Method and apparatus for on-demand stencil chemical etch direct parts marking automation and carrier for chemical etch stencil mesh

Abstract

A unit for on-demand chemical etch. Stencil media is unwound from a stencil unwind hub and passed underneath the thermal print head and printed. The stencil media is a sandwich that is comprised of a porous material married to a pressure-sensitive adhesive coated carrier to supply stiffness and support to the mesh. After the stencil is printed, the carrier is peeled away and is rewound onto a carrier rewind hub, leaving only the printed stencil. This printed stencil is transported underneath the etching electrode, at which time, the electrode actuates downward, sandwiching the printed stencil between the electrode and the target object so that the chemical etching process may be performed. The spent stencil rewinds onto a stencil rewind hub. The stencil printing and etch functions can be provided in a handheld unit. The handheld unit is comprised of an actuating etching head, a print head, a ribbon support system and media support system.

Description

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a method for automatic on-demand chemical etching.

[0004] 2. Description Of Related Art

[0005] Electro-chemical etching uses an electric charge to remove and/or discolor a conductive metal surface. This process uses several items: a power source, etching solution, stencil mask, applicator, and ground electrode. The electrolysis is limited to an area defined by a reverse image on the stencil mask through which the metal surface is oxidized or rusted creating the desired mark.

[0006] At this time, the serialization of parts using direct part marking technologies (laser, dot peen, chemical etch) is not feasible due to the combination of cost and short cycle times. For example, the laser solution is fast, but requires a large capital investment. Chemical etch on the other hand is cheap, but prior to the present invention could not be automated in conjunction with serialization. Manual automated chemical etching processes exist that imprint identical information on many items in an assembly line fashion, for example, marking “Rotation” on a table-saw blade, i.e. the exact same mark on all the blades being manufactured. However, these automated units can only provide marks that have static information, i.e. they reapply the same stencil again and again. There is a need for a method for chemical etch in those applications that require on-demand automation.

[0007] The prior art chemical etch processes are predominately conducted at tabletop locations as both laser and dot-peen marking systems required a fixed location in order to maintain process control.

SUMMARY OF THE INVENTION

[0008] A device for automatic on-demand chemical etching. Stencil media is unwound from a stencil unwind hub and passed underneath the thermal print head and printed using thermal transfer ribbon. The stencil media is a sandwich that is comprised of a porous material (mesh) married to a pressure-sensitive adhesive coated carrier to supply stiffness and support to the mesh. The thermal transfer ribbon is unwound from a ribbon unwind hub and rewinds onto a ribbon rewind hub.

[0009] After the stencil is printed, the pressure-sensitive adhesive coated carrier is peeled away and is rewound onto a carrier rewind hub, leaving only the printed stencil. This printed stencil is transported underneath the etching electrode, at which time, the electrode actuates downward, sandwiching the printed stencil between the electrode and the target object so that the chemical etching process may be performed. The spent stencil rewinds onto a stencil rewind hub.

[0010] The stencil printing and etching functions can be incorporated into a handheld unit. The handheld unit is comprised of an actuating etching electrode “head”, a print head, a ribbon support system and media support system. The thermal transfer ribbon (TTR) is used to print the desired image onto the media. After being printed, the carrier is removed from the printed stencil and rewound on the carrier rewind hub. The stencil is then conveyed underneath the actuating electrode “head”.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is the mesh with cover line.

[0012] FIG. 2 is an embodiment of the invention in a production line.

[0013] FIG. 3 is an alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] An on-demand printed stencil mask is created using a thermal transfer printer and ribbon as described in applicant's prior U.S. application Ser. No. 09/961,740 filed Sep. 4, 2001, now ______ is hereby incorporated by reference. A desired image is printed onto a carrier web/mesh surface 2 in a reverse, inverse format. The ribbon ink acts as an insulator for the etching solution.

[0015] The stencil mesh 4 used to create a mask for the mark/image is a woven mesh fabric 4 that has very low stiffness properties. Alone, the mesh 4 is difficult to reliably feed through a thermal printer. Laminating a carrier liner 8 to the backside of the mesh 4 allows the material to feed through a thermal printer and cutter while printing a mask stencil pattern of the surface.

[0016] The mesh 4 consists of a finely woven polyester filament laminated to a carrier liner 8. The carrier provides the necessary stiffness to properly track and feed the mesh through a thermal printer and cutter mechanism. The carrier liner 8 is held to the backside of the mesh material 4 with a light removable pressure sensitive adhesive 6.

[0017] The carrier 8 may be a paper or film substrate in the range of 0.0005″ to 0.020″ thick. The pressure sensitive adhesive 6 is, for example, a removable microsphere pressure sensitive adhesive 6 with a coating thickness between 0.0001″ to 0.010″ thick. The selected adhesive is compatible with the woven mesh fabric 4 if it does not permanently bond, flow into or otherwise block the mesh openings.

[0018] The inventive device is a unit for automatic on-demand chemical etch. Stencil media 2 is unwound from a stencil unwind hub and passed underneath the thermal print head 22 and printed using the ribbon 24. The stencil media 2 is a sandwich that is comprised of a porous material (mesh) 4 married to a pressure-sensitive adhesive 6 coated carrier 8 to supply stiffness and support to the mesh 4. The thermal transfer ribbon 24 is unwound from a ribbon unwind hub 14 and rewinds onto a ribbon rewind hub 16.

[0019] After the stencil is printed, the carrier 8 is peeled away and is rewound onto a carrier rewind hub 18, leaving only the printed stencil. This printed stencil is transported underneath the etching head 20, at which time, the electrode of the etching head actuates downward, sandwiching the printed stencil between the electrode and the target object 30 so that the chemical etching process may be performed. The spent stencil rewinds onto a stencil rewind hub 12.

[0020] By maintaining the continuous nature of the webs, the process may be automated and controlled through a computer that will control the movement of the target part as well as the etching process. As each target object arrives at the etching station data associated with that object has already been printed to a mesh stencil for etching the object.

[0021] In a second embodiment, an etching unit would etch objects on the conveyor 28 using pre-printed stencil(s). The printing mechanism would be eliminated and the stencils would be loaded into the etching unit and consumed one at a time. This would provide a means of etching the information in a location where the data used in each mark is known beforehand but the printer communication with the host is difficult or unfeasible, for example in a remote warehouse.

[0022] In a third embodiment, the conveyor 28 is modified. The etching process requires a grounding electrode to operate. Rather than have a grounding electrode on the etching head mechanism, this embodiment uses the conveyor 28 as the grounding point. Also, rather than have the etching unit actuate down to the item being etched, the conveyor 28 itself may be actuated upwards to push the object 30 being marked against the etching head 20.

[0023] As shown in FIG. 3, the required media paths, previously described with respect to FIG. 2, may be incorporated into a handheld unit. A fourth, fifth, sixth and seventh embodiment describes equipment and a process that can produce etched marks in a mobile environment. These embodiments describe a way of reducing the chemical etch process to a mobile handheld unit 30 that can be used with complete freedom of movement. The mobile hand-held units would be useful for direct marking in situations that do not lend themselves to a fixed location (i.e. inspections serialization, recalls, process overflow, etc.).

[0024] A fourth embodiment combines the stencil printing and electrode functions into a handheld unit 30. The handheld unit 30 is comprised of an actuating etching head 20 with an electrode, a print head 22, a ribbon support system 14, 16 and media support system 10, 12, 18. The thermal transfer ribbon 24 is used to print the desired image onto the media 2. After being printed, the carrier 8 is removed from the printed stencil and rewound on the carrier rewind hub 18. The stencil is then conveyed underneath the actuating electrode head 20. Once in this position, the electrode extends, sandwiching the stencil between the electrode 20 and the target object 32 surface. The electrode is then energized and the desired mark produced.

[0025] A fifth embodiment consists of a hand-held unit 30 that does not have a printing unit contained within it. Pre-printed stencils are loaded into the unit and are used in much the same way as with the fourth embodiment. This embodiment has the advantage of being a simplified system that is more economical to manufacture and maintain.

[0026] A sixth embodiment would consist of a hand-held unit 30 that uses stencils delivered in a stacked cartridge format. The stencils are loaded into a cartridge, as a stack of pre-printed stencils. These stencils would then be fed individually to the etching head 20, consumed, and then conveyed either out of the unit or into a collection bin (part of the hand-held unit). This would also provide another way of etching using non-roll-form stencil constructions (i.e. stencils made using photographic methods).

[0027] A seventh embodiment would consist of a hand-held unit employing a replaceable etching head that is spherical in shape and would employ several fixed stencils (similar to a Daisy-wheel typewriter head). This unit would provide a means of etching a fixed message to an asset such as “Rejected”, “Quality”, etc. To change the group of messages available for etching, the etching head would be exchanged.

[0028] Each of the above embodiments could also be constructed using a non-actuated, fixed position head 20 that would protrude from the front face of the unit enough for the head to contact the target surface in order to perform an etch. Also, the hand-held etching unit 30 can be either plugged in and used, or be incorporated into a mobile system that consists of the hand-held etching unit, a mobile power source and if desired for the type of part to be marked, a work area to support the part.

[0029] In each of the embodiments, the etching solution is applied prior to activation of the electrode to wet the metal surface to be marked. Etching solution delivery may be via a brush/sponge or applied in a drip fashion to a pad on the electrode which is continuously supplied with an etching solution supply, similar, for example, to a gravity fed oiler.

[0030] Wetting of the electrode head with the etching solution may also be accomplished, for example, via a separate applicator or sponge. If the etching solution is corrosive a part surface wiper 26 may be utilized to remove excess solution from the object after the etching process is complete.

Claims

1. An apparatus for on-demand chemical etch comprising: a stencil web; a media support system; and an etching head mechanism wherein said stencil web transported under said etching head mechanism by said media support system.

2. The apparatus of claim 1 wherein said media support system comprises a stencil unwind hub and a stencil rewind hub.

3. The apparatus of claim 1 further comprising: a printing mechanism, said printing mechanism comprising a print head, a thermal transfer ribbon and a ribbon support system; and a spent carrier rewind; wherein said printing mechanism is located before the etching head mechanism.

4. The apparatus of claim 1 wherein said etching head mechanism extends and sandwiches said stencil web between said etching head mechanism and a target object.

5. The apparatus of claim 4 further comprising a grounding electrode on said etching head mechanism.

6. The apparatus of claim 4 wherein said target object is on a conveyor and said conveyor is adapted to be actuated upwards to push the target object against the etching head.

7. The apparatus of claim 1 wherein said stencil web is preprinted.

8. The apparatus of claim 1 further comprising a part surface wiper.

9. The apparatus of claim 1 further comprising a handheld unit wherein said stencil web, media support system and said etching head mechanism are adapted to be housed in said handheld unit.

10. The apparatus of claim 2 further comprising a handheld unit wherein said stencil web, media support system and said etching head mechanism are adapted to be housed in said handheld unit.

11. The apparatus of claim 3 further comprising a handheld unit wherein said stencil web, media support system and said etching head mechanism are adapted to be housed in said handheld unit.

12. The apparatus of claim 4 further comprising a handheld unit wherein said stencil web, media support system and said etching head mechanism are adapted to be housed in said handheld unit.

13. The apparatus of claim 12 further comprising a grounding electrode on said etching head mechanism.

14. The apparatus of claim 9 wherein said media support system comprises a cartridge and the stencil web is loaded in the cartridge as a stack of preprinted stencils.

15. The apparatus of claim 14 wherein the media support system further comprises a collection bin adapted to hold used stencils.

16. The apparatus of claim 9 wherein the etching head is spherical and comprises with a plurality of stencils.

17. The apparatus of claim 10 wherein the etching head is replaceable.

18. A method for on-demand chemical etch comprising the steps of: obtaining a stencil web; said stencil web on a media support system comprising a media unwind hub and a stencil rewind hub; transporting said stencil web under a print head; printing in reverse on said stencil web to create a stencil; peeling away a carrier from said stencil; transporting said stencil under an etching head; sandwiching said stencil between said etching head and an object; applying a wetting solution; actuating an electrode; rewinding a spent stencil on the stencil rewind hub.