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When Domino Amjet took over "it began to solve a lot of the problems that DEI would have eventually gotten to" says Lapolla. "Right away they found a leakage in the laser tubes and corrected it. As we resolved our problems we began to add more coders. We currently run eight units all installed on the Klockner Ho/oonsel Tevopharm flow wrapping machines."
How they work
Each coder used by Warner-Lambert Canada uses seven identical laser tube assemblies that are arrayed to provide a dot-matrix character format. The entire process is electronic using computer software. No mask or electro-mechanical scanning hardware is required. And since the CO2 is sealed the tubes last for years.
The lasers used by Warner-Lambert Canada are twin-line lasers. This means the laser marks two dates as opposed to one. At the end of each laser head assembly are two mirrors; one is a stationary mirror. The other is mounted to the shaft of a motor. The second mirror rotates 21° from one point to the next. As the printed gum wrap unwinds from the flow wrapper the rotating mirror is positioned at its first point and ready to mark the first date. At this point the laser pulses on and off to generate the appropriate code. As the web continues to move the mirror is rotated 21° to the second position where the laser again pulses on and off to complete the second code. The end result is identical codes for the images printed opposite one another on the web to allow two-up filling and sealing (see related story).
The process has been improved considerably since Warner-Lambert Canada first began laser coding. "We used to use a photoeye to pick up a registration mark for each pack to initiate the coding process" Lapolla notes. "But we had problems with the package colors and web movement so the process was inconsistent. Also the photoeye remained in a fixed position which could be problematic for purposes of shifting the position of the date on the web. Instead we hooked up the input signal for the laser to an electronic cam. This allowed us to rotate the firing position at 360 degrees so we can adjust to the position of the registration mark and pinpoint the laser's firing."
Lapolla says Warner-Lambert is still fine-tuning the entire process. "We designed software that lets us individually program each coder from a single computer. We still need to develop a better method of cleaning the sugar dust from the mirror on the laser" he admits "but we're making progress on that by implementing vacuum and air blowing systems on the face of the mirror. The entire system is based on electronics. There's little wear with the lasers and virtually no clean-up issues compared with our old pad-printing method. And the quality is far beyond anything else we've had. It's exactly what we needed."
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