AIA: Adhesive Is Stronger and Cuts Cure Times
US Endoscopy (Mentor, OH) manufactures accessories for rigid and flexible endoscopes-medical devices that are used for the exploration or biopsy of organs and tissues without performing conventional surgery. One of the company's new products is a biopsy inlet valve that allows an operator to irrigate an organ or tissue without changing instruments.
To successfully bring the device to market, the company established some very specific production requirements. A blue thermoplastic valve, for example, needed to be securely attached with adhesive to a length of clear PVC. Adequate pull strength was critical to ensure it stayed attached during use. To meet production targets, a 15- to 20-second cure time was required.
Additionally, the company had to be careful with the amount of adhesive it used. Too little adhesive, and the bond strength or seal could be compromised. Too much adhesive, and there was the risk that excess material would drip down the side of the valve, creating an aesthetic reject.
Finally, US Endoscopy wanted its adhesive, dispensing equipment and curing equipment to come from one supplier, to ensure both a well-designed process and post-sales support.
Early in the evaluation process, the company tried a UV-cured adhesive used in conjunction with a pair of UV wands. This option, however, resulted in problems that ultimately caused it to be rejected. The first UV wand-a 50-watt device-required a 100-second cure time because much of the light was absorbed by the blue tinted valve. A 200-watt UV wand reduced the cure time. But it created so much heat that it deformed the inlet valve.
A second option incorporated a 7700 handheld LED light source and Loctite 3922 medical device light cure adhesive from Henkel Corp. (Rocky Hill, CT). Using this combination, US Endoscopy was able to consistently cure the assembly in 10 seconds, while at the same time nearly doubling pull strength. This was possible because the spectral 7700 LED light source generates high-intensity visible light of a wavelength that precisely matches the wavelengths absorbed by the adhesive. In addition to being portable and relatively inexpensive, the 7700 generates minimal heat and minimal ultraviolet energy, making it safer to work with than traditional UV light sources.
Ultimately, US Endoscopy set up a two-operator workcell to manufacture the biopsy inlet valves. This workcell includes a Loctite integrated semiautomatic controller dispenser with a light-cure dispense valve. This system was installed in the middle of the work area, providing easy access to both operators. Each operator then has his own 7700 cure station, operated using a timer, foot switch and a custom fixture, which holds the assembly during curing.
For more light-cured adhesives, call 860-571-5100, visit www.loctite.com or eInquiry 5.
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