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Dual Applicators Improve High-Volume Coating Continued from previous page


ing system requires process controls to provide parameter maintenance.


Closed-Loop Process Control Automated conformal coating systems have


software that manages maintenance routines and provides closed-loop process controls for single- and dual-applicator setups. These controls further improve performance and help ensure quality dur- ing high-volume production. Dispense volume can be controlled through


the software by modifying pulse-width modulation, which allows the operator to determine how long the applicator is opened and closed. The timing controls adjust the amount of material passing through the valve and the jetting actuation acceler- ates the fluid to break off. The capability of dis- pensing discrete dots distinguishes the jet from a


needle dispense, which opens and uses fluid reser- voir pressure to push the material through the nee- dle. Dot spacing can be controlled by timing or spacing distance. Appropriate spacing reduces


September, 2016


splashing by keeping wet dots from being placed on top of each other. Employing a viscosity control system main-


tains consistent coating despite temperature fluc- tuations in the production facility. By heating the material, fluid temperature remains consistent throughout the day and can reduce bubbles in the substrate coating. The viscosity control system works best with low-viscosity fluids dispensed with a film coater. When dispensing with a film coater, main-


Jet applicator with needle extension, tip and coating pattern (left), top view of possible patterns (right).


taining the material’s shape and width is critical for uniform dispensing. Multiple factors can alter the dispense pattern, including a change in viscos- ity caused by environmental temperature changes or an obstruction at the nozzle. A laser fan width control system can help maintain a consistent fan width during production. A laser is used to meas- ure the width of the fan pattern at the dispense gap distance from the nozzle bottom. If the fan meas- ures outside the specified tolerance, the system adjusts the fluid pressure to best meet the required dimen- sions. Using an onboard laser fan width control system can measure the fan width at programmed inter- vals during a production run. If using needle or jet applica-


tors, a needle-finder sensor can quickly determine the needle’s posi- tion. When changing needles, or after an impact, the needle finder


The non-atomized


approach, as compared to atomized spraying,


provides superior edge


definition, higher coating speeds, more precise and accurate application, and single-pass coverage.


can compensate for offset or can rec- ognize that the needle is bent out of alignment. If the needle is bent, the material cannot dispense in a clean stream straight downward, reducing the quality of the process. The needle finder can be used with needle dis- pense applicators as well as the jet applicator with needle extension. Conformal coating is used in


high-volume electronics manufactur- ing for the automotive, computer, communications, and consumer pro - duct markets. Many of these prod- ucts require solvent-based coatings, which lend themselves to non-atom- ized application. The non-atomized approach, as


compared to atomized spraying, pro- vides superior edge definition, higher coating speeds, more precise and accurate application, and single-pass coverage. The finer edge definition accommodates tighter keep-out zones while reducing or eliminating the need for masking. The film coater’s faster line


speeds and single-pass coverage in - creases the number of units per hour (UPH). With the addition of a dual non-atomized applicator, the system can also selectively coat smaller areas that might otherwise be impossible to coat without using a mask. For high- volume manufacturers, automated selective coating systems provide an in-line, hands-off process that reduces or eliminates product handling by the operators, protects the coated prod- ucts, and optimizes UPH and repeata- bility. Contact: Nordson ASYMTEK,


2747 Loker Avenue West, Carlsbad, CA 92010 % 760-431-1919 fax: 760-431-2678 E-mail: info@nordsonasymtek.com Web: www.nordson.com r


See at SMTAI, Booth 808


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