Automated assembly and testing of HP DeskJet 1200C print cartridges - ink cartridges for HP DeskJet 1200C and HP DeskJet 1200C/PS printers - Technical

Hewlett-Packard Journal, Feb, 1994 by William S. Colburn, Randell A. Agadoni, Michael M. Johnson, Edward Wiesmeier, III, Glen Oldenburg

The assembly system is flexible and modular. A performance monitor collects data for quality control. A standardized print engine is used in several applications.

As volume requirements for print cartridges increase beyond the capability of laboratory tooling, the need for an automated assembly system becomes apparent. The automated assembly system for the Deskjet 1200C print cartridge is designed to meet a set of objectives that includes autonomy through distributed control, flexibility of assembly process order, and efficiency through commonality of designs and components.

Each process station or small group of process stations has the ability to operate in a stand-alone mode. In this manner, many tools can be debugged and qualified simultaneously without reliance on one large controller. The design of the assembly system allows processes to be added, subtracted, or relocated without significant disruption of the line.

The assembly system is designed around a common set of tooling philosophies and component selections. Designs such as those for print cartridge fixturing mechanisms follow a common concept from tool to tool. In this way, discoveries made on one tool can be easily leveraged to other tools and processes online.

Modules of the assembly system are based around a common tooling platform (see Fig. 1). This approach has helped the team to achieve many of the objectives of the project early on, including integration of material handling, local process control, and management of electrical, pneumatics, and plant vacuum into a standardized design. As a tooling platform nears completion and is ready for qualification, all facets of tool operation can be verified before the tool is installed in the assembly system. Should the need arise to add or relocate a process, tooling platforms can be easily disconnected and moved. A common facilities interface for each platform ensures that a platform can be moved anywhere on the line with minimal impact on adjacent processes. The inherent flexibility of the assembly system has allowed reconfiguration of the line over a weekend with a seamless production startup on the next working day.

A programmable logic controller (PLC) is responsible for monitoring the status of sensors and switches within a platform, the state of guards and shielding, and operation of the pneumatic cylinders, motors, and other peripheral devices used to perform the assembly processes. Input/output flexibility within the PLC allows the same controller to switch TTL logic levels as well as high-current ac loads. In cases where specialized processing capability is required, such as for machine vision measurement for an inspection process, a dedicated controller is used to perform the function and provide a simple go/no-go response to the PLC. The distributed nature of the control system allows many different types of work to proceed simultaneously. For example, an engineer can be qualifying one part of the line while a technician updates code on an adjacent tool.

Factory Performance Monitor

A factory performance monitor system monitors and reports on factory productivity measures such as yields, efficiency, throughput, up time, down time, cycle time, scrap, and production volume. The overall system employs a distributed, client/server architecture and is composed of several programs running on different platforms (PCs and workstations) communicating over a local area network (LAN).

Each tool's PLC maintains a standard set of data including good parts in and out, run time, wait time, down time, cycle time, machine downs, mean time between failures, mean time to repair, and mean time to respond. The PLCs are networked together along with a PC host machine. A program running on the PC continuously queries the production data table on each tool, performs calculations, formats the data and sends it as a package to a server program returning on a separate workstation. The server program receives the data package and makes it available to client programs via the site LAN.

The client program for end users comes in two windows-based flavors: a Microsoft(R) Windows version for desktop PC users and an OSF/Motif version for workstations or X terminals on the factory floor. After connecting to the server, clients receive data packages and update a graphical view of the factory, using buttons that change color to represent each tool and its current status (running, down, or waiting for parts to process). When a tool button is pressed using a mouse pointer, a window pops up to display a real time summary of that tool's performance. A top-level menu is used to select options such as module or overall line performance, to set alarms, or to review production summaries of previous shifts.

Additional client programs are used to pull periodic summaries of production data for reporting and database archiving. The information from this system has proven to be indispensable in managing the factory, identifying areas for improvement, and planning.