# US 8,465,639 B2 · Pin based method of precision diamond turning to make prismatic mold and sheeting

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- Number: US 8,465,639 B2
- Document ID: US8465639B2
- Status: Granted
- Kind: B2
- Application number: 12/082,416
- Filed: 2008-04-09
- Published: 2009-10-15
- Granted: 2013-06-18
- Earliest claimed: 2008-04-09
- Assignees: Orafol Americas Inc.
- Applicants: Xiao-Jing Lu
- Inventors: Xiao-Jing Lu
- Web page: https://patentgrep.com/patent/US8465639B2

## CPC

- C25D 1/10: Moulds; Masks; Masterforms
- B23P 15/24: dies (B21C3/18, B21C25/10, B21D37/20 take precedence)
- B29C 33/302: {Assembling a large number of mould elements to constitute one cavity}
- B29C 33/3842: {Manufacturing moulds, e.g. shaping the mould surface by machining}
- B29D 11/00605: {Production of reflex reflectors}
- G02B 5/124: plural reflecting elements forming part of a unitary plate or sheet
- Y10T 409/303752: Process
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- B23P: METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS (arrangements for copying or controlling B23Q)
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A system, and corresponding method for use, for providing a mass-producible retroreflective material, or sheeting, featuring full cube corner pins is presented. The full cube corner shaping may be provided with the use of a diamond turning tool. The diamond turning tool may be used to simultaneously manufacture a number of pins. The pins may be used to form a mold featuring a triangular or full cube corner surface formation.

## Claims

### Claim 1

A method for making a mold for forming a retroreflective sheeting, the method comprising:
forming a pin bundle from a plurality of pins;
leveling a top and a bottom surface of the pin bundle;
machining the top surface of the pin bundle with a diamond turning tool to provide predefined shapes for each pin on the top surface, wherein machining further comprises cutting three sets of parallel lines, each set being in a different axial direction, with a pitch of at least two of the sets being of equal value, and the pitch of the three sets being larger than the dimensional cross section of each pin in the pin bundle;
selecting a sub-set of pins from the pin bundle to form a sub-set bundle, each pin in the sub-set bundle having a same predetermined shape; and
electroforming the sub-set bundle to provide the mold.

### Claim 2 (depends on 1)

The method of claim 1 wherein the cutting of each of the three sets of parallel lines comprises an associated tool tilt angle.

### Claim 3 (depends on 1)

The method of claim 1 wherein the predetermined shape has three smooth and retroreflective surfaces.

### Claim 4 (depends on 2)

The method of claim 2 wherein the predetermined shape is a full cube corner and the three tool tilt angles comprise an equal value.

### Claim 5 (depends on 4)

The method of claim 4 wherein the pins have a hexagonal cross section.

### Claim 6 (depends on 5)

The method of claim 5 wherein the full cube corner includes a hexagonal aperture and the cube corner has three facets, each facet including a polygon boundary of equal value.

### Claim 7 (depends on 6)

The method of claim 6 wherein the polygon is a rectangle, square, or pentagon.

### Claim 8 (depends on 4)

The method of claim 4 wherein the pins have a rectangular cross section.

### Claim 9 (depends on 8)

The method of claim 8 wherein the full cube corner includes a rectangular aperture, and the full cube corner also includes first and second facets including a trapezoid boundary of equal value and a third facet having a symmetrical polygon boundary.

### Claim 10 (depends on 4)

The method of claim 4 wherein the pins have a circular cross section.

### Claim 11 (depends on 10)

The method of claim 10 wherein the full cube corner includes a circular aperture and, the full cube corner also includes three facets with a same circle sector boundary including a 90° center angle.

### Claim 12 (depends on 1)

The method of claim 1 wherein the pins have a diameter on the order of 10 to 5000 microns.

### Claim 13 (depends on 1)

The method of claim 1 wherein the pins are formed from a material selected from the group consisting of polyethylene, teraphthalate, polymethyl methacrylate, polycarbonate, brass, nickel, copper, and aluminum.

### Claim 14 (depends on 1)

The method of claim 1 further comprising:
specifying diamond turning tool configurations selected from the group consisting of pitch, tilt angle, cutting angle, and depth.