Method of making a compact fluid coupler for thermal inkjet print cartridge ink reservoir

A method for forming a compact, leak-resistant joint between first and second moldable materials which define the frame of an ink-jetprint cartridge, the first material comprising a moldable rigid plastic and the second material comprising a moldable plastic characterized by a shrinkage rate as said second material cools, comprising a sequence of the following steps:

• molding said first material into a predetermined first shot reservoir frame structure defining at a snout end thereof an interior standpipe member through which a channel opening extends, said channel opening for carrying ink in a liquid state from an ink reservoir to a printhead region of said cartridge;
• positioning said first shot structure in a second shot mold, said mold comprising first and second mold halves which can be closed about said first shot structure and define a portion of one or more mold cavities into which said second material is injected under pressure, and which can be opened upon cooling to permit removal of a molded structure therefrom, wherein a portion of said first shot structure also defines a portion of said one or more mold cavities, and wherein the second shot mold is provided with a channel mold pin for extending through said channel opening to prevent said second material from entering said channel during a second shot molding step, and with a cavity mold pin which extends across said channel opening, said channel mold pin stopping against said cavity mold pin;
• injecting said second moldable material in a molten state into said mold as a second shot wherein said second material surrounds said standpipe member, said second material having a shrinkage rate as said material cools, and wherein said first shot structure comprises one or more shutoff surfaces against which said mold halves bear when closed about said first shot structure, and thereby shuts off a path for said molten second moldable material to flow when injected into said mold;
• permitting said second material to cool, whereupon said second material shrinks about the periphery of said standpipe member, thereby forming a leak-resistant seal between said first and second materials about said standpipe, said seal resistant to leaks of said liquid ink out of said standpipe and resistant to air leaks through said seal into said reservoir.