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The USNR ID Printer is a high speed printer system used to apply IDs on boards for tracking purposes. The printer is typically located on the outfeed of the USNR LHG in a planermill application and applies IDs to the boards as they exit the LHG at speeds up to 4000 ft/min. The printer uses a UV Fluorescent ink that gets picked up by a downstream ID Reader (USNR IDR) after the board has been transported to a lugged transfer.
As each board is scanned through the LHG, an ID is assigned to the board for tracking purposes.
The board ID is sent from the FRM to the ID printer over a serial cable interface in plain ASCII format. The ID is converted by the printer to a series of nozzle activations to spray the ID on the board.
Once the ID has been received and processed, the printer holds the ID and waits for a PrintGo signal from FRM to start the printing process. Each nozzle activation is broken down into a series of ‘strokes’ and each stroke is broken down into a number of encoder ticks. The encoder ticks are tracked by the printer to determine the start/stop activation points for each nozzle.
Due to the high speed, the output quantity is reduced to a minimum. The small nozzle (Ø 0.1 mm), together with a valve stroke of 0.06 mm (T2) was chosen to achieve such small droplets. The valves work under limit conditions in this application, USNR invested a lot in the evaluation and testing of different valves. Finally the chosen valve dispensed the ink most accurat.
HIGHSPEED JET
The picture on the left shows a close up of a highspeed valve activation and the resulting ink stream. The valve was activated for 500µs (the lead drop and tail end of the ink stream are visible).
THREAD FASTENING
The screw-in version of the valve is perfect for this application. In the rare event that a valve is damaged, the customer can simply replace the respective valve without removing the entire printhead.
The current Highspeed binary printhead is capable of printing IDs up to 4000 feet/min. Each digit consists of 5 lines sprayed as bits to represent a binary ID. The Printhead is mounted at the LHG outfeed. Lumber passes over top of the printhead at up to 4000 feet/min to have a 10 digit ID printed.
