Finishing of metal surfaces and related applications
AssigneeMegara (Australia) PTY LTD
InventorMario Girolamo
Life of this patent
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Abstract
A process for finishing a metal surface comprises subjecting the surface to successive grit blasting passes including a first series of successive blasting passes using an abrasive grit of a first diameter range applied with a blasting nozzle air pressure in a first range, and a second series of successive blasting passes using an abrasive grit of a second diameter range smaller than the first diameter range, applied with a blasting nozzle air pressure in a second range lower than the first range. Thereafter a third series of successive blasting passes, using glass grit of a third diameter range smaller than the second diameter range, is applied with a blasting nozzle air pressure in a third range lower than the first range.
Claims27
1 A process for finishing a metal surface, comprising subjecting the surface to successive grit blasting passes including:
- (a) a first series of successive blasting passes using an abrasive grit of a first diameter range applied with a blasting nozzle air pressure in a first range;
- (b) a second series of successive blasting passes using an abrasive grit of a second diameter range smaller than said first diameter range, applied with a blasting nozzle air pressure in a second range lower than said first range;
- and
- (c) thereafter a third series of successive blasting passes using glass grit of a third diameter range smaller than said second diameter range, applied with a blasting nozzle air pressure in a third range lower than said first range.
2 A process according to claim 1 wherein said metal surface is of a roller grade steel suitable for being used for embossing rollers.
3 A process according to claim 2, wherein said steel is suitable for subsequent finishing of extruded plastics sheet.
4 A process according to claim 1, 2 or 3 wherein at least one of said first, second and third series of successive blasting passes consists of three passes.
5 A process according to claim 4 wherein each of said first, second and third series of successive blasting passes consists of three passes.
6 A process according to any preceding claim wherein said abrasive grit is metallic oxide grit.
7 A process according to any preceding claim wherein said glass grit consists of spherical glass beads.
8 A process according to any preceding claim further including, after said glass grit blasting passes, providing said surface with a protective metal coating.
9 A process according to claim 8 wherein said surface is provided with a protective metal coating by chroming the surface.
10 A process according to claim 8 or 9 wherein said protective metal coating is of a thickness in the range 10 to 100 micron.
11 A process according to any preceding claim wherein said first range of blasting nozzle air pressure is 50 to 70 psi.
12 A process according to any preceding claim wherein said second range of blasting nozzle air pressure is 30 to 50 psi.
13 A process according to any preceding claim wherein said second and third ranges of blasting nozzle air pressure are substantially the same.
14 A process according to any preceding claim wherein said first and second diameter ranges overlap.
15 A process according to any preceding claim wherein said third diameter range is distinctly narrower than the other ranges.
16 A metal surface treated by a process according to any one of claims 1 to 15.
17 A metal surface according to claim 16, wherein said surface is characterised by a maximum valley-to-peak height generally less than 5 micron.
18 A metal surface according to claim 16 or 17, wherein the average valley-to-peak height is about 3 micron.
19 A metal surface according to claims 16, 17 or 18 characterised by a value of less than 0.5 micron for a roughness parameter representing the arithmetic mean of the departure of the roughness profile from the mean line within a sampling length.
20 A sheet of plastics material finished by contact with a metal surface, which metal surface is finished by a process according to any one of claims 1 to 15.
21 A sheet according to claim 20 wherein said metal surface is a cylindrical surface of a roll, and said contact is by rolling with the cylindrical surface.
22 (amended) A sheet of polypropylene for use as a printing substrate, wherein said sheet has a surface characterised by a valley-to-peak height generally less than 5 micron and a roughness parameter of less than 0.5 micron, which parameter represents the arithmetic mean of the departure of the roughness profile from the mean line within a sampling length.
23 (cancelled)
24 (cancelled)
25 (amended) A sheet according to claim 22 wherein said surface has a topographical valley-to-peak height variation generally less than 4 micron.
26 (amended) A sheet according to claim 25 wherein the maximum profile peak height is less than 2 micron.
27 (new) A sheet according to claim 25 wherein the maximum profile peak height is in the range 1 to 1.5 micron.