The vacuum forming process of high-speed blister packaging machines is a crucial step in the entire packaging process. Blister forming methods can be divided into the following four types:
1. Vacuum Forming (Negative Pressure Forming)
A vacuum is used to draw heated and softened film into the blister cavity of the forming mold, forming a specific geometric shape and completing the blister formation. Vacuum forming generally uses roller molds, resulting in smaller blister sizes, simpler shapes, uneven blister stretching, and a thinner top.
2. Blow Forming (Positive Pressure Forming)
Compressed air is used to blow heated and softened film into the blister cavity of the forming mold, forming the desired geometric shape of the blister. Blow forming is mostly used with plate molds, resulting in more uniform blister wall thickness, a more rigid shape, and the ability to form larger blister sizes.
3. Punch-Assisted Blow Forming
A punch is used to press heated and softened film into the mold cavity. When the punch is fully inserted, compressed air is introduced, causing the film to adhere tightly to the inner wall of the mold cavity, completing the forming process. Punch-assisted forming is mostly used for flat blister packaging. With proper planning, it can produce blister packs that are uniform in size and have complex shapes.
4. Cold stamping with a die
When using packaging materials with high rigidity (such as composite aluminum), thermoforming methods are clearly unsuitable. Instead, cold stamping with a die is used, where the die and liner are closed to form the blister pack, with air vented through the vent holes within the die.
