Must-read for both new and existing users: How to optimize production efficiency through routine maintenance and troubleshooting of Injection Molding Machines?

To maximize the production efficiency of an Injection Molding Machine (IMM), it is essential to focus on two interconnected areas: implementing systematic preventive routine maintenance (PM) and performing efficient, accurate troubleshooting. Together, these efforts minimize unexpected downtime, reduce scrap rates, and extend the equipment’s lifespan.

Part I: In-Depth Routine Maintenance

Preventive maintenance is the cornerstone of a healthy IMM operation, significantly extending equipment life and maintaining machine performance.

1. Hydraulic System and Lubrication: The Machine’s “Lifeline”

The hydraulic system is the power heart of a hydraulic IMM. Its health directly determines the machine’s response speed and clamping precision.

Hydraulic Oil and Filter Management

• Oil Analysis: Beyond checking oil level and color, it is crucial to perform spectroscopic analysis annually. This detects wear metal particles (e.g., copper, iron), silicon (external contaminants), and water content. Excess water or high particle contamination levels (e.g., above NAS Class 8) are clear indicators of impending hydraulic component failure (e.g., servo valves, pumps).
• Temperature Control: The ideal hydraulic oil temperature should be maintained between $40^\circ\text{C}$ and $50^\circ\text{C}$. Excessive temperature (above $60^\circ\text{C}$) leads to rapid oil oxidation, viscosity breakdown, and accelerated seal degradation. Check the efficiency of the oil cooler to ensure its water or air passages are not blocked.
• Filter Element Replacement Cycle: Strictly adhere to the manufacturer’s recommended schedule for replacing high-pressure and return-line filter elements. Never prolong filter life to save costs, as this risks opening the filter bypass valve, allowing contaminants directly into the system.

Lubrication Point Management

• Centralized Lubrication System: Ensure the pressure of the automatic lubrication system’s oil cups or pumps is normal, and that lubricant is accurately delivered to all friction points, such as the toggle linkage, tie bars, and bearings.
• Critical Areas: The toggle mechanism is responsible for transmitting the clamping force and must be lubricated with high-temperature, high-pressure grease meeting specifications. Inadequate lubrication leads to rapid wear of pins and bushings, reducing clamping force accuracy and potentially causing mechanical noise and vibration.

2. Injection Unit: Plasticizing and Metering Accuracy

Maintenance of the injection unit directly affects melt quality and product dimensional accuracy.

• Check Ring Inspection: Check the sealing effectiveness of the check ring (non-return valve). If molten plastic flows backward during injection, it causes metering instability and holding pressure loss, ultimately leading to fluctuations in product weight and dimensions. Testing involves observing the consistency of screw retraction after an air shot.
• Heating System Calibration: Quarterly, use external measuring equipment (such as a thermocouple probe) to calibrate the temperature in each barrel zone. The IMM’s built-in temperature readings might drift due to internal thermocouple wear. Inaccurate temperature control is a primary cause of material degradation and the formation of burned material (scorching).
• Screw/Barrel Wear: Wear leads to melt pressure leakage and poor plasticizing and mixing. When the screw requires higher rotational speed and longer plasticizing time to achieve the set dosage, consider performing a clearance measurement of the screw and barrel.

3. Clamping Unit and Safety System

• Tie Bar Pre-load Check: Tie Bars should be regularly checked for elongation or pre-load. Uneven pre-load leads to unbalanced force distribution across the four tie bars, affecting the uniformity of force on the mold parting line, which is a hidden risk for flash and uneven mold wear.
• Platen Parallelism Calibration: After resetting or changing large molds, use a dial indicator to check the parallelism of the moving platen and the fixed platen, ensuring the deviation is within specification (typically less than $0.05\text{mm}$ per $100\text{mm}$ of guide length).
• Safety Interlocks: At the start of every shift, the mechanical, hydraulic, and electrical three-in-one safety gate interlocks and emergency stop buttons must be tested. This is the last line of defense for operator safety.

Part II: Effective Troubleshooting and Efficiency Optimization

When production issues arise, quick diagnosis and resolution are vital for restoring efficiency. A systematic “observe-measure-analyze-act” process should be adopted.

Key Fault Diagnosis Flow Table

The table below summarizes the three most common defects in injection molding production, along with their potential causes and solutions:

Efficiency Optimization: From Maintenance to Predictive Maintenance (PdM)

To elevate efficiency to the highest level, we must transition from reactive or preventive maintenance to Predictive Maintenance (PdM).

• Vibration Analysis: By monitoring the vibration spectrum of critical rotating IMM components (pumps, motors, screw drives), wear on bearings and gearboxes can be detected weeks or months in advance. This allows for replacement during scheduled downtime, preventing sudden breakdowns.
• Data-Driven Decisions: Collect and analyze OEE (Overall Equipment Effectiveness) data, including availability, performance, and quality metrics. If performance indicators (e.g., cycle time) begin to drift gradually, this is often an early warning sign of an underlying maintenance issue.
• Automation and Cycle Optimization: Utilize the machine’s motion control capabilities to optimize the speed and acceleration curves of non-filling phases (mold open, ejection, mold close). This minimizes Non-Productive Time without compromising mechanical longevity.