NI Products Verify Quality
The automotive industry has unique requirements for high-speed production test methods that verify the quality of their products with high-reliability assembly line test equipment. For navigational interfaces, instrument clusters, and audio equipment, quality assurance is necessary to avoid expensive part recalls. For this reason, automotive manufacturers must maintain a method to monitor and verify the quality of every unit produced. As in this example, a versatile end-of-line tester helped us achieve high-reliability quality verification.
We developed a Windows XP-based turnkey tester using National Instruments data acquisition and image acquisition hardware. We used motion control to position the buttons on the face of the UUT and beneath a series of CCD cameras for pneumatic operation. We did this to verify the UUT operation and detect the presence of cosmetic defects as well as button orientation and position. With the system software, we could train the station via a series of diagnostic and scenario-generation utilities for new UUTs without making any changes to the existing software. The scenario-generation utilities worked not only for the vision requirements but also for the communication messages, protocols, and UUT button responses. Using a Windows-based PC, we developed a test station with flexibilities that would be difficult to achieve with other technologies.
Identifying Mechanical and Communication Defects
Our initial challenge in testing these units involved loading and properly positioning the UUT. We needed to access the UUT throughout multiple tests, inspected it with a CCD camera, and activate its buttons and dials in a controlled manner. We mounted the fixture to an electrical slide that moved the UUT and the camera into multiple positions (including load position). We then placed the UUT beneath the ceiling of pneumatic actuators that we used to automatically press a variety of buttons on the UUT.
We primarily designed the PCI-based test system to observe the button press response through a variety of communication protocols such as CANBUS and J-1850. We provided a total of 42 pneumatic actuators to control the button presses and unit knob actuation, including a nine-position joystick. We activated each of these pneumatic actuators via a reed relay controlled from digital outputs on an NI E Series DAQ card interfaced to a previously developed relay driver circuitry. We provided a parts-scribing unit to mark each passing part upon test completion.
We used the NI PCI-1409 image acquisition board, which was an excellent cost savings solution, to implement multiple cameras in this tester. Each of the four cameras in the system meant the vision portion of the software could analyze different sections of the UUT. We used different cameras to observe LEDs on multiple objects, such as the buttons and knobs. In addition, we used the different cameras to verify various sections of the UUT for cosmetic defects and proper parts placement and orientation. We used the OCR software and advanced image acquisition analysis software to identify text and verify the button responses on the LCD display.
We developed a user interface so that the test engineers could teach multiple UUTs to the test station, each with multiple regions of interest. Then, we utilized these patterns to test parameters including LCD character generation, button physical position (within 1 mm), silkscreen application and defects, and proper LED backlighting.
Customizable Engine with Low Overhead Lowers User Intervention
We developed a LabVIEW-based engine to perform several different test modules from various setup panels, which we access from a network location to allow the assembly line to operate while new parts were added to the system, or as existing parts were modified. We designed the software with minimal overhead while the system exchanged information from one test VI to the next. This meant that the system could perform all tasks as quickly as possible, and it minimized the time between test calls. This architecture resulted in a system with a very low UUT test time (about 35 seconds), which saved the customer money.
The LabVIEW-based test engine had many features with which the system could compute test time, unit statistics, part statistics, and automatically log data. We employed user passwords and permissions to limit operator activity to the appropriate test system sections. Also, the test manager could export and further analyze data formats, such as images and graphs, at his or her discretion. We completed the tester with a powerful set of diagnostic panels to perform both test station and UUT operation verifications.
Cycle Time and Reliability Achieve Major Cost Savings
With cycle times of approximately 35 seconds and a tester that did not have to be taken offline for simple updates or adding new UUTs, this end-of-line tester could test up to 1,000 units a day. Also, by having a completely automated test sequence, the test operator only needed to initiate the tester, which then completed the testing in a fully automatic fashion, allowing the operator to complete other tasks as the system was performing its test. When we compared this tester to the manual testing we had previously used, this tester presented an immediate cost savings to the customer.
For more information, contact:
Radical Systems, Inc.
3313 Memorial Parkway
Suite # 150
Huntsville, AL 35801
Tel: (256) 883-9791
Fax: (256) 883-4030