Automatic Sheet Sorter for separating zero defect sheets from a batch of printed bio-sensor base arrays.
Sensor arrays are produced on sheets that later on make up multiple of finished biomedical sensors. During the manufacturing process of these arrays various in process tests and measurements are performed. This example focuses on the manufacture and inspection of the carbon layer of a blood glucose sensor. Variations in the print process of this layer result in sheets where some of the sensors are outside their acceptable tolerance range but do not deem the entire array defective. However these sensors need to be identified and marked for post processing of the arrays into finished product and future editing out when the sensors get singled out from the array. The previous process was to run all sheets through the marking equipment regardless if zero-defect sheets where present or not. Due to the slow marking and sheet handling process, unnecessary cycle time was used up by processing zero defect sheets through the marker.
A new method was devised to separate the zero defect sheets from others. Purpose of this automated sheet separation unit is to separate zero defect material from sheets that require marking. Rather than adding an extension to the inspection machine it was decided to build a separate module for the separation process. Reasoning was that we did not want to impact the inspection process if there were to be any issues with the downstream separation equipment such as overlapping sheets or other sheet handling issues. Another benefit of the stand alone module is that it utilized a commercial feeder and conveyor system rather than a slower pick and place sheet handling device. The sorter runs at a higher frequency than the inspection equipment and therefore does not slow down the process. The other advantage is that an alternate manufacturing process can be put in place to edit out the sheets manually without impacting automated inspection throughput on the visual inspection equipment in case the sorter is not available. The Stand alone work center with user interface, automatic feeder, sheet detector for bar-code reading, sheet diverter, sheet bins, machine controls, double sheet sensor complete the system.
The user Applications was created in Visual Basic 6.0. Besides hosting the User interface the application also accesses a networked database for information retrieval. The host PC also supports the bar code reader and PLC. A stepper motor enabled diverter plate diverts the presented sheets in their respective bins. During initial sheet detection on the first conveyor, with a sensor, the bar code reading technique is activated. The host computer will retrieve the database record from the remote MySql database and retrieve the pass fail criteria for the entire sensor array sheet. If the sheet has defects it is diverted into the ‘to be marked’ bin. If the sheet has no defects it is diverted into the ‘no defect bin’.