for electric |
| Filter Maintenance | Clean or replace filters regularly | Minimal to none (in electric models) |
| Seal & Cylinder Inspection | Inspect seals and cylinders frequently | Not applicable in electric models; reduced in servo hydraulic |
| Oil Contamination Management | Essential – contamination leads to failures & downtime | Significantly reduced downtime due to extended intervals |
| General Maintenance Level | High – frequent manual checks and servicing | Low – especially in all-electric models (almost maintenance-free) |
Applicable scenarios
① Recommended scenarios for servo injection molding machines:
1. High-precision products: optical lenses, connectors, micro gears, etc.
2. Thin-walled products: mobile phone housings, packaging containers, etc.
3. Medical products with high cleanliness requirements
4. 24-hour continuous production occasions
5. Areas with high electricity costs
② Scenarios where hydraulic moulding plastic machines are still applicable:
1. Ultra-large tonnage molding (>2000 tons)
2. Ordinary products with low precision requirements
3. Projects with limited initial investment budgets
4. Thick-walled products that require extremely high clamping force
Development trend
In the future, injection molding presses technology will show the following development directions:
Hybrid technology: a hybrid model that combines the advantages of hydraulics and servos
Intelligence: an intelligent servo system that integrates IT and AI technologies
Modular design: convenient for rapid switching and functional expansion
Green manufacturing: further reducing energy consumption and noise
Direct drive technology: a direct drive method without transmission componentsIn short, servo injection molding machines have obvious advantages in energy efficiency, precision, and speed, and are particularly suitable for precise, efficient, and continuous production needs. Although the initial investment is high, the long-term operating cost is lower. Traditional hydraulic plastic injection machines are still irreplaceable in large-tonnage and low-cost application areas. Enterprises should conduct a comprehensive assessment based on product characteristics, production scale, and investment payback period, and select the most suitable technical solution. With technological advances and cost reductions, servo technology will become the mainstream configuration of mid-to-high-end injection molding machines.
FAQ’s
Servo presses use electric motors for precise control, while hydraulic presses rely on fluid power systems.
Servo (especially all-electric) presses need far less maintenance compared to hydraulic systems.
Yes—servo systems are significantly more energy-efficient, often reducing power usage by 30–70%.
