Abrading – Abrading process
Reexamination Certificate
1998-12-11
2001-01-09
Scherbel, David A. (Department: 3723)
Abrading
Abrading process
C451S466000, C451S005000, C451S913000, C451S916000, C451S011000
Reexamination Certificate
active
06171175
ABSTRACT:
TECHNICAL FIELD
This invention relates to the technology of finishing metal surfaces, such as free-form surfaces presented by dies, and more particularly to the polishing of such surfaces to a precise contour devoid of overpolishing.
DISCUSSION OF THE PRIOR ART
One of the longest lead time programs needed for making part of a new automobile is that for making tooling for the part. Such tooling may include dies for body panels, dies for casting sand cores used to mold engine components, and die tooling for making injection molded plastic components, such as used in the interior of the vehicle. The basic shape of these dies or tooling is usually obtained by finish machining its free-form shape using a milling or other cutter that is moved back and forth along parallel paths with varying cutting depths according to a numerical control (a computer program that dictates the path of a machining bit to remove metal from a rough formed body). The numerically controlled upright milling cutter is governed to move along a two-dimensional path and is raised or lowered along its upright axis to achieve different depths of cutting. Such milled surface never can obtain an exact contour identical to the computer designed surface because the rotary milling head cutter can only approximate steep radiused contours leaving small corners to be polished away subsequently under manual guidance. Heretofore, manual polishing has involved use of abrasive powders and abrasive stones, commonly known as lapping compounds and polishing stones. The deficiencies of manual polishing is the tendency to remove an excessive amount of material losing the integrity of the surface, or the tendency to not remove sufficient material (underpolishing) which causes the surface to improperly function. Even the best experienced craftsman may hand-polish excessively in certain areas, thus achieving less than the desired mathematical shape and usually in an excessive period of time (such as 20-30% of the total machining time), thus making the process inefficient.
To overcome the difficulties of manual polishing, the prior art has attempted to use costly stoning mills to achieve the desired finish. This is disadvantageous because of the high capital cost, and because toolmakers are required to run and guide the machinery which may introduce error.
The prior art has also attempted to use programmable dexterous robots which tilt the milling cutter to more closely approximate the desired contours, which is then followed by robotic polishing using a similar tiltable axis. This technique suffers from a significant cost penalty, although it approaches more effectively the desired polished form.
And lastly, the prior art has attempted to modify the polishing tool in order to eliminate the need for expensive machinery. For example, in U.S. Pat. No. 4,945,687, a polishing brush was constructed having filaments joined together by foam containing encapsulated abrasive grit (the abrasive was not on the filaments directly). The foam inherently was weak and rapidly disintegrated during use, even though the filaments were initially strengthened by the foam. The brush required a continuous polishing face, as created by the continuous body of foam. Also in U.S. Pat. No 5,355,639, a rotary polishing tool, comprised of coated elastic plates, was used with the plates to act as resilient deflection springs. Such elastic plates were moved at a constant rotary speed to be able to machine plastic or other soft materials limiting the tool's use. Unfortunately, such tools are unable to achieve the desired results sought by this invention.
SUMMARY OF THE INVENTION
A primary object of this invention is provide a cost-effective process (capital cost not greater than $15,000) that can eliminate inaccuracies of polishing while doing so economically.
The method of this invention which meets the above object is a method of automatic finishing of a free-form contoured metal or hard die surface, comprising: providing a rotating brush with a central hub carried by a driving spindle for rotation about the hub axis; providing the brush hub with a plurality of closely spaced resilient and independently flexible strands impregnated with or coated with abrasive polishing particles, each strand being secured at one end in the hub and having its other end extending radially away therefrom to present an apparent curved surface of closely spaced strand ends (the series of touching or closely spaced strand ends forming at least a portion of surface); and rotatingly driving the hub and strands at a constant torque while dragging the ends of aid strands across the die surface while in contact therewith to effect the desired degree of polishing. The coating of abrasive polishing particles can be selected from the group of aluminum oxide, silicon oxide or silicon carbide. The flexible strands are preferably formed of stabilized nylon filament.
REFERENCES:
patent: 1652834 (1927-12-01), Neufeld
patent: 3695563 (1972-10-01), Rands
patent: 4555229 (1985-11-01), Biadigo et al.
patent: 4882879 (1989-11-01), Warner et al.
patent: 4945687 (1990-08-01), Scheider et al.
patent: 5355639 (1994-10-01), Ferard et al.
patent: 5443413 (1995-08-01), Pflager et al.
patent: 5895311 (1999-04-01), Shiotani et al.
patent: 353139789 (1978-11-01), None
patent: 403294165 (1991-12-01), None
Sasaki Paul
Schim Joseph Carl
Shaikh Furqan Zafar
Stoll Christopher
Walther Marc A.
Ford Global Technologies Inc.
Malleck Joseph W.
Nguyen George
Scherbel David A.
LandOfFree
Method of polishing uniform or free-form metal surfaces does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of polishing uniform or free-form metal surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of polishing uniform or free-form metal surfaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2443830