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PADPRINT
NOTEBOOK Useful Tips & Information © ITW Trans Tech An Illinois Tool Works Company |
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 Toothbrush Pad Printing System Specifications: • Substrate: polypropylene; various colors. • Item function: toothbrush with nylon bristles; four different designs.   Two of the four brush designs are shown above. Because the polypropylene substrate has such a "slippery" surface, electrical pretreatment is required for ink to properly adhere. • Imprint: various logo artworks and type on top side only; ink color variable, depending on range of brush colors. • Pad printer: Sealcup 90 closed ink cup printer, equipped with pad clean-off device. • Production goal: 35 parts per minute, depending on operator demand. • Load/Unload: Manual load individual brushes onto cleated conveyor belt. Finished parts are dropped off end of track into bulk container. Auxiliary Equipment: • ANTISTATIC BLOWERS remove dust and any charged particles from parts prior to printing. • PAD BLOWERS direct ambient air onto pad to enhance solvent flashing for proper image transfer. Surface Pre-Treat & Post-Print Cure:  CORONA SURFACE PRETREATMENT: Detail view shows corona surface pretreating unit positioned over brushes on infeed track. As each individual part passes under the high-voltage electrode, the surface energy of the polypropylene substrate is changed sufficiently to enable proper ink transfer.  THERMODIFFUSION CURE: After printing, as each brush passes under the thermodiffusion curing unit (at center of photo), a charge of hot air is directed through a masked opening onto the printed area of the part to accelerate ink curing. From here the conveyor carries it under an ambient air cooldown blower (at far left, above) and finally drops it into a bulk container. IN THIS ISSUE: |
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Toothbrush Pad Printing System:
Pre-Treat, Print & Cure In-Line
DESIGNING, a semi-automatic system for decorating one of the most common household items can be uncommonly challenging as our engineers discovered with this toothbrush pad printing machine.
Several Different Brushes, One Adaptable System
The critical feature that this customer required of the finished machine was adaptability. A range of four toothbrush designs would be decorated using this system, so fixture tooling needed to be changed over to accommodate different brush types.
After examining the four different brushes, our engineers created interchangeable fixtures that could be easily switched, based on demand. Combined with the X-Y table onto which the Sealclup 90 is mounted, the system has plenty of flexibility.
Overview of the toothbrush printing system elements, from right to left, include: infeed track (1), light curtains (2), corona pretreatment (3), anti-static nozzle (4), pad clean-off device (5), Sealcup 90 (6), thermodiffusion curing (7), and cooldown unit (8).
The application sequence begins with the operator manually loading brushes onto a cleated conveyor. Because the polypropylene substrate has such a "slippery" surface, electrical pretreatment is required for ink to properly adhere. Thus a part-present sensor detects each part and locates it at the pretreatment station where a corona electrode is configured in-line above the part as it passes beneath on the cleated conveyor belt.
To ensure print quality, an anti-static blower also removes any remaining charges that might attract dust to the brush surface at this point (for more details on this, see related item on page five).
Detail view of corona pretreatment unit (at right) positioned above brushes and anti-static blower nozzle immediately behind it (at left).
Thermo Cure & Cooldown
The conveyor then moves the part to the print station where the specific brush-holding fixture clamps each part in place while the Sealcup 90 applies the image. From here the conveyor moves the brush further down the line to the thermodiffusion curing unit where the printed area receives a short blast of hot air as it passes beneath the discharge vent.
Finally the part moves under a cooldown blower to return it to ambient air temperature before it falls off the end of the belt into a bulk container.
Depending on operator demand, up to 35 parts per minute can be decorated by this system with it running continuously.
Close-up view of printing area shows details of system as toothbrushes move from right to left: anti-static nozzle (1); pad clean-off device (2); special griper fixture (3); and pad blowers (4).
Pad Clean-Off & Pad Blowers
Our optional pad clean-off device is also interfaced to the Sealcup 90 padprinter to periodically tape off any accumulated ink or debris from the silicone pad that may interfere with proper image transfer. Other features installed are a pair of pad blowers, positioned to direct air at the pad as it descends onto the part to help "flash off" solvents. These serve to enhance fast image transfer, an important factor in sustaining highest production rate and profitability.
Both pad clean-off devices and pad blowers are frequently recommended by our printlab technicians. These accessories enable a higher degree of control over the process and ultimately the final quality of the printed product. The finished unit also has full safety guarding, including light curtains, heavy-duty machine base and blanchard-ground aluminum table top. nls answers to critical, customer specifications.
For more details on our custom-designed automated pad printing systems, feel free to contact your local Trans Tech rep at: www.itwtranstech.com
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