Headless ATE system increases production reliability and efficiency
Rob Putala, Bloomy Controls- June 18, 2012Many manufacturers use manual test equipment that consist of standalone COTS (commercial-off-the-shelf) test instruments, such as digital multimeters, oscilloscopes, and hipot testers. COTS test instruments often require configuration and programming using their front-panels. The required sequences of button presses to program these instruments through multiple selection menus can be cumbersome, prone to errors, and subject the test process to test inconsistency. Quality control processes are driving manufacturers to automate test equipment to ensure consistent configuration control and data collection.
PC-based ATE (automatic test equipment) systems often provide control of the testing process, manage instrument configurations, increase test throughput, and address the issues associated with manual test. Although PC-based ATE is widely accepted, many manufacturers still test manually. PC-based ATE systems deploy a PC with each test system, which requires a minimum level of operator skill level and IT maintenance. For bench-top systems, the keyboard, monitor, and mouse occupy precious space on the production floor. Operator skill level and language barriers may necessitate significant training for some manufacturers. In particular, setup and configuration during product changeover can be challenging. Also, operators using PC-based ATE systems can be distracted by the accessibility of web browsing and other PC software. Responsibility for IT administration of PCs on the production floor is a gray area at some organizations. These issues can lead to operator error, inefficiency, and inconsistency in the testing process.
Headless ATE System
Engineers at Bloomy Controls developed a headless ATE system that is simple to operate and doesn't require PCs on the production floor. The system is headless because it doesn't need a keyboard, monitor, touch screen, or mouse. Instead, it contains a physical interface comprised of a few mechanical buttons, LEDs, and optional barcode scanner. A supervisory application, located on any PC connected to the manufacturer's LAN, can monitor and manage multiple headless ATE systems. The supervisory application provides managers with the opportunity to control configurations sent to each headless ATE system, and track the efficiency of each station, production line, and operator.
The Headless ATE System uses a three-unit (3U) rack-mount cabinet with a 1U shelf that contains a NI Single-Board RIO running LabVIEW, a power supply, and operating panel. In addition to the 1U shelf, the cabinet contains the COTS test instrument(s) as needed for each test system. Figure 1 shows the system, which, in this application, uses an AC power source. The majority of COTS test instruments are found in 1U and 2U form that will fit into a 3U enclosure. The headless ATE system contains a clock that time-stamps test activities that a supervisory application can record.
The headless ATE system contains only the most basic operator controls, such as "Start," "Stop," and "Retest." These controls are implemented using large mechanical buttons on the front panel, which can be configured and modified to meet the needs of the test process. The buttons are clearly labeled and glow with LED lighting. Green and red LED indicators, labeled "Pass" and "Fail," inform the operator of the test result. The front-panel buttons combined with an optional barcode reader is the only operator interface. Consequently, the headless ATE system requires minimal operator training and eliminates the PC and associated maintenance. The headless ATE system in Figure 1 contains a 2U COTS programmable power supply. The buttons are clearly labeled in order of "Test," "Stop," and "Retest."
Figure 1. The headless ATE system uses a 3U cabinet containing NI Single-Board RIO, a power supply, and/or one or more COTS test instruments.
The buttons and LEDs are monitored and controlled by a Single-Board RIO's (Figure 2) digital I/O port. The NI Single-Board RIO contains a real-time processor, an FPGA (field-programmable gate array), and analog and digital I/O. The board also provides integrated communications via Ethernet, USB, CAN, RS-232 and other protocols, which control the COTS instruments, communicate to the UUT (unit under test), and connect to the supervisory PC.
Figure 2. The NI Single-Board RIO embedded controller provides analog I/O, digital I/O, and communication to test instruments, UUTs, and to a network.
The supervisory application gives production managers the opportunity to monitor multiple headless ATE systems and provides central control of the instrument configurations and data collection. Managers can install the supervisory application on a PC in their office or any PC in the production facility and immediately gain control over the test process. Regardless of the number of headless ATE systems that a manufacturer deploys, every test sequence and setting is displayed and controlled from the supervisory application. Also, the headless ATE system and the supervisory application are readily scalable and easy to use for multiple production cells. New headless ATE systems can be automatically detected and configured by the supervisory application as soon as they are added to the LAN. Likewise, if a headless ATE system is disconnected from the LAN then the supervisory application detects it and alerts managers via email. The ability to configure all of the headless ATE systems from the supervisory application eliminates operator error in setup or product change procedures. Each headless ATE system sends test results, calculations, and any other desired data to the supervisory application, where it is displayed, analyzed, and stored in a database. Figure 3 is a block diagram that illustrates how headless ATE systems are controlled by the supervisory application.
Figure 3 Multiple headless ATE Systems can connect to a network through an Ethernet switch, supervised by a host computer over a LAN.
The headless ATE system timestamps and records all test activities, which provides accurate calculations such as yield or test throughput. The time-stamped data lets the supervisory application track operator efficiency at each test station. The test results, yields, SPC (statistical process control) analysis, and operator efficiency are all viewed through the supervisory application, which connects to the production database. Figure 4 contains the SPC display screen, the supervisory application that production managers frequently view. It displays a Histogram, Pareto chart, and X-Bar & R SPC charts based on the data recording from the test process.
Figure 4: The supervisory display screen contains a Pareto chart (lower left), histogram (upper right) and SPC X-Bar chart (upper left). Click on image to enlarge
The supervisory application can generate alerts and alarms throughout the test process. Emails can be sent to a list of supervisors to inform them that an event has occurred. An example of this is having an alarm sound when three consecutive UUT failures occur on any one system. An alarm can trigger an email to production managers when yield drops below a specified value. Figure 5 is the ATE Supervisor's System status-display screen, which displays the status, operator ID, and test times of each headless ATE system on the LAN.
Figure 5. ATE Supervisor's System Status display screen shows each headless ATE system on the network along with test statistics. Click on image to enlarge
The headless ATE System provides an extremely simple operator panel that reduces the possibility of operator error, and minimizes operator training. The supervisory application provides repeatable setup of the headless ATE systems and test sequences, as well as error-free data recording and analysis. Real-time SPC reporting and analysis allows production managers to view the data at any time from any designated PC on the LAN, and receive alerts when there are significant changes in the process or operator efficiency. Simplifying the operator panel and centralizing the setup and configuration of multiple headless ATE systems, the overall system dramatically improves reliability of the test process.
Rob Putala is a senior project engineer at Bloomy Controls. He holds a BSEE from Michigan Technological University and an MBA from Notre Dame University. He previously worked as a test engineer at MKS Instruments and as engineering manager at Digital Equipment Corporation. E-mail: firstname.lastname@example.org.