Patent Application
20060021408
This invention relates to the art of cleaning hot forming dies and, more particularly, to new and improved processes for the rapid and contaminate-free cleaning of metallic buildup from hot working surfaces of quick plastic forming dies to enhance the production of formed sheet metal parts with high quality show surfaces.
Super plastic and quick plastic forming techniques employ equipment in which a ductile metal blank of suitable metallic material is heated and stretched between forming surfaces of a pair of hot dies to create a formed panel of a desired shape. As the blank is stretched between the forming surfaces of the dies, metal particles from the blank may collect on the forming surfaces of the dies. Over time, the accumulation of metal particles on the forming surfaces of the dies may cause indentations and other irregularities to occur on the show surfaces of the formed panel requiring the panel to be scrapped or manually repaired.
Current methods of removing such metallic buildup require the dies to be cooled to room temperature and manually sanded, resulting in production downtime.
The present invention provides a cleaning apparatus operative to remove metallic buildup from forming surfaces of heated forming dies while the dies are operatively mounted in a press and movable between open and closed positions to minimize production downtime.
The cleaning apparatus includes a programmable positioner programmed to move a rotating brush along forming surfaces of forming dies. The positioner includes a robotic arm extending from a base. The arm has an end effector carrying a brush assembly including a rotary drive motor, such as an electric or air driven motor operable to rotate a cylindrical wire brush at rotational speeds greater than 1000 rpm or a circumferential surface speed of at least 5 feet per second.
In an exemplary embodiment, the wire brush has a 6 inch diameter and extends axially between 1 and 6 inches. The brush has a plurality of wire bristles, formed of low carbon steel extending radially to the outer diameter of the brush. Each bristle wire has a cross-sectional diameter of less than 0.015 inches and a tip having a sharp edge (not rounded) or a point to maximize the ability of the brush to remove metal particles from the forming surfaces of the dies.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.
Referring first to
The ram plate 16 is moved by hydraulic cylinders 24 to cycle the ram plate from an open position for blank loading to a closed blank forming position and then back to the open position shown in
The blanks 22 utilized with one preferred embodiment of this invention are flattened sheets of aluminum alloy coated with a dry lubricant 26 such as boron nitride. The lubricant 26 functions as a release agent to prevent the formed panel 28 from sticking to the forming dies 14, 20 and to enhance the stretching and formation of the part during the forming operation.
If desired, optional CO2 cleaning equipment, as shown for example in patent U.S. Pat. No. 6,516,645, may be intermittently used to eliminate accumulations of lubricant collected on the forming surfaces of the dies 14, 20.
The present invention provides cleaning apparatus 32, which includes a programmable positioner in the form of a robot 34 and a brush assembly 35. If appropriate, any other suitable form of programmable positioner may be substituted for the robot within the scope of the invention.
The robot 34 includes a base 36 supporting a jointed arm 38 with an end effector or holder 40 carrying the brush assembly 35, best shown in
In an exemplary embodiment, the brush has a 6 inch diameter and is approximately 1 to 2 inches in length with low carbon steel bristles. The bristles have a cross-sectional diameter of approximately 0.006 inches. However, the brush and bristles may range in length and diameter depending upon the hardness of the bristles and the application.
In operation, metal blanks 22 are serially loaded into the press 11 and formed by the dies 14, 20. During the forming process, quantities of dry lubricant and other foreign matter, such as metallic particles 56 from the metal blanks 22, accumulate on the forming surfaces of the dies 14, 20. The build-up of metallic particles is diagrammatically illustrated in
To prevent the buildup of lubricants on the forming surfaces of the dies 14, 20, a CO2 cleaning device periodically sprays cylindrical pellets of CO2 (dry ice) over the forming surfaces of the dies, in a predetermined pattern, to remove lubricants from the forming surfaces of the dies. The removal of the lubricants prevents surface flaws or imperfections in the form of dimples, streaks or other blemishes formed on the formed panels 28. Since the CO2 cleaning device is unable to remove metallic particles from the forming surfaces of the dies 14, 20, cleaning apparatus 32 removes any remaining metallic particles.
Cleaning apparatus 32 operates by initially activating the drive motor 44 to rotate brush 48 at a cleaning speed of approximately 1,000 RPM. The robot 34 then moves the brush 48 into engagement with the forming surface of the lower forming die 14. As the tips 52 of the bristles 50 contact the forming surface of the die 14, the sharp tips or edges gently scrape the forming surface to remove any metallic buildup indicated by arrows 56. The robot 34 then moves the brush 48 in a predetermined path, along the forming surface of the die 14, to remove the metallic buildup. Preferably, the robot 34 moves the brush 48, so that the brush 48 rotates perpendicular to the arrows 56 or the forming direction of the metallic particles to maximize the removal of metallic particles from the forming surface. After the lower forming die is cleaned, the upper forming die 20 is cleaned by the cleaning apparatus in a similar manner.
After the cleaning operation is complete, the robot 34 withdraws the cleaning apparatus from the forming press 10 to allow resumption of the serial forming of blanks 22 into panels 28.
While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.
