Inkjet printers require a certain distance between the inkjet print head and the paper. If the distance is set incorrectly, the printed images get blurry. Current state of the art printers have the print head nozzles built right into the bottom of the ink reservoir (B) as shown below. When the ink cartridge is installed in the printer, the inkjet nozzles (made out of silicon) essentially become a grounded target through the connections shown at (A) Common inkjet printer head:

print head height measurement

The print cartridge sits in an ink cartridge holder, which sits on a sliding rod. The rod is then adjusted to be a specific distance over the paper media.

The opportunity: 
A system integrator approached MTI for a solution on automating the inkjet cartridge height gap measurement. The measuring range had to be approximately 2 mm; the resolution needed to be less than a micron. The probe needed to be able to be slipped in under the ink cartridge head, and held securely in place while the sliding bar is adjusted.
gap measurement
The solution: 

MTI proposed a custom 500 µm range probe with 4X range extension. The probe configuration was a PCR / PSR pancake style probe, so the probe would easily fit under the ink cartridge. Next the system integrator worked with MTI to design a secure probe holding fixture that mated securely to the printer platen/base plate.

500 micrometer range

Since two channels were needed, to adjust both sides at once, MTI recommended the Accumeasure 9000 dual channel amplifier. The system integrator added a data acquisition system and wrote a program that indicated the gap visually to an assembler, so the sliding rod height could be quickly and accurately adjusted.

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