Control for Wide Blister Webs
Published: March 1st, 2011
Designed for handling wider webs, Pharmaworks’ TF3 blister machine offers unique features including a vertical web orientation at the blister forming module.
“There are some projects out there where customers are still looking for a larger format machine,” says Ben Brower, vice president and sales director, Pharmaworks.
With a maximum blister format of 220 mm X 290 mm, the TF3 suits applications such as high count “bingo cards” for nursing homes, large blisters for medical devices, and “some good old fashioned projects that need “X’ amount of throughput,” he adds.
The web is held vertically for pre-heating, forming, and cooling of the formed blisters at the first module. Besides saving space, the unique orientation prevents sagging and stretching of a warm web placed on the horizontal, Brower says.
The unit features contact cooling for evacuating heat after blister forming and at the seal station after sealing. Chilled plates are clamped to blisters as they are indexing.
“When you are indexing a long web slight deformities and stretching accumulate on you. Some materials will be more prone to shrinking. If you are using a flood feeder, it creates drag. When you get to the seal station, you end up crushing blisters that are out of alignment. This is a number one problem in blister packaging.
“Using contact cooling, we create cold plastic that won’t stretch,” he says.
Full servo control in the TF3 includes three laser-guided servo indexers at the form, seal, and punch stations providing automatic adjustments for registration.
The servo handling seal station registration also takes feed back from a sensor that picks up the print mark and corrects for print registration.
“One servo really can’t register the blister into the seal tool and register the print marks to the base material at the same time. So after setting the pre-printed lidding, we use a unique system that creates drag on the lidding to minutely stretch it so it lines up in the sealing process.”
Past the seal station a compensation loop is created as a buffer supporting “multi-indexing.” The machine’s last module runs at double or triple speed as blisters are indexed row by row for perfing and die cutting. Multi-indexing enables using a smaller die set for cutting the blisters, and configures singulated blisters neatly for transfer to the cartoner or reject chute.