Dimensional Accuracy Of Holes Research Articles

Drilling Strategies to Improve the Geometrical and Dimensional Accuracy of Deep through Holes Made in PA6 Alloy.

This article shows how different drilling strategies may affect the geometrical and dimensional accuracy of deep through holes. The tests were conducted on a three-axis direct-drive turning center. The holes were drilled in cylindrical PA6 aluminum alloy specimens 30 mm in length and 30 mm in diameter using 6 mm Ø VHM HPC TiAlN-coated twist drill bits. The cutting fluid was supplied to the cutting zone through the spindle. The experiments involved applying three strategies to drill deep through (5D) holes. The first required the workpiece to be fixed and the tool to perform both rotary and reciprocating motions. The second assumed that the workpiece performed the primary (rotary) motion whereas the tool moved in reciprocating motion. In the third strategy, the workpiece and the tool rotated in opposite directions and the tool also performed a reciprocating motion. The straightness, roundness, cylindricity, and diameter errors were the key output parameters in the analysis of the geometrical and dimensional accuracy of holes. The Taguchi orthogonal array design of experiment (DOE) was employed to determine the effects of the input (cutting) parameters (i.e., spindle speed and feed per revolution) and the type of hole making strategy on the hole errors by means of multi-factor statistical analysis ANOVA. The use of the highest spindle speed (n = 4775 rpm), the highest feed per revolution (fn = 0.14 mm/rev) and strategy I resulted in the lowest values of the output parameters (STR = 22.7 µm, RON = 8.6 µm, CYL = 28.2 µm, and DE = 9.9 µm). Strategy I was reported to be the most effective for hole drilling in PA6 aluminum alloy because, irrespective of the values of the process parameters used, three out of four output parameters, i.e., straightness, roundness and diameter errors, reached the lowest values.

Influence of the Kinematic System on the Geometrical and Dimensional Accuracy of Holes in Drilling.

This article attempts to show how the kinematic system affects the geometrical and dimensional accuracy of through-holes in drilling. The hole cutting tests were performed using a universal turning center. The tool was a TiAlN-coated Ø 6 mm drill bit, while the workpiece was a C45 steel cylinder with a diameter of 30 mm and a length of 30 mm. Three kinematic systems were studied. The first consisted of a fixed workpiece and a rotating and linearly moving tool. In the second, the workpiece rotated, while the tool moved linearly. The third system comprised a rotating workpiece and a rotating and linearly moving tool, but they rotated in opposite directions. The geometrical and dimensional accuracy of the hole was assessed by analyzing the cylindricity, straightness, roundness, and diameter errors. The experiment was designed using the Taguchi orthogonal array method to determine the significance of the effects of the input parameters (cutting speed, feed per revolution, and type of kinematic system) on the accuracy errors. A multifactorial statistical analysis (ANOVA) was employed for this purpose. The study revealed that all the input parameters considered had a substantial influence on the hole quality in drilling.

Influence Axial Vibration on Lateral Bending Deformation of Twist Drill in Machining Small Hole

According to material mechanics theory and drilling practice, the equation of lateral bending deformation (LBD) of drill was built and the inclined angle of drill tip was solved when drilling small hole. And then the drilling test was done and the character of drilling force was analyzed. Based on this, the LBD of drill was studied. The result shows that, the rise of lateral force and thrust force will increase the inclined angle of drill tip in drilling process, and lateral force is the main factor of generating LBD. By choosing suitable axial vibration parameter, axial vibration drilling can reduce the LBD of drill and improve the dimensional accuracy of hole evidently.

Research on Hole Expanding with Spiral-Fluted Electrode in ECM

A manufacturing technology applying a special spiral-fluted electrode in traditional ECM (Electro-chemical Machining) is introduced, this method is provided with the advantages of both narrow-gap ECM and pulsed current ECM. It is a new technological method for expanding holes in hard metal materials parts. In this paper, a new type ECM electrode is proposed to solve hole expanding problem in carbide drill bush. The machining principles and the influence of some operating parameters of ECM on the machining precision and productivity are described. Experiments results indicate that the accuracy and quality of the machined surface and the machining efficiency could be improved greatly by applying spiral-fluted electrode in ECM. It is also showed that the inner surface of the carbide bush was finished easily by this method with the optimal operating parameters, at the same time, the surface roughness of a machined hole is improved to 1ess than 0.2m Ra, and the dimensional accuracy of hole can reach 0.02mm.