I. Disposing of concealed hazards at the source during the rehabilitation phase
Recalculate thermal expansion clearance:** Follow the thermal expansion formula ΔL = L × α × ΔT strictly to recalculate the allowance, allowing a safety margin of two times. The axial allowance for a 100mm manifold plate heated to 200℃ is ≥0.7mm, which is significantly greater than the conventional standard.
Replace the floating positioning structure: Substitute the original rigid positioning ring with a high-precision floating positioning ring. The hot runner can be freely displaced along the expansion direction, as the coaxiality of the positioning ring is maintained at a minimum of ≤0.02mm, in accordance with the H7/js6 standard.
Optimise the local structure of the template by incorporating an independent cooling circuit around the heated runner plate. This will allow for the precise regulation of the template's temperature rise, the mitigation of the template's own thermal expansion, and the prevention of bidirectional compression lock-up. II. Stringent Control During Processing and Reassembly
Mirror Polishing of Mating Surfaces: The inner walls of the repaired mounting holes are mirror polished to a roughness Ra≤1.6μm, which completely eliminates any residual burrs and prevents jamming during thermal expansion.
Full-Dimensional Re-measurement with a Coordinate Measuring Tool: Following the repair, the coaxiality of the mounting apertures and all mating clearances are re-measured using a coordinate measuring machine to verify that all parameters fully meet the design requirements. The reassembly of elements that are not qualified is prohibited.
Standardised Fastening Process: The preset torque value is strictly adhered to as hot runner bolts are tightened using a diagonal, step-by-step tightening process. To prevent skewed stress on the heated runner plate, single-sided, one-time tightening is prohibited.
Pre-coating with a High-Temperature Anti-Gas Agent: A high-temperature molybdenum-based anti-gasting agent is applied to all metal mating surfaces in an even manner to prevent adhesion and seizing of the metal contact surfaces at high temperatures. III. Comprehensive Process Monitoring During Operation and Maintenance
Implement a Segmented Heating Strategy: Increase the temperature by 50°C every 30 minutes during the initialisation of the hot runner. To guarantee that all components of the hot runner expand uniformly and in synchrony, refrain from immediately increasing the temperature to the operating temperature.
Install Displacement Monitoring Sensors: In order to monitor thermal expansion displacement in real time, install high-precision displacement sensors on the side of the heated runner plate. Immediately activate an audible and visual alarm to identify potential interference if the displacement surpasses the limit.
Establish a Specialised Inspection System: Conduct a two-monthly disassembly of the machine to monitor the wear of the mounting hole mating surfaces, restock anti-seize agents, retest the thermal expansion clearance, and proactively identify potential issues.
The long-term stable mass production requirements of high-value precision injection moulds can be entirely satisfied by this closed-loop prevention system, which can reduce the recurrence rate of similar faults to zero after level four lock-up repair.
