Development of the HP DeskJet 1200C print cartridge platform - includes related articles on ink cartridges for large-format color plotters and of design of print cartridges for environmental responsibility - design of ink cartridges for HP DeskJet 1200C and HP DeskJet 1200C/PS printers and HP DesignJet 650C plotter - Technical

Hewlett-Packard Journal, Feb, 1994

* Dot-to-dot alignment requirements, modeling, and effects on print cartridge head and body alignment and printer carriage alignment

* Different print-cartridge-to-carriage alignment datum systems, and their effects on cartridges and printers

* Print cartridge operating orientation in different printers and plotters

* Disposable print cartridge ink volume trade-offs for cost per copy, printer size, and carriage acceleration

* Minimum print cartridge width (printer footprint) consistent with other needs

* Print cartridge form factor aspect ratio (depth-to-height ratio) and related form factor of printers and plotters

* Electrical interconnect configuration and compliance concept

* Ink level indicator needs for each printer and resultant design objectives.

Convergence of the platform design concepts allowed definition of a focused set of design goals to meet the overall platform goals of large production capacity, fast time to market, low cost, manufacturability, robust quality and multiple uses:

* Minimum number of parts and processes

* Narrow form factor for office desktop printing

* Precision alignment to meet print quality goals

* Reliable system electrical interconnect solution

* Inert ink reservoir with tunable backpressure

* Maximum delivered ink volume within narrow form

* Robust leak-free ink containment through shipping and drops

* Ink level indicator for users

* Environmentally friendly minimum packaging

* Print quality tested to specifications

* Quality assurance processes designed along with the print cartridge.

Narrow Form Factor

To meet the objective of a small-footprint desktop printer, the print cartridge size needed to be minimized, especially the width. Narrow width had to be traded off against minimum size for the desired ink volume and printhead layout. From the product objectives, two distinct sets of design features were developed. These sets led to the development of a two-material frame that includes a back-end design to accommodate the ink reservoir assembly and a front-end design to accommodate the printhead assembly (see Fig. 2).

The first set of design features focused on the external geometry of the print cartridge. While it was our goal to minimize print cartridge width, this minimum is constrained by the printhead design and its flexible electrical interconnect circuit. In addition to space for the printhead assembly, room is required for carriage locating features and print cartridge service station functions. Finally, manufacturing tolerances and tooling features must be included to ensure ease of assembly. Besides space constraints, the external frame needed to be rigid for stability in the print cartridge carriage, to withstand temperatures of up to 70[degree]C, and for printhead attachment, to be manufacturable to very tight tolerances.

The requirements of the ink delivery system drove the second set of design features, which focused on the internal frame. The spring bag system required a heat-sealable material that was impervious to the ink and robust under environmental conditions, as discussed later. Tight tolerances and structural rigidity were less of an issue.