Maintenance and care of die casting machines
Die-casting machine maintenance is crucial for extending equipment life and ensuring stable production. A comprehensive maintenance system is essential, encompassing daily maintenance, regular overhauls, and specialized maintenance, comprehensively protecting the equipment’s mechanical, hydraulic, and electrical systems. Neglecting maintenance can lead to frequent equipment failures. For example, a die-casting plant experienced severe wear and tear on its hydraulic pumps due to long-term failure to replace hydraulic oil, resulting in repair costs exceeding hundreds of thousands of yuan. Regular maintenance can reduce sudden failures by over 80%. Maintenance should adhere to the principle of “prevention first, timely resolution” to nip any problems in the bud and ensure that equipment remains in optimal operating condition.
Daily maintenance is the responsibility of the operator and is performed before, during, and after each shift, focusing on checking the basic condition of the equipment and safety devices. Pre-shift checks include: checking the hydraulic oil level for leaks; ensuring cooling water pressure and flow meet standards; ensuring compressed air pressure is between 0.6 and 0.8 MPa; and ensuring the sensitivity and effectiveness of safety devices such as the emergency stop button and infrared hand guard. During the shift, close attention should be paid to parameters such as operating sound, oil temperature, and pressure. Any abnormal noise, sudden rise in oil temperature (above 55°C), or pressure fluctuations should be immediately stopped and inspected. Post-shift maintenance includes: cleaning residual metal and scale from the pressure chamber and mold cavity; shutting off the power, water, and air sources; cleaning oil and dust from the equipment surface; and recording equipment operating conditions and any abnormalities. By strictly implementing daily maintenance, one factory reduced the average daily downtime of its equipment from 1 hour to 0.1 hour, increasing production efficiency by 15%.
Regular maintenance is performed on a weekly, monthly, quarterly, and annual basis, with specific maintenance tasks tailored to each component. Weekly maintenance includes: checking the lubrication of all moving parts, such as tie rods, guide rails, and toggles, and adding grease (such as lithium-based grease) to ensure adequate lubrication; cleaning the air and hydraulic oil filters to prevent clogging that could affect system pressure; and checking the tightness of mold mounting bolts to prevent loosening. Monthly maintenance includes: checking the hydraulic system’s pressure and flow, testing the sensitivity of each relief valve and pressure relay; checking electrical connections, tightening terminals, and cleaning dust from contactors and relays; and measuring the motor’s insulation resistance to ensure it is greater than 0.5MΩ. Quarterly maintenance includes: replacing the hydraulic oil filter element; inspecting cylinder seals for deterioration and replacing them if leaking; and calibrating the pressure and temperature sensors to ensure data accuracy. Annual maintenance requires a comprehensive overhaul, replacing worn hydraulic hoses, seals, bearings, and other consumable parts; verifying the integrity of the PLC program; and performing a full precision calibration of the equipment.
Specific maintenance of the hydraulic system is crucial to equipment performance, with hydraulic oil management being key. Hydraulic oil should be replaced regularly, starting three months after initial use and every six to twelve months thereafter. During replacement, the oil tank and lines should be thoroughly cleaned to remove sludge and impurities to prevent contamination of the new oil. Oil contamination should be maintained within NAS Level 8 and can be regularly tested with an oil tester. Any contamination exceeding this level should be promptly filtered or replaced. Check the operating status of the hydraulic pump and motor, listening for steady operation and measuring temperature rise to ensure normal operation (should not exceed 40°C above ambient temperature). Any abnormalities may indicate internal wear and require disassembly and inspection. Hydraulic valves, such as reversing valves, flow valves, and pressure valves, should be regularly disassembled and cleaned, inspecting the valve core and seat for wear. Replace any severely worn valves to ensure smooth operation without sticking. A factory failed to replace the hydraulic oil filter promptly, allowing impurities to enter the reversing valve, causing the valve core to stick and resulting in equipment downtime for eight hours, causing significant losses.
Maintenance of the mechanical and electrical systems is crucial, as wear and tear on mechanical components directly impacts equipment accuracy. The toggle and hinge areas of the clamping mechanism are key areas for maintenance and require regular inspection for wear and clearance measurement. If the clearance exceeds 0.2mm, the bushing or pin should be replaced to prevent a decrease in clamping force. The tensile deformation of the tie rod should be regularly checked, and its straightness measured using a dial indicator. Any deviation exceeding 0.1mm/m requires straightening or replacement, otherwise uneven clamping will result. The injection rod and guide sleeve of the injection mechanism require regular lubrication and inspection for wear. If the clearance is excessive, the guide sleeve should be replaced to ensure injection accuracy. Electrical system maintenance requires keeping the control cabinet clean and dry to prevent dust and moisture from entering. The operating status of core components such as the PLC, touch screen, and servo drive should be regularly checked, and programs should be backed up to prevent loss. Sensors such as position sensors and pressure sensors require regular calibration to ensure accurate signals and avoid equipment malfunctions due to sensor failure.
Maintenance records and analysis are the foundation of continuous improvement, and comprehensive equipment maintenance files need to be established. Record the time, content, replaced parts, equipment operating parameters, and other information for each maintenance session. Use data analysis to identify high-incidence areas and causes of failures, and develop targeted preventive measures. For example, statistics show that the hydraulic pump of a die-casting machine fails every 18 months on average. Preventive maintenance and replacement of wearing parts can be performed 15 months in advance. Regular equipment maintenance meetings are held where operators, maintenance personnel, and technicians jointly analyze problems found during maintenance and optimize maintenance processes and cycles. Introducing equipment management systems (such as CMMS) enables automatic reminders of maintenance plans, digital management of maintenance records, and statistical analysis of failures to improve maintenance efficiency. By establishing digital maintenance files, a large die-casting company increased its overall equipment efficiency (OEE) from 65% to 82%, significantly improving production efficiency.
