We initiated research and development on blister-packing machines in 1985 and introduced our prototype in 1989. Through continuous improvement, our products have gained widespread acceptance among customers in China and Southeast Asia. We take great pride in our contribution to the popularization of blister packing machines for pharmaceutical applications.
Below is a brief overview of the functions and characteristics of our machine, including a comparative analysis with similar packaging equipment.
I. Roller-Type vs. Plate-Type Molds
Functions and Characteristics of Roller-Type Machines
Heating and Cooling Constraints: In a roller-type mold, the PVC sheet is placed tightly against the mold as it enters the heating section. Because heating occurs in limited die orifices while the roller rotates, circulating water cooling is required to dissipate excess heat.
Vacuum Forming Limitations: Vacuum forming is the only viable option for this setup. Consequently, the forming temperature must remain relatively high (around 170°C), which is dangerously close to the PVC melting and chloride decomposition point of 180°C. This results in a thin blister bottom and uneven wall thickness.
Material Sensitivity: If the PVC sheet has scratches, the concentrated stress makes the blister prone to breaking. Therefore, vacuum forming demands exceptionally high-quality PVC sheets. (Note: Vacuum forming relies on evacuating air inside the mold—typically generating a negative pressure between 1.33 × 10⁻² and 1.33 × 10⁻⁵ Pa—to create a pressure differential utilizing standard atmospheric Pressure).
Shape Limitations: It is highly difficult to process molds for “irregular-shaped drugs, limiting the machine’s versatility.
Primary Advantage: The most significant merit of the roller-type machine is its excellent structural synchronization.
Functions and Characteristics of Our Plate-Type Machine
Positive Pressure Forming: Our machine uses a plate-type mold, in which the heated PVC sheet is conveyed for positive Pressure forming.
Superior Blister Quality: Utilizing high compressed air pressure (typically 0.3 MPa), a lower forming temperature (around 100°C, with PVC softening at 90°C), and a larger heating and forming area, the blister is drawn not only from the rigid PVC at the mold orifice but also from the surrounding material. This results in an even wall thickness and high structural strength, lowering the quality requirements for the rigid PVC sheet.
Versatility: The mold is easy to process, making it well-suited for packaging abnormally shaped pharmaceutical products.
The Synchronization Challenge: The historical difficulty with plate-type machines lies in synchronizing the forming mold with the heat-sealing mold to ensure the formed blister drops perfectly into the heat-sealing orifice.
II. International Comparisons
German Technology: German machines use complex and expensive shift counters on the forming mold to closely track the movement of the PVC sheet.
Italian Technology: The Italian FA3 machine employs a synchronized motor to drive the roller, supplemented by photoelectric feedback controls to minimize errors; however, this yields limited practical effectiveness.
Our DGB-250 Innovation: Our DGB-250 multifunctional roller-plate automatic blister packing machine integrates the smooth processing and clear production procedures of the FA3 machine. We redesigned the mechanical transmission synchronization mechanism for intermittent action. This configuration allows the driving roller to execute four intermittent movements per revolution. Driven by the main motor and other moving parts, the equal error is limited to a single revolution, effectively eliminating accumulated error and resolving the machine’s synchronization issues (National Patent No. 90203244.5).
III. Solving Printing Ink Volatilization
Surface Printing Drawbacks: Surface printing (typically using resin plates) is the standard choice for German, Italian, and domestic blister-packing machines. However, this method produces rough lines, deckle edges, and unavoidable ink stains in blank areas, making the product aesthetically unappealing.
Gravure Printing Challenges: Photogravure (intaglio printing) produces fine lines and sharp images, accommodating a wide range of characters and complex trademark shapes. However, traditional gravure processes require diluting the ink with volatile chemical solvents, such as dimethylbenzene (xylene), which causes severe environmental pollution. While foreign institutions have invested heavily in developing non-toxic inks, results have been poor, and manufacturing costs remain exorbitant (around 70,000 RMB/ton).
Our Patented Solution: We independently designed and manufactured a “Sealed Gravure Printing Device.” This innovation harnesses all the aesthetic benefits of gravure printing while eliminating the environmental pollution caused by solvent volatilization. Furthermore, it allows for the use of standard plastic film gravure ink, significantly reducing costs to approximately 10,000 RMB/ton (National Patent No. 91228830.2).
Author: Yang Yijun, Jornen Machinery Co., Ltd.
(Originally published in Pharmaceutical Machinery News on May 30, 1992)