Hydraulic Machine Debugging Guide
Traditional hydraulic machines and servo-hydraulic machines transmit power through hydraulic oil to drive cylinders or hydraulic motors. This guide focuses on hydraulic-system warm-up, PQ pressure/flow matching, and smooth motion tuning.
Core debugging concept: All hydraulic-machine actions are based on pressure (P) providing force and flow (Q) determining speed. Hydraulic-oil viscosity changes with temperature, so final tuning should be performed after the machine reaches a stable warm condition.
1. Hydraulic System Preparation and Warm-Up
The physical state of hydraulic oil directly affects machine repeatability. Do not start high-pressure or high-speed production while the machine is cold.
Check Oil Level and Peripherals
Confirm that the oil level is within the normal range. Start the bypass filtration system and check whether the water valves for the oil cooler or cooling tower are open.
Warm Up the Oil
Start the motor and run low-pressure, low-speed idle cycles, such as air shots or slow mold opening and closing.
- Target oil temperature: wait until the oil temperature rises and stabilizes between 40°C and 50°C.
- Note: below 30°C, hydraulic oil is highly viscous, causing slow motion and high pressure loss. Above 55°C, the oil becomes thin and internal leakage may occur, reducing position-control accuracy.
2. Clamping System and Toggle Lubrication
Most hydraulic machines use a toggle-type clamping mechanism. During commissioning, both mechanical lubrication and high-pressure clamping must be checked.
Debugging Steps
- Lubrication check: manually trigger the centralized lubrication pump and observe whether fresh lubricant appears at each toggle bushing.
- Mold-height adjustment and high-pressure clamping: adjust mold height according to mold thickness. The toggle should pass the dead-center position smoothly, the clamping pressure gauge should reach the required tonnage, and no abnormal machine vibration should occur.
- Low-pressure mold protection: set the low-pressure protection value for mold closing, usually between 15 and 30 bar. The pressure should be as low as possible while still overcoming toggle friction.
3. Hydraulic Response Control for Injection and Holding
Due to fluid compressibility and pipeline expansion, hydraulic injection response is slower than that of all-electric machines. Parameters should compensate for this inertia.
Ramp setting: To prevent hydraulic shock, advanced systems allow rise/fall ramp time settings for proportional valves during injection-speed transitions, for example 0.1 s.
- When the speed difference between stages is large, increase ramp time to make the action smoother.
4. Pressure and Flow (PQ) Linear Matching
Hydraulic motion is determined by both pressure and speed settings. Generally, the set flow rate can be fully output only when the set system pressure is higher than the resistance required by the actual motion.
At this stage, compare the real injection-speed curve and pressure curve on the molding-monitoring screen. If the speed curve shows a flat-top cutoff, the system pressure is usually insufficient to overcome current injection resistance, so the actual speed cannot reach the set value.
5. Maintenance and Common Troubleshooting
Hydraulic-machine faults are often related to oil. Regular oil-circuit maintenance is essential for stable processing.
| Symptom | Possible Cause | Troubleshooting Suggestion |
|---|---|---|
| Process parameters drift during the day | Excessive oil-temperature fluctuation | Check cooling tower operation and clean scale inside the oil cooler |
| Large vibration during motion switching | Valve ramp not set or air in the system | Adjust speed-transition ramp and run full-stroke slow motion to exhaust air |
| Injection pressure cannot reach the set value | Cylinder internal leakage or stuck proportional pressure valve | Check cylinder seals and clean the proportional-valve spool |
| High-pressure clamping builds up slowly | Mold-height adjustment too tight or oil foaming | Readjust mold height and check oil level to prevent suction air |
Safety reminder: Hydraulic systems contain high pressure, up to 140–160 bar. Before handling oil leakage or replacing hydraulic pipelines, turn off the main motor and release residual system pressure. Never work under pressure.