Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
2000-02-04
2001-08-28
Banks, Derris H. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S028000
Reexamination Certificate
active
06280288
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to grinding tools such abrasive wheels and coated abrasive belts and discs. When a new grinding tool is developed it represents a complex series of selections of alternatives. For example a new abrasive belt involves the selection of a backing, any backing treatment used, abrasive grit nature, abrasive grit size, binder, filler, other additives, surface treatments, and so on. This belt therefore will not perform at exactly the same performance level under identical conditions as previously made belts. Add to this the variation of the different designs of grinding machines with which the belt might be used, the coolants that might be used, the belt and workpiece speeds and so on, and the problem of using the belt to the best effect becomes overwhelming. In practice the operator is often left to find the best conditions for himself by trial and error. More commonly however, the machine settings are determined by long usage on previous belts and the new belt is operated under the same conditions regardless of whether these represent the optimum conditions for the new belt on that machine.
The result of the previous usages is often inefficient operation and sometimes the rejection of genuinely useful new products because they are incapable of performing at previously approved levels under the traditionally used sets of conditions.
There is therefore a need for a process for generating easily understood information that is helpful in determining how a grinding tool might be used with optimum effect. The present invention provides such a process and generates a unique means for conveying the information to an operator using the tool.
GENERAL DESCRIPTION OF THE INVENTION
The present invention provides a process for identifying optimum grinding conditions for the use of a specific grinding tool which comprises:
a) operating a grinding machine incorporating a specific grinding tool on a specific substrate at a first set of process conditions;
b) measuring the grinding performance of the grinding tool under said first set of process conditions;
c) repeating steps a) and b) at a plurality of further sets of different values of the same process conditions; and
d) using the grinding performance data to generate a topographical map identifying the combinations of conditions in which optimum grinding performance results were obtained.
The key to the above process is the topographical map generated from the data. As used herein the term “topographical” is intended to convey a map in which sets of conditions which would give identical performance are connected by lines in much the way the contour lines on a map connect points of equal elevation above sea level. Such topographical maps can be generated by computer-aided statistical manipulation of data points obtained in a routine manner in an initial evaluation of a new tool on a given machine operating on a given substrate. Thereafter the map is effective for the same combination of machine, tool and substrate, wherever the grinding takes place. It therefore becomes possible to guide a new user of a tool to identify exactly the conditions under which the best results will be obtained.
The topographical map can be generated in actual or simulated three dimensions, (with or without color coding such as are used in conventional geographical maps), but generally it is more useful if the map is two dimensional with different colors indicating the different levels of performance. For example a red color might be used to indicate the area within which the optimum grinding performance might be obtained with blue indicating conditions in which the worst performance might be expected. Intermediate levels can be indicated by varying shades from red, through orange and yellow and green, to blue.
The data points used to produce the map can be generated on the specific machine in connection with which the information is to be used, or alternatively it can be generated on an identical machine at a remote location depending on the availability of machine downtime to conduct the preliminary data generation. The “tool” used to generate the data, as the term is used herein, can be for example a grinding wheel, such as an organic, vitreous, rubber or metal bonded wheel or a composite abrasive wheel in which abrasive particles are bonded to the fibers of a tangled fibrous substrate; a bonded abrasive segment or mounted point; a composite abrasive pad or block; or a coated abrasive such as a belt, disc or sheet. Other options could also be devised for use with the present invention. Likewise the “machine” in connection with which the tool is used can be any commercial device for contacting an abrasive tool with a substrate, which itself can be any substrate conventionally treated with an abrasive tool to remove material or improve the surface finish of a substrate such as a metal, wood, ceramic or a painted surface.
In addition to identifying optimum use conditions, the procedure can be use to select between options of tool design. Thus when, for example, two belt designs are available for use in a particular grinding operation, the production of a performance map enables the user to determine which would be the most cost-effective in the preferred use conditions employed. This can be done for example by measuring the critical performance parameters for both belts under the same range of process conditions, and plotting, instead of the parameter itself, the ratio of the critical performance parameters for the two belts under the same sets of process conditions. In practice this is best done by generating an equation representing the variation of the process conditions and the value of the critical parameter being measured for each belt, then using these equations to predict the critical process parameter for each belt at a set of combinations of process conditions and the ratio of the critical parameter obtained for each belt at each set of process conditions. This statistically adjusts each measurement to give a higher confidence level in the value used and therefore the ratio between the two. It is this statistically more reliable ratio that is preferably plotted to give the comparative product map. Such a map will show clearly the degree of improvement, (if any), of one over the other under a wide range of process conditions. The selection of the appropriate design can thereafter be based on solid data rather than on perceptions based on incomplete data.
Where the tool is a coated abrasive belt, used on a conventional machine to treat a metal substrate, the design of the machine will often pre-determine conditions such as area of contact and belt dimensions. Other conditions such as pressure of contact between the belt and the substrate, time of contact and intervals between contacts, lubricant/coolant used and so on can however be changed. The measure of quality of the grinding performance might be metal removal rate, number of parts treated before the belt needs to be replaced or the surface finish of the substrate. In these circumstances it is necessary to identify the two most important variables and keep all other variables constant throughout the data collection operations which focus on the measurement of the parameter that is most indicative to the user of “quality”. Thus in a concrete situation, the key variables monitored could be pressure and contact time and the “quality” variable might be the number of parts that could be finished to the desired quality in a given period. A topographical chart generated on the basis of the data collected would immediately inform the operator how best to use the new belt on his machine by selecting the pressure and contact time indicated by the chart as offering the optimum number of parts produced in a unit time. Another example of the use of the process of the present invention relates to the selection of an appropriate coated abrasives with an engineered surface. These are coated abrasives in which the abrasive surface is in the form of repeating shapes compr
Gaeta Anthony C.
Kinisky Thomas G.
Swei Gwo Shin
Wei Paul
Banks Derris H.
Bennett David
Norton Company
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