Liquid blister packaging machines are mainly used for automated packaging of small-dose liquids (such as oral liquids, eye drops, cosmetic samples, disinfectants, etc.). The core processes include blister forming, liquid filling, film sealing, punching and slitting. In actual production, a series of pain points are prone to occur due to the characteristics of the liquid (fluidity, viscosity, corrosiveness, etc.), the characteristics of the packaging materials and the performance of the equipment. Today we will start with the aspects of forming and filling.
一. Poor quality of blister forming (pain points in the forming process)
Pain point
· Incomplete blister forming (such as missing corners and deformed shapes), unable to stably hold liquids;
· Uneven blister wall thickness (partially too thin and easy to break, too thick affects sealing);
· Slow forming speed under low temperature environment, and easy coking of materials under high temperature.
Causes of pain points
·Irrational mold design (such as corner radian, depth and material stretching rate do not match);
·Uneven temperature distribution of heating system (such as aging of infrared heating tube and low heat conduction efficiency);
·Insufficient molding pressure/vacuum control accuracy (too low pressure leads to incomplete blister, too high pressure leads to material rupture).
Solutions
1.Optimize mold design: According to the liquid capacity and the tensile properties of packaging materials (such as PVC, PET), design a blister cavity with rounded corners to reduce stress concentration; use precision machining molds (tolerance ≤0.02mm) to ensure molding consistency.
2.Upgrade heating system: Use quartz heating tubes with zoned temperature control (support ±1℃ precision control), with real-time feedback from infrared temperature sensors to avoid local overheating or under-heating; add preheating modules in low temperature environment to ensure uniform softening of materials.
3.Precision pressure control: Use a servo-driven vacuum/positive pressure system to preset the molding pressure curve according to the material thickness (such as low pressure and slow molding for thin materials, high pressure and fast molding for thick materials), and adjust the pressure parameters in real time through PLC.
二. Low liquid filling accuracy (pain point in filling process)
Pain point
·Large dosage deviation (such as more than ±5%), which does not meet the measurement standards of drugs/foods;
·Liquid dripping during filling (polluting equipment or packaging materials);
·High-viscosity liquids (such as syrups and pastes) are not filled smoothly, and “drawing” or residues appear.
Pain point reasons
·Insufficient filling pump accuracy (such as measurement error caused by gear pump wear);
·Irrational pipeline design (dead corners cause liquid residue, or pipe diameter does not match viscosity);
·Liquid state fluctuations (such as temperature changes cause viscosity changes, or contain bubbles).
Solutions
1. Use high-precision filling components: ceramic plunger pumps (accuracy ±0.5%) are used for small doses (≤10ml), and screw pumps (with heating and insulation pipelines) are used for high-viscosity liquids to avoid metal wear and pollution.
2. Optimize pipelines and filling heads: The pipelines use food-grade silicone tubes (smooth inner wall to reduce residue), and the filling heads are designed with anti-drip structures (such as spring-loaded check valves + diversion nozzles); high-viscosity liquids add pipeline heating jackets (control temperature to stabilize viscosity).
3. Eliminate bubbles and real-time calibration: Add a vacuum degassing device before filling (to remove bubbles in the liquid); equip with an online weighing sensor (automatically calibrate the filling amount every 50 pieces), and automatically compensate for deviations through PLC.
