Patent Document

TECHNICAL FIELD 
     The present invention relates generally to a chemical method for cleaning stamping or other work piece deformation tools by removing locally adhered build-up of work piece metal. 
     BACKGROUND OF THE INVENTION 
     It is well known that steel tools used for extruding metals such as aluminum can collect substantial amounts of aluminum or other work piece metal within the cavities after the completion of the extrusion process. These tools are typically cleaned by immersing them in warm caustic solutions for several days to dissolve the aluminum without affecting the steel tooling. While this method works well for the aluminum extrusion industry, it is impractical with stamping tools due to the length of time required for cleaning and the relatively small amounts of aluminum and/or other metals remaining in localized regions on the stamping tools after use. Currently, tooling used for stamping at room temperature is hand wiped to remove buildup. An alternative approach is to cool the tool to room temperature and then polish with sandpaper and diamond paste. The problem with this approach is that some of the ferrous tooling material in the vicinity of the aluminum that is built up is also removed which can locally change dimensions or deformation conditions like friction, both of which are critical for part forming and dimensional control. Additionally, if the tool is coated for some desirable characteristics, there is a danger that some of this coating could get damaged or removed. 
     SUMMARY OF THE INVENTION 
     This invention is believed to provide advantages and alternatives over prior practices by providing a method of cleaning stamping and other metal forming tools which utilizes localized application of a solution of caustic character in the form of basic or mild acid compositions that only attack the buildup (depending on the metal being formed) to remove metal buildup within a few minutes. This avoids the necessity of taking the tool off line or applying aggressive shape-deforming treatments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings which are incorporated in and which constitute a portion of this specification illustrate an exemplary practice according to the present invention wherein; 
         FIG. 1  is an exemplary cross sectional view of a stamping tool and a metal work piece prior to stamping; 
         FIG. 2  is an exemplary cross sectional view of a stamping tool and a metal work piece after stamping; 
         FIG. 3  is an exemplary cross sectional view of a stamping tool and a metal work piece with an applied cleaning composition; and 
         FIG. 4  illustrates a cleaned stamping tool. 
     
    
    
     While embodiments of the invention have been illustrated and generally described above and will hereinafter be described in connection with certain potentially preferred procedures and practices, it is to be understood and appreciated that in no event is the invention to be limited to such embodiments and procedures as may be illustrated and described herein. On the contrary, it is intended that the present invention shall extend to all alternatives and modifications as may embrace the broad principles of the invention within the true spirit and scope thereof. 
     DETAILED DESCRIPTION 
     While the following description will be presented in terms of a stamping operation, it is to be understood that reference to such a stamping operation is intended to be illustrative only and that practice of the invention is in no way limited to stamping tools. To the contrary, it is contemplated and intended that the inventive cleaning practices may be equally applicable to any number of forming tools that apply controlled deformation to a work piece including cutting tools, extrusion tools and the like as will be well known to those of skill in the art. 
     Reference will now be made to the various drawings wherein to the extent possible, like elements are designated by corresponding reference numerals in the various views. In  FIG. 1 , a stamping tool  10  of tool steel or the like and a metal work piece  20  of a deformable metal such as aluminum or the like are illustrated prior to stamping. As will be appreciated, the stamping tool  10  has a contoured workface defining a pattern  12  of indentations and protrusions of varying size and shape. During the stamping operation the pattern across the stamping tool is pressed in relief across the work piece  20 . 
       FIG. 2  illustrates the stamping tool  10  and the metal work piece  20  subsequent to the stamping operation. As can be readily observed, following the stamping operation localized regions of small amounts of metal substrate residue  20   a  become adhered to the stamping tool. These deposits will normally build up over time so as to change of the profile of the stamping tool  10  and affect friction conditions that were optimized for forming. 
       FIG. 3  depicts the inventive method of cleaning the stamping tool  10 . This method uses a solution of caustic material in the form of a base or mild acid that does not attack the tooling material, which can be either in the form of a gel or saturated onto a cloth  15 . The gel or saturated cloth  15  is placed into contacting relation with critical areas of the stamping tool  10  which have localized regions of metal substrate residue buildup. After approximately 5 minutes of contact the gel is neutralized or wiped off or the saturated cloth is removed. The contact is preferably substantially static in nature with the gel or cloth  15  being held in a substantially fixed position so as to promote uninterrupted chemical reaction. To facilitate the cleaning action an optional ultrasonic vibration device  25  may be secured at least partially around the gel or saturated cloth  15  to promote loosening of the substrate residue  20   a.    
       FIG. 4  illustrates the cleaned stamping tool  10  in which the localized buildup of metal substrate residue  20   a  is no longer evident. The stamping tool requires no additional cleaning or polishing. 
     According to potentially preferred practices, the caustic material may be either basic or acidic in nature. By way of example only, and not limitation, exemplary caustic compositions include NaOH, KOH, acetic acid, phosphoric acid and chemicals with similar caustic properties, and any combination of such materials depending on the adhered material and the tooling material used. By way of example only, and not limitation one caustic material that has been found to be effective is a gel marketed under the trade designation DRANO®. In accordance with a particularly preferred practice, the cleaning operation may be performed at slightly elevated temperatures such as 50-100° C. in order to accelerate the reaction. 
     The present method is believed to be particularly beneficial for cleaning ferrous stamping tools with deposits from aluminum and aluminum alloy metal work pieces. However, the practice can also be applied to clean other tooling materials including ceramics and the like and other work piece metals that stick to such tooling including magnesium, titanium, zinc coatings on steel and the like. The composition of the cleaning agent preferably in gel form is tailored such that it is reactive to the adhered material and has no reaction with the tooling material, which can be steel or another material suitable for tooling. 
     It is to be understood that while the present invention has been illustrated and described in relation to potentially preferred embodiments, constructions, and procedures, that such embodiments, constructions, and procedures are illustrative only and that the invention is in no event limited thereto. Rather, it is contemplated that modifications and variations embodying the principals of the invention will no doubt occur to those of skill in the art. It is therefore contemplated and intended that the present invention shall extend to all such modifications and variations as may incorporate the broad aspects of the invention within the true spirit and scope thereof.

Technology Category: c