End-of-line testing is a final verification step / fail safe between you and your customer. We understand your reputation is on the line.
At Viewpoint, we’ve developed the software (and interfaced with the tester hardware) for over 800 end-of-line test systems, with some hardware involvement (e.g. NI hardware selection) for ~300 of those, and delivered the complete package (both hardware & software) for roughly 100 end-of-line test systems. All that is to say we know our way around end-of-line test.
Our client already had a test system in place, but the tester (really two test systems testing two different product variants) was becoming obsolete. The tester was old, hardware was failing, and it was getting harder and harder to keep it reliably running. They wanted a new tester to improve reliability, but maintain the functionality of the existing tester to keep the FDA-mandated verification and validation time to a minimum.
The updated end-of-line manufacturing test system maintains the functionality of the old test systems, but with updated hardware and software. The same software is utilized for both the manual test system update and the automated test system update. Our client deployed 6 manual testers and 1 automated tester.
- Improved maintainability and reliability with updated hardware and software
- Maintains existing test system functionality to keep certification time down
There were two variants of the new test system. One was for an older product line that utilized manual test, with an operator that connected/disconnected the UUT, and initiated the test. The other was an automated tester, integrated into a manufacturing machine. Both testers utilized custom fixtures (provided by the client), off-the-shelf NI measurement hardware (selected by Viewpoint), and custom test software (developed by Viewpoint). The software is configurable for both the manual test system and the automated test system.
|Read UUT limits from config file|
|Perform tester self-test|
|Measure UUT output|
|Perform leak down pressure test|
|PLC interface (for automated tester) for start, done, pass, fail|
|Custom test fixture (provided by client)|
|PXI Multifunction I/O Module|
|PXI Digital I/O Module|
|PXI Relay Module|
|PXI Digital Multimeter Module|
|PXI Switch Matrix Module|
*- images are conceptual, not actual
The client already had an existing manufacturing test system in place. They wanted Viewpoint to enhance the tester due to an increase in production volume demand. Viewpoint reviewed the existing test system and noted 3 areas for improvement:
- Automation available in the measurement instruments – most of the test equipment was automatable, via some combination of serial, GPIB, or Ethernet interfaces. Furthermore, some equipment, such as an oscilloscope, had the ability to store and recall setup configurations. The test operators already used these configurations to decrease setup time for the next test step. Most test equipment did not have automated setup.
- Operator time spent on each test step – the client had been through a Lean assessment and had already done a good job of timing operations. However, we specifically noted that the operator was manually connecting to the test points and manually transcribing to paper the measurement results from instrument displays.
- Automating the connections – many types of product models were being tested at this test system. Connecting the test equipment to all sorts of products would require either 1) many types of test harnesses and connectors or 2) a redesign of the products to make test connections simpler and quicker.
The enhanced automated test system included automation of instrumentation interfaces, a test executive to run the test sequences, automated test report generation, and automated test data archiving for the electronic UUT.
- Reduced total test time across several products by an average of ~25%.
- Time to create paperwork was reduced by ~2/3 due to automated data collection.
The enhanced test system included the following updates:
- Test sequence automation
- Automated test report generation
- Automated test data archiving
- Automation of instrumentation interfaces
- Configurable automated test steps associated with each type of measurement instrument. The test operators would create a sequence of steps to setup each instrument and record the resulting measurement. The sequence of steps could be saved and recalled for each product to be tested, so the instruments could be used automatically.
- New programmable meter – integrated the new DMM meter with a programmable interface to replace the one that was not automatable.
- Foot switch integration – Since the connections to the test points were manual, a foot switch allowed the operator to take the measurement and advance to the next step.
The StepWise platform managed the multiple test procedures created for the different products. StepWise also handled creation of HTML reports for every part tested.
|Test Data Archiving|
|LabVIEW RT – for managing the microcontroller functions and overall data collection and safety monitoring|
|Microcontroller application – to provide precision pulsing of the batteries|
|Communicate to the host PC – to both receive pulsing instructions and configurations and to return pulse waveforms for each battery tested.|
|MAIN HARDWARE COMPONENTS|
|PXI chassis & controller|
|PXI analog input modules|
|SCXI multiplexing switches|
|INTERFACES / PROTOCOLS:|
Important elements of a end-of-line testing equipment
Important elements for an end-of-line tester will vary somewhat based on whether it’s a high-mix/low-volume production scenario or a high-volume production scenario.
Common key elements of an end-of-line tester:
- Aggregate results – so you can look for efficiency gains and common component issues
- Verification that every step was executed, especially critical when traceability is important or required by your customer
- Reduction in operator errors by automating the setup and reading of any computer controllable measurement equipment
- Ability to identify prominent reject modes by analyzing the electronic records produced by the test station
Aspects specific to high-mix/low-volume end-of-line test:
- Combine step-by-step work instructions and step-by-step feedback from the operator along with semi-automated measurements. Merge the assembly instructions and testing steps into one system – so the operator doesn’t have to flip back and forth (ease of use and less prone to error).
- Track assembly status and test results across multiple assembly cells, due to different tests on the same part or subcomponent testing leading to final assembly
- Have a simple way to manage the work instructions for all the different types of parts you make – electronic docs simplify the setup of the assembly & test for each part so you don’t have to physically locate the assembly manual for the part being built.
- Cost savings based on increased efficiency in operator performance
- Coordinated test results according to a part’s serial number when a particular part is tested at several test stations
Aspects specific to high-volume production end-of-line test:
- # of changeovers: How much effort is involved in a changeover? Can aspects, such as test equipment reconfiguration, be automated?
- Up-time: Can maintenance of the test equipment, such as annual calibration and replacement of worn-out parts, be executed quickly? Are spare parts readily available for both COTS and custom tester components, such as cables and harnesses?
- Database organization: Is consideration being given to the performance of data archiving after several years of operation while the test system has stored huge amounts of data.