Radial Force Analyzing And Experimental Investigation Of Indexable Drills

With the development on engineering materials and coating technology,indexable drills have been very widely used in the workshop production.However, there is a gap between the Chinese and foreign product in terms of thequality of drilling, and the problem of the radial forces of indexable drills is themost important factor affecting the quality of drilling.The holes drilled by indexable drills are much better than that by twistdrills, and thrust in indexable drilling is lower than that in twist drilling even athigh cutting speeds and feed rates. However, the non-axisymmetricalarrangement of the inserts assemblied in indexable drills can easily causeunbalanced radial forces in the drilling process of indexable drills, and theunbalanced radial forces can cause minor vibration of indexable drills, makingthe precision of the drilled hole to be poor. Therefore, how to minimize theradial force in the drilling process of indexable drills becomes the key of thedesign and optimization of indexable drills.In this paper, the shear stress on the shear plane was calculated based on themodel of unequally divided shear zone, then using the equivalent plane approach,the orthogonal cutting theory based on unequal division shear zone was extended and applied to the single-edge oblique cutting, the cutting forces of thesingle-edge oblique cutting were calculated according to the transformationrelationship between orthogonal cutting sections and the oblique cutting. Thecutting edges of an indexable drill were discretized a series of differentialoblique cutting sections for analyzing the radial force of indexable drills. Byanalyzing the geometric angles of the cutting edges and based on the obliquemodel, cutting forces of the drill were calculated according to the transformationrelationship between oblique cutting sections and the indexable drill, and then amathematical model was established for analyzing radial force in drilling withindexable drills. Finally, the numerical calculation and experimental results werecompared under different cutting parameters for drilling Al7050-T7451; thevalidity of the model was verified. The main content of this paper is:1．Selecting the indexable drill with two WCMX-inserts as the researchobject of this paper, a mathematical model for the geometric angles (the normalrake angle, inclination angle, cutting edge angle，etc.)analyzing of indexabledrills was developed. With the help of this model, the changes of geometricangles of the cutting edges along the radial direction were analyzed, and thencompared by the changes of geometric angles analyzed with the vector method.2．The shear stress on the shear plane was calculated by the model ofunequally divided shear zone. In the primary shear zone, the materialconstitutive relationship is represented using Johnson-Cook equation， andcombining the governing equations of the velocity, strain, stress and temperature of the material flowing through the primary shear zone, the shear stress on theshear plane was calculated by numerical method. Subsequently, using theequivalent plane approach, the orthogonal cutting theory based on unequaldivision shear zone was extended and applied to the single-edge oblique cutting.Finally, the cutting forces of the single-edge oblique cutting were analyzedaccording to the transformation relationship between orthogonal cutting sectionsparalleled to the equivalent plane and the single-edge oblique cutting.3. The process that the edges of an indexable drill were discretized a seriesof differential single-edge oblique cutting sections was analyzed. By analyzingthe geometric angles of the cutting edges and based on the single-edge obliquemodel, the cutting forces of the indexable drill were analyzed according to thetransformation relationship between oblique cutting sections and the indexabledrill, then the value of the cutting forces of the indexable drill was calculatedthrough the numerical integration. Finally, the mathematical model wasestablished for analyzing radial force in drilling with indexable drills.4. The numerical calculation and experimental results were compared underdifferent cutting parameters for drilling Al7050-T7451with the indexable drill;the validity of the model for analyzing radial force in drilling with indexabledrills was verified.