A "servo injection molding machine" is a type of injection molding equipment that uses a servo motor as its primary power source. "Servo" refers to the drive system's ability to respond precisely and quickly to control commands.
1. Traditional Hydraulic Injection Molding Machine vs. Servo Injection Molding Machine
Traditional hydraulic injection molding machines: Use a constant-speed asynchronous motor to drive a hydraulic pump. The hydraulic pump runs continuously, generating a fixed pressure and flow rate. The machine uses proportional valves or servo valves to adjust the pressure and flow rate required for different operations (such as mold closing, injection, holding pressure, cooling, mold opening, and ejection).
The disadvantages of this method are:
Significant energy waste: The motor and pump continuously run at full capacity, consuming energy. Even when the machine is cooling or waiting, a significant amount of energy is required to maintain system pressure and overflow.
Rapid oil temperature rise: Overflow and friction generate significant heat, requiring an additional cooling system.
High noise: The continuously running pump generates considerable noise.
Limited control accuracy and response speed: Relying on valve regulation, the accuracy and speed are inferior to direct motor control. Traditional all-electric machines use multiple servo motors to directly drive each axis of motion (such as mold closing, injection, and ejection) via mechanisms such as ball screws or synchronous belts.
Advantages include high precision, clean operation, and energy efficiency. Disadvantages include complex structure, high cost, and generally lower clamping force than hydraulic models.
Features and Operating Principles of Servo Injection Molding Machines:
Core Power Source - Servo Motor: Replaces the traditional constant-speed motor.
Closed-Loop Control System:
The controller issues commands based on set process parameters (pressure, speed, and position).
The servo drive precisely rotates the servo motor.
The servo motor directly drives a fixed-displacement hydraulic pump (typically an internal gear pump or a plunger pump).
A feedback device (such as an encoder) mounted on the motor or pump monitors the motor's speed (corresponding to the pump's output flow) and torque (corresponding to the pump's output pressure) in real time.
The feedback signal is sent back to the controller, which continuously compares the actual value with the set value and adjusts the command sent to the drive, forming a closed-loop control system to ensure that the output precisely matches the flow and pressure required for the current operation phase. On-demand oil supply:
This is the core advantage of servo hydraulic injection molding machines.
The system drives the motor and pump only when an action is required, and the speed and torque (i.e., flow rate and pressure) are precisely adjusted in real time based on the specific requirements of that action.
When an action is completed and the next stage begins (such as when injection ends and pressure is held), or when the machine is in cooling or standby mode, the servo motor and the hydraulic pump can stop completely, consuming virtually no energy.
No overflow valve is required to regulate pressure and flow, reducing energy loss and oil heating.
Advantages of servo injection molding machines:
Energy savings: Compared to traditional hydraulic presses, energy savings of 30%-70% are typically achieved, depending on the product cycle, process parameters, and the machine itself.
High responsiveness and precise control: The servo motor's extremely fast response speed and precise torque control greatly improve the control accuracy and repeatability of key process parameters such as injection speed, holding pressure, and position control, thereby enhancing product quality and consistency. It is particularly suitable for precision molding. Lower Oil Temperature: Due to significantly reduced energy waste (especially the elimination of overflow losses and reduced frictional heat), the temperature rise of the hydraulic oil is significantly lower, extending the life of the hydraulic oil and seals.
Low Noise: The motor runs at low speed or is stopped most of the time, resulting in significantly lower noise levels than the continuously running noise of a traditional hydraulic press.
Higher Production Efficiency: Faster response speed can sometimes shorten cycle times (such as during mold opening and closing acceleration).
Clean and Environmentally Friendly: Lower oil temperatures reduce the tendency of oil oxidation and leakage, resulting in a cleaner working environment.
The structural differences between servo injection molding machines and traditional hydraulic injection molding machines:
The main difference lies in the power drive unit.
Traditional hydraulic presses: Constant speed motor + metering pump/variable pump + proportional valve/servo valve.
Servo hydraulic presses: Servo motor + metering pump + servo drive + high-precision feedback device.
The main structure of the machine, including the clamping mechanism, injection mechanism, barrel screw, etc., is similar to that of a standard hydraulic press.
2. Common faults of servo injection molding machines
(1) Servo drive alarm/fault:
Overcurrent/overload: Mechanical jamming, excessive load (such as poor lubrication, mold problem), internal short circuit of the drive or motor, improper parameter setting.
Overvoltage/undervoltage: Unstable power supply voltage, brake resistor failure or improper selection, excessive regenerative energy, internal fault of the drive.
Overheat: Poor heat dissipation (fan failure, dust on the heat sink), high ambient temperature, overload operation.
Encoder fault/communication error: Encoder cable damage, poor contact, encoder damage, severe interference, drive interface problem.
Excessive position deviation: Sudden or excessive load change, unreasonable response parameter setting, excessive mechanical clearance, encoder feedback problem.
(2) Servo motor fault:
Motor overheat: Overload operation, poor heat dissipation, high ambient temperature, bearing damage leading to increased friction, winding problem. Abnormal noise/vibration of the motor: Bearing wear or damage, motor shaft bending, coupling loose or damaged, load imbalance, mechanical resonance.
Motor does not rotate/is weak: The driver has no output, the motor winding is open or short-circuited, power supply problem, brake is not released (if any), parameter setting error.
(3) Abnormal system pressure:
Insufficient pressure: Insufficient output of the servo pump (insufficient motor speed/torque, internal wear of the pump), pressure sensor failure/calibration offset, pressure regulating valve failure or setting error, overflow valve failure, serious leakage in the cylinder, oil filter blockage resulting in insufficient flow.
Pressure fluctuation/instability: Air in the oil, pressure sensor failure, air in the oil, pressure sensor failure, unstable servo control response, hydraulic valve (such as proportional pressure valve) stuck or failed, oil contamination resulting in poor valve core movement.
Excessive pressure: Pressure sensor failure, pressure regulating valve failure, control signal error.
(4) Hydraulic oil related problems:
Excessive oil temperature: Cooling system failure (cooler blockage, fan failure, insufficient cooling water/high temperature), severe system leakage resulting in large energy loss, excessively high ambient temperature, improper oil viscosity selection, insufficient oil volume.
Oil contamination: Water intrusion (causing emulsification and rust), particle contamination (causing valve sticking and pump wear), oxidation and deterioration (viscosity changes and sludge generation). This is the most common and most harmful root cause of hydraulic system problems.
Leakage: Loose joints, aging and damage of seals, damage to pipelines or cylinders/valve bodies.
3. Frequently Asked Questions about Servo Injection Molding Machines
Q1: What is a servo injection molding machine?
A1: An injection molding machine that precisely controls the movement of a hydraulic pump or mechanical components using a servo motor. Its core principle is "energy on demand"—energy is consumed only during movement, and the motor stops when stationary, resulting in energy savings of up to 30%-70%.
Q2: Servo injection molding machines vs. traditional hydraulic presses vs. all-electric presses?
A2: Traditional hydraulic presses: Constant speed motor + relief valve → High energy consumption and high noise.
All-electric presses: Direct drive with multiple servo motors → High precision and no hydraulic oil, but complex structure and high cost.
Servo hydraulic presses: Servo motors drive hydraulic pumps → Balance energy savings, precision, and high clamping force, offering the best value for money.
Q3: What should I do if the servo drive alarm "Overload" (OL)?
A3: Step-by-step troubleshooting:
Check whether the machine is stuck (e.g., foreign matter in the mold, insufficient lubrication). Check the motor insulation resistance (use a multimeter to measure winding-to-ground resistance > 5 MΩ).
Check the drive parameters (if the motor power setting is incorrect).
Q4: What could be causing the slowdown?
A4: Abnormal hydraulic oil viscosity (thinner at high temperatures/thicker at low temperatures).
Clogged filter → insufficient flow (check the differential pressure indicator).
Cylinder seal wear and internal leakage (verify with a pressure holding test).