Case Studies

Customer Solutions

Lexmark Improves Measurement Accuracy of Ink Cartridge Test

Author(s):

Ed Coleman, Lexmark International Inc

Industry:

ATE/Instrumentation

Product:

LabVIEW, Modular Instruments, Oscilloscopes/Digitizers, PXI/CompactPCI

The Challenge:

Improving the measurement accuracy and digital I/O rate of an inkjet cartridge electrical test.

The Solution:

Upgrading an existing PC-based test instrumentation to use the matched 100 MHz mixed signal suite including the PXI-5122 high-resolution digitizer and PXI-6552 digital waveform generator/analyzer.

At Lexmark, we are a global developer, manufacturer, and supplier of printing solutions. These include laser and inkjet printers and associated consumable supplies for the office and home markets. Companies in the highly competitive printer market rely on high volume production and short time-to-market cycles with a critical focus on managing costs to maintain margins. In this environment, test engineers must develop test systems quickly for high volume production. Total system cost and maintenance is a concern for us because we must replicate and deploy the test system for the inkjet product line in manufacturing plants worldwide. For this reason, we chose a PC-based solution to test ink cartridges used with the inkjet family of printers, including the Lexmark P707, Z705, Z605, Z65, X5150, X6150, X6170 models

Starting from the Beginning
In 1997, we began using the National Instruments NI 5102 digitizer installed in a PC, and developed the tests using LabVIEW. The NI 5102 PCI digitizer features 8-bit resolution and a 20 MS/s sampling rate. For testing the ink cartridge, the NI 5102 sequentially measured the resistance of more than 200 inkjet nozzles. We stimulate the cartridge using a custom designed digital driver card that emulated the digital patterns typically generated by the printer. We pulled the current through a single resistor connected to an operational amplifier (Op Amp), and the NI 5102 measured the output of the Op Amp. Another requirement for the test systems was that each nozzle could not be stimulated longer than 1 s. Otherwise, the nozzle would be damaged. A PC-based solution, combined with a digitizer, is capable of acquiring an accurate signal in that 1 µs window.

In 1999, we met more stringent test requirements of improving quality and increase production yield by integrating the NI 5911 flexible resolution digitizer with 12 bits of resolution at a sampling rate of 12.5 MS/s. The migration from the NI 5102 to the NI 5911 was straightforward, as both digitizers used the same driver software.

Meeting Today’s Demands to Increase Speed and Accuracy with the NI 5122 and NI 6552
In 2003, we upgraded to the NI 5122 PXI-based digitizer with 14-bit resolution and 100 MS/s sampling rate. Not only did the NI 5122 exceed our speed and accuracy specifications, but we were able to preserve our investment in the automated test software. Using the shipped examples, the existing software for the 5102 was easily updated to run the 5122. We continue to use the same software developed for the NI 5102, while evolving to meet our current and future test requirements with the NI 5122 high-resolution digitizer.

We need high-speed digital I/O to drive the inkjet print head for the resistance measurements. Once again, National Instruments products delivered the performance we require while minimizing equipment costs. In 2001, we migrated to the NI 6534 high-speed digital I/O card away from alternative solution that was three times as expensive. This has led to an aggregate savings of several hundred thousand dollars. Using the NI 6552 100 MHz PXI-based digital waveform generator/analyzer, we have upgraded the test system in a few weeks by taking advantage of the intuitive programming interface and more than 40 shipping examples. Alternative solutions were higher cost, required longer development times and did not have the required 10 nanosecond resolution.

Transitioning Made Simple
We continue to adapt our test systems to meet our latest requirements with minimal development time with the use of PC-based modular instrumentation and industry standard software. Upgrading to the NI 5122, NI 6552, and , we increased the quality of our products and production yields while increasing our test performance with minimal development expense.

For more information, contact:
Ed Coleman
Lexmark International Inc
Phone: 859-232-2803
E-Mail: Coleman3@Lexmark. Co.

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