Patent Application
20060203038
The present embodiments relate generally to electroforming of complex shaped ink jet print heads.
Electroforming is a technique used to make intricate precision structures that are difficult to fabricate by other processes, such as machining. Useful devices, such as wave guides and printing screens, have been made by electroplating onto a preformed shape and subsequently selectively removing the shaped structure or mandrel to leave a free standing part made from the electroplated metal. When good corrosion properties are required, nickel works very well as the electroplated metal.
Drop generators for full page width print heads of 8.5 inches or more are difficult to fabricate by ordinary machining methods. As shown in Wood U.S. Pat. No. 4,999,647, the preferred drop generator shape is long and narrow. The channel for ink delivery has a specific and well defined geometry, as shown in
Other solutions simplifying fabrication of internal passages include symmetrically dividing the drop generator into two machined halves and then brazing these two together to make the whole part. This solution cannot be done with long narrow drop generators due to warping that occurs from exposure to high brazing temperatures.
A need exists for a method to fabricate reproducibly the internal cavities of the drop generator smoothly and without irregularities that normally occur in machining.
The present embodiments meet this need.
Embodied herein is a method for fabricating a drop generator. The method entails identifying a non-conductive dimensionally stable structure with a shape adapted to define a fluid cavity for the drop generator for an ink jet printer. The structure includes at least one portion to be formed into a channel for a drop generator and at least one portion to be formed into a slot for transferring fluid from the channel to an orifice plate. Caps are added to each end of the structure and a conductive base is mounted to each non-conductive dimensionally stable structure surrounding the portion to be formed into a slot.
The method continues by electroforming metal from the conductive base to encapsulate the non-conductive dimensionally stable structure between the caps to a thickness at least equivalent to a desired outer dimension. The caps and the non-conductive dimensionally stable structure are removed from the encapsulated structure, thereby forming a drop generator with a channel adapted to receive fluid and a slot adapted to communicate fluid from the channel to the orifice plate.
The present embodiments are advantageous over known techniques because the methods are easy to implement, multiple parts can be formed in one session, and the straight channels are smooth without defects to block channels and slots that feed ink to the nozzles of the ink jet.
In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which:
The present embodiments are detailed below with reference to the listed Figures.
The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.
The present embodiments relate to methods for making drop ejection devices (i.e., drop generators) having long, smooth, and straight internal bores. The methods and resulting apparatus are useful for metallic inkjet printer manifolds. The methods can be useful for other devices that require precision internal geometries, such as waveguides, as well.
Typically, inkjet printer manifolds are difficult and expensive to machine. Internal passages of machined manifolds are difficult to clean due to retained machining chips and recast layer.
The methods herein provide a method to electroform channels in substrates to form drop generators which are less expensive and more versatile than those conventionally available.
Channels that are made by electroforming are inherently free of machining debris. For example, a typical manifold costs hundreds of dollars to machine from a solid block of metal, whereas the cost to fabricate an electroformed structure with internal channels using the embodied methods costs up to twenty percent less, because numerous machining operations are eliminated.
The embodied methods provide more reliable printheads at lower costs.
The methods herein are used to create a uniquely formed non-conductive structure or mandrel, which when encapsulated with electroplated metal, shapes and defines the internal ink channel of a drop generator. Subsequent removal of the mandrel and the dimensionally stable structure provides a smooth and straight internal passage.
An embodiment of a method for fabricating a drop generator entails identifying a non-conductive dimensionally stable structure with a shape adapted to define a fluid cavity for the drop generator for an ink jet printer. The structure includes at least two portions. The first portion of the structure is formed into a channel for a drop generator. The second portion of the structure is formed into a slot for transferring fluid from the channel to an orifice plate. The ends of the structure are covered with caps.
A conductive base is mounted to the non-conductive dimensionally stable structure to surround at least part of the portion of the structure used as a mandrel for forming a slot to transfer fluid from the channel to an orifice plate. The conductive base can alternatively contain a cavity to receive the structure. The conductive base is preferably mounted so at least a section of the slot in the structure is disposed between a first part of the base and a second part of the base.
The method continues by electroforming metal outward from the conductive base to encapsulate the non-conductive dimensionally stable structure between the first and second caps to form an encapsulated structure. The metal is electroformed onto the structure to a thickness that is at least equivalent to a desired outer dimension. The thickness of the metal from the conductive base to encapsulate the non-conductive dimensionally stable structure is preferably at depth that can sustain machining of the encapsulated structure in order to form the exterior of the drop generator. Examples of metals used in the electroforming step include copper, nickel, gold and other metals. Nickel is the preferred electroform material for forming the drop generator.
The caps on the ends of the structure are composed of a non-conductive material adapted to shield the first and second ends from electroforming metal.
The method continues by removing the first cap and second cap from the encapsulated structure and removing the non-conductive dimensionally stable structure to form a drop generator. The formed drop generator includes a channel adapted to receive fluid and a slot adapted to communicate fluid from the channel to the orifice plate. The step of removing the nonconductive structure is typically performed by etching, vaporizing, melting, dissolving, or combination thereof.
The method can include the step of machining the encapsulated structure in order to form the exterior of the drop generator.
With reference to the figures,
In order to form the drop generator desired, a positive replica of the channel and slot is created from a material that can later be removed by selectively etching from the electroformed material.
A conductive base 24a, as depicted in
The embodiment in
The metal portion 38 is preferably an etchable, dimensionally stiff material, such as aluminum, steel, nickel, copper, and combinations thereof. The metal portion 38 can be a dissolvable or vaporizable material. The metal portion 38 can be a brass sheet. The metal portion 38 can be placed between the two layers of non conductive film 40. The metal portion 38 can be segmented.
As discussed above, the non-conductive dimensionally stable structure 10a can be a metal tube wrapped with an adhesive-coated polyimide material, preferably Dupont Pyralux™ LF0220, to make the structure 10a non-conductive. The adhesive-coated polyimide material provides a smooth non-conductive surface for the inner bore of the drop generator. Pyralux™ is typically used in the fabrication of flexible electrical cables and has a B-stage acrylic adhesive on the inner side that does not become tacky until heated to 250 F. The Pyralux can be stretched around the structure or mandrel and clamped around the metal portion 38. The nonconductive dimensionally stable structure 10a is then formed by heating the wrapped substrate to about 200 F and at least 250 psi pressure in a heated platen press to form a very rigid tube and fin structure upon cooling.
Producing electroplating in great thicknesses requires that fresh electrolytes be provided uniformly to all areas of the part being plated. The method contemplates that at least four drop generators can be made simultaneously, but the method is not limited to four assemblies and can be constructed with one or more.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
