Product performance test results.

Automated test equipment using the latest technology allows manufacturers to bring higher quality products to the marketplace at lower cost. Utilizing the power of standard personal computers and single board controllers, automated production testing systems a battery of tests and provide a tracking system that allows long-term data storage of test results for further analysis and plant-wide access through a Web-based interface.

Using a PC as the main system controller eliminates maintenance concerns associated with custom testing platforms and also allows for the creation of intuitive, familiar user interfaces. Setup and diagnostic utilities reduce down time.

Automation streamlines the production process with automated kickoffs and barcode tracking. With a central tracking system interfaced to the conveyor control PLCs, a bad unit can be identified and sent to repair without any operator action. Fixed barcode scanners read the unit’s serial number and, with the unique identifier, the tracking system can verify the unit has passed necessary tests. Kickoffs at various stages of the production process send the unit to repair at a stage where repairs can be performed efficiently.

With a touch screen interface and the same hardware as an on-line tester, the repair operator has instant access to the results of tests performed on a unit and the diagnostic tools required to fix the problem. Once repaired, the unit is returned to the line.

Safety testing

Delta temperature results.

One of the most important aspects of production testing is assuring the product meets all applicable UL and BEAB agency standards. At various phases of the production process, ground bond, hipot and line-line short testing is done. To prevent extensive repairs in the case of a problem, a typical test system performs safety tests after key components or assemblies are in place. In the case of a refrigerator test system, the entry point to the test system begins after the sealed system is assembled and installed. Initial safety testing is performed prior to the charging system. It is much more expensive to correct a problem such as shorted compressor windings once the system is charged and sealed.

As more screws are driven and more assemblies are added to the product, it is important to identify problems early in the process to prevent repeated defects from causing a rework bottleneck. If a screw inadvertently pierces a wire causing a short in the product, the safety test portion of the test system will identify this and send the unit to repair.

Functional testing

With an increasingly wide array of products run on the same production line, it is important to identify that the proper components are installed in a specific model. This is achieved by isolating the critical components and applying Resistance, Watts, Current, and VARs tests. Using a PC interfaced to Watts, Current, and VARs transducers, the components are activated either by the operator or by the PC interaction.

Many new products contain on board computers controlling the functions and operation of the product. For these “smart” products, functional testing can be further automated by linking directly to the product and issuing commands to activate components. In a refrigerator, for example, the unit’s control can be commanded to activate the defrost heater, allowing measurement devices in the tester to confirm that the right product with the right quality characteristics is installed correctly. The characteristics are logged as a test result and stored for trending to define predictable process changes internally and externally.

In the case of a reject, the data is used to help the repair operator identify and correct the problem.

Once the defrost heater wattage has been verified, it is deactivated and the wattage is verified to correspond to the off state. All the components will be verified for operational characteristics. The data is retained for future reference.

Performance testing

Performance testing often requires that a product be run for an extended period of time to verify that the fully assembled unit is operating correctly. One example is a refrigeration test system. In this case, to verify quality, the unit is run for a period of 25-45 minutes to check that the sealed system, compressor, fans, and all other critical components are functioning correctly and to confirm the cooling rate. The challenge here is to create a system that provides an extended run time for the product without slowing down the production process.

This was accomplished by means of a “test loop” that powers up refrigerator and runs it for 20 minutes. Each refrigerator is connected to a single-board, computer-based tester traveling with the unit. The single-board computer communicates with a central computer via wireless transmitter stations so that the single-board controller knows the limits for the product undergoing performance.

To initiate testing, the single-board controller issues serial commands to the product to start running in normal run mode. The controller then queries the unit’s on-board thermistors, again using the serial link to the product. Every 30 seconds during performance testing, the thermistor values located inside the unit are recorded, as well as a wattages and power-factor reading. These values are logged and transmitted to the central computer via a wireless modem. With this data, four temperature curves, Watts and VARs can be graphed and compared to ideal units to verify that the sealed system is operating correctly. This prevents defective refrigerant systems from being shipped to the consumer. The example illustrates how an automated production test system can improve both quality and productivity.