How to Install Ceramic Liners in High-Concentration Scenarios

I. Pre-Installation Preparation Material Verification: Confirm that the ceramic liner is made of high-purity alumina (99.5% or higher), free of dark lines and pores, with inner and outer diameter tolerances controlled within ±0.01mm, and a thermal expansion coefficient matching the nozzle substrate H13 steel ≤5%. Tool Preparation: Prepare a digital display temperature-controlled heating table, hydraulic pressing fixtures, anhydrous ethanol, lint-free cloths, high-temperature fluorine passivation paste, and a micrometer. All tools should be cleaned and degreased beforehand. Substrate Pretreatment: Pre-machine the existing flow channel holes of the hot runner nozzle to an interference fit of 0.02~0.03mm with the outer diameter of the ceramic liner. Perform mirror polishing on the inner wall of the holes, achieving a roughness Ra≤0.8μm. Thoroughly remove any residual iron filings and oil. II. Core Installation Steps for Hot Fitting Substrate Heating: Place the entire nozzle on a digitally controlled temperature-controlled heating platform and heat it evenly to 280℃. Hold for 30 minutes to ensure uniform thermal expansion of the nozzle flow channel orifice. Use a micrometer to re-measure the orifice diameter in real time, confirming that the interference fit has been released to within 0.005mm. Low-Temperature Pre-cooling: Place the high-purity alumina ceramic liner in an industrial refrigerator and hold at -20℃ for 2 hours to allow slight contraction of the liner, reducing the risk of breakage during pressing. Precise Pressing: Apply a thin, even layer of high-temperature resistant fluorine passivation paste to the outer wall of the ceramic liner. Align it with the center of the nozzle flow channel orifice and use a hydraulic pressing fixture to press it in at a low, uniform speed of 0.05mm/s. Monitor the pressing pressure throughout the process; stop immediately if the pressure suddenly increases to prevent liner breakage. Cooling and Shaping: After pressing, place the entire nozzle in a dust-free environment to cool naturally and slowly to room temperature. Avoid sudden cooling with water or air to prevent cracking of the ceramic liner due to thermal stress. III. Post-Installation Verification and Post-Processing Appearance and Dimensional Verification: After cooling, inspect the inner wall of the liner with an endoscope to confirm there are no cracks or misalignments. Re-measure the overall coaxiality of the nozzle flow channel to ≤0.02mm, ensuring no melt stagnation steps. Industrial Run Verification: Install the installed nozzle into the hot runner and gradually increase the temperature to 320℃ at a rate of 50℃/h, holding for 2 hours to confirm there are no issues with liner loosening or adhesive leakage. Sealing Optimization: Equipped with perfluoroelastomer rubber sealing rings at the nozzle splicing surfaces, completely preventing high-concentration fluorine decomposition products from penetrating and corroding through the tiny gaps between the liner and the substrate.