1. Mold Materials: From Ordinary Metals to Special Alloys and Coating Technologies
Traditional gelatin capsule molds: Mostly made of ordinary stainless steel, with only simple surface polishing required, due to the low viscosity and easy demolding of gelatin solution.
HPMC capsule molds:
- Material upgrading: 316L medical-grade stainless steel or titanium alloy must be adopted to improve corrosion resistance and surface hardness, so as to cope with the wear caused by high-viscosity plant-based adhesives.
- Surface treatment: Nano-ceramic coatings, Teflon-modified coatings, etc., have been developed to reduce adhesive viscosity, solve the problem of HPMC capsule adhesion, and increase demolding efficiency by more than 30%.
- Integration of heating function: Some high-end molds are equipped with built-in heating elements to achieve precise control of mold pin temperature (±0.5℃), promote rapid curing of the adhesive, and eliminate the need for gelling agents.
2. Mold Pin Design: From Uniform Specifications to Customized Precision Manufacturing
- Spacing optimization: Due to the high viscosity and surface tension of HPMC adhesive, the distance between mold pins has been increased from the traditional 8-10mm to 12-15mm, so as to eliminate the impact of surface tension on capsule uniformity and ensure the effective dip-coating area of each mold pin.
- Shape improvement:
- A gradual taper design is adopted, with the root diameter slightly larger than the top, to solve the problem of uneven wall thickness caused by the downward flow of adhesive after dip-coating.
- Arc transition is added to the top of the mold pin to avoid capsule top damage caused by stress concentration.
- Precision improvement: The tolerance of mold pin diameter is reduced from ±0.05mm to ±0.01mm, and the surface roughness Ra < 0.05μm, ensuring the consistency of inner and outer diameters and surface smoothness of capsules.
- Function integration: High-end mold pins are equipped with built-in micro-sensors to real-time monitor dip-coating thickness and temperature, providing feedback signals for the servo control system.
3. Mold Structure: From Single Function to Modular Intelligent Integration
- Adaptation to multi-dip coating process: To adapt to the double-dip / triple-dip process, the mold is designed into a quickly replaceable modular structure. Different dip-coating stations can be equipped with mold pins of different specifications to realize the manufacture of multi-layer capsule shells.
- Optimization of flipping mechanism:
- The traditional 900° (two and a half turns) flipping is improved to segmented flipping: first, slow flipping by 450° to evenly distribute the adhesive, then fast flipping by 450° to accelerate curing.
- Servo motor-driven flipping achieves an angle precision of ±0.5°, avoiding wall thickness defects caused by adhesive agglomeration.
- Lightweight mold frame: Adopting aluminum alloy + carbon fiber composite structure, the weight is reduced by 40%, improving the response speed of servo drive and reducing energy consumption.
- Upgrading of demolding system:
- From mechanical ejection to air pressure-assisted demolding, reducing scratches and damage rate on the capsule surface.
- Some high-end molds are equipped with ultrasonic demolding devices, suitable for ultra-thin wall (<0.05mm) and special-shaped capsules.
4. Dip-Coating Auxiliary System: From Passive Adaptation to Active Collaborative Control
- Coordination between glue tank and mold:
- The glue tank adopts a double-roller stirring design, with bidirectional rotation to make the adhesive flow evenly, eliminating bubbles and uneven thickness.
- Linked control of mold lifting and glue tank stirring speed: low-speed stirring (5-10rpm) during dip-coating to ensure dip-coating effect, and high-speed stirring (30-50rpm) when leaving to ensure adhesive uniformity.
- Improvement of lubrication system:
- From manual oiling to automatic quantitative oiling, the felt roller rotates to evenly apply medical-grade silicone oil, with the oil application amount controlled below 0.01g per pin.
- Some high-end production lines adopt oil-free demolding technology, realizing self-lubrication through special surface coatings of molds to avoid silicone oil residue affecting capsule quality.
- Temperature control system: Linked temperature control between mold and glue tank, the mold pin temperature is 2-5℃ lower than the adhesive temperature, promoting rapid gelatin of the adhesive and improving production efficiency.