Method for providing particle-free ink jet printer components

Abstract: A method is provided for improving the operation of ink jet components. The components are machined using known, conventional machining techniques. All of the machined surfaces are then treated using non-abrasive, intrinsically leveling polishing processes to eliminate particulate sources. The conventional machining may be any known technique, such as electro discharge machining. The polishing processes include, but are not limited to, electrochemical means such as electropolishing, electrochemical deburring, and electrochemical grinding. The polishing processes may further comprise vapor polishing, and laser treatment to reflow the machined surface.

Description: The present invention relates to continuous ink jet printers and, more particularly, to an improved method for manufacturing the ink jet printer and components. Ink jet printing systems are known in which a print head defines one or more rows of orifices which receive an electrically conductive recording fluid, such as for instance a water base ink, from a pressurized fluid supply manifold and eject the fluid in rows of parallel streams. Printers using such print heads accomplish graphic reproduction by selectively charging and deflecting the drops in each of the streams and depositing at least some of the drops on a print receiving medium, while others of the drops strike a drop catcher device. The operation of ink-jet printers involves pumping fluid through small orifices, about 25 micron in diameter. This makes these machines sensitive to particles in the ink. To remove particulates from the ink, the filters are always used in the fluid systems. Typically the fluid systems include two filters: a primary filter to remove dirt which enters the fluid through the catcher line or from wear in the pumps and valves, and a final filter just ahead of the printhead to remove dirt produced in the fluid lines. Even with this filtering, it is necessary to vigorously clean the printhead components during assembly to ensure reliable, operation. This cleaning typically includes extensive ultrasonic cleaning and flushing. In spite of this extensive cleaning, failure due to particulate remains excessive during both manufacturing and use of the printheads. US-A-5574486 discloses an ink jet print head including an ink ejecting component which incorporates an orifice plate having electropolished surfaces. It is seen then that there is a need for an improved method for eliminating particulates in the printhead components, to reduce failure rates during manufacture and use of the printheads. This need is met by the particle-free ink jet printer cleaning concept in accordance with the present invention, wherein various polishing concepts are provided. The invention provides a method of producing an ink jet component including a fluid supply in fluid cavity of an ink jet head, the method comprising the steps of: a. machining the component using conventional machining techniques; b. treating all machined surfaces using non-abrasive, intrinsically leveling polishing processes to eliminate particulate sources, said machined surfaces include the internal fluid supply surfaces in the fluid cavity. The conventional machining may be any known technique, such as electro discharge machining. The polishing processes include, but are not limited to, electrochemical mears such as electropolishing, electrochemical deburring and electrochemical grinding. The polishing processes may further comprise vapor polishing, and laser treatment to reflow the machined surface. The particle-free ink jet printer according to the present invention provides a variety of advantages. First, it results in ink jet printer components with particle-free surfaces. This, in turn, reduces or eliminates several undesirable print problems, including crooked ink jets, and clogging of the orifices with the contaminant or debris. As a result of the reduction in crooked jets, manufacturing yields and printhead lifetimes are improved. Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. The invention will now be described in more detail and by way of example only, with reference to the accompanying drawings, in which: Fig. 1 illustrates a portion of a print head structure, including a resonator, for describing the technique of the present invention; Figs. 2A and 2B are surface views of the resonator after application of a machining process, illustrating the burr-like edges and flakes caused by the typical machining process; Fig. 3 is a surface view of the resonator after application of the electropolishing process according to the present invention, illustrating elimination of burr-like edges and particulate sources; and Fig. 4 is a flow chart illustrating the steps employed to improve the surface finish of the resonator of Fig. 1. Referring to the drawings, in Fig. 1 a portion of a print head 10 of an ink jet printer system is illustrated. The print head 10 is comprised of a resonator 12, typically constructed of a stainless steel material in the form of a predeterminedly dimensioned rectangular solid, and a drop selection means 14. The print head 10 defines orifices on an orifice plate 16 of the resonator 12 which receive an electrically conductive recording fluid, such as a water base ink, from a pressurized fluid supply contained in a fluid cavity 18. The fluid is ejected from the resonator through aperture 19, in rows of parallel streams 20 as ink droplets 22. The fluid cavity is typically produced by an EDM process. A drop catcher device 24 and a charge plate 26 define the drop selection means 14 for selectively charging and deflecting the drops 22 in each of the streams and depositing at least some of the drops 22 on a print receiving medium. It will be understood that the print head 10 and resonator 12 cooperate with other known components used in ink jet printers. The print head 10 and resonator 12 function to produce the desired streams of uniformly sized and spaced drops in a highly synchronous condition. Other continuous ink jet printer components, such as charge and deflection electrodes, drop catcher, media feed system and data input and machine control electronics (not shown) cooperate with the drop streams, produced by the print head 10 to effect continuous ink jet printing. Manufacturing the various printhead components involves machining processes which are intrinsically dirty. Machine tools produce numerous burrs flakes and other forms of debris in both metal and plastic parts. Careful examination with high powered microscopes or a scanning electron microscope reveals burrs and flakes of material as small as a few microns produced by machining with such processes as lathe turning, milling, and drilling. Such burrs and flakes can break off from the surface with time to cause a failure. Even grinding and honing operations can produce similar particulate sources. Abrasive material can also be left behind by these operations. Electro-discharge machining (EDM) is well known to produce a layer of recast material that can break off, yielding printhead failures. The surface views of Figs. 2A and 2B illustrate numerous burr-like edges and flakes ready to break off, which remain after a lathe turning operation, before the concept of the present invention is applied. As seen in Figs. 2A and 2B, burr-like edges 28, flakes 30, and other contamination have been formed on ink jet printer component surfaces. As flakes such as shown in Fig. 2B are still attached, cleaning steps such as flushing or ultrasonic cleaning may not readily remove them. During operation of the printhead, such flakes might break loose as the result of shocks or fatigue. Additionally, the rough surfaces can act as temporary traps of externally generated particles. Such particles might remain attached through the cleaning steps and still come loose during operation of the printhead. Therefore, it must be concluded , the machined surface serves as a source of particles which can produce crooked ink jets, and clogging of the orifices on orifice plate 16. Chemical polishing is one prior art technique employed to try to eliminate such particles. Chemical polishing is not an intrinsically leveling process. That is, the metal removal rate is fairly uniform across the surface, not preferentially from the sharp edges. As a result, burr- like edges, flakes, or recast are not effectively removed by chemical polishing. In some cases, the flakes, etc., remain on the surface, but the metal which holds the flake to the surface may be weakened by the chemical polishing. Such flakes are therefore more inclined to break off due to a shock or fatigue during printhead operation than they would have been prior to chemical polishing. The present invention eliminates these undesirable print problems created by the manufacture of the various printhead components. As illustrated in Fig. 3, the present invention proposes applying electrochemical means such as electropolishing, electrochemical deburring or electrochemical grinding, to smooth the surface finish of the printer components. When the printhead components comprise metal parts, fine burrs and flakes can be eliminated through use of electrochemical means according to the present invention. The parts are placed in appropriate solutions, well known in the electropolishing and electrochemical deburring industries. A voltage is then applied between the part and a second electrode, or cathode. Under such conditions, metal from the part is forced to go into solution. Due to the nature of the electric fields involved, the metal removal rate is highest at sharp edges. As a result, burrs, flakes, and the splatter and recast from EDM is readily removed. The result is a surface with no potential sources of particles. When the particulates to be removed are on internal surfaces of the ink jet printer components, electrodes internal to the fluid cavity can be used for polishing. Alternatively, when the fluid cavity does not have an adequate opening for receiving electrodes, a pulsing technique can be used for polishing deeper into the component. Since the polishing processes in accordance with the present invention yield surfaces which are quite smooth, with no sharp edges, particles from external sources are also less likely to be trapped on the surfaces. This provides the advantage of making these surfaces easier to clean than normal surfaces. Electropolishing and electrochemical deburring yield quite similar results in terms of surface finish, differing mainly in the type of solutions used. The solutions used in electropolishing keep the metal which is removed in the form of soluble salts in the solution until they are plated out onto the other electrode. With electrochemical deburring, the metal forms non-soluble metal salts. These salts form a precipitate which either settles onto the parts or is filtered out. Any precipitate left on the parts can be removed using various acids. In accordance with the present invention, these processes have been found to be much more effective than chemical polishing at removing the sharp burrs and edges produced by the various machining processes. This is because these processes are intrinsically leveling, since metal removal is highest at the edges. Therefore, thin burrs are either polished away or rounded considerably, making them less likely to break off during printhead operation. A chemical polish, on the other hand, tends to remove material fairly uniformly from surfaces. As a result, chemical polishing can make thin burrs thinner and, therefore, more likely to break off during printhead operation. Larger burrs, such as those produced at intersecting holes, or when threaded holes break out into a side wall, can also be effectively removed from the metal components by means of thermal deburring. This process involves placing the components in a sealed chamber with an explosive gas mixture. Exploding the gas produces an intense heat pulse. Burrs which have large surface to volume ratios can be vaporized or melted back by this process. A fine etch may be needed to remove the fine oxide layer which is produced. Since this treatment does not tend to remove the fine burrs as effectively as the electrochemical processes described above, a thermal deburring should be followed up with one of the electrochemical polishing processes described above. In another embodiment of the present invention, lasers can also be used to process the surface. A laser with enough power to melt the material, but not sufficient to cut the material, is used. By scanning the laser over the surface, a thin layer of the surface, including the burrs and EDM splatter, can be melted. After the laser passes, the surface resolidifies yielding a smoother surface free of burrs, EDM splatter or other sources of particles. Even when the components are plastic, it is still desirable to have all burrs, flash, and flakes removed. For materials such as Ultem and PVC, cryogenic deburring is effective for removing the larger burrs. This process involves freezing the plastic parts using liquid nitrogen or other suitable cryogen. Since this makes the burrs quite brittle, they can then be readily removed by using either a tumbling type deburrer or by grit blasting with fine plastic beads, both processes being well known in the art. It is also possible for some plastic parts to be effectively deburred by means of thermal deburring, as described above relative to metal parts. In a further embodiment of the present invention, even with the normal burrs removed, the surface can still be covered with fine burrs and flakes, such as the ones seen microscopically for the metal surfaces. These are effectively removed using vapor polishing. Vapor polishing involves exposing the parts to the vapors of a chemical solvent, and is known in the art. For plastics such as PVC or Ultem, methylene chloride is an appropriate solvent. The vapors locally attack and dissolve the surface. Once the vapors are removed, the surface rehardens. The result is a virgin surface free of burrs, flakes, or fine fractures. A particle-free surface is therefore produced. Referring now to Fig. 4, flow chart 34 illustrates the steps employed to achieve the particle-free surface of the ink jet printer components. First, ink jet printer components are manufactured (36) using typical machining processes (38). A deburring process is then applied (40). When the component is metal, the deburring process is preferably a thermal deburring process, which is applied before an electrochemical polishing process (42) which removes undesirable particulates. Likewise, when the component is plastic, the deburring process is preferably a cryogenic deburring process, applied before a vapor polishing process (44) which removes any remaining minuscule burrs and flakes. In accordance with the present invention, a method is provided for improving the operation of ink jet components, by machining the components using known, conventional machining techniques, and then treating all the machined surfaces using non-abrasive, intrinsically leveling polishing processes to eliminate particulate sources. The conventional machining may be any known technique, such as electro discharge machining. The polishing processes include, but are not limited to, electrochemical means such as electropolishing, electrochemical deburring, and electrochemical grinding. The polishing processes may further comprise vapor polishing, and laser treatment to reflow the machined surface. Industrial Applicability and Advantages The particle-free ink jet printer assembly according to the present invention is useful in the continuous ink jet printing field. Normal manufacturing operations for ink jet printer parts produce undesirable particulate sources and abrasive material on the components. The present invention utilizes electrochemical means and vapor polishing to provide particle-free ink jet printer component surfaces. Having described the invention in detail and by reference to the preferred embodiment thereof, it will be apparent that other modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims: A method of producing an ink jet component including a fluid supply in fluid cavity (18) of an ink jet head (10), the method comprising the steps of: a. machining the component using conventional machining techniques; b. treating all machined surfaces using non-abrasive, intrinsically leveling polishing processes to eliminate particulate sources, said machined surfaces include the internal fluid supply surfaces in the fluid cavity (18). A method as claimed in claim 1 wherein the step of machining the components using conventional machining techniques comprises the step of applying electrical discharge machining to said surfaces of the component. A method as claimed in claim 1 wherein the step of treating all machined surfaces using polishing processes comprises the step of using electrochemical means to eliminate particulate sources. A method as claimed in claim 3 wherein the step of using electrochemical means comprises the step of electropolishing the component. A method as claimed in claim 3 wherein the step of using electrochemical means comprises the step of applying electrochemical deburring to the component. A method as claimed in claim 3 wherein the step of using electrochemical means comprises the step of applying electrochemical grinding to the component. A method as claimed in claim 1 wherein the step of treating all machined surfaces using polishing processes comprises the step of vapor polishing to eliminate particulate sources. A method as claimed in claim 1 or 2 wherein the step of treating all machined surfaces using polishing processes comprises the step of laser treating to reflow the machined surface.

Inventors: KATERBERG JAMES A, KATERBERG, JAMES A.
Applicants: SCITEX DIGITAL PRINTING INC, SCITEX DIGITAL PRINTING, INC.
Application year: 1998
Main classification: B41J2
IPC codes: B41J2