Method of fabricating low-cost transfix drums for solid ink transfer

A printer has a print head arranged to jet molten ink onto a surface, a transfix surface arranged to provide the surface for the print head, the transfix surface having a core and an outer shell of a predetermined grade of aluminum arranged on the core, the outer shell forming the surface for the print head. The printer also has a transport subsystem to transport a print substrate past the transfix surface such that the molten ink transfers from the transfix surface to the print substrate.

BACKGROUND

Solid ink jet printers typically dispense or jet molten ink onto either a print substrate directly or onto an intermediate transfer surface. In the case where the printer uses an intermediate transfer surface, the transfer surface typically consists of an aluminum drum made of a specific grade of aluminum, sometimes manufactured under the trade name ‘3003 A1.’ The particular grade of aluminum has appropriate ink-accepting and transfer properties to enable reliable operation of the print systems. The drum may be referred to as a transfix drum. The designation of 3000 means that the aluminum is alloyed with manganese. The particular alloy of 3003 typically has a range of 1.0 to 1.5% weight of manganese and a range of 97 to 98% by weight of aluminum.

Currently, the entire transfix drum consists of the particular grade of aluminum. This contributes to a large portion of the cost of the transfix drum subsystem, in some estimates up to 5/6thof the subsystem cost. However, the print system only needs the particular characteristics of the aluminum on the surface of the transfix drum, the entire drum need not be manufactured of that grade of aluminum.

One such approach would use inexpensive stainless steel tubing or other inexpensive material used in a variety of industries. These materials may have the desired diameter and thickness to ensure correct stiffness of the final drum. This drum would then receive a coating of the desired grade of aluminum such as electroplating.

However, metal deposition methods are inherently complicated when it comes to precisely controlling the presence of certain impurities that may be desirable. For example, the presence of manganese as an impurity with the grain structure of the aluminum imparts beneficial properties to the current transfix drum surface that play a critical role in the reliable operation of the print process. This would require process controls and precision that may result in the transfix drum costing more than if it were manufactured entirely out of the proper grade of aluminum.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1shows a solid ink jet printing system10using an intermediate transfer surface. The printer has a print carriage12having a print head14. The print head14dispenses ink onto the intermediate transfer surface16, in this embodiment a drum. The print head dispenses ink under direction of the controller24in accordance with image data stored in the memory26. The surface of the intermediate transfer surface16may receive treatment with a release agent20that allows any ink on the surface to release onto the print substrate22.

As the surface16moves, it contacts the print substrate as the print substrate passes by a roller18. The roller servers to transfer and fix, ‘transfix’ the ink on the surface of the drum to the print substrate. The intermediate transfer surface may be referred to as a transfix surface. The print substrate22may be routed by the rollers23aand23bto the roller18. The region where the substrate comes into contact with the intermediate transfer surface may be referred to as the nip.

FIG. 2shows one embodiment of a transfix drum40. The drum40has a core44that may consist of many different types of materials. In one embodiment, the core44may consist of steel or stainless steel that costs far less than the high grade of aluminum currently in use. The outer surface of the drum40consists of a shell42of aluminum. This allows the transfix drum to meet the necessary requirements for the printing system, while drastically reducing the costs.

The intermediate transfer surface has certain properties that make it more effective as a transfer surface. The surface must have a particular stiffness when pressed by the roller that brings the print substrate into contact with the surface, such as roller18. The surface cannot deform or flex in any manner that will affect the quality of the image being transferred to the substrate. The drum must have sufficient stiffness to prevent any flexing of the drum. For example, experiments have shown that any flexing beyond 1/1000 of an inch across the drum length can degrade image quality. This is merely provided as an example and is not intended to limit the scope of the embodiments or claims in anyway.

The surface must have a certain smoothness, such that the ink remains smooth and without divots or protrusions when it transfers to the substrate. Additionally, the surface must transfer as much of the ink as possible from itself to the paper, with no residue or ink remaining on the surface. This affects both the quality of the image, as any ink not transferred will reduce the vividness and clarity of the image, especially with regard to graininess.

One should note that in this embodiment, the shell42fits over the edges of the core44. The manufacturing process may use this approach, as it does eliminate issues with aligning the edge of an overlay to the drum if it does not fit over the edges. However, other methods of ensuring proper fit of the shell to the core may include undercutting a portion of the aluminum drum into which the shell would fit, having a grooved edge to which the edge of the shell mates, inlaying the shell to the drum, etc.

FIG. 3shows an embodiment of a manufacturing process to make a transfix drum having a core and an outer shell. A shell42of the appropriate grade of aluminum is formed. The formation may take many forms, such as extrusion, die casting, etc. The resulting shell has a minimum thickness and smoothness required by the printing process. The shell is formed in this embodiment such that the edges of the shell extend beyond the edge of the core and cover a portion of the sides of the core.

The aluminum shell is expanded to allow it to fit over the core, shown as42′. In one embodiment, the shell is temporarily thermally expanded. The shell then slides over the core44. The core44may have an array of holes such as37that penetrate the core to its center bore45. The center bore allows the core to be mounted on an axel to rotate. The sliding of the shell over the core may be aided by introducing a flow of air over the surface of the core. A pump33may have a nozzle35that inserts into the center bore45. This allows air to flow out of the holes such as37that penetrate the bore to the surface and aid in the movement of the shell over the core.

The shell will then clamp down onto the core as it cools forming the drum40. As mentioned above, the edges of the shell extend beyond the edge of the core and cover a portion of the sides of the core, fixing the shell more robustly to the core. This provides a surface appropriate for receiving and releasing ink allowing the drum to operate as a transfix drum, or intermediate printing surface, in a printing system.

One should note that the intermediate transfer surface discussed here consists of a cylindrical drum. However, it is possible that the intermediate transfer surface may take a different form, such as a belt, a plate, etc. (If so, I don't think it would have anything to do with this patent? I don't understand the purpose of this paragraph?)

One should note that the term ‘printing system’ is not limited only to devices that receive image data from a computer and produce printed output. The term encompasses any device having a print engine, including scanners, fax machines, printers, photo printers, kiosk printers, multi-function peripherals capable of performing more than one of the above functions, etc.