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

The platform includes all of the parts of the print cartridge except the printhead assembly and the ink. It is designed to accept different printheads and inks to support different printer applications. It features a slim form factor, a spring-bag ink reservoir, and an ink level indicator.

The print cartridges for the HP Deskjet 1200C printer and the HP Deskjet 650C large-format drafting plotter (Fig. 1) are derived from a common ink delivery system "platform" to which are added different TAB (tape automated bonding) and printhead assemblies and inks. The platform includes all parts of the print cartridge and packaging except the TAB/ printhead assembly and the ink, and brings the following key benefits to printers and customers:

* Flexibility for a wide range of printheads, printing down or sideways

* Slim form factor to reduce the footprint and cost of multi-cartridge printers

* Volumetrically efficient "spring bag" ink delivery with tunable backpressure and ink design independence

* User-friendly ink level indicator usable in and out of the printer

* Ink containment robustness under environmental conditions (thermal, altitude, shipping), combined with environmentally sensitive packaging

* Assembly process improvements such as two times better head alignment and online print quality Inspection.

The primary emphasis during development of the platform was design for manufacturability and assembly. This emphasis was key to achieving at least three of the four platform goals. The first goal, to achieve both large capacity and fast time to market, was achieved through simultaneous design, process development, and tooling from the beginning of the project, by early concurrent engineering with vendors, and by the use of "demo tools" for early demonstration of assembly processes and cycle times. The second goal, low cost, was achieved by reducing complexity in parts, processes, controls, and non-value-added steps, by leveraging proven HP assembly processes and designs, and by focusing on manufacturing cost drivers such as tolerances and direct material cost. The third goal, to ensure manufacturability for automated assembly, was achieved by means of "seam teams" made up of R&D and manufacturing engineers and charged with maximizing design for manufacturability and assembly, by organizing the manufacturing line module teams at the start of the project, and by including vendor engineers on the platform design team early in the project. The fourth goal, to meet the needs of multiple cartridges and products, was achieved through a design convergence team for multiple printers sharing the platform, and seam teams for cartridge and primer issues.

Seamless and Concurrent Engineering

The design for manufacturability add assembly emphasis was implemented in several ways. The platform engineering team was formed nearly fully staffed, with strong manufacturing influence from the start. The overall team included both R&D and manufacturing engineers and managers. Engineering responsibilities were seamless, with no distinction between R&D and manufacturing engineers. Individual engineers owned broad part design, assembly process development, and tooling responsibilities throughout the project. In this way, design for manufacturability and assembly comes naturally since each engineer designing a part is also developing the assembly processes for that part, and will be responsible for the manufacturing machines to assemble that part. A second way that the design for manufacturability and assembly emphasis was implemented was through the active concurrent engineering involvement of experienced manufacturing equipment vendors. The vendors' highly experienced engineers were an integral part of the platform design team early. Each month, the vendors' engineers participated in intensive working design review meetings. Between meetings, HP and vendor participants designed and investigated alternatives in preparation for the next joint working session.

Convergence of Platform Design Concepts

The key purpose of designing a platform print cartridge was to enable one common design to satisfy multiple customers in both the office printer and large-format markets. The requirements were to design a low-cost platform in terms of parts and assembly, yet allow for various TAB/printhead assemblies and inks for different products. A narrow form factor in the scanning direction was essential to allow multicartridge products a compact desktop footprint. Compatibility with the range of ink types needed for different product applications was also required, preferably decoupled from ink interactions altogether. To accommodate the different ink and architecture needs of different products and applications, the platform's ink delivery starting backpressure needed to be adjustable, both in engineering and on the manufacturing line. Moreover, the overall platform had to be robust and reliable for all products and all customers.

Immediately at the start of platform development a process was needed to set t, he fundamental design direction quickly for fast time to market, to resolve issues and select among competing concepts, and to ensure that the platform would meet the needs of multiple office printers and large-format plotters. The fundamental platform design direction needed to be set concurrently and interactively. The process used was the convergence team. Functioning within weeks after the project's start, the platform convergence team included representatives from each of the print cartridges and each of the printers. The team met weekly until the key design concepts that strongly affected both print cartridge and printer design were resolved. The key design areas addressed by the platform convergence team included: